Mold polishing stones come in a variety of materials, including ceramic, diamond, and silicon carbide. The selection of a mold polishing stone depends on the type of mold being polished, the material from which it is made, and the desired finish. In this article, we will explore the different types of mold polishing stones, their uses, and how to choose the right one for the job.
Types of Mold Polishing Stones
EDM stone is made of high-purity white aluminum oxide of high quality and it is a vitrified product with outstanding maching capability and removers curved surface or stains after electirc-discharge machining. This polishing Stone is suitable for rough grinding or semifinishing of hard steel tool for the heat treatment mold and micro knurling mold.It is used mainly to finish EDM surface and grind the corners and small deep-grooves.
Ceramic stones are made from a combination of aluminum oxide and ceramic fibers, which make them very durable and resistant to wear. They are best used for polishing soft metals, plastics, and composite materials.
Ceramic stones are available in different grit sizes, from coarse to fine. Coarse grit ceramic stones are used to remove scratches and other imperfections from the mold surface, while finer grit stones are used for achieving a smoother finish.
One of the advantages of using ceramic stones is that they generate less heat than other types of polishing stones, making them ideal for polishing heat-sensitive materials. However, they do tend to wear down faster than other types of stones and may require more frequent replacement.
3.Diamond Stones
Diamond stones are the most abrasive and durable of all polishing stones. They are made with industrial-grade diamonds that are embedded in a metal matrix, making them ideal for polishing hard metals, such as steel, titanium, and carbide.
Diamond stones are available in different grit sizes, ranging from coarse to ultra-fine. Coarse grit diamond stones are used for removing material quickly, while finer grit stones are used for achieving a high-quality finish.
Diamond stones generate a lot of heat during the polishing process, so it's important to use a lubricating fluid to cool the surface being polished and prevent damage to the mold or die. They are also more expensive than other types of stones, but their durability and effectiveness make them a good investment in the long run.
Silicon carbide stones are made from a combination of silicon and carbon, which gives them their abrasive properties. They are best used for polishing hard metals, such as stainless steel and titanium.
Silicon carbide stones are available in different grit sizes, from coarse to fine. Coarse grit stones are used for removing scratches and other imperfections, while finer grit stones are used for achieving a smoother finish.
Silicon carbide stones generate more heat than ceramic stones but less heat than diamond stones, so it's important to use a lubricating fluid to prevent damage to the mold or die. They are also more durable than ceramic stones and less expensive than diamond stones, making them a good choice for many polishing applications.
How to Choose the Right Mold Polishing Stone
Choosing the right mold polishing stone depends on several factors, including the type of mold being polished, the material from which it is made, and the desired finish. Here are some tips to help you choose the right mold polishing stone for your needs:
Different materials require different types of polishing stones. For example, hard metals like steel and titanium require diamond or silicon carbide stones, while softer materials like plastic and composite materials are best polished with ceramic stones.
The grit size of the polishing stone determines how aggressive the polishing action will be. Coarse grit stones are used for removing scratches and imperfections, while finer grit stones are used for achieving a smooth and uniform finish.
The desired finish will also determine the type
]]>Ideal for deburring, polishing, and removing cutter marks on inner diameters
Features
-After cutting process, this product removes burrs with the burr root thickness of 0.2 mm or less. It is also ideal for cutter mark removal and surface polishing.
-The tip of the bristle remove burrs and finish the edges.
-CNC deburring and cutter mark removal can be achieved by installing onto a machining center, robot, drilling machine, or other machining equipment(Can be installed on machining equipment with a collet chuck, milling chuck, drill chuck, or similar means.)
-The original brush material (ceramic fibers)enables consistent deburring and polishing capability without changes to the cutting performance or brush shape.The abrasive material is ceramic fiber that contains no abrasive grains at all.
-The product can be used for both dry and wet machining.
Features
-Centrifugal force generated by rotation causes the brush to expand and remove fine burrs from the crosshole inside the cylinder.
-It polishes and removes black scale from the inside surface of the cylinder, and removes cutting particles and foreign substances from the hole bottom surface.
-The abrasive material is ceramic fiber that contains no abrasive grains at all.
-The brush tip generates grinding power. The tip of the bristle removes burrs and finishes the edges.
-Install onto a machining center, robot, or other processing equipment to remove burrs and cutter marks.
-The original brush material (ceramic fibers) enables consistent deburring and polishing capability without changes to the cutting performance or brush shape.
Are you looking XEBEC Brush ,Please send messages us
]]>EDM polishing stone
It is a hard-structured aluminum oxide stone for polishing EDM (electrical discharge machining) surfaces on all types of mold and die steel. It performs particularly well on heat treated steels. This stone is hard, strong and will hold its shape while penetrating surface scale easily making it ideal for polishing sharp corners and small details either by hand or with the use of reciprocating profilers like our U-Lap and Turbo-Lap Air Profilers and Diprofil Die Profiler. Can also be used with ultrasonic polishers.
Gesswein EDM Stones
-This stone removes the tough, hard scale left by the Electric Discharge Machining (EDM) process much faster than any of our other polishing stones.
-Contains premium-grade white aluminum oxide abrasive that fractures into sharp pieces (friable) during finishing to extend the life of the abrasive grit.
-Medium and Hard tool steels as high as Rockwell C 62.
AS-9 Similar to the AM-8, the AS-9 is engineered for hand stoning EDM scale surfaces.The special formulation provides a fast smooth cutting action during hand stoning.
AO offers excellent breakdown characteristics and yet retains its shape well, especially when polishing mold cavity details. Because the AO is filled with lubricant during the manufacturing process, it does not require lengthy pre-lubrication. 220 grit is an ideal “start up stone” for machined surfaces. Grits 220 and 320 work well in removing EDM scale
Bellstone Polishing Stone(VH series)
It is made of high-purity white aluminum oxide of high quality, is a vitrified product with outstanding machining capability and removes curved surface or stains after electric-discharge machining.This product is suitable for rough grinding or semifinishing of hard steel tool for the heat treatment mold and micro knurling mold.
Because of high grade of grinding stone and high impact resistance, it does not break easily and is used mainly to finish EDM surface and grind the corners and small deep grooves. This product is oil impregnated often and its grinding ability
is excellent without creating surface scratches.
Ceramic polishing stones
It is made of long ceramic fibers that will not break even under the most strenuous conditions, This polishing stones can be used in ultrasonic polishers, reciprocating profilers, or by hand (with our Ceramic Super Stone Holders).
These strong yet flexible stones are ideal for polishing small intricate areas on all types of metals producing consistent and uniform surface finishes.Ceramic fiber stones are non-loading and can be shaped with the Super Dresser and offer an improved cutting ability, longer life.
Xebec ceramic polishing stones
Xebec ceramic stone are used for detailed finishing of detailed surfaces.It can be shaped easily for the required use. They are excellent for getting into detailed tight areas.It traditionally used in Mould tool and Die polishing to get in very tight spaces.
These stones are available in a huge range of grits 120g which is very coarse for rapid stock removal or coarse spark surface to be removed to 3000 grit which is similar to 10 micron and used for polishing.
Ceraton ceramic polishing stone
Ceraton ceramic stone has the Japanese line of sticks made with high quality self-lubricating ceramic fibers.it is an excellent stone for EDM removal and it suitable for using on all types of mold and dies,fine and super fine finshing.Especially for engraving parts,slight ribs,radius ribs,corners,complicated area and details.
If you need some abrasives stone for mold die polishing.Plaese check the mold polishing stones link for price.
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Mini Ceramic Fiber Stone
Crystal Mini Fiber stone and Sharp Shield Mini ceramic stone are cut into various tiny sizes such as 0.3 x 0.3mm ~ 1 x 2 mm, and are mainly used for detailed grinding of concave seams and small grooves. Generally, traditional petroleum or ruby petroleum stone will be easy to break if cut into the same size, but crystal mini-fiber stone and Sharp Shield mini-fiber stone have high strength and toughness and are the preferred grinding tools for detailed processing.
Uses: It is good for all type of molds and dies fine and super fine finishing. Especially for engraving parts, slight ribs, R ribs,corners,complicated area and details.Besides,all other tool parts that needs details lapping.Our mini crystal fiber stone and Mini ceramic fiber stone will be the wonderful tools.
Ceramic diamond stones
Ceramic diamond stones are made of diamond abrasives and ceramic fibers
bonded together with thermosetting resin. The combination of diamond and
ceramic fibers creates the outstanding cutting performance. Ceramic diamond
stone is a perfect lapping tool.
Features :
1. The machinability of ordinary ceramic fiber stone comes from the end face of the stone, but all parts of the diamond fiber stone such as the plane, side or tip can be used.
2. Compared with the general traditional stone and fiber stone, diamond fiber stone is not easy to plug holes and has more cutting force.
3. Generally, traditional stone cannot process many special materials such as ultra-hard dies, but diamond fiber stone has no such limitation.
4. Diamond fiber stone can be used for various processing such as: surface grinding after EDM discharge, polishing of tungsten steel mold, ceramic processing and grinding, and glass surface grinding.
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Diamond paste is a kind of paste carefully prepared from diamond powder, carrier and dispersant. It belongs to soft abrasive and can be divided into oil-soluble grinding paste and water-soluble grinding paste; oil-soluble grinding paste and water-soluble grinding paste are oil-soluble grinding paste and water-soluble grinding paste respectively. Grinding with water as a diluent, although the grinding method is the same, but the grinding effect is different. The oil-soluble grinding paste has good lubrication effect and high smoothness. It is suitable for metal workpieces, such as hard alloys, parts of high-hard materials, instrumentation, Grinding and polishing of measuring tools, cutting tools, molds, etc.; the viscosity of water-soluble abrasive paste is small, the grinding debris is easy to discharge, the grinding efficiency is high, and the surface finish is good. It can be arbitrarily selected according to the needs in the actual application process; it can be said that it is mainly used in the grinding and polishing of gemstones, glass, ceramics, cemented carbide and hardened steel with high finish; when grinding and polishing different materials , you need to choose products with different particle sizes according to your experience and relevant knowledge.
Dispersant is a kind of surfactant with two opposite properties of lipophilicity and hydrophilicity at the same time in the molecule. It can uniformly disperse the solid particles of inorganic and organic pigments that are difficult to dissolve in liquids, and at the same time prevent the sedimentation and agglomeration of solid particles, and form the pharmaceutical required for stable suspension.
Surfactant refers to a substance with fixed hydrophilic and lipophilic groups that can be aligned on the surface of the solution and can significantly reduce the surface tension. Surfactants are molecules formed from two distinct particles, one extremely lipophilic and the other extremely hydrophilic. When dissolved in water, it reduces the surface tension of water and increases the solubility of organic compounds. The properties of surfactants provide a variety of functions for specific applications, including: foaming effects, surface modification, cleaning, emulsions, rheology, environmental and health protection, etc., and are therefore used as performance additives in many industrial formulations, such as Personal and home care, and countless industrial applications: metal handling, industrial cleaning, oil extraction, pesticides, and more.
Commonly abrasive paste:
1. Corundum type abrasive paste - mainly used for grinding steel parts
2. Silicon carbide - boron carbide abrasive paste, mainly used for grinding cemented carbide, glass, ceramics and semiconductors, etc.
3. Chromium oxide abrasive paste - mainly used for fine polishing or non-metallic grinding
4. Diamond abrasive paste - mainly used for grinding hard alloys and other high hardness materials
Ingredients and Uses :
1. Silicon carbide abrasive paste 83%, Vaseline 17% coarsely ground
2. Boron carbide grinding paste 65%, paraffin 35% semi-finishing
3. Mixed grinding paste 35%, white corundum (F600~F1000) and mixed grease 15%, oleic acid 35% semi-fine grinding
4. Boron carbide grinding paste 76%, paraffin 12%, ocean oil 10%, turpentine 2% finely ground
Do you know how many series are there in Cerabon Bellstone mold stone?
VH series mold stone
It is made of high-purity white aluminum oxide of high quality, is a vitrified product with outstanding machining capability and removes curved surface or stains after electric-discharge machining.This product is suitable for rough grinding or semifinishing of hard steel tool for the heat treatment mold and micro knurling mold.
Because of high grade of grinding stone and high impact resistance, it does not break easily and is used mainly
to finish EDM surface and grind the corners and small deep grooves. This product is oil impregnated often and its grinding ability
is excellent without creating surface scratches.
※ Can be used for all manual work or with the power tool
MS series mold stone
This is a vitrified product made of aluminum oxide with high impact resistance and superior machining ability. A variety of uses
ranges from rough surface grinding to final grinding, and it is suitable for grinding general steel.
※ Can be oil impregnated
MF series mold stone
This is a vitrified product, made of high-purity white aluminum oxide, that is able to grind smoothly and process fast without
loading It is generally used for grinding alloy tool steel, die steel and general mold steel.
HS(GC) series mold stone
This is a vitrified product, made of high purity silicon carbide, that has fine hard grains and grinds fast with naturally high
recovering sharp blades. This is mainly used for grinding high hardness stainless steel, casting mold, superhard alloy steel,
SUS400 and non-metallic materials like glass.
CX series mold stone
This is a vitrified product, made of silicon carbide with hardness inbetween the hardness of ruby and the hardness of diamond,
that is mostly used for machining steam mold die forLCD, LED, etc. As well as and is easy to work on non-ferrous metal for final
mirror finishing of the hard mold.
The Specification of Bellstone mold stone
Grits | Size (Standard Dimension) / T x W x L (mm) |
#80 #100 #120 #150 #180 #240 #320 #400 #600 #800 #1000 #1200 #1500 #2000 #3000 |
1.5 x 6 x 100, 2 x 6 x 100, 3 x 6 x 100, 3 x 13 x 100, 3 x 6 x 150, 3 x 13 x 150, 5 x 13 x 150
|
Selection
Product | Taget Workpiece | Features |
Stick type G series |
Materials up to HRC57 (e.g. plastic mold steel, carbon steel) |
Ideal for mold polishing & deburring Only use the tip Suitable for removing EDM scales Easy to form the tip |
Rod type G series |
Materials up to HRC57 (e.g. plastic mold steel, carbon steel) |
Ideal for mold polishing & deburring Only use the tip Suitable for removing EDM scales Easy to form the tip |
Xebec ceramic fiber stone G series sizes/grits/codes
Grits
|
#180
|
#220
|
#250
|
#400
|
#600
|
#800
|
#1000
|
#1200
|
Sizes
(colors)
|
Brown
|
Coffee
|
Orange
|
Yellow
|
Gray
|
Blue
|
White
|
Red
|
1*4*100
|
GG-1004M
|
GD-1004M
|
GA-1004M
|
GO-1004M
|
GP-1004M
|
GB-1004M
|
GW-1004M
|
GR-1004M
|
1*6*100
|
GG-1006M
|
GD-1006M
|
GA-1006M
|
GO-1006M
|
GP-1006M
|
GB-1006M
|
GW-1006M
|
GR-1006M
|
1*10*100
|
GG-1010M
|
GD-1010M
|
GA-1010M
|
GO-1010M
|
GP-1010M
|
GB-1010M
|
GW-1010M
|
GR-1010M
|
Φ3*100
|
GG-30M
|
GD-30M
|
GA-30M
|
GO-30M
|
GP-30M
|
GB-30M
|
GW-30M
|
GR-30M
|
Features
Stick type
High grinding power on the tip
Efficient polishing performance and strength
Rod type
Cutting edges are exposed over the entire surface; both the tip and sides has high grinding power
Can be used with high rotational speed without splitting the tip
How to Use
Stick type
Press the tip against the surface at an angle of approximately 45 degrees.
It can be used by directly holding in your hand, or can be used with the optional stick holder to improve work efficiency.
Use with a vibrating tool (electric, ultrasonic and pneumatic type) improves efficiency.
The use of metal polish liquid is recommented to prevent clogging and improve polishing efficiency.
Rod type
For the rod type, the entire surface (tip and sides) has grinding power. To improve work efficiency, make contact the tip with the polishing surface at angle of approximately 45 degrees.
It can be used by directly holding in your hand, or can be used with the optional stick holder to improve work efficiency.
Use with a rotating tool (electric and pneumatic types) improves work efficiency.
The use of mental polish liquid is recommended to prevent clogging and improve polishing efficiency.
Precautions
Before using a vibration tool or a hand grinder, carefully read the usage precautions and respective manuals. When using the rod type (Φ2.34mm, Φ3mm) with a hand grinder, cut off the stone less than 50mm in length, and use at less than the maximum rotation speed of 30000min-1.
Ultra Polisher
Check the appropriate output. The tool may break or generate heat when the output is too large.
Check the appropriate length. If the length is inappropriate, the tool may not vibrate, or cause heat generation due concentrated output.
Clamp the tool securely. Poor clamping may concentrate output, resulting in excessive heat generation. Carefully read the instruction manual of an ultrasonic polisher because polishing perfomance differes depending clamping method.
Maintenance
Truing
If the tip is worn out, form it with diamond disc blade or grinder. You can also customize the shape depending on the application or workpiece shape. For the rod type, you can use a rotary tool to precisely form the tip.
Opreator Safety Measures
For Protective Equipment
Always wear protective goggles, gloves and masks when operating the tool. Wear long sleeves, tight cuff, and clothing to minimize skin exposure.
Beware of Gringding Powder
Grinding powder and burrs may scatter within an area around the work as the brush revolves; please stay clear of this area.
Be Aware of Your Surroundings
The area around your work is hazardous in case flying pieces of fiber rods from the tools and grinding powder may scatter, enclose your working area to prevent other people entering, or have the people surrounding your work area protective equipment as well.
!Warning!
By not following the above safety measures, you are vulnerable to the following risks:
A tool or a part of a tool may crack, drop off, distort or break.
Broken pieces of a tool or grinding dust may stick into your skin and eyes, causing irritation and/or blindness.
Dust generated by machining process may cause allergic reactions.
Ceraton ceramic fiber stone is an excellent stone for EDM removal and it suitable for using on all types of mold and dies,fine and super fine finshing.Especially for engraving parts,slight ribs,radius ribs,corners,complicated area and details.
Grits | Applications |
#180#220#250#280 |
Grinding and polishing of rough surfaces and removal of hard EDM |
#360 #400 | Surface treatment for processing minor scratches |
#700 #1000 #1200 | Fine grinding and surface treatment |
Φ3mm |
lt has the effect of a shaft grindstone, and after the top is processed sharply, it can be used for precision polishing of fine seams and othersubtle places |
3 major product advantages
01:Not easy to break,strong resistance to fracture.
CERATON fiber stone with a unique combinnation of materials and manufacturing method of stong resistance to fracture,not easily broken.
02:Fiber cross arrangement,does not produce scratches.
The fibers are arranged crosswise, the whetstone sand grains are uniform and full,not easy to fall off, and there will be no scratches on the surface of the grinding workpiece.
03:Swipe vertically and horizontally,not easy to fever.
Sliding vertically and horizontally to improve the grinding speed and the strengthof the whetstone.
lt is not easy to generate heat during grinding and will not cause the workpiece to become hot.
The main features
-Ceraton Fiber stone provides better cutting force, higherheat resistance and longer service life,especially the heat resistance is about 45%higher than the traditional one.
-It is not easy to generate heat during polishing and not cause the workpiece to become hot.Super mini fiber stones is suitable for using on all types of molds and dies,fine and super fine finishing.It has the characteristics of high hardness.
-The shape of fiber sotnes can be arbitrarily trimmed and changed freely.In addition to being used for hand polishing.It is also suitable for pneumatic and electric reciprocating grinder.The effect is better when using ultrasonic grinder.It can also be ground and processed on various die steels of different materials.It is suitable for general hard-to-grind processing.such as narrow groove walls,groove bottoms,hole slip marks,auxiliary parts and small and fine parts. Especially for the fast removal and polishing effect of the carbon deposit layer after electric discharge machinning.
What is it use for?
-mold die tooing fine polishing
-Jade polishing
-Jewelry polishing
-Metal precision polishing
If you need the ceraton fiber stone,please click on here
]]>Oilstone is a sintered natural mineral. "oilstone" is originally black or brownish-black, while those exposed on the ground are grayish white due to weathering. The surface does not look like oil, but when it is distilled with hot gas, the organic matter in it decomposes into kerosene, hence the name. Its texture is fine and tough, and can be used as an abrasive tool. Later, the strip-shaped consolidated abrasive tools made of abrasives and bonding agents were also called whetstones.
The Features
Oilstone is similar to coal, kerosene, and bitumen because it is made of organic matter accumulated by ancient animals and plants. The accumulation of its beds is always in shallow coastal waters, which are rich in inferior organic plants, scales, insects and other deformed animals that are difficult to identify. The structure is very fine, with lime and sand inside, and the texture is tough. It is a kind of delicate rock, used to sharpen tools and other metal surfaces.
Industrial application
Ruby oilstone: It is a kind of microcrystalline corundum product that is sintered at high temperature. It has a compact and delicate structure, and has high hardness and strength.
The product is rose red, and the products are divided into three categories: small grinding wheel type whetstone, standard type whetstone, and grinding head type whetstone. When grinding a workpiece, it can maintain a sharp edge and a stable geometry for a long time.
It is suitable for forming and grinding of instrument industry, precision parts, micro tools, tools, precision abrasives, etc. The processing precision and surface roughness can reach about 0.05μm.
Product specifications: small grinding wheel type flat grinding wheel whetstone with a diameter of less than 100, standard type whetstone with various geometric shapes within 200*50*25cm, and grinding head whetstone of various shapes with a grinding head diameter of less than 25cm.
The oilstone classification
Diamond oilstone
It has the advantages of good elasticity, cutting force, wear resistance, etc. It is difficult to reach for mold manufacturing, tool repair, various workpiece bends, holes and ordinary abrasive tools. It is an ideal abrasive tool and other oilstone Irreplaceable.
The specifications are 100*2-10*0.5-1.2, and the grits is 320#-1200#
Ordinary oilstone
Widely used in machinery manufacturing, mold manufacturing, instrumentation and other fields
Super fine grinding oilstone
Super fine grinding stone and powerful grinding stone are widely used in machinery manufacturing, mold manufacturing, instrumentation and other fields. Ergonomics is twice that of ordinary oilstone
Ruby oilstone
Ruby is a kind of corundum microcrystals made from alumina powder and sintered at high temperature. The structure is compact and delicate, with high hardness and strength. Because it is a sintered product, it has no characteristics such as various hardness grades, particle sizes and different strength ranges, but it has a dense structure and a pore structure. Therefore, the product is marked with a structure and the product is rose red.
Boron Carbide oilstone
Boron carbide is a hard black shiny crystal. Hardness is lower than industrial diamond, but higher than silicon carbide. Whetstone particle size is between 400 and 1000, the smaller the particle size, the rougher, the greater the amount of grinding, used for the grinding of semi-finished tools. Because of its strong hardness, it is particularly wear-resistant and not easy to scratch.
Grinding method
Diamond paste, the particle size ranges from W40 to W0.5. W40 is the coarsest and has a large amount of grinding, and W0.5 is the finest. It is used for polishing, and even harder knives can be ground without annealing.
Coating coarse W40 grinding paste on the boron carbide whetstone can speed up the increase of the grinding amount without annealing.
Then, after cleaning the rough abrasive paste on the knife, apply W0.5 abrasive paste to ruby or natural jade for polishing. The result is a mirror surface.
The three types of green silicon carbide, white corundum, and brown corundum are not hard enough. In addition, the grain size is a bit coarse, which makes it easy to grind the knife. Moreover, the other three types of whetstone will not be annealed during polishing and grinding.
There is no difference if the particle size is greater than 1000. It is mainly determined by the abrasive paste used. Apply the W1.5 abrasive paste on the ruby of 1000 mesh, and its abrasive effect is the effect of the W1.5 abrasive paste, which is 2500 grit. Whetstone effect.
Diamond paste is also divided into water-soluble abrasive paste and oil-soluble abrasive paste. The oil-soluble grinding paste has good wettability, low grinding force and low grinding heat. It is mainly used for processing high-finish hard alloy and other high-hard alloy parts, instruments and meters, measuring tools, cutting tools, abrasive tools, etc. The water-soluble abrasive paste has low viscosity, easy removal and high processing efficiency. It is mainly used for processing slightly corrosive metals, circuit boards, glass, ceramics, gems, agate and other non-metallic hard and brittle materials. According to the difference of the diamond powder used, it can be divided into polycrystalline diamond abrasive paste and single crystal diamond abrasive paste. Different from single crystal diamond abrasive paste, polycrystalline diamond abrasive paste uses polycrystalline diamond powder as the main abrasive, which has strong self-sharpening properties and can meet the high standards of customers.
Uses of diamond paste
Diamond paste is a commonly used polishing agent, if used properly, a very good polishing effect can be obtained.
Polishing tools, from different types of fibers to sticky pads, are suitable for materials of different hardness. Such as nylon, paper, velvet, cotton, etc.
Pay attention to when polishing:
a. Polishing should be carried out in a dust-free and ventilated place, because hard dust particles are easy to adhere to the diamond paste and will damage the surface that is about to be polished;
b. Each polishing tool should only be used for one type of diamond paste, and pay attention to dust:
c. Wash hands and workpieces every time the diamond paste is changed;
d. Adjust the polishing pressure to match the hardness of the polishing tool and the particle size of the diamond paste. For the finest diamond paste, the pressure is only as large as the weight of the polishing tool.
e. Polishing should start from the corners, edges, pieces or other parts of the mold.
4.0 Solution to problems in polishing:
The main problem with polishing is over-polishing. The so-called over-polishing means that the longer the polishing time, the worse the surface condition. Excessive surface polishing usually refers to the following two phenomena: "orange peel-like peeling" and "pinholes". It should be pointed out that the chances are usually greater when using machine polishing.
4.1 Orange peel-like peeling layer:
After polishing, orange peel-like irregular peeling appears on the surface of the workpiece. The main reason is that the material is soft and the polishing pressure is too large. The hard material can withstand higher polishing pressure and is not easy to be over-polished.
When the polishing surface is deteriorated, increase the polishing pressure to continue polishing. Doing so will inevitably increase the polishing of the surface.
To re-repair the surface of the material after deterioration, the following methods can be used:
Method 1: Use fine sanding to remove the deteriorating layer of the surface before polishing, and then start polishing after the final polishing is completed. A lower polishing pressure should be used during polishing.
Method 2: Release the stress when the temperature is lower than the last tempering temperature of 25°C (45F), and repeat the polishing before polishing until the surface condition is satisfactory. Start polishing again, but the polishing pressure should be lower than the previous polishing pressure.
Ceramic fiber stone is made by combining ceramic particles and resin with a special process, and it is mainly used for polishing precise and subtle parts. According to the shape, it can be divided into two types: flat and round.
The characteristics and uses of Xebec fiber stone
It has strong toughness and generally used for precision polishing of the bottom of the mold, fine seams, etc. Fiber whetstone is used for narrow grooves on molds, jade handicrafts, cemented carbide workpieces, and hard-to-grind curved surfaces and deep polishing. It is also suitable for removal of hardened surfaces after EDM, mechanical cutting, removal of rough tool marks, removal of finishing marks, and treatment before general polishing, fine grinding or mirror polishing.
1. It adopts a crystal structure suitable for grinding, which greatly improves the grinding efficiency compared with traditional oilstone.
2. The fibers are arranged crosswise, the sand particles are uniform and full, not easy to fall off, and there will be no scratches on the surface of the grinding workpiece. It can slide vertically and horizontally to improve the grinding speed and the strength of the whetstone.
3. It is not easy to generate heat during polishing, and will not cause the workpiece to become hot and the oil stone to deteriorate.
4. The shape of the fiber stone can be arbitrarily trimmed and changed freely.
5. In addition to being used for hand-held grinding, it is also suitable for pneumatic and electric reciprocating grinding machines. Use on the ultrasonic vibration grinder, the effect is very good (use at a 45 degree angle with the grinding surface). Ceramic fiber whetstone can be ground and processed on various mold steels of different materials. It is suitable for places that are generally difficult to grind and process, such as narrow groove walls, groove bottoms, holes, slip marks, ribs and small and fine places. Especially for the quick removal and polishing effect of the carbon deposit layer after electric discharge machining.
Xebec fiber stone color classification
According to the different grits, ceramic fiber stone is divided into different colors.
1.Brown: 220# grit, it mainly used to remove carbon deposits on the surface after power generation processing (electric discharge grinding)
2.Coffee: 300# grit, it mainly used to remove carbon deposits on the surface after power generation processing (electric discharge grinding)
3. Orange: 400# grit, used for grinding cutting tool marks
4. Black: 600# grit, used for grinding cutting tool marks
5. Blue: 800# grit, used for grinding cutting tool marks
6.White:1000#grit,used fine grinding or grinding before mirror polishing
7.Red:1200#grit,used fine grinding or grinding before mirror polishing
The higher the of grits, the finer the ceramic particles.
How to use xebec ceramic fiber stone?
Flat Shape
First, press the end face part on the surface so that it is at an angle of about 45 degrees with the surface.
Xebec ceramic fiber whetstone flakes are all made of ceramic fiber cross mesh, so there is cutting force on the side.
It can be used directly in your hand, or you can use the handle bracket to improve work efficiency.
You can also use vibration tools (electric, ultrasonic and pneumatic) to improve efficiency.
If you are using ultrasonic vibration tools, it is recommended that you use xebec heat-resistant ceramic whetstone, which can withstand temperatures up to 200 degrees.
Xebec ceramic fiber whetstone soft grinding disc (BS-2006M) cannot be used with vibration tools.
It is recommended to use metal polishing liquid to prevent clogging and improve grinding efficiency
Round Shape
The entire surface (tip and side) of the round shape has the ability to grind. To improve work efficiency, you can make the end face contact with the surface of the workpiece at an angle of about 45 degrees.
It can be used directly in your hand, or you can use the handle bracket to improve work efficiency.
You can also use vibration tools (electric, ultrasonic and pneumatic) to improve efficiency.
Xebec ceramic fiber stone soft grinding disc (PBS-30M) cannot be used with vibration tools.
It is recommended to use metal polishing liquid to prevent clogging and improve grinding efficiency
Precautions for use
Before using vibrating tools or manual grinders, please read the precautions and related manuals carefully.
The rod-type manual grinder (φ2.34mm, φ3mm) can be used to cut stones with a length not exceeding 50 mm, and the maximum speed should be less than 30000 min.
Mold polishing has two purposes; one is to increase the finish of the mold, so that the surface of the product from the mold is smooth, beautiful, and beautiful, and the other is to make the mold easily demolded, so that the plastic is not stuck on the mold and cannot be taken off .
Polishing is a very important process in the mold making process. With the increasingly widespread use of plastic products, the appearance quality of plastic products is also getting higher and higher. Therefore, the surface polishing quality of plastic mold cavity should be improved accordingly, specially Mirrors and high-gloss high-gloss surfaces require higher mold surface roughness and therefore higher polishing requirements. Polishing not only increases the aesthetics of the workpiece, but also improves the corrosion resistance and wear resistance of the surface of the material. It also facilitates subsequent injection processing, such as making plastic products easy to demold and reducing production injection cycle time.
Mold polishing is a polishing method that obtains a smooth surface by cutting and plastic deformation of the material surface to remove the polished convex parts. Generally, whetstone strips, wool wheels, sandpaper, etc. are used, mainly by manual operation. Special parts such as the surface of the rotating body can be Use auxiliary tools such as turntables, and those with high surface quality can use the method of super-finishing polishing. Super-precision grinding and polishing is the use of special grinding tools, in the grinding and polishing liquid containing abrasives, tightly pressed on the surface of the workpiece to be processed for high-speed rotation. Using this technology, the surface roughness of Ra0.008um can be achieved, which is the highest among various polishing methods, and this method is often used in optical lens molds.
The mold polishing in plastic mold processing is very different from the surface polishing required in other industries. Strictly speaking, the polishing of molds should be called mirror processing. It not only has high requirements for polishing itself but also has high standards for surface smoothness, smoothness and geometric accuracy. Surface polishing generally only requires a bright surface. The standard of mirror processing is divided into four levels: A0 = Ra0.008um, A1 = Ra0.016um, A3 = Ra0.032um, A4 = Ra0.063um, it is difficult to accurately control the geometric accuracy of parts due to electrolytic polishing, fluid polishing, etc Degree, and the surface quality of methods such as chemical polishing, ultrasonic polishing, magnetic grinding and polishing can not meet the requirements, so the mirror processing of precision molds is still mainly mechanical polishing.
Serial No. | Code | Level | Methods and Tools | Roughness | Grade | Remarks |
---|
1 | #200000 | — | — | 0.003~0.01 | Optical | for optical finishes |
2 | #14000 | 1 |
diamond buff (optical finishes) |
0.019~0.025 | A0 |
for mirror or optical finishes,
most time consuming and costly finishes to achieve, steel srade important to results |
3 | #10000 | 2 |
3#diamond buff (mirror) |
0.02~0.028 | A1 | |
4 | #8000 | 3 | 3#diamond buff(mirror) | 0.025~0.03 | A1 – A2 | |
5 | #5000 | 4.5 |
6#diamond buff (mirror) |
0.029~0.04 | A2 | |
6 | #3000 | 6 | 6#diamond buff(mirror) | 0.032~0.045 | A2 – A3 | |
7 | #2000 | 8 |
15#diamond buff (mirror) |
0.04~0.06 | A3 | |
8 | #1000 | 15 |
15# diamond buff (mirror) |
0.06~0.07 | A3 | |
9 | #1000 | 15 | Grit Paper | 0.07~0.08 | — |
removes all tools and machining marks,
provides sood mold release, light reflecting finish on molded Dart and some sheens |
10 | #800 | 21 | Grit Paper | 0.08~0.095 | — | |
11 | #600 | 30 | Grit Paper | 0.09~0.1 | B1 | |
12 | #400 | 37 | Grit Paper | 0.11~0.12 | B2 | |
13 | #320 | 45 | Grit Paper | 0.12~0.16 | B3 | |
14 | — | 30 | diamond buff | 0.16~0.17 | C1 |
removes all tools and machining marks, provides good mold release, mute finish on molded part,no sheen, |
15 | — | 37 | diamond buff | 0.23~0.27 | C2 | |
16 | — | 45 | diamond buff | 0.34~0.39 | C3 | |
17 | — | 11# | sandblast | 0.92~0.99 | D1 |
for decorative finishes, helps hide shrink marks and other inperfections, dull non-reflecting finish on molded or cast part |
18 | — | 240# | sandblast | 1.77~1.89 | D2 | |
19 | — | 24# | sandblast | 3.15~3.58 | D3 | |
20 | — | = | sandblast | 1.83~1.99 | SPI5 | |
21 | — | 3A | EDM | 3.62~4.31 | 3A | |
22 | — | 2A | EDM | 2.33~2.41 | 2A | |
23 | — | 1.5A | EDM | 2.07~2.14 | 1.5A | |
24 | — | 1A | EDM | 1.31~1.53 | 1A | |
25 | 140# | — | Grinding Miller | 3~4 | — | |
26 | 230# | — | Grinding Miller | 2~3 | — | |
27 | 400# | — | Grinding Miller | 1~2 | — | |
* International Mold Polishing SPI (Society of Plastic Industry) standards |
Polishing tools
1. Auxiliary grinding and polishing tools
1) Handheld electric straight rod rotary grinding and polishing tool
As shown in the figure, the chuck with the abrasive polishing tool rotates at high speed to achieve abrasive polishing. A special diamond grinding wheel with p2 ~ p12 can be arranged on the chuck to grind and polish the concave arc surface with different curvature. It can also be equipped with R4 ~ RI2 plastic grinding and polishing sleeves or felt polishing wheels, which can grind and polish cavity or hole with complex shapes.
2) Electric elbow rotary handheld electric elbow rotary abrasive polishing tool
As shown in the figure, it can be extended into the cavity to grind and polish the angled corners and corners.
2. Whetstone
Strip-shaped consolidating abrasives pressed and sintered with abrasives and bonding agents. Whetstone is usually lubricated when it is used, hence the name. Whetstone is generally used for manual grinding parts, and it can also be clamped on the machine tool for honing and super-finishing. There are two types of whetstone, man-made and natural. Man-made whetstone has two types of structure due to different abrasives, as shown in Figure 8.2.3.
2. Sandpaper
Sandpaper is made of aluminum oxide or silicon carbide and other abrasives bonded to paper. It is mainly used for rough polishing. The abrasives such as 400 #, 600 #, 800 # and 1000 # are commonly used according to particle size.
3. Grinding and polishing paste
Grinding and polishing paste is composed of abrasives and abrasive liquids, divided into hard abrasives and soft abrasives. The abrasives in hard abrasive polishing pastes include alumina, silicon carbide, boron carbide, and diamond. The abrasives and fine powders with a common particle size of 240 # and W40; soft abrasive abrasive polishing pastes contain oily active substances and are available when used Kerosene or gasoline dilution. Mainly used for fine polishing.
4. Polishing fluid
It is an abrasive material used for super-finishing. It is made of W0.5 ~ W5 chromium oxide and emulsion. It is mostly used for polishing product molds with high appearance requirements, such as optical lens molds.
1. Mould Polishing Process Orders
Mold polishing generally uses rough oilstone to roughen the surface of the machined mold cavity, to remove the mark of the machine tool, then use a fine oilstone to remove the rough oilstone to achieve the mark, and then use fine sandpaper The polished surface of the fine oil stone is then polished, and finally the polishing cavity or the polishing paste is used for the final fine polishing of the cavity surface of the mold, and finally the effect as bright as a mirror is achieved. This is the general process of polishing the mold. Of course, if possible, you can use an ultrasonic polisher to polish the mold, which is more efficient. People are also more effortless.
To obtain a high-quality polishing effect, the most important thing is to have high-quality polishing tools and auxiliary products such as oilstone, sandpaper and diamond abrasive paste. The choice of polishing program depends on the surface conditions after the pre-processing, such as mechanical processing, EDM, grinding and so on. The general process of mechanical polishing is as follows:
① The surface after rough polishing, milling, electric spark, grinding and other processes can be selected for polishing with a rotating surface polishing machine or an ultrasonic grinding machine with a speed of 35000 to 40000rpm. A common method is to use a wheel with a diameter of 3mm and WA # 400 to remove the white electric spark layer. Then there is manual whetstone grinding, with strip whetstone plus kerosene as a lubricant or coolant. The general order of use is # 180 ~ # 240 ~ # 320 ~ # 400 ~ # 600 ~ # 800 ~ # 1000. Whetstone polishing method, this operation is the most important and difficult operation, according to the different specifications of the processed products, the cross-grinding is carried out in a balanced angle of about 70 degrees. The ideal round-trip range is about 40 mm to 70 mm. Whetstone operations also vary depending on the material of the processed product. Many mold makers choose to start with # 400 in order to save time.
② Semi-precision polishing Semi-precision polishing mainly uses sandpaper and kerosene. After the whetstone operation is sandpaper operation, pay attention to the generation of round edges, rounded corners and orange peels of the mold kernel. Therefore, the whetstone process is as fine as possible. Emphasis on sandpaper polishing. Sandpaper is combined with a harder wooden rod to grind at a cross angle of about 70 degrees like a whetstone operation. The number of sandpaper grinding on one side is about 10 to 15 times. If the grinding time is too long, the grinding force of the sandpaper will be reduced, which will cause unevenness on the processed surface (this is also one of the reasons for the orange peel).
In the sandpaper operation, bamboo chips are generally used for grinding. It is most ideal to use a wooden rod with a low elasticity or an aluminum rod with a low hardness at about 45 degrees. No rubber or highly elastic materials can be used for the polishing surface, and sharp angles can be used for shapes that cannot be polished at a 45-degree angle. The order of sandpaper is: # 220 ~ # 320 ~ # 400 ~ # 600 ~ # 800 ~ # 1000 ~ # 1200 ~ # 1500. In fact, # 1500 sandpaper only uses mold steel suitable for hardening (above 52HRC), but not for pre-hardened steel, because it may cause burns on the surface of pre-hardened steel parts.
③Precision polishing mainly uses diamond polishing paste. If the polishing cloth wheel is mixed with diamond grinding powder or grinding paste, the usual grinding sequence is 9um (# 1800) ~ 6u m (# 3000) ~ 3um (# 8000) 9um diamond abrasive paste and polishing cloth wheel can be used to remove the hair-like scars left by # 1200 and # 1500 sandpaper. Then use sticky felt and diamond abrasive paste for polishing, the order is 1um (# 14000) ~ 1 / 2um (# 60000) ~ 1 / 4um (# 100000).
The polishing process with an accuracy requirement of more than 1um (including 1μm) can be performed in a clean polishing room in the mold processing workshop. For more precise polishing, an absolutely clean space is necessary. Dust, smoke, dandruff, and saliva foam can all be scrapped after a few hours of high-precision polished surfaces.
CAUTIONS and SKILLS of Mechanical Polishing:
I. Should pay attention to the following points when polishing with sandpaper:
① Polishing with sandpaper requires the use of soft wooden or bamboo sticks. When polishing round or spherical surfaces, using cork rods can better match the curvature of the round and spherical surfaces. The harder wood strips, like cherry wood, are more suitable for polishing flat surfaces. The end of the wooden strip is trimmed to keep it consistent with the shape of the surface of the steel piece, so that the sharp angle of the wooden strip (or bamboo strip) can contact the surface of the steel piece and cause deep scratches.
②When changing to different types of sandpaper, the polishing direction should be changed from 45 ° to 90 °, so that the streak shadow left by the previous model of sandpaper after polishing can be identified. Before changing to different types of sandpaper, the polishing surface must be carefully wiped with 100% pure cotton and a cleaning solution such as alcohol, because a small grit left on the surface will destroy the entire polishing work. When changing from polishing with sandpaper to polishing with diamond paste, this cleaning process is equally important. Before polishing continues, all particles and kerosene must be completely cleaned.
③ In order to avoid scratches and burns to the workpiece surface, special care must be taken when polishing with # 1200 and # 1500 sandpaper. Therefore, it is necessary to apply a light load and use a two-step polishing method to polish the surface. When polishing with each type of sandpaper, it should be polished twice in two different directions, each time between two directions 45 ° ~ 90 °
II diamond grinding and polishing should pay attention to the following points:
① This kind of polishing must be carried out under light pressure as much as possible, especially when polishing pre-hardened steel parts and polishing with fine abrasive paste. When polishing with # 8000 abrasive paste, the common load is 100 ~ 200g / cm2, but it is difficult to maintain the accuracy of this load. To make this easier, you can make a thin and narrow handle on the wooden strip, such as adding a copper sheet; or cut a part of the bamboo strip to make it more soft. This can help control the polishing pressure to ensure that the mold surface pressure is not too high.
②When using diamond grinding and polishing, not only the working surface needs to be clean, but also the hands of the workers must be carefully cleaned.
③ The polishing time should not be too long each time. The shorter the time, the better the effect. If the polishing process is too long, it will cause “orange peel” and “pitting”.
④ In order to obtain high-quality polishing effect, polishing methods and tools that are easy to generate heat should be avoided. For example: polishing wheel polishing, the heat generated by the polishing wheel can easily cause “orange peel”.
⑤ When the polishing process is stopped, it is very important to ensure that the surface of the workpiece is clean and carefully remove all abrasives and lubricants, then a layer of mold anti-rust coating should be sprayed on the surface.
Because mechanical polishing is mainly done manually, polishing technology is still the main reason for the polishing quality. In addition, it is also related to the mold material, the surface condition before polishing, and the heat treatment process. High-quality steel is a prerequisite for obtaining good polishing quality. If the hardness of the steel surface is uneven or the characteristics are different, it will often cause polishing difficulties. Various inclusions and pores in the steel are not conducive to polishing.
(3) The impact of different hardness on the mold polishing process
The increased hardness increases the difficulty of grinding, but the roughness after polishing decreases. As the hardness increases, the polishing time required to achieve a lower roughness increases accordingly. At the same time, the hardness increases and the possibility of excessive polishing decreases accordingly.
(4) The influence of the surface condition of the workpiece on the polishing process During the crushing process of steel cutting, the surface layer will be damaged by heat, internal stress or other factors. Improper cutting parameters will affect the polishing effect. The surface after EDM is more difficult to grind than the surface after ordinary mechanical processing or heat treatment. Therefore, before the end of EDM, precision quasi-EDM should be used for finishing, otherwise the surface will form a hardened thin layer. If the electric spark refining standard is not properly selected, the depth of the heat-affected layer can be up to 0.4mm. The hardness of the hardened thin layer is higher than the hardness of the substrate and must be removed. Therefore, it is better to add a rough grinding process to completely remove the damaged surface layer to form an average rough metal surface, which provides a good basis for polishing.
The most important point in ultra-mirror polishing is the size of the polishing. The distance between the grindstone and the mirror polishing is 10 & micro ;. (The ideal is to start grinding # 1500 (# 1000) oilstone. The number of sandpaper is: (# 320 ~) # 400 ~ # 600 ~ # 800 ~ # 1000 ~ # 1200 ~ # 1500 ~ # 01 ~ # 02 ~ # 03 ~ # 04 ~ # 05 ~ # 06 ~ # 015) The most basic principle, before proceeding to the next step, the mold kernel must be thoroughly cleaned to achieve good results. Be very careful not to repeat changes (repeated changes will affect quality issues)
(1) Selection of tool materials
Polishing with sandpaper requires the use of soft wooden or bamboo sticks. When polishing a round or spherical surface, using a cork rod can better match the curvature of the round and spherical surfaces; while the harder wood strip is suitable for polishing a flat surface. The end of the wooden strip is trimmed to keep it consistent with the shape of the surface of the steel piece, which can avoid the deep angle of the wooden strip (or bamboo strip) contacting the surface of the steel piece and causing deep scratches.
2) Selection of polishing direction and cleaning of polishing surface
When changing to different types of sandpaper, the polishing direction should be changed from the previous polishing direction by 50 ° ~ 45 ° to polish, so that the streak shadow left by the previous type of sandpaper after polishing Can be distinguished. For the sub-mold mold, the final polishing pattern should be consistent with the demolding direction of the plastic part.
Before changing to different types of sandpaper, it is necessary to carefully wipe the polishing surface with a cleaning solution such as alcohol and cotton wool. The polishing paste of the previous process is not allowed to enter the next process, especially in the fine polishing stage. When changing from sandpaper polishing to diamond paste polishing, the cleaning process is even more important. Before polishing continues, all particles and kerosene must be completely cleaned.
(3) Possible defects and solutions during polishing When grinding and polishing, not only the work surface needs to be clean, but also the hands of the worker must be carefully cleaned; each polishing time should not be too long, the shorter the time, the more effective it is good. “Overpolished”
“Orange peel” and “pitting” will occur. In order to obtain a high-quality polishing effect, polishing methods and tools that are prone to heat should be avoided. For example, the heat generated during polishing and excessive polishing force will cause “orange peel”, or impurities in the material will be separated from the metal structure during the polishing process, forming “pitting corrosion”.
The solution is to increase the surface hardness of the polishing material, use soft polishing tools, high-quality alloy steel; apply appropriate force during polishing, and use the shortest time to complete the polishing. When the polishing process is stopped, it is important to ensure that the surface of the workpiece is clean and carefully remove all abrasives and lubricants. At the same time, a layer of mold anti-rust coating should be sprayed on the surface.
Since the general polishing is mainly done manually, the polishing technology is still the main reason for affecting the polishing quality. In addition, it is also related to the mold material, the surface condition before polishing, and the heat treatment process.
(1) The effect of different hardness on the polishing process
The increased hardness increases the difficulty of grinding, but the roughness after polishing decreases. As the hardness increases, the polishing time required to achieve a lower roughness increases accordingly. At the same time, the hardness increases and the possibility of excessive polishing decreases accordingly.
(2) The influence of the surface condition of the workpiece on the polishing process During the mechanical cutting process of the steel, the surface of the workpiece will be poor due to heat, internal stress or other factors; a thin layer of hardening will form on the surface after EDM. Therefore, it is best to add a rough grinding process before polishing to completely remove the poor surface layer of mud on the surface of the workpiece to provide a good basis for polishing.
Also known as “electrolytic polishing”, is a polishing method that uses the phenomenon of electrochemical anode dissolution of metals in the electrolyte to dissolve the surface of the workpiece to form a smooth surface. The principle is shown in Figure 8.2.4.
The electrochemical polishing process is divided into two steps:
The first step is macro leveling. The dissolved product diffuses into the electrolyte, and the geometric roughness of the material surface decreases, Ra> 1um.
In the second step, the shimmer is smooth, the anode is polarized, and the surface brightness is increased, Ra <1um. · Its characteristics are as follows.
① Electrolytic polishing is not limited by the material and performance of the workpiece. Carbide, powder metallurgy, hardened steel, stainless steel, heat-resistant steel, etc. can be polished.
② After electrolytic polishing, a dense and firm oxide film is often formed on the surface of the workpiece, which can improve the corrosion resistance of the workpiece surface without generating new metamorphic layer and surface residual stress.
③High polishing efficiency, such as polishing margin is 0.10 ~
At 0.15mm, the electrolytic polishing time is 10 ~ 15min, which is several times the efficiency of manual polishing.
④The process is simple, the operation is easy, the equipment is simple, and the investment is small.
⑤ Electrochemical polishing cannot eliminate the “coarse ripples” on the original surface. Therefore, there should be no ripples on the surface of the parts before electrochemical polishing.
Factors affecting the quality of electrochemical polishing
· Electrolyte, composition and ratio of electrolyte.
· Current density, the current density is too high, the anode precipitates oxygen and boils.
· Electrolyte temperature, electrolyte filtration, temperature uniformity. · Polishing time, specific metal materials have an optimal polishing time.
· Metal structure of metal materials.
· The original roughness of the polished surface, the best when the original roughness reaches Ra0.8-2.5.
· Vibration waves with a frequency exceeding 16,000 times per second are called ultrasonic waves. The ultrasonic frequency for ultrasonic polishing is 16000 Hz to 25000 Hz. The characteristics of ultrasonic waves different from ordinary sound waves are: high frequency; short wavelength; large energy; significant phenomena such as reflection, refraction, resonance, and loss during propagation. Vibration waves with a frequency exceeding 16,000 times per second are called ultrasonic waves.
· Ultrasonic polishing is the use of ultrasonic energy to transmit high energy. The ultrasonic vibration device is used to drive the end face of the tool to make ultrasonic frequency vibration, forcing the abrasive suspension between the tool and the workpiece to hit the part to be added to the soil a way. Ultrasonic choke is suitable for the polishing of brittle and hard materials. Its basic principle is shown in Figure 8-7.
Put the workpiece in the abrasive suspension and put it in the ultrasonic field together, relying on the oscillation of the ultrasonic wave to make the abrasive grinding and polishing on the surface of the workpiece. Ultrasonic processing has a small macro force and will not cause deformation of the workpiece, but tooling is difficult to manufacture and install. The picture on the right is a schematic diagram of the principle of ultrasonic polishing.
During mold polishing processing, add working fluid with abrasives to the polishing area, and maintain the polishing tool with a certain static pressure (3N ~ 5N) to the workpiece, and push the polishing tool to reciprocate parallel to the surface of the workpiece, with a movement frequency of 10 times per minute ~ 30 times. The ultrasonic transducer generates ultrasonic frequency longitudinal vibration above 16000Hz, and amplifies the amplitude to about 10um ~ 20um with the aid of a horn, driving the polishing tool end face for ultrasonic vibration, forcing the abrasive particles suspended in the working fluid at a great speed and The acceleration constantly strikes and grinds the surface to be processed, crushing the material in the processing area into very fine particles and striking it off the material. Although there is very little material struck each time, there are still certain accelerations due to the number of hits per second reaching more than 16,000. At the same time, the high-frequency, alternating hydraulic positive and negative shock waves and “cavitation” generated by the ultrasonic vibration of the end face of the working fluid prompt the working fluid to drill into the micro-cracks of the processed material, which exacerbates the mechanical damage It means that when the tool end face leaves the workpiece surface with great acceleration, negative pressure and partial vacuum are formed in the machining gap, and many air pockets are formed in the working liquid. When the tool end face approaches the workpiece surface with great acceleration, the bubble bursts. Causes extremely strong hydraulic shock waves, causing cavitation on the vibration surface and the corresponding processing surface.
Cavitation has two functions: first, when the bubbles generated by the cavitation rupture, the surrounding medium is subjected to a large impact force at an instant, and this force produces a small mechanical erosion effect on the surface of the workpiece; Due to the impact of the abrasive on the surface and the micro-cracks caused by cavitation, the fine particles are stripped off the surface of the workpiece by the attracting effect of cavitation in the subsequent instant. This shows that the ultrasonic cavitation can strengthen the processing process. In addition, the positive and negative alternating hydraulic shocks also force the suspension working fluid to circulate in the machining gap, so that the dull abrasive particles are updated in time, and the chips can be removed in time. Ultrasonic vibration makes the tool self-cutting, which can prevent the pores of the abrasive tool from clogging and improve the grinding performance.
(1) Surface quality of ultrasonic polishing and its influencing factors
Ultrasonic polishing has good surface quality, and will not produce surface burns and surface modification layers. Its surface roughness can reach Ra less than 0.16um, which can basically meet the surface roughness requirements of plastic molds and other molds. The surface roughness of the ultrasonically polished surface depends on the size of the dents left after each abrasive impinges on the surface of the workpiece, the true diameter of the abrasive particles, the nature of the material being processed, the amplitude of the ultrasonic vibration The composition of the abrasive suspension working fluid is related.
Abrasive particle size is the main factor that determines the surface roughness value of ultrasonic polishing. With the decrease of the abrasive particle size, the roughness of the workpiece surface also decreases. Using the same size of abrasive and different super-reed amplitudes, the resulting surface roughness is also different. Table 5.15 shows the maximum surface roughness that can be achieved with various abrasive grain sizes under three different ultrasonic amplitudes: large, medium and small.
When the size of the abrasive particles is small, the hardness of the workpiece material is large, and the ultrasonic amplitude is small, the degree of the processed surface will be improved, but the productivity will be reduced, and the efficiency will be improved.
2) Selection of working fluid
The working fluid for ultrasonic polishing can be kerosene, gasoline, lubricating oil or water. The influence of the performance of the abrasive suspension working liquid on the surface roughness is more complicated. Practice shows that replacing water with kerosene or lubricating oil can improve the surface roughness. When the surface of the workpiece is required to reach the brightness of the mirror surface, the dry throwing method can be used, that is, abrasives are used, and no working fluid is added.
3) Polishing speed, polishing margin and polishing precision
①Polishing speed
The level of ultrasonic polishing speed is related to the workpiece material, hardness and abrasive material.
Generally, the surface roughness is small from Ra5um to Ra0.04um, and the polishing speed is 10min / cm2 ~ 15min / cm2.
②Polishing allowance
When ultrasonic polishing the EDM surface, the minimum polishing margin should be greater than the depth of the electromachined metamorphic layer or the etched pockets, so as to throw away the heat-affected layer. Therefore, the thickness of the polished removal is also different due to the different standards used for electrical machining. The polishing amount of rough machining by EDM is about .15mm. The polishing amount of precision machining in EDM is 0.02mm ~ 0.05mm. In order to ensure the polishing efficiency, the surface roughness Ra after electrical processing is generally required to be less than 2.5um, and the maximum should not be greater than Ra5um.
· Ultrasonic polishing has the following characteristics.
· ①Ultrasonic polishing is suitable for processing all kinds of hard and brittle materials, especially non-conductive non-metallic materials, such as glass, ceramics, quartz, diamond, etc.
· ②The ultrasonic polishing equipment is simple, easy to use and maintain, and can be made into a polishing tool with a complex shape from a softer material than the workpiece, and the complex surface and cavity can be carried out without complicated relative movement between the tool and the workpiece during processing. polishing.
· ③ The force and heat influence on the material are small, no deformation, burn and metamorphic layer will occur. Thin walls, thin slices, narrow slits and low-rigidity parts can be polished. The processing accuracy can reach 0.01 ~ 0.02mm and the surface roughness. The value can reach 0.63 ~ 0.08ulm.
Also known as abrasive flow processing, it uses a sludge-like abrasive polishing agent composed of an abrasive and an organic polymer medium with a large viscosity to pass through the processed surface under the pressure, and the microscopic unevenness of the processed surface is removed by the abrasive scraping Material technology. The principle of extrusion grinding and polishing is shown in the figure.
Squeeze grinding polishing has the following characteristics.
· ①_Wide range of use. Because the abrasive polishing agent is a semi-fluid viscous substance, it can pass through the complicated surface to be processed. At the same time, a wide range of processing materials, metal materials, ceramics and hard plastics can be processed.
· ②Good mold polishing processing quality. This is due to the good scraping uniformity, which can remove the surface modification layer and microscopic inequality defects formed in the previous process without destroying the original shape accuracy of the workpiece. Generally, the dimensional accuracy of extrusion grinding and polishing can reach 0.01 ~ 0.0025mm, and the surface roughness R value can reach 0.04 ~ 0.025ulm.
· ③_High processing efficiency. Extruding, grinding and polishing of the 6 towers of the tight 6 takes 5 minutes and 19 minutes, it is manual.
On the other hand, it is possible to achieve simultaneous polishing of multiple pieces.
2. Technological characteristics of squeeze grinding polishing
(1) Scope of application Since viscous abrasive is a viscoelastic material in a semi-flow state, it can be used for polishing and deburring of various complex surfaces, such as various types of holes and profiles. Moreover, it can process almost all metal materials, as well as ceramics and hard plastics.
(2) Polishing effect The surface roughness after polishing is related to the original state. It can reach 1/10 of the original surface roughness, which can be improved by about 3 levels. The best surface roughness can reach the mirror surface of Ra0.025um. Abrasive flow processing can remove the surface residual stress at a depth of 0.025mm; it can remove the surface modification layer and other surface micro-defects formed by the previous processes (such as EDM, wire cutting).
(3) Processing efficiency The material removal amount is between 0.01mm and 0.1mm, and the processing time is usually 1min-5min, which can be completed in a maximum of ten minutes. Compared with manual polishing, the processing time can be reduced by more than 90%. For some small parts, multiple parts can be processed at the same time, and the efficiency can be greatly improved.
(4) Processing accuracy Squeeze grinding is a surface processing technology, so it cannot correct the shape error of the parts. The cutting uniformity can be kept within 10% of the cutting amount, therefore, the original shape accuracy of the part is not damaged. Due to the small amount of removal, high dimensional accuracy can be achieved, and the general dimensional accuracy can be controlled in the order of microns.
3. Viscous abrasive media
Viscous abrasive media is a mixture of abrasive and special matrix media. Its role is equivalent to that of cutting tools. It is the most critical factor for machining. Its performance directly affects the polishing effect.
(1) The performance of viscous abrasive media
① It has a certain fluidity and viscoelasticity to adapt to the processing of different surfaces, so that when passing through the hole of the part, the abrasive can produce sufficient cutting force on the hole wall.
② Abrasive particles are evenly dispersed in the medium, and the medium is required to have strong cohesion.
The medium cannot stick to the abrasive particles, so that a film is formed on the abrasive particles, which wraps the cutting edges of the abrasive particles, so that it cannot play a good polishing role.
③ Must have very little internal friction. Only in this way can the abrasive itself transmit pressure well, so that the abrasive can smoothly pass through the surface of the part for reciprocating cutting movement. Increase the friction of the abrasive against the parts and reduce the internal friction of the abrasive, thereby improving the efficiency of polishing.
④Good stability and long service life. When reciprocating the viscous abrasive in the upper and lower abrasive chambers and on the surface of the parts, it is necessary to overcome the resistance, and heat must be generated. Reduce polishing effect.
⑤Although the abrasive is soft after preparation, it must not be sticky. It should not stick to the parts, causing difficulty in cleaning, nor sticking to the operator’s hand, affecting the normal work of the operator.
⑥The cutting effect is strong, the processing speed is fast, and there must be a significant polishing effect. The medium has no corrosive effect on the parts, no harm to the human body, and will not cause irritation and cause skin allergies.
① Matrix medium It is a semi-solid, semi-fluid polymer. Its composition belongs to a viscoelastic rubber-like polymer compound, which mainly plays the role of binding abrasive particles.
When processing a surface with a large pore size or a relatively simple pore shape, a more viscous matrix medium is generally used. When processing small holes, long curved holes or fine holes, and narrow slits, a matrix medium with low viscosity or relatively easy flow should be used.
②Additives This is an ingredient added to the matrix medium in order to obtain ideal viscosity, consistency and stability. Its types include thickeners, viscosity reducers, lubricants, etc. ③ Abrasives Generally, alumina, boron carbide, and silicon carbide are used. When processing hard materials such as cemented carbide, diamond powder can be used. The abrasive particle size range is 80 # ~ 1200 #; the mass fraction range is 10% ~ 60%. The specific abrasive type, particle size and content should be determined according to different processing objects.
Coarse abrasive can get faster removal speed, fine abrasive can get smaller surface roughness. Therefore, fine abrasives are generally used for polishing, and coarse abrasives are used for deburring. Use finer abrasives for polishing small holes. In addition, the fine abrasive can also be used as an additive to adjust the consistency of the matrix medium. In actual use, it is often a mixture of several abrasive sizes to obtain better performance.
4. Squeeze grinding fixture
The fixture is an important tool that uses squeeze grinding to achieve the ideal polishing effect for the working parts of the mold. The fixture is an important part of extrusion grinding, and also a relatively flexible factor in processing. It needs to be designed according to the specific workpiece shape, size and processing requirements, but sometimes it needs to be determined through experiments.
The main function of the fixture is not only used to install, clamp parts, contain media and guide it through the parts, but also more importantly to provide one or several “disturbances” during the flow of media to control the flow of the media. . Because the flow of viscous abrasive media is the same as that of other fluids, it is easiest to pass through the paths with the shortest path, the largest cross-section, and the least resistance. In order to guide the medium to the required parts for cutting, you can use specially designed fixtures to block, bend, and interfere in certain parts to force the viscous abrasive to pass through the desired polished parts. The seal inside the fixture must be reliable, because small leaks will cause the wear of the fixture and the workpiece, and affect the polishing effect.
The concave model surface of the mold is divided into four types: through hole, stepped hole, cavity, convex model surface, etc. Table 5.17 shows the processing principle diagram of the 4 types of mold surface and fixture.
During the plastic mold polishing of the stepped hole, due to the different resistance when the medium flows through the large and small diameter holes, if the core jig as shown in FIG. 3 is not provided, it is difficult to produce the grinding pressure at the A and B parts. The flow medium near the corner is also reduced, and only part C can achieve the grinding effect. Therefore, it is necessary to place a core jig as shown in the figure to adjust the cross section of the medium to achieve the purpose of uniform grinding pressure.
As shown in the gear mold, it is possible to squeeze and grind the tooth surface at the bottom A, and a core jig should be equipped to form a channel. Figure 5.35 shows the clamp for squeezing and grinding the cavity that does not pass through the bottom. When the shape of the punch is squeezed and ground, the fixture is made into a structure that surrounds the punch.
5. Post-processing of extrusion grinding
After the squeezing and grinding, the workpiece and fixture are filled with media, which needs to be taken out. Due to the strong binding force of the medium itself, when it is difficult to peel the medium, a small amount of medium can be prepared to be combined with the medium on the work piece and simply led out. Use the compressed air to clean the place where the hand is out of touch. If the convex and concave mold surfaces blown with compressed air are immersed in an organic solution, the medium is easily dissolved and cleaned better. It will be better if combined with ultrasonic cleaning methods.
6. Squeeze grinding polishing process parameters and process rules
Extrusion grinding process parameters in addition to the thick viscosity of the viscous abrasive medium, abrasive type and particle size, the main ones are extrusion pressure, abrasive medium flow rate (or unit time media flow and processing time, etc. extrusion pressure, flow, processing The time is controlled by the extruder. The extrusion pressure is generally controlled in the range of 3MPa ~ 15MPa, the flow rate is generally controlled in the range of 7L / min ~ 25L / min, and the processing time is in the range of several minutes to tens of minutes.
In order to improve the surface roughness R. The polishing speed of the workpiece above 1.6um is combined with ultrasonic and special high-frequency narrow pulse high peak current pulse power for polishing. The impact of ultrasonic wave and the corrosion of electric pulse act on the surface of the workpiece at the same time, which quickly reduces the surface roughness. It is very effective for rough and hard surfaces processed by turning, milling, EDM and wire cutting.
The glass bead spray method is a kind of spray processing method. It sprays small diameter glass beads together with compressed air, and is widely used in the polishing process of removing flash of parts, descaling, descaling and forming a dark glossy surface.
Figure 5.45 shows a schematic diagram of the glass bead spray method. The processing principle is the same as the sand blasting method, and it is especially suitable for polishing the softened surface like the wire cutting surface. After the wire is cut, the parts covered by the melt become uniform and smooth after being sprayed. The surface roughness value can be reduced by about 50%, and it is particularly suitable for the polishing of free-form surfaces.
(1) The effect of the glass bead particle size on the polishing quality When the surface roughness value of the wire cutting processing surface is large, the glass bead polishing with a larger particle size is used, and the effect is more obvious. If the surface roughness value of the original electro-machined surface is small, glass beads with a small particle size should be used; otherwise, due to the large particle size of the glass beads, the impact force and polishing effect are too strong, resulting in a rougher surface. Therefore, there is an optimum glass bead particle size for the roughness of the wire-cut surface.
(2) Influence of injection pressure on polishing quality
As shown in Figure 5.46, it is better to use a higher jet pressure for rough wire-cut surfaces. For finer wire-cut surfaces, jet pressure has little effect on the polishing effect.
(3) Effect of spray time on polishing quality Figure 5.47 shows the relationship between the spray processing time and the surface roughness of the wire cutting surface. For any wire-cut surface, within a few seconds of the initial spraying, the surface roughness value decreases sharply, and thereafter, with time, the surface roughness value hardly changes. For the finished surface with a small surface roughness value, the blast processing time is too long, but the surface tends to be rough. The improvement of the surface roughness of glass beads in the initial short time (5s ~ 20s).
(4) The influence of the glass bead spray method on the machining accuracy of parts. For the heat-treated mold steel, the glass bead spray method can remove the covering and the electric erosion part of the wire cutting processing surface. However, it is difficult to completely remove the metamorphic layer generated during electrical processing. The reason is that the hardness of the glass beads used is about 500HV, which is slightly lower than the hardness of the die steel of the processed material. Therefore, the shape of the processed parts will not be damaged, and at the same time, it is beneficial to the control of the size and shape accuracy.
]]>Before you start: It is our opinion that a lubricant should be used with every stone type for faster material removal and better surface finishes. Bellstone VH type stones also require a lubricant to prevent the stones from "loading up" and to promote rapid stock removal and a smoother, superior surface finishes. Lubricants are generally made of a "kerosene" based substance (i.e. odorless mineral spirit).
How to accomplish a fine finish: Lets assume, based on the surface finish you have on hand, that you wish to start with a 220 grit stone, you proceed by applying some lubricant on the surface area to be polished (and/or dip the stone frequently in a jar of lubricating fluid). Now move the stone in a reciprocating motion forward & back (about 3/4 inch or less depending on available space to move around) over the entire surface area to be polished. Upon finishing this first step and having completely removed all pits, deep scratches, waves, etc., you can now proceed to step two, the next finer grit stone. Before going on to a finer grit stone however (for a finer finish) make sure to clean the surface thoroughly from all debris left by the previous stoning process.
NOTE: It is always better to start your finishing process with a stone that has a finer grit size. Meaning, if the surface looks to you that you should start with a 120 grit stone, try the next finer grit like the 220 grit stone first. Doing so, you may find that the 220 grit stone will do the job as well and thus, you saved you an extra step in the entire finishing process!
When moving onto the next step, a finer grit stones, use the same reciprocation motion, but change the direction previously used by 30 to 45 degrees. Doing so, will allow you to remove the previous finish (all lines gong in the previous directions) and you will be able to clearly see when each step is completed and is ready for the next finer grit. perhaps a 320 or even 400 grit?
NOTE: As you move on to the next finer grit stone, make sure the surface is always cleaned before going on to the next step until you have accomplished the desired final "stoned" finish.
Upon reaching a 600 or even a 900 "stoned finish" you may continue by applying diamond compound (or other quality buffing material) and use felt bobs, felt sheets or polishing brushes to obtain the final, highly polished mirror finish.
We would like to thank you for visiting our online store . If you have additional questions please contact us
]]>In the polishing process, the commonly used whetstones include ordinary whetstone, super refined whetstone, diamond whetstone, ruby whetstone, and boron carbide whetstone. At present, the mesh of fishing oilstone used in mold mirror polishing are: grits120~grits3000. Among them, the more commonly used are grits120, grits180, grits200, grits240, grits400, grits600, grits1000, grits1200#, etc.
According to the experience of mold polishing maker
For rough polishing: grits120~gring 600 mold polishing stone is generally used,
For fine polishing :grits 600- grits 800 mold fishing stone is generally used,
For Super-finish polishing: about grits1200 mold stone is best.
If you have another mold polishing stone problem,please feel free contcat us:kay@moldaccessories.com.
]]>How to judge the surface quality of the mold
There are two methods for judging the surface quality of the mold
(1) The operator judges with the naked eye whether the geometry of the mold surface is correct, whether there are undulating and long wavy lines, if it is caused by grinding with a grinding wheel or whetstone. defect. Whether the surface of the mirror-treated mold has scratches, small holes, orange peel (orange peel) and pits (pinholes) and other defects.
(2) Because the judgment with the naked eye will cause deviation, the plane that looks smooth and clean is not completely flat in geometry. In more complex situations, the surface quality of the mold needs to be tested with instruments, such as optical interference technology.
Factors affecting mold surface polishing
(1) The quality of tool steel.
(2) Heat treatment process.
(3) Polishing technology. It is generally believed that polishing technology is the most important factor, and proper polishing technology, high-quality tool steel and correct heat treatment process can be used to obtain a satisfactory finish. On the contrary, improper polishing technology will not achieve a high degree of mirror effect even if high-quality steel is used.
Mold grinding and oilstone polishing
The cavity of the mold is usually processed by milling machine processing, EDM processing or compression molding method. To obtain a very smooth surface, the following processing procedures must be followed:
(1) After the milling machine is processed, rough grinding, fine grinding and polishing are carried out.
(2) After EDM, fine grinding and polishing are carried out.
(3) After the molding process, only one polishing is required after the heat treatment.
The grinding result directly affects the quality of the polishing effect. After the scratches left by mechanical processing are removed by grinding, a pure metal surface with the correct shape is obtained. To improve work efficiency and ensure mold quality, mechanical grinding and manual grinding operations must follow the following processing rules: excessive heat and excessive pressure should not be generated during grinding, so as not to affect the structure and hardness of the steel; use when grinding A lot of coolant.
(1) For the surface with higher hardness, only clean and soft oilstone can be used for polishing tools.
(2) When the sand number level needs to be changed during grinding, the workpiece and the operator's hands must be cleaned to avoid bringing coarse abrasive particles and dust to the next level of finer sand number grinding operation.
(3) The finer the abrasive grit, the more important the cleaning between each level.
(4) When the next finer grinding is to be performed, the grinding direction should be at a 45° angle with the previous grinding direction until the scratches of the previous grinding are eliminated. After the previous level of grinding scratches are eliminated,
Extend the grinding time by 25%, and then switch to the next finer sand number. The purpose of this is to remove the deformed layer of the grinding surface caused by the mechanical stress during the previous level of grinding.
(5) Changing the grinding direction is also very important to avoid the formation of defects and unevenness.
(6) When grinding the flat surface of a large mold, avoid using manually operated grinding wheels. The use of oilstone polishing can reduce the formation of large area defects.
Polishing of the mold
Diamond paste is the most common abrasive material for polishing operations.
Using the correct grinding paste polishing tool can obtain an excellent polishing effect. Commonly used tools for manual polishing include grinding rods and grinding blocks, and common tools for mechanical polishing include polishing cloth wheels and polishing brushes. The polishing operation is a time-consuming and expensive process, and following certain rules can reduce the cost of the polishing operation. Every step of polishing must be kept clean, which is the most important.
(1) Polishing must be carried out in a clean and dust-free room. Hard dust particles can contaminate the abrasive material and damage the surface of the nearly finished mold.
(2) Only one grade of polishing diamond paste is used for each polishing tool and stored in a dust-proof or air-tight container.
(3) Due to the addition of diamond paste, the polishing tool will appear saturated, and the situation will improve with continuous use.
(4) When you want to change the finer one-level sand number, you must wash your hands and the workpiece. Wash your hands with soap and wash the workpiece with a degreasing solvent.
(5) During manual (manual) polishing, the diamond paste should be applied to the polishing tool, and during mechanical polishing, the abrasive paste should be applied to the workpiece.
(6) The pressure used during polishing, the hardness of the polishing tool and the grade of the abrasive paste should be adjusted and adapted to each other. When performing the finest level of polishing, the pressure should be adjusted to match the polishing tool
The weight is similar.
(7) To obtain a larger steel removal rate, a harder polishing tool and a diamond paste with a coarser grit must be used.
(8) The final polishing of the plastic mold should be carried out in the direction of demolding the workpiece.
(9) When you start polishing, you must first deal with corners, corners, and rounded corners that are difficult to polish.
(10) Be especially careful when handling sharp corners and corners. Be careful not to form rounded corners or rounded edges. Try to use harder polishing tools.
Polishing procedure
How to choose the operation sequence of grinding and polishing depends entirely on the experience of the polishing operator and the tools and equipment he uses. The characteristics of the material also have an influence on the operating procedure. Polished
Two methods are usually used in the process. The first method is to determine the appropriate particle size of diamond paste, first use harder polishing tools, and then use softer and softer polishing tools. The second method is
Choose a medium-hardness polishing tool, first use coarse-grained diamond paste, and then switch to increasingly fine-grained diamond paste. Combining the above two methods is more effective.Such as:
——First use harder polishing tools and coarse-grained diamond paste.
——Use diamond paste with the same particle size, but use softer polishing tools instead.
——Use medium-hardness polishing tools and medium-grain diamond paste instead.
——Use a softer polishing tool, but use diamond paste of the same particle size.
——Finally, use softer polishing tools and diamond paste of grain size.
Various surface conditions before polishing
(1) The surface after EDM is more difficult to grind than the surface after ordinary machining or heat treatment. The fine EDM procedure should be used before finishing the EDM. If the fine EDM procedure is operated correctly, no problems will occur. Otherwise, a thin layer of re-hardening will form on the surface. The hardness of the hardened thin layer is higher than that of the substrate and must be removed.
(2) The surface of nitrided or surface hardened steel is more difficult to grind than its base material, but the polished finish is higher, and the fine processing defects on the surface make it difficult to achieve a good light effect.
(3) For the flame-hardened or skirt-welded mold, there is a softer area between the processed part and the steel base layer. In order to avoid grooves during grinding, oilstone strips with a wider contact area should be used.
How to solve the problems in polishing
The biggest problem encountered in polishing is "over-polishing". Over-polishing means that the longer the polishing time, the worse the mold surface quality. There are two phenomena when over-polishing occurs, namely "orange peel" and "micropits". Excessive polishing occurs mostly in mechanical polishing.
(1) "Orange peel". Irregular, rough surfaces are called "orange peels", and there are many reasons for "orange peels". The most common reasons are due to overheating or excessive carburization of the mold surface, plus excessive polishing pressure and excessive polishing time. Harder steel can withstand greater polishing pressure, and softer steel is prone to over-polishing. Studies have shown that the time for over-polishing varies with the hardness of the material. If the surface quality is not good, many people will increase the polishing pressure and prolong the polishing time. This practice often makes the surface quality worse. The following methods can be used to remedy:
Method 1: Remove the defective surface, and the grinded grain size is one level coarser than the previous sand size. Then carry out fine grinding, the polishing pressure is lower than the previous pressure.
Method 2: Perform stress relief at a temperature 25°C lower than the tempering temperature. Before polishing, use the finest sand number to grind until a satisfactory result is achieved. Finally proceed with a slightly lower pressure
polishing. If the effect is still unsatisfactory, the hardness of the mold must be increased. There are two methods:
①Using nitriding or carburizing methods to increase the surface hardness of the steel.
②Using heat treatment technology to improve the steel
The overall hardness of the material.
(2) "Micro-pits". The formation of "micro-holes" is due to non-metallic inclusions in the steel, which are usually hard and brittle oxides; they are pulled out from the surface of the steel during the polishing process to form "micro-pits". The main influencing factors are as follows:
①Polishing pressure and polishing time.
②The purity of steel, especially the content of hard inclusions.
③Polishing tools.
④Grinding materials.
The reason for the micropits is that the hardness of the steel matrix and the inclusions are different. During polishing, the substrate is polished and removed at a faster rate than inclusions. If polishing continues, the inclusions will protrude and will eventually be pulled out, leaving micro-pits. If the grit size of the diamond paste is less than 10um and soft polishing tools are used, micro-pits are most likely to appear. The following measures can be adopted:
① Carefully regrind the surface, and the sand grain size is one level coarser than the previously used grain size. Use soft and sharp whetstone for the final step of grinding and then polishing.
②When the size of sand particles is less than 10um, avoid using the softest polishing tool.
③Take the shortest polishing time and minimum polishing pressure as much as possible
1:Tungsten carbide rotary file--made of high-quality tungsten carbide material, also known as tungsten steel rotary file;
2:high-speed combination gold steel rotary file-made of high-quality high-speed alloy steel material. Usually used with high-speed electric grinder or pneumatic tools.
It can be used for a variety of job requirements, such as processing cast iron, cast steel, carbon steel, alloy steel, stainless steel, hardened steel, copper and aluminum.
2: International general standard shape classification
Generally, the rotary file can be divided into the above 19 shapes, the most commonly used are cylindrical, spherical, flame head shape, etc. In China, the letters A, B, C and other letters directly represent each shape, and the letters ZYA, KUD, RBF are usually used in the world.
Of course, there are also five-tooth shapes specially used in the high-speed rail industry, such as:
3:Blade tooth classification
Generally, single-edged tooth-shaped rotary files are more suitable for processing operations such as soft non-ferrous metals, plastics, soft high-stretch steels or hard woods, while cross-shaped toothed files are more suitable for producing higher cutting performance on hard materials. Grinding of workpieces made of cast iron, cast steel, glass fiber plastic materials
For each shape of the rotary file, the tooth profile of the blade teeth can be selected according to the specific operation requirements. The general international standard tooth profile can refer to the above six types.
What conditions are each tooth profile suitable for?
1:Tooth pattern for aluminum-especially suitable for soft metals such as aluminum alloy, brass, magnesium, etc., because of its wide tooth spacing, it is conducive to rapid removal and cutting.
2:Coarse tooth pattern-soft materials such as bronze, tin, zinc, pure copper and other materials that are easy to process are recommended.
3:Medium tooth pattern/standard tooth pattern-suitable for processing all kinds of steel (including tempered steel), cast steel and almost all metal materials. The surface processing quality of this tooth profile is excellent, and the processing efficiency is relatively high.
4:Diamond tooth profile-this tooth profile is suitable for the processing of high alloy steel, stainless steel, magnesium alloy, gray cast iron and zirconium-nickel steel, and effectively avoids the adverse phenomena caused by the crushing of chips during operation.
5:Close tooth pattern-suitable for finishing operations that require high surface quality such as finishing, especially tempered steel with Rockwell hardness (HRC) below 66.
6:Cross tooth pattern-this tooth profile is suitable for all kinds of metal materials (including tempered steel and corrosion resistant materials), the vibration during processing is small, and it is easy to control and operate
There is also a chip-breaking tooth pattern, which is selected on the basis of a single-tooth file, which can be used to process materials with longer chips, and can be applied to ①②③⑤file tooth.
4:Rotary file size selection
The size of the carbide rotary file is mainly based on the head diameter Dc and the shank diameter D2, of which the head blade diameter L2 and the total length L1. It can be selected according to specific job requirements.
Standard type rotary file: The shank diameter (D2) mainly has 3mm, 6mm, 8mm, and 2.35mm is also optional. The length of the handle is a common specification .
Extended shank rotary file: This kind of shank length can be selected according to special working conditions to extend the shank, generally the most commonly used are 75mm, 100mm, 150mm, 300mm. It is very suitable for processing hard-to-reach or deep areas. The longer the handle of the extended handle is not the better, because too long will cause a certain vibration during the grinding operation and affect the work effect.
Miniature rotary file: Therefore, the diameter of the head of this kind of rotary file is small, and the diameter of the shank is generally 3mm. Because of its high degree of concentricity, it is suitable for the trimming of precision work station parts, etc.
5:Rotary file coating
Generally speaking, there is no special requirement, and the rotary file has no coating treatment. Unless special operations require plating. Then the rotary file with coating treatment can mainly extend the service life of the tool, improve the cutting chip removal condition, have better heat resistance and anti-adhesion characteristics, and enhance the cutting force.
]]>To achieve the results you want from deburring or edge-breaking, the key is to choose the most suitable mounted point for your application. These 4 steps can help you evaluate your application and select the best abrasive for your job.
At Rex-Cut, we suggest aluminum oxide for the majority of applications calling for mounted points. Aluminum oxide is a versatile grain and paired with our specialty bonds, it grinds exceptionally well on stainless steel, carbon steel, mild steel, aluminum, as well as certain alloys. For applications requiring high purity or brighter surface finish, such as medical implants or select aerospace components, silicon carbide, a sharper grain than aluminum oxide, may be preferable.
Zirconi alumina points are an excellent option for heavier stock removal.
As a guideline for selecting the bond of the point, softer bonds work best on harder metals, and harder bonds on soft metals. Soft bonds such as our GFX, are able to shed easier, allowing fresh grain to be revealed for faster grinding. Harder bonds such as our MTX, hold on to the grain longer resulting in more controlled metal removal, in turn the point lasts longer.
Within the last year we started making mounted points with a rubber bond. These rubber points are often used in edge breaking applications. Removing the edge on stainless steel sheet metal before fabrication is one specific application we see regularly
Tip: For aluminum, you will want to look for a non-loading bond. Because aluminum has a low melting temperature, it can load up the abrasive product you are working with. A naturally non-loading bond such as our GFX, JTX, and MTX, will work great on aluminum without needing compounds or waxes.
In a perfect situation you would have full access to the area you are working on, but often burrs and sharp edges are in hard to reach areas. Mounted points come in A, B, and W shapes to fit many different applications. There are small shapes to deburr tiny i.d.s, larger points such as the W222 which is often used in the edge breaking application we mentioned, and even specialty points such as the seat track cleaner which were designed to remove grime and corrosion on aircraft seat track.
Before running the mounted point, check to make sure the tool you are using does not exceed the maximum operating speed of the point. This is an important safety step. In addition, operating at too high of a speed can reduce the life of your point and decrease the quality of the deburring job.
After you go through the steps of selecting a mounted point, test it. If it is not giving you the results you want, make notes of what isn't working. If you are getting a surface finish that is too rough, go with a finer grit. If the point is taking off too much metal, go with a harder bond. Sometimes it takes more than one try to find the right mounted point(From rexcut.com)
We would like to recommend a complete buffing wheel set to meet all your needs for polishing a wide variety of workpiece.
Bellstone whestones is widely used in molds & die tool polishing and knives polishing. Because the polishing effect is very good,so it is very popular among consumers.However, more and more buyers found that it is not the brand "Bellstone" they bought, and that is why?
Usually, buyers find the supplier of Bellstone mold polishing oiltstone by Google or Alibaba . When you found some suppliers, after communicated and finally bought some bellstones.But when you received the polishing whestones, you open the package and find that it is not Bellstones whetstone, and then you communicated with the seller. The seller told you: "They are both bellsone oiltstone, one is new packaging, and the other is old." 'oh,my god' you are very confused and doubted whether the supplier has sent the poor quality or fake oilstone to you.And it is very difficult for your customers to accept the new packaging when they have already recognized the quality of the old version.
Now let me tell you why you recived with ''yanzhistone" oilstones not "bellstone" whetstone. The manufacturer used the trademark "yanzhistone" in all products after August 2019. And the manufacturer guaranteesd that the product quality and packaging specifications remain unchanged. After more than a year of sales, all the "bellstone" oilstones in the old packaging have been sold out, and now There are only new packages of bellstone on the market. So you only receive all new packaging of Bellstone.
"Our customers still want to buy "Bellstone", where to buy it ?" said one buyer
We would like to introduce to you "bellstone" oilstones with black packages
1:It has strong bonding force, strong impact resistance, and is not easy to break. It is suitable for electrical discharge machining, surface finishing , edge and corner polishing, and deep groove polishing.
2:It will not damage the dimensional accuracy of the original workpiece when polishing.
3:It does not blockand when polishing and has high efficiency
4:It can not only process the workpiece at various angles, but also can be flat-grinded and polished.it is very convenient to use.
If you need the brand "bellstone" oilstones ,please contact us!Thank you.
]]>1. Mould steel
Use high-quality mirror steel such as S136, M333, 1.2083, etc., and must be heat treated to 50~53 degrees
2. Pre-processing
Use high-speed machining center or mirror electric discharge machining, and there should be no bomb knives or electric discharge carbon deposits.
3. Polishing tools and consumables
①A small polishing machine with stable spindle;
②Mold polishing whetstone of 1500 mesh and 2000 mesh (Bellstones is fine);
③Pig hair brush with a diameter of 5mm;
④ 15μm, 5μm, 3μm, 1μm diamond paste;
⑤3mm diameter cylindrical cork stick or bamboo stick;
⑥Long fiber pure cotton;
⑦Bamboo chopsticks for polishing;
⑧ Kerosene
4. Trimming of polishing consumables
① Use a small file to trim polishing oilstones into a small rectangular strip with a smaller width than the narrow width of the workpiece. It is standard to be able to move back and forth between the narrow strip of the workpiece. Make a shallow groove at the center point of the upper end of the small rectangular oilstone.
②According to the width of the narrow strip of the workpiece, trim the diameter of the bristles to a little smaller than the width of the narrow strip of the workpiece.
③ Sharpen the tip of the wooden stick
5. Polishing process
①Put the trimmed small rectangular oilstone on the narrow area of the workpiece, drip kerosene, and use bamboo chopsticks to move the oilstone evenly on the shallow groove on the oilstone. Until the knife pattern or fire pattern is ground clean. Attention should be paid to timely trimming the bottom end of the small oil stone, keeping its bottom surface must be flat. Make a smaller oilstone clear corner at the corner R in the cavity. Do not bring it straight across the cross, and grind in sections, otherwise the R angle will rise due to improper grinding. If there are deep traces of whetstone falling off the sand, save it with sandpaper.
② Use 15μm diamond paste and trimmed pig hair brush to remove the 2000-mesh oilstone traces.
③Wrap the cotton on the tip of the wooden stick, install it on the polishing machine, and use 5μm diamond paste to remove the brush marks.
④Wrap the cotton on the tip of the wooden stick, install it on the polishing machine, and use 1μm diamond paste to remove the brush marks.
Depending on the application and requirements we can distinguish between two types of surface finishing methods; high gloss polishing and functional polishing.
High gloss polishing
Tools for plastic moulding do require a high surface finish especially when extreme transparency and/or high gloss are aimed for. In such cases it is of utmost importance to choose a proper tool material and establish a suitable surface preparation technique. To achieve a reflective surface with mirror finish the preparation process must involve several grinding and diamond polishing steps and these have to be performed in a clean workplace. The use of proper working tools facilitates the process a lot.
High surface finish reduces the risk of local corrosion and fracture or cracking due to temporary over loading or pure fatigue.
The tool surface finish may also have an impact on productivity as in the case of injection moulding. Here, the release forces of the plastic component from the tool steel surface are dependant on the adhesion properties of the polymer to the mould surface. An improved smoothness of the tool surface may lead to higher release forces and eventually to sticking phenomena, which partly can be overcome by an optimal choice of tool steel and preparation strategy.
Functional polishing
Most cold work applications do not need high gloss polished tool surfaces, but it is always advantageous to create functional surfaces for a prolonged tool life. In forming operations where lubricants are involved a preparation strategy may consist of removing larger peak formations on the surface and preserving a controlled depth of valleys as lubrication pockets, which then will contribute to a reduced friction during forming. However, it is always important to consider the final tool steel surface quality in relation to the application. If a high quality surface coating is going to be applied, then it is always recommended to perform high gloss polishing of the tool surface before the coating process.
]]>1. The polishing worker must be trained and pass the examination to get ithe nduction certificate before they can start.
2. Define the workpiece process requirements, material , processing part, shape, size and polishing precision requirements
3. Before polishing, it is necessary to check whether the polished surface has sags,overcuts, deformations and blisters, and whether the remaining polishing margin is sufficient.
4. According to the process specifications to select applicable tools, fixtures, main and auxiliary materials.
5. Properly protect the workpiece according to the process requirements.
2. Clamping and protection of workpiece
1. For below 20Kg --higher or longer workpieces, it requires vise clamping on the polishing table.
2. For larger and heavier workpieces must be used on the polishing table before and after the magnet, screw clamping code for fastening.
3. When using work car to polish the workpiece, it must be used wedges or related measures to ensure work safety.
4. For small and easy to bump or scratch workpieces, rubber plates must be used to protect the surface.
5. Workpieces with sharp corners and corners must be protected with tape to avoid to damage the personnel and workpieces.
6. For workpieces that need to maintain edges and sealing positions, stoppers (saw blades or iron sheets) or stoppers can be used to prevent edge chamfering and rounding on the side that is not being polished.
3. Self-inspection content and scope
1. Whether the sealing surface is rounded or collapsed;
2. Whether to destroy the original draft angle;
3. Check the size of each polishing surface to see if it exceeds the reserved amount;
4. Whether the fillet at the bottom of the cavity is recessed into the side and bottom surface;
5. Whether there is an inversion phenomenon;
6. Whether its roughness has reached the drawing requirements;
7. After passing the self-inspection, send it to the team leader (or inspector) for inspection.
4 What is the matters needing attention in polishing operation
1. Before grinding, check whether the grinding allowance is sufficient, and the grinding and polishing amount cannot exceed the reserved amount
The surface polishing amount after grinding can not exceed the reserved amount by 0.05~0.06mm;
Unground surface, electro-erosion or wire-cut surface grinding and polishing can not exceed the reserved amount by 0.08~0.1mm;
The amount of single side and deep grinding of ribs cannot exceed the reserved amount by 0.03~0.08mm.
2. When operating with the polishing machine,Staff must concentrate on preventing grooves, exceeding the margin, not allow long time processing in the same part
3. After each polishing, it must be cleaned with a whiskey cloth and then proceed to the next polishing step.
4. After each polishing, it must be cleaned with cotton or soft paper, and then the next step of polishing.
5. Before polishing the mold, first determine the processing procedure:
According to different surface conditions and roughness, to select the appropriate process and suitable tools (such as diamond file, sandpaper, mold oil stones) for the start and required sequence.
According to the geometry, roughness and process requirements of the mold cavity,determine the range of power tools and grinding tool heads to achieve targeted processing.
6. Pay attention to the grinding and polishing of the sealing surface, especially the part of the special identification symbol of the product and the sealing surface should not cause rounded corners and collapsed corners;
7. The polishing area requires a clean environment. Pay attention to the protection of the polished surface during the polishing process;
8. If some parts need to be polished together after assembly, they are not allowed to be polished separately;
9. After polishing, the polished surface should be sprayed with anti-rust oil after self-inspection and inspection, and protection work should be done to prevent bumps and scratches;
10. All kinds of oilstone, sandpaper, diamond grinding paste and diamond files must be placed in a special tool box with corresponding labels according to their model and specifications.
5:Ultrasonic polishing machine
1.The clamping sintered diamond file mainly processes and removes the electric processing layer of the bottom plane and the side plane of the cavity;
2.Install electroplated diamond files to remove the electro-processed layer and rough cutting marks in narrow planes, cavity side walls, dead corners and sharp corners;
3.Clamp various oilstones to trim the shape and position tolerances caused by rough machining and improve the roughness;
4.Clamping copper, soft and hard wood and adding various grit sizes of abrasive pastes to achieve fine polishing of the processed surface
Before polishing, what kind of mold polishing tools do we need to prepare? First, we need to use a small file to repair the mold polishing stones into a small rectangular strip and it should be narrower than the workpiece.so that it can move back and forth on the workpiece and it is necessary to cut a shallow slot at the center of one end of a small rectangular mold oilstones.At the same time, according to the length of the workpiece, the bristles on the brush should be trimmed to be smaller than the narrow part of mold workpiece. And also you need to grind the front end of the stick to a sharper shape.
When polishing material is ready,we will polish the workpiece now. First of all, you need to put the trimmed small rectangular oilstone in a narrow area of the workpiece, with kerosene, using bamboo chopsticks to press the oilstone and move the mold oil stones in the working area, and then to grind the turning tool line or fire pattern on the surface clean. Please pay attention to adjust the bottom surface of the whetstone to keep the bottom surface is flat.
At R position of the cavity corner, it need a smaller mold whetstone to clean the corners, and it can not be polished by straight line in the cross area. It needs to grind in sections, otherwise these R angles will be higher due to poor grinding. If there are deep traces of mold whetstone, it needs to use sandpaper to clean it. After that,using a 15-nanometer diamond abrasive paste with a suitable brush to remove the mold whetstone marks on the surface. Finally,using a professional polishing machine to polish the mold suface a mirror effect step by step.
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1: The steel hardness
Different hardness of the mold steel will influence the quality of the mold polishing. As the hardness increased,it is more difficult for mold polishing , but the roughness after polishing will be reduced. Due to increase the hardness of mold steel, it will take more time to achieve a lower roughness.
2:The quality of workpiece surface
Workpiece surface condition is also affected the mold polishing technology. During the machining process with the steel cutting machine, it will cause the surface layer to be damaged because of heat and internal stress or other factors, and the cutting parameters of the mold are improper to make it easy to affect the effect of mold polishing.
The surface after EDM is more difficult to grind than ordinary machining or heat treatment. Therefore, after the EDM processing is completed, a fine EDM trim should be used, otherwise the surface of the mold will form a hardened layer. However, if the EDM trimming rules are not selected properly, it will also affect the mold polishing quality.
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There are a variety of finishes that can be put onto an injection mold surface, from etching the surface to polishing the surface to a high sheen. For an etched surface, normally if possible, a ground finish is best to start with. However, if the cavity needs to be polished after general machining, you will need to polish the surface by hand in order for the part to release during the injection molding process. This is done by using different grades of mold polishing stones usually ranging from 150 grit to 600 grit. This procedure requires you to have a cutting solution to use with the polishing stones, usually kerosene. The stone is dipped into the kerosene and then you push the polishing stone in different directions along the surface to be polished.
An example of this technique is when you use sandpaper to smooth wood before staining or varnishing. A general rule as in using sandpaper on wood is that you must go in increments from a low grit step by step until you reach the finish desired. For example you would start with a 220 grit then use a 320 grit then use a 400 grit, etc.
A shinier finish is accomplished when you use a high grit. The effect is that when you rub a stone once with a 220 grit along the surface the 220 scratches are made with every motion. Thus, if you use a finer mold polishing stones, for example 600 grit, you are creating 600 scratches which make the scratches closer together giving a more lustered appearance. Once you reach a 400 to 600 grit stoned finish you can move onto using a 400 to 600 grit aluminum oxide sandpaper which gives an even finer mold finish.
Generally, only a 320 grit finish is required to prepare an injection mold for etching. Etching is the process of using acid to burn in different finishes from a pebbled finish to any numerous grains that are available. They are reproduced on the part during the injection molding process. Etching can also be used to put in lettering or numbers onto hard to reach surfaces.
To get a “mirrored” surface finish you must continue to keep increasing the grit from the sandpaper. The next item to use is called diamond polishing compound. This is a paste which has fine grit dispersed throughout. The paste usually comes in grits from 500 microns to 10,000 microns. Once again, the higher the grit, the more close the scratches which will give an appearance of a shinier surface. When using the diamond compound to polish, you do not need to use kerosene because the paste acts as a lubricant. However, when using the paste, it is best applied by using felt pads, bristle brushes, or cotton. To get a faster motion than just using your hand, a grinding tool such as a Dremel Hand Grinder can be used.
Summing up, polishing of an injection mold is very tedious and time consuming but the final results are amazing and are a key part of the injection molding process.
]]>Polishing is a very important process in the mold making. With the widespread use of plastic products, the appearance quality requirements of plastic products are getting higher and higher, so the surface polishing quality of plastic mold cavities should be improved accordingly.In particular, molds with mirror and high-gloss surfaces have higher requirements for mold surface roughness, and therefore higher requirements for polishing. Polishing not only increases the beauty of the workpiece, but also improves the corrosion resistance and abrasion resistance of the surface of the material. It can also facilitate subsequent injection molding, such as making plastic products easy to demold and reducing production injection molding cycles. The commonly used polishing methods are as follows.
Mechanical polishing
Mechanical polishing is a method that relies on cutting and plastic deformation of the material surface to remove the polished protrusions to obtain a smooth surface. Maily using oil stone sticks, wool wheels, sandpaper, etc by hand.For some special surface,it would be used other auxiliary tools, and the ultra-precision polishing method can be used if the surface quality is high. Ultra-precision polishing is the use of special abrasive tools, which are pressed against the processed surface of the workpiece in a polishing liquid containing abrasives for high-speed rotation. Using the technology,the surface can be achieved roughness of Ra0.008μm .which is the highest among various polishing methods. Optical lens molds often use this method.
How to make high quality polishing surface?
The most important thing is to use high-quality polishing tools and auxiliary products such as oilstone, sandpaper and diamond abrasive paste.
The general process of mechanical polishing.
The surface after rough polishing, milling, electric spark, grinding, etc. can be polished by a rotating surface polishing machine or an ultrasonic grinder with a speed of 35 000-40 000 rpm. Commonly used methods are using the wheels (diameter Φ3mm, WA # 400) to remove the white EDM layer. Then using whetstone grinding by hand with #180 ~ #240 ~ #320 ~ #400 ~ #600 ~ #800 ~ #1000. According to the different specifications of the processed products, the angle of about 70 degrees is respectively cross-polished. The most ideal round-trip range is about 40 mm ~ 70 mm.
Semi-precision polishing mainly uses sandpaper and kerosene. After the oilstone polishing finished, we can use sandpaper polishing. When polishing, pay attention to the rounded edges, rounded corners and orange peel of the mold core. so the oilstone process is as fine as possible. The key point of sandpaper polishing is that sandpapaer should be combined with a hard wood stick to grind at an angle of about 70 degrees. The life of sandpaper grinding is about 10 to 15 times. If the grinding time is too long, the grinding force of the sandpaper will be reduced, which will cause unevenness in the processed surface (this is also one of the reasons for the orange peel). Actually, it is best way to use wood rods with low elasticity or aluminum rods with low hardness for grinding at an angle of about 45 degrees. Rubber or high elasticity materials can not be used for the grinding surface. The grit of sandpaper is: #220 ~ #320 ~ #400 ~ #600 ~ #800 ~ #1000 ~ #1200 ~ #1500. In fact, #1500 sandpaper only suitable for die steel and hardening (above 52HRC), not pre-hardened steel. because it may cause burns on the surface of the pre-hardened steel.
Fine polishing mainly uses diamond abrasive paste. If the polishing cloth wheel is mixed with diamond abrasive powder or abrasive paste, the usual polishing order is 9μm(#1800)~6μm(#3000)~3μm(#8000). 9μm diamond abrasive paste with polishing cloth wheel can be used to remove hair-like wear marks left by #1200 and #1500 sandpaper. Then use sticky felt and diamond paste to polishing. the order is 1μm(#14000)~1/2μm(#60000)~1/4μm(#100000).If accuracy requirements above 1μm (including 1μm) ,it can be carried out in a clean polishing room in the mold processing workshop. For more precise polishing, an absolutely clean space is necessary. Dust, smoke, dandruff and saliva can all scrap the high-precision polished surface obtained after hours of work.
Skills in mechanical polishing
Pay attention to the following points when polishing with sandpaper
1:It should be use soft wood or bamboo sticks for polishing with sandpaper. When polishing round or spherical surfaces, use a cork stick to better match the curvature of the round and spherical surfaces. The harder wood strips like cherry wood are more suitable for polishing flat surfaces. The ends of the wooden strips are trimmed to keep them consistent with the surface shape of the steel parts, so as to prevent the sharp angles of the wooden strips (or bamboo strips) from contacting the surface of the steel parts and cause deep scratches.
2:When change a different of sandpaper, the polishing direction should be changed from 45° to 90°, so that the streaks and shadows left by the previous type of sandpaper after polishing can be distinguished. Before changing a different of sandpaper, you must carefully wipe the polishing surface with a 100% pure cotton moistened with a cleaning solution such as alcohol, because a small gravel left on the surface will destroy the entire polishing work that follows. This cleaning process is equally important when changing from sandpaper polishing to diamond paste polishing. Before polishing to continue, all particles and kerosene must be completely cleaned.
3:In order to avoid scratches and burns on the surface of the workpiece, it must be careful when polishing with #1200 and #1500 sandpaper. Therefore, it is necessary to apply a light load and use a two-step method to polish the surface. When polishing with each type of sandpaper, it should be done twice and turn 45°~90° in two different directions.
Pay attention to the following points in diamond grinding and polishing
1: This kind of polishing must be carried out light pressure, especially polishing pre-hardened steel parts and polishing with fine abrasive paste. When polishing with #8000 abrasive paste, the usual load is 100~200g/cm2. But it is difficult to maintain the accuracy of this load. To make this easier, you can make a thin and narrow handle on the wooden strip, such as adding a copper sheet, or cut a part of the bamboo strip to make it softer. This can help control the polishing pressure to ensure that the pressure is not too high in mold surface.
2: When using diamond grinding and polishing, not only the working surface must be clean, but the hands of worker also be cleaned.
3:The polishing time should not be too long each time, the shorter time, it well be better the effect. If the polishing process is too long, it will cause "orange peel" and "pitting".
4 In order to obtain high-quality polishing surface, it should be avoided using heated polishing methods and tools. For example: polishing wheel polishing. It will easily cause "orange peel".
5 When the polishing process is stopped, it is very important to ensure that the surface of the workpiece is clean and carefully remove all abrasives and lubricants. Then it should be sprayed mold anti-rust coating on the surface.
Since mechanical polishing is mainly done manually, polishing technology is still the main reason affecting polishing quality. In addition, it is also related to the mold material, the surface condition before polishing, and the heat treatment process. High-quality steel is a prerequisite for obtaining good polishing quality. If the surface hardness of the steel is uneven or there are differences in characteristics, polishing difficulties will often occur. Various inclusions and pores in the steel are not conducive to polishing.
The influence of different hardness on polishing process
It will more difficult of grinding by increases hardness, but the roughness after polishing decreases. As the hardness increases, the polishing time required more, but the possibility of over-polishing decreases accordingly.
The influence of the surface condition of the workpiece on the polishing process
During the crushing process of the cutting machine, the surface will be damaged due to heat, internal stress or other factors. Improper cutting parameters will affect the polishing effect. The surface after EDM is more difficult to grind than the surface after ordinary machining or heat treatment. Therefore, before the end of EDM, it should be trimmed with precision EDM, otherwise the surface will form a hardened thin layer. If the EDM fine-tuning are not selected properly, the depth of the heat-affected layer can reach up to 0.4mm. The hardness of the hardened thin layer is higher than that of the substrate ,so it must be removed. Therefore, it is best to add a rough grinding process to completely remove the damaged surface to provide a good foundation for polishing.
The polishing of plastic mold is very different with the surface polishing required in other industries. Strictly speaking, the polishing of the mold is mirror processing. It not only has high requirements for polishing , but also has high standards for surface flatness, smoothness and geometric accuracy. Surface polishing generally only requires a bright surface. The standard for mirror surface processing is divided into four levels: AO=Ra0.008μm, A1=Ra0.016μm, A3=Ra0.032μm, A4=Ra0.063μm. It is difficult to precisely control the geometric accuracy of parts due to methods such as electrolytic polishing and fluid polishing. However, the surface quality can not meet the requirements by chemical polishing, ultrasonic polishing, magnetic abrasive polishing and other methods, so the mirror processing of precision molds is still mainly mechanical polishing.
Key points of mirror polishing
The most important point is the polishing size in super mirror polishing. The distance from oilstone grinding to mirror polishing is 10µ. (The most ideal is #1500 (#1000) Whetstone to start grinding. The number of sandpaper is: #320 ~ #400 ~ #600 ~ #800 ~ #1000 ~ #1200 ~ #1500~ #01~ #02 ~ #03~ #04~ #05~ #06~ #015) .The most principle is that the mold must be thoroughly cleaned before proceeding to the next step in order to achieve good effect and be very careful not to make repeated modifications (repeated modifications will affect quality issues).
Polishing is a time-consuming process. It can reduce the cost of polishing by following the step. Every step of polishing must be kept clean, which is the most important.
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1) Common tools for mold polishing include: sandpaper, oilstone, felt wheel, abrasive paste, alloy trowel, diamond grinding needle, bamboo, fiber whetstone, round rotary grinding machine.
2) Sandpaper: 150#, 180#, 320#, 400#, 600#, 800#, 1 000#, 1 200#, 1 500#;
3) Oil stone: 120#, 220#, 400#, 600#;
4) Felt wheel: cylindrical, rounded, square tip;
5) Grinding paste: 1# (white) 3# (yellow) 6# (orange) 9# (green) 15# (blue) 25# (brown) 35# (red) 60# (purple);
6) Sickles: square, round, flat, triangular and other shapes;
7) Diamond grinding needle: generally 3/32 shank or 1/8 shank, with round shape, cylindrical shape, long straight column shape and long round cone shape;
8) Bamboo: Each shape is suitable for operator and shape of mold. Function is to press sandpaper and grind it on workpiece to achieve required surface roughness.
9) Fiber whetstone: 200# (black) 400# (blue) 600# (white) 800# (red)