China Shenzhen Perfect Precision Product Co., Ltd. company news

In the field of mechanical parts processing industry, often plastic as a raw material for further processing, now the market is a very large variety of plastic, so in the processing of mechanical parts should choose what kind of plastic? Let me tell you today! 1. The requirements of transparent available organic glass. 2. Polyimide, polysulfone, PTFE, etc. are available for high temperature resistance. 3. Self-lubricating for wear reduction, PA, PTFE, etc. 4. Gear transmission PA, polycarbonate, polyformaldehyde, etc.

The final heat treatment of mechanical parts machining is to improve the mechanical properties such as hardness, wear resistance and strength of the parts in order to better realize their use value. So do you know what is the specific purpose of heat treatment of mechanical parts processing? Let me share it with you today! 1. Remove the internal stress of the blank. Mostly used for castings, forgings, and welded parts. 2. Improve the processing conditions, so that the material is easy to process. Such as annealing, normalizing, etc. 3. To improve the overall mechanical properties of metal materials. Such as, tempering treatment. 4. To obtain hardness. Such as, quenching, carburizing quenching, etc.

Full CNC process? die-casting? CNC+die-casting? Before restoring the manufacturing process of the mobile phone shell, let's first make clear several concepts: full CNC process and die-casting process, as well as CNC+die-casting. The full CNC mobile phone middle frame is a piece of aluminum plate (or other metal materials) milled into a specific shape through the CNC machining center. The die-casting is to use the mold cavity to apply high pressure to the molten metal, and to die-casting and stamping the liquid metal into a solid metal shell or middle frame, Of course, there is also the practice of combining the two processes. Using the appendix, we can see that the full CNC process costs more and wastes more materials. Of course, the quality of the middle frame or shell under this process is better. The principle of die casting is not to waste, save time and cost, but it is not conducive to the later anodic oxidation process, and may also leave small problems affecting quality and appearance, such as sand hole flow marks. Of course, manufacturers have a concept of yield, and reliable manufacturers will not let these inferior products flow into the later production links. After understanding the similarities and differences between the two processes, I started to talk about the metal shell processing technology that is also emerging on the 1000 yuan machine. After the bombardment of various large mobile phone conferences, we believe that everyone can break their fingers. Today, here, we are not just a dog's tail. Today, we mainly talk about the whole process of die casting+CNC process of metal mobile phone shell: one 1、 Die casting stage Before die-casting, we saw the original aluminum. Because the strength and hardness of pure aluminum are not enough, in fact, the mobile phone uses aluminum alloy, and has different characteristics according to different formulas. For example, the 6000 series aluminum alloy used for iPhone 6 is not strong enough, but it is easy to be bent due to its better ductility. The 7000 series used in the iPhone 6s has much higher strength, but is more brittle. It is more difficult to be compressed and deformed. However, once it exceeds the stress load, it will not bend, but break. Well, the formula of aluminum alloy varies according to the demands of manufacturers. For example, rare earth, titanium, cobalt and other precious metals are added to the aluminum below. Of course, the proportion of these precious metals is very low, and they are not so expensive compared with real precious metals such as gold and platinum. Since it is die-casting, it is not possible to directly cut the aluminum, but to melt the aluminum into a fluid, which is convenient for subsequent stamping in the mold. So the picture below is with temperature. When these metals become liquid, it is time to inject them into the die-casting machine. This is the hardest time in aluminum's life. The aluminum water slowly flows down from the spider shaped groove, accepts the unimaginable stamping, and finally becomes the prototype of a shell. Although it looks simple, even in such a link, sand holes should be kept away from during shell processing. Once there are sand holes, there will be small pits in the subsequent processing and cutting. Therefore, there is still a need to improve the process and mold structure. This process of trial and error improvement will waste a lot of raw materials. When strands of aluminum water are pressed one after another, the manipulator will peel off the rough shell and send it to the assembly line for the next round of test. When strands of aluminum water are pressed one after another, the manipulator will peel off the rough shell and send it to the assembly line for the next round of test. 2、 Painting stage After the previous die casting stage, these rudimentary shells should accept the next choice. Should they be anodized like the iPhone to achieve a cold metal texture, or should they be painted to wear a warm coat? This seems to be a difficult choice. However, the reality has nothing to do with aesthetics: die-casting shell is not conducive to anodizing, and there are also some product differentiation considerations. After the machine tool processing, the excess part is washed off, and the burrs are removed, it can be seen that the shell has been basically formed. As for the upper opening, it is reserved for injection molding. The holes on the back cover are processed by CNC for injection molding and reinforcement of the body. This logic is the same as the white ribbon on the back of the iPhone 6. In order to make the antenna signal smooth, the back cover cannot use a whole piece of metal. So in the antenna part, we always see traces of plastic, which can not be overcome at present, and the plastic in this part is not a spray point. After the injection molding is completed, after polishing again, the next step is the painting process. The manufacturers will certainly not take the plain shell directly. The painting process is also a technical activity. The plastic and metal parts on the back of the mobile phone have a clear boundary. If the painting process is not good enough, the boundary will still be visible. Therefore, whether the metal and plastic parts can be seen is an important indicator to judge whether the painting process is good or not. The lower mobile phone case will move slowly on the assembly line. Eight groups of 16 nozzles will spray the case in all directions to ensure uniformity. After painting, the paint is baked. The process of painting is like a mushroom forest. In addition, spray painting and baking paint are generally not only good once, but also repeated. In addition, there will be another polishing between paint baking and painting. This group of mobile phone cases will eventually undergo five painting, five painting and two polishing. Generally, the first coat is primer, and pearl powder or aluminum powder will be added to the last coat of paint to ensure the texture and appearance. 3、 CNC stage At this stage, mobile phone manufacturers like to release the most, because this part has a very pleasant part, called diamond cutting. However, before the diamond is cut, manufacturers need to make holes for cameras, volume keys, speakers and other parts. Below is the picture of camera holes for the shell. After each hole is opened, it is a popular diamond cutting link. To speak of diamond cutting, it is not because the cut frame looks like a diamond, but the cutting tool is a diamond. The yellow part in front of the cutting props can be seen below, that is, the diamond. As for why it looks dull and ordinary compared with the diamond on the diamond ring, I guess it should be an artificial diamond, with the hardness of natural diamonds, but without the luster of diamonds after cutting. It can also be seen below that the cut shell edge has a good highlight. It is not similar to the previous painting and baking varnish. The diamond cutting here can not be completed once. At least two times and three times are the conscience of the industry. After all, one more step is more expensive. It should be pointed out that in order to ensure that the cutting width and angle are strictly consistent, a laser tool setting instrument is also used here to control the thickness and width of the cutting edge. After all, the straightest thing in the world is not Wang Leehom, but the light. In simple terms, the laser tool setting first walks around the place to be cut, and the measured data according to the shape of the object is fed back to the CNC machine tool, and then the cutting can start. OK, here is a close-up of the MVP diamond cutter on this mobile phone case manufacturing trip. The manufacturers showed us a brilliant process, but in the field, we found that the process from a lump of aluminum pimple to a delicate shell has gone through a lot, and some processes can even be described as cumbersome, but just like girls are willing to use a knife on their face to look good, they should also use a knife on the shell.

Machining of mechanical parts can not be completed in one process all the surface of all the processing content, so we know the mechanical parts processing can be divided into several stages? Let me tell you today! (1) Roughing stage. Most of the machining allowance of each machining surface is cut off, and a fine reference is machined, mainly considering the greatest possible increase in productivity.   (2) Semi-finishing stage. Cut out the defects that may arise after rough machining, and prepare for the finishing of the surface, requiring a certain machining accuracy and ensuring the appropriate finishing allowance, while completing the machining of the secondary surface.   (3) Finishing stage. In this stage using a large cutting speed, small feed and depth of cut, remove the finishing margin left by the previous process, so that the surface of the part to meet the technical requirements of the drawing.   (4) finishing stage. Mainly used to reduce the surface roughness value or strengthen the machined surface, mainly for surface roughness requirements are very high (Ra ≤ 0.32 μm) surface processing.   (5) Ultra-precision machining stage. Machining accuracy in 0.1-0.01 μm, surface roughness value Ra ≤ 0.001 μm processing stage. The main processing methods are: diamond tool precision cutting, precision and mirror grinding, precision grinding and polishing, etc. The parts will be divided into processing stages of the main purpose of the following points.   (1) to ensure the quality of processing. Rough machining stage cutting amount is large, the resulting cutting force is large, cutting heat, the required clamping force is also larger, so the parts residual internal stress and process system of force deformation, heat deformation, stress deformation are larger, the resulting machining errors can be gradually eliminated through semi-finishing and finishing, so as to ensure machining accuracy.   (2) Reasonable use of equipment. Rough machining requires high power, good rigidity, high productivity and low precision equipment; finishing requires high precision equipment. After dividing the processing stage, you can give full play to the strengths of roughing and finishing equipment, so that the reasonable use of equipment.   (3) facilitate the arrangement of heat treatment process. For example, after rough machining parts residual stress, can arrange aging treatment, eliminate residual stress, heat treatment caused by deformation and can be eliminated in the finishing process.   (4) to facilitate the timely detection of problems. Various defects of the blank such as porosity, trachoma and insufficient machining allowance, etc., can be found after rough machining, to facilitate timely repair or decide whether to scrap, to avoid subsequent processes to complete the discovery, resulting in a waste of man-hours, increasing production costs.

The deformation of thin-walled parts during turning is multifaceted. The clamping force when clamping the workpiece, the cutting force when cutting the workpiece, and the elastic deformation and plastic deformation generated when the workpiece blocks the tool cutting make the temperature of the cutting area rise and generate thermal deformation. The cutting force is closely related to the cutting parameters. From the Metal Cutting Principle, we can know that the back cutting amount ap, the feed rate f and the cutting speed V are the three elements of the cutting parameters. During the test, it was found that: 1) With the increase of back cut and feed, the cutting force and deformation are also increased, which is extremely unfavorable for turning thin-walled parts. 2) Reduce the back cut and increase the feed rate. Although the cutting force decreases, the residual area of the workpiece surface increases and the surface roughness value is large, which increases the internal stress of the thin-walled parts with poor strength and also leads to the deformation of the parts. Therefore, during rough machining, the back cutting amount and feed amount can be larger; During finishing, the back cut is generally 0.2-0.5 mm, the feed is generally 0.1-0.2 mm/r, or even less, and the cutting speed is 6-120 m/min. The cutting speed shall be as high as possible during fine turning, but not too high. Reasonable selection of the three elements can reduce cutting force and thus reduce deformation.

There are various classification methods for steel, and the main methods are as follows: 1. Classified by quality (1) Ordinary steel (P ≤ 0.045%, S ≤ 0.050%) (2) High quality steel (P, S ≤ 0.035%) (3) High quality steel (P ≤ 0.035%, S ≤ 0.030%) 2. Classification by chemical composition (1) Carbon steel: a. Low carbon steel (C ≤ 0.25%); b. Medium carbon steel (C ≤ 0.25 ～ 0.60%); c. High carbon steel (C ≤ 0.60%). (2) Alloy steel: a. Low alloy steel (total content of alloy elements ≤ 5%); b. Medium alloy steel (total alloy element content>5~10%); c. High alloy steel (total alloy element content>10%) 3. Classification according to forming method: (1) Forged steel; (2) Cast steel; (3) Hot rolled steel; (4) . Cold drawn steel. 4. Classification according to metallographic structure (1) Annealed state: a. hypoeutectoid steel (ferrite+pearlite); b. Eutectoid steel (pearlite); c. Hypereutectoid steel (pearlite+cementite); d. Ledeburite steel (pearlite+cementite); (2) Normalized: a. Pearlitic steel; b. Bainitic steel; c. Martensitic steel; d. Austenitic steel; (3) No phase change or partial phase change occurs. 5. Classification by use (1) Steel for building and engineering: a. Ordinary carbon structural steel; b. Low alloy structural steel; c. Reinforcement steel. (2) Structural steel: a. Steel for mechanical manufacturing: (a) quenched and tempered structural steel; (b) Case hardened structural steel: including carburizing steel, ammonia carburizing steel and surface hardening steel; (c) Free cutting structural steel; (d) Steel for cold plastic forming: including steel for cold stamping and steel for cold heading b. Spring steel c. Bearing steel (3) Tool steel: a. Carbon tool steel; b. Alloy tool steel; c. High speed tool steel. (4) . Special performance steel: a. Stainless acid resistant steel; b. Heat resistant steel: including oxidation resistant steel, heat strength steel and air valve steel; c. Electric heating alloy steel; d. Wear resistant steel; e. Low temperature steel; f. Steel for electrical purposes. (5) Professional steel - such as bridge steel, ship steel, boiler steel, pressure vessel steel, agricultural machinery steel, etc. 6. Comprehensive classification (1) Ordinary steel a. Carbon structural steel: (a) Q195; (b) Q215(A、B); (c)Q235(A、B、C); (d) Q255(A、B); (e)Q275。 b. Low alloy structural steel c. Ordinary structural steel for specific purposes (2) High quality steel (including high quality steel) a. Structural steel: (a) high-quality carbon structural steel; (b) Alloy structural steel; (c) Spring steel; (d) Free cutting steel; (e) Bearing steel; (f) High quality structural steel for specific applications. b. Tool steel: (a) carbon tool steel; (b) Alloy tool steel; (c) High speed tool steel. c. Special performance steel: (a) stainless acid resistant steel; (b) Heat resistant steel; (c) Electric heating alloy steel; (d) Electrical steel; (e) High manganese wear-resistant steel. 7. Classification according to smelting method (1) . Classification by furnace type a. Converter steel: (a) acid converter steel; (b) Basic converter steel. Or (a) bottom blown converter steel; (b) Side blown converter steel; (c) Top blown converter steel. b. Electric furnace steel: (a) electric furnace steel; (b) Electroslag furnace steel; (c) Induction furnace steel; (d) Vacuum consumable furnace steel; (e) Electron beam furnace steel. (2) According to deoxidation degree and pouring system a. Rimmed steel; b. Semi killed steel; c. Killed steel; d. Special killed steel

1. Yield point（ σ s) When the steel or sample is stretched, when the stress exceeds the elastic limit, even if the stress does not increase any more, the steel or sample continues to undergo obvious plastic deformation. This phenomenon is called yield, and the minimum stress value when the yield phenomenon occurs is the yield point. If Ps is the external force at the yield point s and Fo is the sectional area of the sample, then the yield point σ s =Ps/Fo(MPa) 2. Yield strength（ σ 0.2) The yield point of some metal materials is very unobvious, which is difficult to measure. Therefore, in order to measure the yield characteristics of materials, it is stipulated that the stress when the permanent residual plastic deformation is equal to a certain value (generally 0.2% of the original length) is generated, which is called conditional yield strength or yield strength for short σ 0.2。 3. Tensile strength（ σ b) The maximum stress value reached by the material during the tensile process from the beginning to the time of fracture. It indicates the resistance of steel to fracture. The compressive strength and bending strength are corresponding to the tensile strength. If Pb is the maximum tensile force reached before the material is broken, and Fo is the cross-sectional area of the sample, then the tensile strength σ b= Pb/Fo(MPa)。 4. Elongation（ δ s) The percentage of the length of plastic elongation of the material after breaking to the length of the original sample is called elongation or elongation 5. Yield ratio（ σ s/ σ b) The ratio of yield point (yield strength) to tensile strength of steel is called yield strength ratio. The greater the yield ratio, the higher the reliability of structural parts. The yield ratio of general carbon steel is 0.6-0.65, and that of low alloy structural steel is 0.65-0.75, and that of alloy structural steel is 0.84-0.86. 6. Hardness Hardness refers to the ability of a material to resist hard objects pressing into its surface. It is one of the important performance indexes of metal materials. Generally, the higher the hardness is, the better the wear resistance is. The commonly used hardness indicators are Brinell hardness, Rockwell hardness and Vickers hardness. Brinell hardness (HB) Press a hardened steel ball of a certain size (generally 10mm in diameter) into the material surface with a certain load (generally 3000kg) for a period of time. After unloading, the ratio of the load to the indentation area is the Brinell hardness value (HB). L Rockwell hardness (HR) When HB>450 or the sample is too small, the Brinell hardness test can not be used but Rockwell hardness measurement. It uses a diamond cone with a vertex angle of 120 ° or a steel ball with a diameter of 1.59 and 3.18 mm to press it into the surface of the tested material under a certain load, and the hardness of the material is calculated from the depth of the indentation. According to the different hardness of the test material, it can be expressed by three different scales: HRA: the hardness obtained by using 60kg load and diamond cone indenter, used for materials with extremely high hardness (such as cemented carbide). HRB: hardness obtained by using 100kg load and 1.58mm diameter hardened steel ball, used for materials with low hardness (such as annealed steel, cast iron, etc.). HRC: the hardness obtained by using a 150kg load and a diamond cone indenter, used for materials with high hardness (such as quenched steel). L Vickers hardness (HV) Press the material surface with a load within 120kg and a diamond square cone indenter with a top angle of 136 °. Divide the surface product of the material indentation dent by the load value, which is the Vickers hardness value (HV)

As we all know, machining accuracy refers to the degree to which the actual size, shape and position of the machined part surface conform to the ideal geometric parameters required by the drawing. Therefore, when we have a demand for precision machining, our first reaction is to find a precision machining equipment, and our inventory of precision machining equipment comes from parameters. In fact, for the definition of this precision, the standards of each country are different. Let's take a strict look at the accuracy of those things! Accuracy: refers to the closeness between the measured results and the true values. High measurement accuracy means that the system error is small. At this time, the average value of the measured data deviates from the true value less, but the data is scattered, that is, the size of the accidental error is not clear. Precision: refers to the reproducibility and consistency between the results obtained by repeated determination with the same kind of standby sample. It is possible that the precision is high, but the accuracy is inaccurate. For example, the three results measured with a length of 1mm are 1.051mm, 1.053 and 1.052 respectively. Although their precision is high, they are inaccurate. Accuracy indicates the correctness of the measurement results, precision indicates the repeatability and reproducibility of the measurement results, and precision is the prerequisite for accuracy. In a promotional article on CNC machine tools, the "positioning accuracy" of machine tool A is 0.004mm, while in the sample of another manufacturer, the "positioning accuracy" of similar machine tool B is 0.006mm. From these data, you will naturally think that the accuracy of machine tool A is higher than that of machine tool B. However, in fact, it is very likely that the accuracy of machine tool B is higher than that of machine tool A. The problem is how to define the accuracy of machine tool A and B respectively. Therefore, when we talk about the "precision" of CNC machine tools, we must make clear the definition and calculation method of standards and indicators. 1、 Definition of precision: Generally speaking, accuracy refers to the ability of the machine tool to position the tool tip to the program target point. However, there are many ways to measure this positioning capability. More importantly, different countries have different regulations. Japanese machine tool manufacturers: JISB6201 or JISB6336 or JISB6338 standards are usually used when calibrating "precision". JISB6201 is generally used for general machine tools and general CNC machine tools, JISB6336 is generally used for machining centers, and JISB6338 is generally used for vertical machining centers. European machine tool manufacturers, especially German manufacturers, generally adopt VDI/DGQ3441 standard. American machine tool manufacturers: generally adopt the NMTBA (National Machine Tool Builder's Assn) standard (this standard is derived from a study of the American Machine Tool Manufacturing Association, issued in 1968, and modified later). When calibrating the accuracy of a CNC machine tool, it is very necessary to mark the standards used together. The JIS standard is adopted, and its data is significantly smaller than that of the NMTBA standard in the United States or the VDI standard in Germany. The same indicator has different meanings It is often confused that the same indicator name represents different meanings in different precision standards, while different indicator names have the same meaning. The above four standards, except JIS standard, are all calculated through mathematical statistics after multiple rounds of measurement of multiple target points on the CNC axis of the machine tool. The key differences are: 1. Number of target points 2. Number of measurement rounds 3. Approach the target point from one way or two ways (this point is particularly important) 4. Calculation method of precision index and other indexes This is a description of the key differences between the four standards. As expected, one day all machine tool manufacturers will follow the ISO standard. Therefore, the ISO standard is selected as the benchmark. The four standards are compared in the following table. In this paper, only linear accuracy is involved, because the calculation principle of rotation accuracy is basically consistent with it. 2、 Temperature influence on accuracy: thermal stability Steel: 100 x 30 x 20 mm Change of size when the temperature drops from 25 ℃ to 20 ℃: at 25 ℃, the size is larger by 6 μ m. When the temperature drops to 20 ℃, the size is only 0.12 larger μ m. This is a thermally stable process. Even if the temperature drops rapidly, it still needs a continuous time to maintain the accuracy. The larger the object, the more time it takes to restore the accuracy stability when the temperature changes. The recommended values of temperature to be maintained for high-precision machining are shown in the table below. If high-precision machining is performed, it is very important not to take temperature changes lightly!

Machining process procedures is one of the process documents that specify the mechanical machining process and operation methods of parts, it is in the specific production conditions, the more reasonable process and operation methods, written in accordance with the prescribed form into process documents, after approval used to guide production. So we know what tips in the process of machining mechanical parts? Let me share it with you today! First mechanical parts processing in the vise jaws removed, another two M4 threaded holes, two flush with the jaws of 1.5mm thick steel plate 2, with aluminum countersunk rivets riveted on 0.8mm thick hard brass plate 3 will be fastened to the jaws with M4 countersunk screws 1, forming a durable soft jaws. This can also protect the parts are clamped bad, but also has interchangeability.   Second, mechanical parts processing with a magnet to absorb small parts (fee parts) suck and take are not convenient. Can suck an iron plate 2 under the magnet 1, not only can suck a lot of small parts, and the iron plate will be pulled away from the small parts will immediately and automatically dumped into the collection box. Not enough to impress the heart but very practical   Third, mechanical parts processing in the pulley drive when the pulley often slipped between the pulley and the axle, in the axle with ￠ 15 ~ 18mm scratch nest drill bit to scratch a series of nest, so that adsorption can be formed to prevent slippage, turning waste into treasure.   Fourth, in the machining of mechanical parts, when the hexagonal wrench 1 handle is short and can not be force, the tube with an inner diameter slightly larger than the wrench can be milled from a section of the slot, the wrench will be inserted into the slot, which can be used as a long handle.   In mechanical parts processing, there will be a number of workpieces are not produced through a one-time production, but when the workpiece is produced, it is only a rough model, if the factory into a real product, which will have to be mechanically processed with the help of some mechanical equipment, according to the different product needs for mechanical processing, and finally to become a product with use value In order to ensure the efficiency of mechanical processing, and the production of qualified product quality, in the time of mechanical processing, must follow the four principles.   1, the benchmark first. In the use of machinery and equipment for product processing, a datum must be determined, so that in the subsequent processing to have a positioning reference, to determine the datum, then the datum must first be processed.   2、Division of processing stages. Products in mechanical processing, according to the different product requirements to carry out different degrees of processing, the degree of processing needs to be divided, if the requirements for precision is not high, then a simple roughing stage on the line. The progress of the product requirements are becoming more and more stringent, the subsequent semi-finishing and finishing stages will be carried out.   3、Face first and then hole. In the time of machining, for such a workpiece as the bracket, it is necessary to both plane processing and mechanical hole processing, in order to process the hole accuracy error is smaller, first processing plane after processing hole is conducive to reducing the error.   4、Light finishing processing. This processing principle is roughly the processing of some grinding and polishing, it is usually in the product all finished architecture after the step.

In the field of mechanical parts machining industry, there exists the concept of machining accuracy, and everyone should have an understanding of it. So today we share with you what are the process measures to improve machining accuracy! 1. Reduce the original error This method is a basic method that is widely used in production. It is to identify the main factors that produce machining errors, and then try to eliminate or reduce these factors. For example, the turning of slender shafts, now using a large walking tool reverse turning method, basically eliminates the bending deformation caused by axial cutting force. If supplemented with a spring tip, the effect of thermal elongation caused by thermal deformation can be further eliminated.   2. Compensation of the original error Error compensation method, is to artificially create a new error, to offset the original process system in the original error. When the original error is negative when the artificial error to take a positive value, and vice versa, to take a negative value, and try to make the two equal in size; or the use of an original error to offset another original error, but also try to make the two equal in size and opposite direction, so as to reduce the processing error, improve the processing accuracy of the purpose.   3. Transfer of the original error Error transfer method is essentially transferring the geometric error, force deformation and thermal deformation of the process system. Error transfer method of many examples. Such as when the machine tool accuracy can not meet the requirements of the parts processing, often not just improve the machine precision, but from the process or fixture to find ways to create conditions so that the geometric error of the machine tool does not affect the machining accuracy of the aspects to transfer. Such as grinding spindle taper hole to ensure its coaxiality with the journal, not by the machine tool spindle rotation accuracy to ensure, but by the fixture to ensure. When the machine tool spindle and the workpiece with a floating linkage, the original error of the machine tool spindle is transferred away. 4. Equalization of the original error In processing, due to the blank or the previous process error (hereinafter collectively referred to as the "original error"), often resulting in the process of processing errors, or due to changes in the material properties of the workpiece, or the process of the previous process changes (such as the blank refinement, the original cutting process cancellation), resulting in a large change in the original error. This change in the original error affects this process in two main ways. (1). The error is reflected, causing the process error; (2). Positioning error expansion, causing errors in this process. To solve this problem, it is best to use the method of grouping and adjusting the mean error. The essence of this approach is to divide the original error into n groups according to their size, each group of blank error range is reduced to 1/n of the original, and then adjust the processing according to each group separately.   5. Equalize the original error For shafts and holes with high requirements of fit accuracy, grinding process is often used. The grinding tool itself is not required to have high precision, but it can make relative movement with the workpiece in the process of micro-cutting on the workpiece, the high point is gradually ground off (of course, the mold is also part of the workpiece grinding) and finally make the workpiece to achieve high precision. This process of friction and wear between surfaces is the process of continuous reduction of errors. This is the error equalization method. The essence of it is the use of closely linked surfaces to compare with each other, check each other to find out the differences from the comparison, and then carry out mutual correction or mutual benchmark processing, so that the workpiece is processed surface error constantly reduced and even. In production, many precision benchmark parts (such as flat, straight, angle gauge, end teeth indexing disc, etc.) are processed using the error equalization method.   6. In-situ processing method In the processing and assembly of some precision problems, involving the interrelationship between the parts or components, quite complex, if you focus on improving the accuracy of the parts themselves, sometimes not only difficult, or even impossible, if the use of in situ processing method (also known as their own processing repair method) method, it may be very convenient to solve the seemingly very difficult accuracy problems. In-situ machining method is commonly used in the machining of mechanical parts as an effective measure to ensure the accuracy of parts processing.