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

In milling, the accuracy of milling machine itself directly affects the size and shape position accuracy of machined parts. Therefore, in addition to the regular accuracy inspection of the milling machine, the faults of the milling machine should be found and eliminated in time. For the common fault phenomena and causes of milling machines, the solutions are also different. 1. Great vibration during milling It cannot be processed according to the conventional milling amount, and it is easy to cut during milling, and the surface roughness value of parts is large, so forward milling cannot be used. There are two main factors causing large vibration: one is the looseness of the spindle and the poor rigidity of the cutter shaft system; The other is the looseness of the workbench and the poor rigidity of the workpiece fixture system. (1) Loose spindle: whether the spindle is loose can be determined by checking the radial circular runout and axial runout of the spindle. The main reasons for the loosening of the main shaft are the excessive clearance of the main shaft bearing and the pitting of the raceway of the main shaft bearing. For the solution of spindle looseness, the former can readjust the clearance of spindle bearing to make it meet the specified requirements, while the latter needs to replace the bearing. (2) Worktable looseness: the main reason for worktable looseness is that the gap between the guide rails of the worktable is too large. The solution is to readjust the guide rail clearance. In addition, if the clearance is too small, there will be crawling when the workbench moves at low speed. The guide rail inlay is not straight, which will also cause the workbench to move unsteadily, so it is necessary to repair or replace the inlay with a new one. (3) The clearance between the lead screw and nut of the workbench is large: the solution is to readjust the clearance and tighten the relative position between the fastening screw and the fastening worm and the adjustable nut. (4) Other factors: the taper of the milling cutter head is not consistent with the taper hole or the milling cutter head is not tightened. The solution is to check and repair the taper; Tighten the milling cutter head. The foundation of the machine tool is poor, and the solution is to rebuild the foundation as required. The vibration of the main motor is large, and measures are taken to dynamically balance the motor rotor. The main drive gear is noisy. The solution is to check and replace the unqualified gear. 2. The tension is uneven when the workbench is moved longitudinally by hand in the whole process The main causes are bending of the table lead screw, local wear, or the axis of the lead screw is not parallel to the longitudinal guide rail. Solution: for the bending or local wear of the lead screw, the lead screw should be straightened, repaired or replaced; If the axis of the lead screw is not parallel to the longitudinal guide rail, the lead screw shall be re installed and the locating pin hole shall be reamed. 3. The lifting table crawls when lifting at low speed The reason is that the pressing iron of the column guide rail is not loosened and the lubrication is poor. The solution is to loosen and adjust the pressure iron and good lubrication. 4. Worktable rapid feed cannot be disengaged In the actual operation process, it is often used to quickly return or move the feed (fast forward) with a large empty distance to shorten the non cutting time. When starting the slow working feed after the rapid feed, the fault that is still the rapid feed is regarded as the rapid feed cannot be disengaged. Although the probability of this kind of failure is very small, it is very dangerous and should be paid special attention. The main reasons are that the remanence of the electromagnet is too large or the spring force of the slow return is insufficient. Repair and adjustment should be carried out by electricians and mechanics. 5. Feed system safety clutch failure When the feeding system of the machine tool is overloaded, the feeding movement cannot stop automatically. The reason for the failure of the safety clutch is that the torque regulated by the clutch is too large. The solution is to readjust the safety clutch.

In the process of machining, the tool is the direct participant of cutting, and it is also the most active factor in the whole machining process system. How to give full play to the advantages of cutting tools and reduce processing costs is an important part of tool management. Tool selection Tool selection includes the choice of tool material, structure and cutting parameters, which will directly affect the production efficiency, processing quality and tool life. When selecting models, it is necessary to integrate various factors such as cost input, project time node, production pace and capacity demand from the perspective of project management; In combination with the technical point of view, that is, the material and geometric characteristics of the processed object, processing equipment, accuracy and other conditions, analyze together and select the appropriate cutting tools. Tool material upgrade Using polycrystalline diamond tools to cut aluminum alloy workpieces and ceramic or cubic boron nitride tools to cut cast iron workpieces can greatly improve the cutting efficiency and reduce the tool cost. In addition, coated tools have the advantages of high surface hardness, good wear resistance, stable chemical properties, heat and oxidation resistance, small friction coefficient and low thermal conductivity, which can bring qualitative improvement to tool performance. Localization of cutting tools In recent years, the domestic tool industry has developed rapidly, and the product quality has been significantly improved. In particular, the manufacturing level of cutting tools made of high hardness materials such as diamond and cubic boron nitride has caught up with the foreign advanced level, which can replace imported cutting tools, and the price has obvious advantages. On the premise that the performance can meet the processing needs, choosing domestic tools as much as possible can greatly reduce the cost of tools, and provide more convenience in terms of delivery time, after-sales service, etc. Cutting optimization If you want to reduce the tool cost, but you can't sacrifice the processing quality and efficiency, you need to find a balance between the three. Generally speaking, it can be achieved by optimizing cutting parameters and cutting paths. If necessary, the geometry of the tool needs to be changed. When setting cutting parameters and paths, the speed and feed of the tool can be adjusted according to the changes of cutting load and cutting force, so as to complete the machining with the optimal cutting parameters and paths. For example, variable speed cutting in rough machining can effectively reduce the load of machine tools, while variable speed cutting in finish machining can significantly optimize the cutting quality, and the cutting efficiency of both machining methods can be improved by variable speed cutting. In addition to theoretical speculation, the method of cutting optimization can also be simulated. Simulation processing adopts software with specific functions. By establishing a model and previewing the whole cutting process in the computer, it can well simulate various conditions occurring in processing and provide reference for cutting optimization. Related software includes NC programming, tool path simulation software Mastercam, tool simulation software advantagedge, etc. Secondary utilization of cutting tools Not all tools must be scrapped once they are damaged. Sometimes we can find ways to reuse them to reduce the cost of replacing tools. For example, the precision machining blade can be used for semi precision or rough machining after use; There are also some right-hand cutters, due to structural limitations, some of the cutting edges are worn and cannot be used. The non worn cutting edges can be used by making a left-hand cutter head; In addition, drill bits, taps and blades can be reused through grinding. Tool management In addition to technical improvements, management progress can also reduce costs. Specifically, it includes tool selection, test, purchase, adjustment, grinding, repair, inventory setting and control, tool life control, tracking analysis and solution of processing problems in production, tool optimization and improvement, etc. This is a complex process, and a perfect tool management system needs to be established to ensure that the process is stable, controllable and efficient.

Machined parts need to be inspected after production, which can not only detect the defective products in processing and production, but also provide beneficial help for the use of products in subsequent work. Machining inspection report is one of the important documents delivered to customers. Then, what is the factory inspection report of mechanical parts processing? 1、 General 1. Inspectors need to have professional knowledge and practical work experience, and also need to meet the requirements of leading products for inspection work. 2. The measuring instruments used by the inspectors need to be verified by the measurement department and within the specified verification cycle. 3. Before accepting products, inspectors need to be familiar with relevant drawings and technical documents, and understand the key dimensions of parts and the key points of assembly. 4. The inspectors need to judge the parts in strict accordance with the requirements of the drawings and technical documents. 5. The inspectors shall mark the products in process in the workshop as required. 2、 Inspection system 1. First inspection system: for the first part processed by each operator, it is necessary to conduct a comprehensive inspection and keep it. 2. Patrol inspection system: ensure that key parts can be controlled throughout the process. 3. Transfer inspection system: parts that are about to be transferred to the next process should be inspected to prevent unqualified products from flowing into the next process. 4. Completion inspection system: for products that are about to be warehoused after production, completion inspection shall be carried out, including size and shape, whether there are missing processing procedures, etc. 3、 Inspection method 1. Basic dimension and shape inspection (1) Measurement of outer diameter When measuring the outer diameter, it is necessary to measure and record in two parts in the circumferential direction. When the length of the part with the same diameter is greater than 50mm, the straightness should be checked, the working surface of the knife edge ruler should be in contact with the outer diameter bus, the width of the building should be observed, and then it should be judged by comparing with the standard optical gap. (2) Measurement of inner diameter When measuring the inner diameter of parts, only measure in three parts in the circumferential direction, and make records at the same time. When the length of the same diameter is greater than 40mm, the cylindricity should be checked, and the measurement should be made at two positions with a large interval within the length direction of the same diameter. Calculate the cylindricity error. (3) Length measurement External thread measurement: the pitch diameter of external thread is measured with thread ring gauge or three pins, and the minor diameter is detected with thread ring gauge (go gauge). Internal thread measurement: the external diameter of internal thread is inspected with thread plug gauge (go gauge), and the medium diameter is inspected with thread plug gauge. The large, medium and small diameter of threads shall be accepted according to the accuracy level required by the drawing. The effective length tolerance of thread: according to the requirements of hy/qt001 fastener inspection specification. 2. Detection of surface plane (1) Surface roughness detection: sample block comparison method is used for comparison and judgment. (2) Inspection of Flatness: use the marking method to detect. Place three adjustable supports on the flat plate, place the measuring surface of the part upward on the support point, adjust the support point, and make the three points equal in height. The peak and valley values measured by marking the table are the flatness error of the plane.

Whether the tool used is suitable depends not only on the unit price, service time and renewal frequency of the tool, but also on the value created by the tool in unit time. For the mold processing industry, the concept of a new generation of machine tools and cutting tools has completed research and development, is entering the stage of practical production and application, and has a far-reaching impact on the entire mold manufacturing industry. As a manufacturing enterprise producing molds, sometimes it doesn't have to passively accept the common cutting tools in the market around it. Instead, it can actively introduce new cutting tool technology through cooperation with cutting tool suppliers and find cutting tools suitable for its own processing type to improve the production process, improve the processing quality and improve the processing efficiency. Process of introducing tool technology The process of mold manufacturing enterprises investing in the introduction of new tool technology is not as complex as expected. Mold manufacturing enterprises only need to establish cooperative relations with tool manufacturers and their professional technicians. Tool experts are usually exposed to a large number of machining examples, and have accumulated rich experience in which kind of machining is suitable for what kind of tools to use, as well as the advantages and disadvantages of common and uncommon tool types. According to the processing needs of enterprises, combined with the latest tool design and production concepts, they can recommend the most handy processing tools for enterprises. Tool introduction cost For the introduction of new tool technology, mold manufacturing enterprises are probably most worried about the introduction cost of tools. As long as it is done properly, the introduction of new tools will increase the cost on the surface, but in fact, on the contrary, it can play a great role in saving tool costs. Because the cutting tools developed with the latest technology can provide processing solutions with higher efficiency and better economy. By applying the latest cemented carbide blade pressing technology, tools and blades with more cutting edges and higher strength can be produced, so as to make better use of cemented carbide materials. Such cutters usually have a longer service life and can produce greater value per unit time. Taken together, this is a good deal. Import tool application example The processing material of a mold manufacturer is annealed aisi/sae 4140 low alloy steel mold. In the process of tying up the rough machining die base plate, slope milling and groove milling are required to carry out heavy-duty rough milling on the workpiece. The existing cutting tools in the market can not achieve the desired processing effect, so businesses seek solutions from a cutting tool supplier. After analyzing the machining process, the tool supplier recommended a sleeve milling cutter specially designed for rapid metal cutting as a possible solution. This kind of cutter has the advantages of short installation time, long service life and high feed rate, which is suitable for rough milling. The geometric structure of the large circular arc cutting edge enables the tool to achieve high feed machining even when each tooth bears a large chip load. At the same time, the bottom of the blade can be firmly clamped in the fitting hole of the cutter base to increase the maximum cutting force that can be borne. After this kind of tool is assembled, it can not only mill at an unconventional feed rate, improve the metal removal rate, but also improve the processing stability and the completion efficiency of processing projects. The reduction of working hours enables the workshop to have enough production capacity to accept more additional processing tasks, and the investment of enterprises in introducing new technologies quickly brings several times the income.

Heat treatment of mechanical parts is mainly to improve the mechanical properties of parts, such as hardness, wear resistance and strength, in order to better realize the use value of products. The quotation of heat treatment will vary according to different materials, quantities, heat treatment methods, precision of parts, etc. In order to regulate the market, ensure the stability of economic order and avoid unfair competition, a price management opinion for the heat treatment industry was formulated. This opinion is widely used in the quotation of heat treatment of small parts and is an important basis for the quotation of heat treatment of small parts. 1、 Processing cost of heat treatment The processing cost of heat treatment mainly consists of basic power consumption, auxiliary materials, labor costs and other factors. In the heat treatment process, the basic power consumption and basic industrial power consumption are taken as the cardinal number, and are calculated according to the characteristics of various heat treatment processes and implementation conditions. The calculation formula needs to refer to the comprehensive evaluation index system and management of heat treatment industry: Basic power consumption = standard industrial power consumption * conversion process coefficient * heating mode coefficient * production mode coefficient * industrial material coefficient * loading coefficient 2、 Quotation of processing technology content The processed technology was known by the Han Dynasty as the technological level or technical level of the processed parts. The technical level is often divided into three levels: high, intermediate and low. Advanced: it mainly adopts important parts such as tools and dies, spindles and guide rails processed by vacuum or laser, with a coefficient of 1.5. Intermediate: various mechanical parts of controllable atmosphere heat treatment, ion nitriding, gas nitriding, soft nitriding, high and medium frequency, with a coefficient of 1.2. Low level: quenching and tempering, normalizing, annealing, well type furnace carburization, salt bath furnace quenching, etc. of general equipment, with a coefficient of 1.0. 3、 Guide price for quotation of heat treatment of small parts 1. Annealing class (1) High temperature annealing: 1.0-2.0 yuan (2) Complete annealing, spheroidizing annealing, isothermal annealing: 1.0-2.5 yuan (3) Recrystallization annealing, high temperature tempering, artificial aging: 0.4-1.4 yuan (4) Bright annealing and packing annealing: 1.2-2.5 yuan 2. Normalizing class (1) Box furnace normalizing: 0.8-1.5 yuan (2) Well furnace normalizing: 1.0-2.0 yuan (3) Salt bath normalizing: 1.4-2.0 yuan 3. Conditioning class (1) Box furnace and trolley furnace (less than 950 ℃): 1.0-2.5 yuan (2) Box furnace and trolley furnace (more than 950 ℃): 1.5-5 yuan (3) Mold and high alloy steel: 3-6 yuan 4. Salt bath furnace quenching (salt bath, alkali bath cooling plus 30%) (1) Carbon steel and low alloy steel parts: 2-4.5 yuan (2) High alloy steel (mold, etc.): 2.7-6 yuan (3) High speed steel (three times tempering and cleaning): 8-20 yuan (4) High alloy steel: 5-8 yuan 5. Protective quenching (1) Controllable atmosphere furnace heating: 3-4 yuan (2) Well cementation furnace protection heating: 1.5-3.3 yuan The above are some common quotation methods for heat treatment of small parts. In the process of heat treatment, the quotation personnel need to select the quotation method according to the specific information of the product and the process used in the treatment, so as to ensure the accuracy of the quotation.

The emergence and application of the third generation random copolymer PP-R pipes marks the maturity of polypropylene pipes. Its superior performance is that it has the last laugh in the front PK with the traditional galvanized pipe, and has the opportunity to show its talents in fields such as floor heating, central air conditioning, cold and hot water. The processing of PP-R pipes needs to strictly control the processing temperature, cooling rate, die compression ratio and geometric size changes. Let's have a detailed look below. Influence of processing temperature Polymer PP-R materials have three states: glass state, high elastic state and viscous flow state at different temperatures, and their mechanical properties are also very different. When the raw material enters the barrel, it is in glass state. From the compression section to the homogenization section, it must change from high elastic state to viscous flow state, and from high elastic state to glass state when it is cooled from the outlet mold to full sizing. Every state change is controlled by temperature. If the temperature is too low, the brittleness of the pipe will be too large at low temperature, and the compressive strength will be reduced; If the temperature is too high, it will cause excessive plasticization and prone to thermal aging. Therefore, strictly controlling the processing temperature is very important to ensure product quality. Effect of cooling rate The good impact resistance of PP-R pipes comes from the voids between its internal molecules, which can play an effective buffer role when impacted by external forces. The cooling rate during processing plays a decisive role in the formation of appropriate voids in the pipe. During the cooling process, the relative positions of polymer chains in the material are rearranged. If the cooling speed is too fast, the gaofeizi chain has been frozen before it enters the best position, which not only cannot obtain the ideal impact resistance effect, but also causes the problem of stress concentration. Usually, constant temperature water tank is used to control spray for cooling during processing, and gradient gradual cooling method is used to make the materials pass through multiple water tanks with different temperatures in turn, so as to slow down the cooling rate, obtain high enough impact resistance and prolong the service life. Influence of die compression ratio Pure polypropylene material has obvious pressure orientation characteristics, that is, the polymer is orderly arranged in one direction, and its compression resistance is very strong; And in the direction perpendicular to it, the arrangement is more disordered, and its compressive capacity is much weaker than the former. In order to solve this problem, the compression ratio of the die was adjusted in the production of PP-R pipe, and the random copolymerization method was used to break the original orientation characteristics and make its compressive capacity tend to be consistent in all directions. The manufacturer uses the inner spiral multi channel head to make the plastic melt cross rotate into a dynamic flow direction before exporting the mold into the blank. Using this mold with good material, high precision and advanced design, combined with the selection of high-quality PP-R raw materials, we can get an isotropic ideal controlled state, without affecting the plasticizing effect, and improve the quality of the pipe. Influence of geometric dimension change In the processing technology of PP-R pipe, the geometric size, especially the outer diameter size, has a great impact on the service performance. It is easy to understand that if the wall thickness of the pipe is different for the sizing sleeve of the same size, even if the cooling water temperature, cooling rate and vacuum degree are the same, the shrinkage rate will be different. The thicker the pipe wall, the greater the shrinkage, and the smaller the pipe wall, the smaller the shrinkage. According to previous experience, when the pipe wall thickness is 6.8 mm, the processing error is 0.7 mm; When the thickness of the pipe wall is 12.5 mm, the machining error reaches 1.4 mm. In addition, the geometric dimension also has a certain impact on the use of pipes. When the outer diameter of the pipe is too large, too many overflow edges will be formed during welding, reducing the diameter of the pipe; When the outer diameter of the pipe is too small, the bonding strength is low when welding, and the overflow is too small, and the peripheral auxiliary effect is poor. Therefore, the outer diameter size should be strictly controlled to ensure the quality of pipes.

In order to ensure the flexibility and versatility of parts, it is necessary to have strict requirements on the machining accuracy of parts. With the development of science and technology, the processing of parts can be completed by CNC lathe. Only the graphics and process parameters of parts need to be input into the CNC system in the form of data, so that the machine can complete the whole processing process, and various required parts can be manufactured, which is widely used in life. However, the quotation of CNC lathe processing is relatively complex and prone to errors, so how to accurately quote CNC lathe processing has become the focus of many people's attention. The main factors that make the quotation of CNC lathe more complicated are as follows: 1. There will be obvious differences in the processing batch, single piece processing and mass processing prices of CNC lathes. 2. Complexity of the workpiece: the complexity and tolerance of the workpiece, especially the geometric tolerance, that is, the accuracy level. The higher the accuracy, the more complex the process, the higher the price, but this is not absolute. This also has a great impact on the quotation. 3. Labor hour price in the market: due to the location and environment of the factory, there will be a big gap in the labor hour cost of workers. 4. Material cost: material quality, easy cutting degree, etc. These factors all affect the quotation, so the quotation is a comprehensive problem. Sometimes the price of processing waste has to be calculated when the batch is large, and sometimes the waste is often a large quotation expense. Due to the flexibility of machining, that is to say, a part can have many kinds of process arrangements, and the results of quotation will be very different. Quotation method of CNC lathe We take the screw processed with raw materials as an example. First of all, the outer diameter of the car needs a knife. Record the speed and feed rate, and then you can calculate that the time of a knife is 24 ÷ (speed × Feed rate) is about 2min (24= tool 20 + tailing width and cutter width). The next step is to turn the screw thread. When you know the pitch in the thread, you can calculate the length of the turn. Add the estimated turn of the tailing width, and calculate the time according to the speed. The return time of each knife is generally calculated according to the time. Add up to turn the screw thread, and you can calculate the time of losing the knife. The last step is to cut off, and then add the time of the above steps to get the corresponding working hours. And this method of calculating working hours is more accurate. Attachment: Hourly processing price of CNC lathe 1. C616 lathe: Φ three hundred and twenty × 750~1000, 22 yuan / hour 2. C6140 lathe: Φ four hundred × 1000~2000, 26 yuan / hour 3. J1-mazak lathe: Φ four hundred and sixty × 1000~2000, 30 yuan / hour 4. C6150 lathe: Φ four hundred and sixty × 1000~2000, 32 yuan / hour 5. C630 lathe: Φ six hundred and thirty × 1000~2000, 42 yuan / hour 6. C650 lathe: Φ eight hundred × 1500~5000, 60 yuan / hour

Stamping, together with forging, is called forging processing, both of which belong to the category of plastic processing. They both use the hammer head, anvil block, punch of forging machinery, or exert pressure on the blank through the mold to produce plastic deformation, so as to obtain the machined parts with the required shape and size. In the world, 60% to 70% of steel is processed by stamping, which is widely used in the field of industrial manufacturing. In the process of stamping, scrap is a common phenomenon, and its reasons are various. This article will analyze various possible reasons and propose feasible solutions to minimize the production of stamping waste and help readers improve the yield of processing. Characteristics of stamping processing Stamping processing is a production technology of product parts with the help of the power provided by conventional or special stamping equipment, so that the sheet metal is directly affected by the deformation force in the mold and deforms, so as to obtain the required shape, size and performance. Stamping can be divided into cold stamping and hot stamping according to the temperature. The former is often used to process thin plates, while the latter can play a better effect on plates with high deformation resistance and poor plasticity. Stamping can produce workpieces with stiffeners, stamping ribs, undulations or flanging that are difficult to manufacture by other methods, which is very helpful to improve the rigidity of workpieces. Due to the use of precision dies, stamping parts can achieve complex geometry and micron level high precision, which generally does not need, or only requires a small amount of subsequent cutting. Its surface quality is better than that of castings and forgings. Causes of stamping scrap Materials, dies and equipment are the three elements of stamping processing. The die used for stamping is called stamping die, which is a special tool for batch processing of materials into required stamping parts. Only when the three elements are combined and matched with each other, can high-quality stamping parts be obtained. If the three do not cooperate properly, it may cause the scrap of stamping parts. For example, using low-quality raw materials, it is difficult to eliminate the production of waste products from the root. Moreover, the installation, debugging or use methods of stamping dies are inappropriate; After long-term use, the clearance of the die has changed or its working parts and guide parts have been worn; Or because the punching die has been impacted and vibrated for a long time, the fastening parts have become loose, so that the installation positions of the punching die have changed relatively. These reasons will lead to problems in the punching die, thus scrapping the punching parts. In addition, the operators of stamping process make mistakes, fail to correctly feed the strip along the positioning according to the operating procedures, or fail to feed according to a certain gap, which are also common reasons for the scrapping of stamping parts. Main measures for waste prevention First of all, the raw materials used must be strictly inspected, and their specifications and brands must be checked to ensure that the quality of the materials is consistent with the specified technical conditions. If it is a precision punch press, if conditions permit, the workpiece with high dimensional accuracy and surface quality requirements should also be tested and checked. Secondly, before stamping, the press, die and other tooling equipment used should be checked to ensure that they work under normal working conditions. In addition, a strict inspection system should be established in the production process. The first piece of stamping parts must be comprehensively inspected and can be put into production only after passing the inspection. If it is unqualified, find out the reason and correct the processing method in time. At the same time, patrol inspection should be strengthened, and accidents should be handled in time. Finally, the operators should strictly abide by all links specified in the process specification, such as the transfer of workpieces and blanks must use appropriate station tools, otherwise the workpiece surface will be crushed and scratched, affecting the surface quality of the workpiece; In the process of stamping, it is necessary to ensure that the mold cavity is clean, and the workplace should be organized, and the processed workpieces should be placed neatly.

The machining accuracy and machined surface quality of parts are two important aspects of the machining quality of parts. Part quality is one of the contents that need to be inspected after production and processing. The quality of parts has a great influence on the production of products. Therefore, the quality inspection of parts is an essential and important process in production. 1、 Machining accuracy of parts Machining accuracy is the actual geometric parameters of parts after machining, such as shape, size and the mutual position of surfaces. The consistency of these parameters with the ideal geometric parameters. The higher the degree of conformity, the higher the machining accuracy. The machining accuracy of parts mainly includes dimensional accuracy, shape accuracy and position accuracy. 1. Dimensional accuracy The degree to which the actual values of the diameter, length, surface distance and other dimensions of the part are close to the values is the dimensional accuracy, which is mainly controlled by dimensional tolerance. 2. Shape accuracy Shape accuracy is the degree of conformity between the actual shape and the ideal shape of the line and surface on the part. The evaluation items of shape accuracy include straightness, flatness, roundness, cylindricity, West Bank profile and surface profile. 3. Position accuracy Position accuracy refers to the actual position of points, lines and surfaces on the part after machining and the degree of compliance with the ideal position. During the inspection, the parallelism, verticality, inclination, coaxiality, symmetry, position, circular runout and total runout shall be inspected according to the provisions of gb/t1182-1996. 2、 Machined surface quality of parts Machining surface quality mainly includes the geometric characteristics of the machined surface and the changes of the material of the machined surface layer. In fact, the surface of machined parts is not an ideal smooth surface. There are different degrees of surface roughness, cold hardness and cracks on its surface. These will affect the accuracy, wear resistance, fitting accuracy, corrosion resistance and fatigue strength of mechanical parts, and even endanger the service performance and life of products. 1. Influence of surface quality on wear resistance of parts The surface roughness is too large, the actual pressure on the contact surface increases, and the rough peaks bite, crack and cut each other, so the wear is intensified. If the surface roughness is too small, it will also lead to increased wear. Because the surface is too smooth, the lubricating oil cannot be stored, and the oil film cannot be formed on the contact surface, molecular bonding is easy to occur, which intensifies the wear. 2. Influence of surface quality on fatigue strength of parts The greater the surface roughness, the worse the ability to resist fatigue damage. It has a great influence on the fatigue strength of parts under alternating load. Under the action of alternating load, the concave part of surface roughness is easy to cause stress concentration and fatigue cracks. The smaller the surface roughness value is, the less defects are avoided, and the better the fatigue resistance of the workpiece is; On the contrary, the rougher the machined surface, the deeper the striation marks on the surface, and the smaller the radius of the bottom of the striation, the worse its ability to resist fatigue damage. 3. Influence of surface quality on working accuracy of parts The greater the surface roughness, the lower the fitting accuracy. The surface layer has large residual stress, which will affect the stability of their accuracy. 4. Influence of surface quality on corrosion resistance of parts The rougher the part surface is, the more corrosive substances are likely to accumulate, and the deeper the valley is, the stronger the effect of penetration and corrosion will be. Therefore, in order to improve the corrosion resistance of parts, the common method in production is to reduce the surface roughness of parts.

NC sheet metal processing mainly includes single stamping, continuous blanking, single or continuous forming, nibbling and array forming. In this article, we will introduce the specific contents of these methods, as well as the process characteristics of sheet metal processing. Specific content of NC sheet metal processing Single stamping is a stamping process that includes arc distribution, grid holes, etc. in a single time. Continuous blanking is divided into continuous blanking in the same direction and continuous blanking in multiple directions. Continuous blanking in the same direction adopts the mode of die overlapping for processing, which is suitable for the processing of long holes. In contrast, multi-directional continuous blanking is more suitable for machining large holes with small dies. Single forming processing is a sheet metal processing method of shallow drawing and one-time forming according to the nature of the mold, and the single forming processing requires more times of stretching than the former, which is more suitable than the mold forming. Nibbling refers to the continuous arc punching process with small circular die and small step distance. Finally, array forming is suitable for processing multiple workpieces on large plates, and the types of workpieces can be the same or different. The application of numerical control technology in sheet metal processing industry shows unique advantages and characteristics, which mainly includes the following aspects: Low threshold, easy to use and less investment First, the threshold is low, which is not only relatively simple and convenient to use, but also has less investment cost. NC sheet metal processing has its own unique advantages in the processing of all kinds of sheet metal parts, especially in the case of automatic processing of machined parts with complex and irregular shapes, or sheet metal parts. In addition, NC sheet metal can also automatically process holes of different sizes and shapes according to the requirements of the drawings, or use small punching dies to process the contour curves of various shapes with large sizes in the way of small step punching. Compared with traditional sheet metal metallography, the die used by NC sheet metal technology is simpler, but the processing range is wider and the processing capacity is stronger. For sheet metal parts with special processing requirements, such as shallow stretching, flanging holes, etc., as well as large-scale processing needs, it can also win, and create good economic benefits for processing enterprises. Stable quality and high machining accuracy The product quality of NC sheet metal processing is more stable than that of traditional sheet metal processing, and the processing accuracy is also higher. The workpiece processed by NC sheet metal has better flatness than the traditional sheet metal workpiece, higher punching accuracy and less burr. The stability and accuracy of product forming quality have been well strengthened. The processing speed is greatly improved Using automatic control system for NC sheet metal processing can realize the small batch processing of the same workpiece and the simultaneous processing of different parts, and the processing speed is faster than that of traditional sheet metal. This function effectively improves the efficiency of sheet metal processing. In addition, NC sheet metal processing also reduces the subsequent processing and other links, and realizes the NC integrated processing of sheet metal parts, which greatly improves the production efficiency and reduces the input of production costs.