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

Generally, CNC machining usually refers to computer numerical control precision machining, numerical control machining lathe, numerical control machining milling machine, numerical control machining boring and milling machine, etc. It is a new processing technology. Its main work is to compile processing programs and convert the original manual work into computer programming. Manual processing certainly requires experience. Working principle of CNC processing: When the numerical control system is activated, the required machining dimensions are programmed into the software and assigned to the corresponding tools and machines, which perform the specified dimensional tasks like robots. In numerical control programming, the code generator in the digital system usually assumes that the mechanism is perfect. Although there is the possibility of error, this possibility is greater when the NC machine is instructed to cut in multiple directions at the same time. The placement of tools in the CNC system consists of a series of input overviews called part programs. Use the numerical control machine tool to input the program through the punch card. In contrast, the program of CNC machine tools is input into the computer through the keypad. NC programming is retained in the computer memory. The code itself is written and edited by the programmer. Therefore, CNC system provides a wider range of computing power. It is important that the CNC system is never static, because the updated prompt can be added to the pre-existing program by modifying the code. Advantages of CNC machining: ① The number of tooling is greatly reduced, and complex tooling is not required for machining parts with complex shapes. To change the shape and size of parts, only need to modify the part processing program, which is suitable for the development and transformation of new products. ② The processing quality is stable, the processing accuracy is high, and the repetition accuracy is high, which meets the requirements of aircraft processing. ③ In the case of multi variety and small batch production, the production efficiency is high, which can reduce the time of production preparation, machine tool adjustment and process inspection, and reduce the cutting time due to the use of cutting volume. ④ It can process complex surfaces that are difficult to be processed by conventional methods, and even some unobservable processing parts.

Numerical control lathe processing is a general designation for parts processing on numerical control machine tools. Computer controlled machine tools are generally called numerical control lathes in the mechanical processing industry, while computers specially designed to control numerical control machine tools or general computers are called numerical control systems. Numerical control lathe processing is widely used in the precision parts processing industry. Now let's introduce the process characteristics of precision parts processing with CNC lathes: The program of CNC system is compiled by professional engineers according to the material of parts, process requirements and machine tool characteristics. The NC system program sends operation or interruption information to the machine tool to control the operation of the machine tool. After the processing of precision parts is completed, the machine tool will automatically stop running under the instructions of the program. The characteristics of CNC machine tool itself determine that its main function is to process products with a certain degree of complexity. Such products generally have complex shapes and surfaces, which is mainly to solve some problems that cannot be solved by ordinary processing methods. The biggest feature of NC machining in the application of precision parts processing is that it can use the perforated belt to control the machine tool for automatic machining.

CNC machining of high-precision parts is not suitable for precision machining of all materials. Some materials are too hard, exceeding the hardness of the processed parts, which may cause the collapse of machine parts. Therefore, these materials are not suitable for precision machining unless they are machine parts made of special materials or laser cutting. The requirements are specific to every work, because it will directly affect the quality of products produced. Therefore, in order to ensure the quality of products, we should not only have requirements for equipment, but also for operators and some processed materials. These all need to have certain standards. Only if these meet the standards, can the products produced be our ideal appearance. Let's know what the material requirements for precision parts processing are? The processed materials are divided into two categories, metallic materials and non-metallic materials; For metal materials, stainless steel has the highest hardness, followed by cast iron, followed by copper, and finally aluminum. The processing of ceramics and plastics belongs to the processing of non-metallic materials. For the hardness requirements of materials, in some cases, the higher the hardness of materials, the better, but it is inferior to the hardness requirements of machined parts. The processing materials should not be too hard; If it is harder than mechanical parts, it cannot be processed; The material must be moderate in hardness and softness. At least one grade lower than the hardness of the machine. At the same time, it also depends on the function of the processed equipment and the reasonable choice of the machine. In the process of CNC parts processing and manufacturing, due to the different production requirements and conditions of each part, the manufacturing process plan is also different. When different process schemes are used to produce the same parts, their production efficiency and economic benefits are also different.

Heat treatment is an important process to improve the properties of metal materials, and the key of heat treatment clock is undoubtedly the heating process. If errors occur in heating, resulting in heating defects, it will have a serious impact on the metal performance, and sometimes even cause irreparable losses. Then, what are the types of heating defects in heat treatment and what are the reasons for them? One of the heating defects: overheating When the temperature of steel material is too high or the holding time at high temperature is too long, the austenite grain coarsening is caused. This phenomenon is called overheating. Austenitic grain coarsening will lead to higher brittleness and lower toughness of steel, increase the tendency of deformation and cracking during quenching, and thus reduce the mechanical properties of parts. The out of control of the furnace temperature instrument is usually the main cause of overheating. Generally, the overheating of steel can refine the austenite grain by annealing, normalizing or multiple high-temperature tempering of the overheated structure. However, even if the steel material with overheated structure is refined again, there will inevitably be some coarse granular fractures, which is called fracture heredity. This is usually caused by impurities such as manganese sulfide dissolving into the austenite crystal interface when overheating. When steel is impacted, it is easy to fracture along the coarse austenite grain boundary. When austenitizing heat treatment is carried out again for steel materials with coarse martensite, bainite and widmanstatten structures, even if the steel is heated to the conventional quenching temperature with a slow heating speed, and overheating does not occur, the austenite grains will still show the tendency of coarsening. This phenomenon is called structural heredity. The heredity of coarse structure can be eliminated by intermediate annealing or multiple high-temperature tempering. Heating defect 2: overburning In addition to coarsening austenite grains, too high heating temperature will also cause another bad result - local oxidation or melting of grain boundaries. This situation will lead to the weakening of metal grain boundaries, serious deterioration of properties, and cracking during quenching. This phenomenon is called overburning. As overburning involves both physical and chemical processes, once it occurs, the metal structure is difficult to recover, so it can only be discarded. Therefore, in the process of heat treatment, we must avoid overheating due to high heating temperature. Heating defect 3: decarburization and oxidation Steel materials with a certain concentration of carbon can enhance the hardness, fatigue strength and wear resistance of metals. However, during heating, the carbon on the steel surface will be oxidized by oxygen, hydrogen, carbon dioxide, water vapor and other substances due to direct contact with the medium or atmosphere, which will reduce the carbon concentration in the steel surface, affect the surface hardness, fatigue strength and wear resistance, and cause residual tensile stress concentration on the steel surface, thus forming surface network cracks. This phenomenon is called decarburization. Not only the carbon element on the surface of steel will be oxidized, iron and alloy will also be oxidized by oxygen, hydrogen, carbon dioxide, water vapor and other substances in the medium or atmosphere to form an oxide film. This phenomenon is called oxidation. The dimensional accuracy and surface brightness of high-temperature workpiece will be reduced after oxidation, and steel parts with poor hardenability of oxide film are prone to quenching soft spots. In order to prevent decarburization and oxidation, the surface of steel parts should be packed and sealed with stainless steel foil, heated by salt bath furnace or flame combustion furnace, and the purified inert gas should be used as the protective atmosphere. Heating defect 4: hydrogen embrittlement When high-strength steel is heated in a hydrogen rich atmosphere, its plasticity and toughness will decrease. This phenomenon is called hydrogen embrittlement. Hydrogen embrittlement can be avoided by heating in vacuum, low hydrogen atmosphere or inert atmosphere. Hydrogen embrittlement can be eliminated by tempering, aging and other hydrogen removal treatments for workpieces that have appeared hydrogen embrittlement. In some cases, hydrogen embrittlement can also be used to achieve special processing purposes, such as alloy crushing.

There are many kinds of CNC lathes, but they are generally composed of three parts: lathe body, CNC device and servo system.  Lathe body 1. Spindle and headstock The rotation accuracy of the spindle of CNC lathe has a great influence on the accuracy of machining parts, and its power and rotation speed also have a certain impact on the machining efficiency. If the spindle box of CNC lathe is a CNC lathe with level automatic speed regulation function, the transmission structure of its spindle box has been simplified. For the reformed CNC lathe with dual functions of manual operation and automatic control processing, basically the original headstock is still being retained. 2. Guide rail The guide rail of CNC lathe provides guarantee for feeding movement. To a large extent, it will have a certain impact on the rigidity, accuracy and stability of the lathe at low speed feed, which is also one of the important factors affecting the quality of parts processing. In addition to some CNC lathes using the traditional sliding guide rail, CNC lathes that have been finalized for production have adopted more plastic coated guide rails. 3. Mechanical transmission mechanism In addition to some gear transmission mechanisms in the spindle box, the CNC lathe has made some simplification on the basis of the original ordinary lathe transmission chain. The change gear box, feed box, slide box and most of its transmission mechanisms are cancelled, but only the longitudinal and transverse screw transmission mechanisms are retained, and a gear pair (not added in a few lathes) that can eliminate its side clearance is added between the driving motor and the lead screw. Numerical control device In the field of numerical control machine tools, numerical control device is the core of machine tools. It mainly receives the numerical control processing program sent by the input device from the internal memory, compiles it through the circuit or software of the numerical control device, and outputs control information and instructions after calculation and processing, so as to control the work of each part of the machine tool, so that it can carry out orderly movement.  Servo system The servo system includes two aspects: one is the servo unit, and the other is the driving device. Servo unit is the link between CNC and lathe. It can amplify the weak signal in CNC device to form the signal of high-power driving device. The servo unit can be divided into pulse type and analog type according to the received instructions. Drive decoration is to program the CNC signal expanded by the servo unit into mechanical motion, drive the lathe through simple connecting parts, make the workbench accurately locate the relative motion of the trajectory, and finally process the required products according to the requirements.

Controlling the quality of outsourced machined parts needs to be carried out according to the characteristics of their own enterprises. Only when it is targeted, can the effect be remarkable. 1. Strengthen the quality awareness of enterprise leaders Although the awareness of enterprise leadership is not directly related to product quality, it is one of the key factors affecting product accuracy. Managers of enterprises should establish the strategy of quality first and strengthen the idea of keeping improving. At the same time, leaders should appear from themselves and standardize the scope of responsibility of enterprises. 2. Pay more attention at the initial stage of the product Many enterprises do not pay enough attention to the initial stage of products in the process of production. So with the error until the completion of product processing, the quality of the products produced will have great problems. Therefore, we need to pay attention to it at the early stage of product manufacturing. The early stage of development and design determines the degree to which the product meets the needs of users. Market research results and economic form analysis are indispensable work contents in the early stage of the product. 3. Improve the content of technical documents of outsourced machined parts Even mature outsourced parts need trial production, evaluation, evaluation, experiment and other processes. Therefore, it is very important for outsourcing supply to be technically transparent to customers. Especially for the technical documents, technical requirements, inspection process and other contents, we need to communicate in the early stage to ensure the correct understanding. 4. Process quality monitoring In the process of processing outsourced parts, the whole process tracking should be well controlled at the initial stage, so that problems can be found and improved in time. In the subsequent processing process, it is necessary to conduct quality review and spot check on the production site regularly or irregularly. This has played a supervisory role in processing and can receive products with better quality. 5. Clarify the responsibilities of outsourced processing plants In order to meet the technical requirements in the ordering process, both parties need to sign a contract or agreement before processing. This document needs to indicate the scope of rights and responsibilities of both parties, determine the liability for breach of contract, and also need to develop an incentive mechanism. At the same time, the outsourced machinery processing plants with many quality problems need to be reviewed again. Combined with the quality standards, determine whether the quality defects are technical or production, and make rectification plans and adopt relevant corrective measures. The quality control of outsourced machined parts of machining enterprises not only has the above aspects, but also these aspects introduced above are problems that are easy to be ignored in the production process. I hope we can pay attention to them and produce outsourced machined parts that meet the standards, high quality and high precision.

 Main contents of machining quality and accuracy testing The content of machining quality and accuracy testing is divided into many aspects. Inspectors can choose to test all or carry out targeted testing according to the characteristics of their own products. 1. The size and behavior tolerance of each part of the geometry and simple mechanical performance testing. 2. The appearance inspection can be directly judged by the naked eye, observe whether the surface has bumps, bruises, defects and other conditions, and check whether the surface roughness meets the requirements. 3. Observe whether the material of the product meets the requirements, whether the brand is complete and whether the specification is correct. Basic steps of machining inspection 1. Professional inspectors need to undergo pre job training and obtain relevant qualifications before they can engage in full-time inspection work. 2. When inspecting the first toad slice, you should check whether the process paper is a valid version, whether the circulation card material has a material seal, and whether the filling of the third inspection card meets the requirements. 3. Inspectors need to know every step of the processing process very well. 4. Inspectors need to select special machine universal measuring tools and use them correctly according to the processing process requirements. 5. After the first inspection, it is necessary to fill in the identification for filing. During batch inspection, it is also necessary to group the original records for future content search. Precautions for machining inspection 1. When inspecting the long shaft, special attention should be paid to the deformation of the workpiece. In many cases, it is more likely to cause excessive heat due to the improper processing method of the processor, eliminate the stress equipment, and deform the straight line during cooling, exceeding the free tolerance range, resulting in unqualified dimensions. 2. After the detection of slender workpieces, it is necessary to pay attention to the storage and transportation at the same time. Improper operation can easily cause deformation. For example, slender lead screws need to be transported and stored with hangers to prevent parts from deformation. 3. When machining slender holes, the workpiece will have certain requirements for the hole diameter. When the straightness and surface roughness are high, the following points should be paid attention to: (1) Whether the aperture is polygonal can be processed by the central axis grinding method. (2) The roundness and straightness of the section can be measured by measuring together. (3) The surface roughness requirement is not high, which can be judged by visual inspection, or by comparison method, sample block method, etc. 4. When inspecting slender workpieces, such as Fitter's slender holes, the size may be qualified, but there may also be drift, dislocation, etc. Therefore, this requires the inspectors to have rich testing experience and pay attention to the vertical direction.

The cutting part of the tool will be gradually worn under the action of high temperature and high pressure. The causes of tool wear are very complex. It involves mechanical, physical, chemical and gold functions, including abrasive wear, bonding wear, diffusion wear, phase change wear and oxidation wear. Tool wear will affect the surface quality, production efficiency and processing cost. Now let's introduce the main forms of tool wear and the process of tool wear.  Form of tool wear The main forms of tool wear are rake face wear, flank wear and simultaneous front and rear face wear. 1. Wear of rake face When cutting plastic metal, the cutting speed is high and the cutting thickness is large, and the crescent groove is ground on the rake face. When the tool wear continues to expand, it will lead to edge collapse and tool damage. 2. The flank is worn When cutting brittle metals with high hardness, such as low cutting speed and feed rate, flank wear usually occurs. This form of wear occurs on the flank connected with the cutting edge, and the flank with a back angle equal to or less than zero is ground. 3. The front and rear knife surfaces are worn at the same time In the process of cutting plastic metal, this kind of wear often occurs when using medium cutting speed and medium feed rate. Tool wear process 1. Initial wear stage: tool wear is fast in this stage. This is caused by the rough surface of the tool or the surface structure defects. 2. Normal wear stage: in this stage, the contact area increases, the pressure decreases, the wear speed has slowed down, the wear increases evenly with the increase of time, and the cutting is stable. 3. Sharp wear stage: after the normal wear of the tool reaches a certain limit, if you continue to cut, the temperature will increase sharply, the cutting force will increase, the wear will accelerate, and even cause the edge to collapse and damage the tool. In use, it should be strictly stipulated that the tool should be changed before entering the sharp wear stage. Cutting tool dulling standard The tool should not be used again when it is worn to a certain limit, which is called the blunt standard. Generally, the width of the wear band measured on the tool surface later is specified as the blunt standard of the tool. In actual production, it is often judged whether the tool has been blunt according to some phenomena occurring in cutting. During rough machining, you can observe whether there are bright bands on the machined surface, whether the color and shape of chips are different, whether there are abnormal sounds, etc. During finish machining, observe whether the roughness of the machined surface changes and measure the size and shape accuracy of the parts. In mass production, due to the stable cutting conditions, the tool dulling standard can be determined through process tests, and the dulling standard can be transformed into the easily controlled number of machined parts or cutting time, so as to forcibly change the tool edge grinding to ensure that the tool does not enter the stage of sharp wear. Due to different processing conditions, the blunt standards are also different. The standard value of finish machining is less than that of rough machining. Different materials and types of cutting tools have different blunt standards.

As a beginner in the machining industry, do you often get confused by the "slang" in the mouth of some "old drivers"? "Light", as mentioned in the title of this article, is a typical representative. "Light" usually refers to the last process of finishing. The source of this usage is said to be the surface finish of the workpiece. Its derivatives include "light knife" (finishing tool) and so on. The scope of "light" is very wide, which can refer to the final step of fine grinding, fine milling or fine turning process in processing. In the implementation of "light once", there are high requirements for machining accuracy. How about the "slang" in the machining industry? Isn't it simple? There are many examples like this. Let's make a simple inventory. "Pulling waste" and "opening up rough" The words "waste pulling" and "rough opening" have the same meaning and refer to the rough machining steps in machining. Compared with finish machining, rough machining requires less precision and higher machining speed. The word "reclaiming wasteland" may come from "reclaiming wasteland" or "reclaiming wasteland". It is thought to be relatively grounded. It is widely used in the machining industry in Northeast China. The word "bold" is popular in southern China. "Dip in fire" and "stuffy fire" "Dip in fire" is what we usually call quenching, "quench fire" is what we usually call tempering. These are important processes in heat treatment. The quenching stone austenitizes the steel and then cools it at an appropriate rate to make the workpiece undergo martensite and other unstable structural transformation. Tempering is a heat treatment process in which the quenched workpiece is heated to an appropriate temperature below the critical point for a certain time, and then cooled by a certain method to obtain the required structure and properties. "Tao", "silk" and "Ge" Literally, these words should represent a certain unit. Indeed, they are all length units, "Dao" and "silk" refer to millimeters, while "Ge" refers to 1mm. Among them, the rough name "Dao" is more popular in the machining field in Northeast China, just like the forthright character of northeast people; And "silk", a kind of elegant calling principle, is popular in the machining field in the south, which reminds people of the softness of southerners. "Milling" and "air milling" These two are about machining tools. "Milling" does not mean milling cutter, but reamer. It is a rotary tool with one or more cutter teeth, which is used to cut the thin layer of metal on the surface of the machined hole. It is a rotary finishing tool with a straight edge or a spiral edge, which is often used for hole enlarging or hole repairing. "Air mill" is a rotating tool similar to a milling cutter installed on the air wheel, which is usually operated and processed by fitters. "Le Dao", "Da Dao" and "Wei Dao" These three words are all some faults of cutting tools in the process of machining. Because of extrusion deformation, the "cutting tool" has plastic deformation and can no longer be used for cutting. This kind of accident usually occurs in milling cutters. "Cutting" means that the tool has cracked or broken, and it can no longer be used. It is not the tool that is damaged, but the workpiece. It refers to that the tool plunges into the workpiece, causing the workpiece to be damaged. In addition to the above, there are many "slang" in machining, which is difficult to summarize. All beginners of machining should slowly understand their meanings through their own learning and accumulation, so as to better integrate into your circle.

1、 Grinding characteristics of titanium alloy (1) High grinding temperature. The deformation coefficient of titanium alloy is small, and extrusion chips are often formed, resulting in serious friction. The stress is concentrated near the cutting edge, producing a lot of heat; The coefficient of thermal conductivity and thermal conductivity of titanium alloy is small, which is only 1/5 of that of carbon steel, making it difficult to emit grinding heat and easy to cause excessive temperature in the grinding area. Under the same conditions, the grinding temperature is about 1.5-2 times that of 45 steel, up to 1000 degrees. (2) Titanium alloy has high chemical activity at high temperature. Due to the high grinding temperature, the grinding debris is easy to react with oxygen, nitrogen and other elements in the air to form a hard and brittle layer, which accelerates the wear of the grinding wheel. (3) Because titanium alloy has high chemical activity. Coupled with the local high temperature and high pressure in the grinding area, the adhesion between the abrasive particles and the metal surface occurs due to the affinity, which accelerates the wear of the grinding wheel, affects the quality of the machined surface, and it is difficult to ensure the dimensional accuracy. (4) Large grinding force. Generally, the grinding force per unit width is about 2-3 times that of ordinary carbon steel, and its radial force is greater than the tangential force. (5) Easy to burn and crack. Due to the high grinding temperature, large thermal stress is generated on the grinding surface, which not only causes grinding burns, but also grinding microcracks. These microcracks are hairline shaped, and their direction is roughly perpendicular to the grinding direction, and the grinding surface presents yellowish brown spots. Due to the influence of grinding heat, residual tensile stress is produced on the workpiece surface, which reduces the fatigue strength of parts and affects the service life of parts. (6) Low production efficiency. During grinding, the grinding ratio is very low because the grinding wheel is easy to passivate, adhere and block. Under the condition of ensuring the quality of the workpiece, only the productivity can be reduced. 2、 Selection of grinding wheel When cubic boron nitride wheel is used to grind titanium alloy, the grinding temperature and residual stress on the machined surface are very low, which can effectively inhibit the generation of cracks, and obtain higher workpiece surface quality and grinding efficiency. Wheel bond: resin bond should be used for green silicon carbide wheel. Because the grinding force and grinding temperature of ceramic bonded wheel are higher than those of resin bonded wheel. Generally, when the hardness of the grinding wheel is at the J-L level, the productivity is higher. When a soft grinding wheel is selected, its grinding force and grinding temperature are lower, but the grinding wheel consumption increases significantly. In addition to cooling and flushing, the grinding fluid is required to inhibit the adhesion and chemical action of titanium and abrasive particles when grinding titanium alloys. Water soluble grinding fluid containing a variety of extreme pressure additives should be selected. For example, the grinding fluid containing chlorine extreme pressure additive has strong lubricating permeability and can inhibit the occurrence of grinding cracks and adhesion. When using, mainly increase the flow and pressure of grinding fluid; The capacity of the water tank should be large enough to keep the grinding fluid at a low temperature. In addition, when grinding titanium alloy, the temperature is high and the chips are flammable. When using oil grinding fluid, pay attention to safety and fire prevention.