Stamping technology is a kind of production technology which makes the sheet metal deform directly by deformation force in the die with the help of the power of conventional or special stamping equipment, so as to obtain product parts with certain shape, size and performance. Sheet metal, die and equipment are the three elements of stamping. According to the processing temperature of hot stamping, it can be divided into hot stamping and cold stamping. The former is suitable for plate processing with high deformation resistance and poor plasticity; The latter is carried out at room temperature and is a common stamping method for thin plates. It is one of the main methods of metal plastic working (or pressure working) and also belongs to material forming engineering technology.
The die used for stamping is called stamping die, or stamping die for short. Stamping die is a special tool for batch processing materials (metal or nonmetal) into required stamping parts. Stamping die is very important in stamping. Without the required stamping die, it is difficult to carry out mass stamping production. Without advanced stamping die, advanced stamping technology cannot be realized. Stamping technology, die, stamping equipment and stamping materials constitute the three major elements of stamping processing, and only by combining them can stamping parts be obtained.
Basic introduction Chinese name: stamping mbth: sheet metal forming; ; Stamping Note: chòng yā full name: cold stamping application field: automobile production and processing characteristics, existing problems, solutions, process classification, separation process, forming process, materials, molds, special equipment, lubrication, safe production and processing characteristics Compared with castings and forgings, stamping parts are thin, uniform, light and strong. Stamping can produce workpieces with stiffeners, ribs, corrugations or flanging that are difficult to manufacture by other methods, so as to improve their rigidity. Due to the adoption of precision mould, the precision of workpiece can reach micron level, with high repeatability and consistent specifications, and it can punch holes and bosses. Generally, cold stamping parts are no longer cut, or only a small amount of cutting is needed. The precision and surface state of hot stamping parts are lower than those of cold stamping parts, but they are still better than those of castings and forgings, with less cutting. Stamping of stamping parts is an efficient production method. Using compound die, especially multi-station progressive die, multiple stamping processes can be completed on one press (single station or multi-station), and fully automatic production from uncoiling, leveling and punching to forming and finishing can be realized. High production efficiency, good working conditions and low production cost. Usually hundreds of pieces can be produced per minute. Compared with other mechanical processing and plastic processing methods, stamping has many unique advantages both technically and economically. The main performance is as follows. Stamping tee (1) has high production efficiency, convenient operation and easy mechanization and automation. This is because stamping depends on stamping die and stamping equipment to complete the processing. The number of strokes of an ordinary press can reach dozens of times per minute, and the high-speed pressure can reach hundreds or even thousands of times per minute. Every stroke of stamping may be punched. (2) During stamping, because the die ensures the accuracy of the size and shape of the stamping parts, it generally does not damage the surface quality of the stamping parts, and the die life is generally long, the stamping quality is stable, the interchangeability is good, and it has the characteristics of "identical". (3) Parts with large size range and complex shapes can be processed by stamping, such as the second hand of clocks, the longitudinal beam of automobiles, panels, etc. The cold deformation hardening effect of materials during stamping makes the stamping strength and stiffness higher. (4) Stamping generally does not produce chips and waste materials, requires less materials, and does not need other heating equipment. It is a material-saving and energy-saving processing method, and the cost of stamping parts is low. Because stamping has such advantages, stamping technology is widely used in various fields of national economy. For example, aerospace, aviation, military industry, machinery, agricultural machinery, electronics, information, railways, posts and telecommunications, transportation, chemical industry, medical equipment, household appliances, light industry and other industries all have stamping processes. Not only is it used in the whole industry, but everyone is directly related to stamping products. There are many large, medium and small stamping parts on airplanes, trains, cars and tractors. Body, frame and rim are all stamped. According to relevant survey statistics, 80% of bicycles, sewing machines and watches are stamped parts; 90% of televisions, tape recorders and cameras are stamped parts; There are also food metal cans, steel boilers, porcelain bowls and stainless steel tableware, all of which are products stamped with molds; Even the hardware of the computer needs stamping parts. Problem 1, mold problem. The dies used in stamping are generally special. Sometimes a complex part needs several sets of molds to process and shape, and the mold manufacturing accuracy is high and the technical requirements are high. It is a technology-intensive product. Therefore, only mass production of stamping parts can fully reflect the advantages of stamping and obtain better economic benefits. 2. There are also some problems and shortcomings in safety stamping. Mainly manifested in the noise and vibration produced by stamping, and the safety accidents of operators occur from time to time. However, these problems are not entirely due to the stamping process and the die itself, but mainly due to the traditional stamping equipment and backward manual operation. With the progress of science and technology, especially the development of computer technology and electromechanical integration technology, these problems will be solved as soon as possible and perfectly. 3. High-strength steel stamping Today's high-strength steel and ultra-high-strength steel realize the lightweight of vehicles and improve the collision strength and safety performance of vehicles, so it has become an important development direction of automotive steel. However, with the improvement of plate strength, the traditional cold stamping process is easy to crack in the forming process, which can not meet the processing requirements of high-strength steel plate. At present, under the condition that the forming conditions cannot be met, the hot stamping technology of ultra-high strength steel plate is being studied step by step internationally. This technology is a new technology integrating shape, heat transfer and microstructure transformation. It is mainly a forming process by using the characteristics of increasing plasticity and decreasing yield strength of metal plates in high temperature austenite state. However, hot forming requires in-depth study of process conditions, metal phase transformation and CAE analysis technology. At present, this technology is monopolized by foreign manufacturers, and its domestic development is slow. Solution In the past, when producing deep drawing or heavy stamping workpieces, everyone thought that ep lubricating oil was the best choice to protect the mold. It has a long history to mix sulfur and chlorine extreme pressure additives into pure oil to improve the service life of dies. However, with the appearance of new metal-high strength steel and strict environmental protection requirements, the value of EP oil-based lubricating oil has been reduced and even lost the market. EP oil-based lubricating oil loses its performance when forming high-strength steel at high temperature, so it cannot provide physical mold protection diaphragm in extreme temperature applications. IRMCO high solid polymer lubricant at extreme temperature can provide necessary protection. With the deformation of metal in stamping die and the increase of temperature, EP oil-based lubricating oil will become thinner, and in some cases it will reach flash point or burn (smoke). IRMCO water-based stamping lubricant usually has a much lower consistency at the beginning of spraying. With the increase of temperature in the molding process, it will become thicker and tougher. In fact, polymer extreme temperature lubricants are "heat-seeking" and will stick to metals, forming a diaphragm that can reduce friction. This protective barrier allows the workpiece to extend, and there is no fracture and adhesion in the most demanding workpiece forming process, thus controlling friction and metal flow. Effectively protect the mold, prolong the service life of the mold and improve the stamping strength. Process classification Stamping is mainly classified by process, which can be divided into two categories: separation process and forming process. The separation process, also known as blanking, aims to separate the stamping parts from the sheet along a certain contour line and ensure the quality requirements of the separated section. The purpose of forming process is to make the sheet metal plastically deform and make the workpiece have the required shape and size without destroying the blank. In actual production, a workpiece often goes through multiple processes. Stamping, bending, shearing, stretching, bulging, spinning and straightening are the main stamping processes. The separation process of stamping parts (blanking) is the basic stamping process of separating materials by using dies. It can be directly made into flat parts or prepared for other stamping processes such as bending, stretching and forming, and can also be cut and trimmed on the formed stamping parts. Blanking is widely used in automobile, household appliances, electronics, instrumentation, machinery, railways, communications, chemical industry, light industry, textiles, aerospace and other industrial sectors. The stamping process accounts for about 50% ~ 60% of the whole stamping process. Bending in forming process: a plastic forming method of bending metal plates, pipes and profiles into a certain angle, curvature and shape. Bending is one of the main processes widely used in stamping parts production. The bending of metal materials is essentially an elastic-plastic deformation process. After unloading, the workpiece will produce elastic recovery deformation in the direction, which is called springback. Springback affects the accuracy of the workpiece and is the technical key that must be considered in the bending process. Deep drawing: Deep drawing, also known as drawing or calendering, is a stamping method of turning a flat blank into an open hollow part with a die. Thin-walled parts with irregular shapes, such as cylinder, step, cone, sphere and box, can be manufactured by deep drawing process. If combined with other stamping processes, parts with extremely complex shapes can also be manufactured. In stamping production, there are many kinds of deep-drawn parts. Because of its different geometric characteristics, the position, nature and distribution of deformation zone and the stress state and distribution law of each part of blank are very different, even essentially different. Therefore, the determination method of process parameters, the number and order of processes, and the principles and methods of mold design are all different. According to the characteristics of deformation mechanics, various deep drawing parts can be divided into four types: straight wall revolving body (cylindrical part), straight wall non-revolving body (box), curved surface revolving body (curved surface special-shaped part) and curved surface non-revolving body. Stretching means that the sheet is stretched by the drawing die, resulting in uneven tensile stress and strain, and then the joint surface between the sheet and the drawing die is gradually expanded until it is completely attached to the drawing die surface. The application object of stretch forming is mainly to manufacture hyperbolic skin with certain plasticity, large surface area, mild and smooth curvature change and high quality requirements (accurate shape, smooth streamline and stable quality). Because the process and equipment used in stretch forming are relatively simple, the cost is low and the flexibility is great; But the material utilization rate and productivity are low. Spinning is a metal rotating process. In the process of machining, the blank actively rotates with the spinning die or the spinning head actively rotates around the blank and the spinning die, and the spinning head makes feeding movement relative to the core die and the blank, so that the blank generates continuous local deformation and the required hollow rotary parts are obtained. Shaping is to use the established grinding tool shape to carry out secondary dressing on the shape of the product. Mainly reflected in the pressing surface, spring feet and so on. In view of the elasticity of some materials, secondary processing is adopted when the quality of primary molding cannot be guaranteed. Bulging is a processing method to obtain parts by stretching and thinning sheet metal and increasing local surface area with dies. Commonly used are wave forming, cylindrical (or tubular) blank bulging and flat blank drawing forming. Bulging can be achieved by different methods, such as rigid die bulging, rubber bulging and hydraulic bulging. Flanging is a plastic processing method to bend the material in the narrow band area of the edge of thin plate blank or the edge of prefabricated hole on blank into vertical edge along curve or straight line. Flanging is mainly used to strengthen the edge of parts and remove trimming, so that parts assembled and connected with other parts or three-dimensional parts have complex and special shapes and reasonable space, and at the same time improve the rigidity of parts. It can also be used as a means to control the cracking or wrinkling in the forming of large metal plates. Therefore, it is widely used in automobile, aviation, aerospace, electronics and household appliances and other industrial sectors. Necking is a stamping method to reduce the diameter of the open end of a drawn flangeless hollow part or tube blank. Before and after necking, the end diameter of the workpiece should not change too much, otherwise the end material will wrinkle due to severe compression deformation. Therefore, it is often necessary to shrink the neck from a larger diameter to a very small diameter. The surface and internal properties of metal sheet used for material stamping have great influence on the quality of stamping products. The requirements for stamping materials are: ① accurate and uniform thickness. The stamping die is precise and the gap is small. If the thickness of the plate is too large, it will increase the deformation force, cause material jamming and even crack the female die. Too thin sheet will affect the quality of finished products, and even cracks will appear during drawing. The surface of stamping raw material ② is smooth, without spots, scars, scratches and surface cracks. All surface defects will remain on the surface of the finished workpiece, and crack defects may spread in the deep and wide direction during bending, stretching and forming, resulting in waste products. ③ The yield strength is uniform and there is no obvious directionality. Anisotropy (see plastic deformation of sheet metal in stamping process, such as drawing, flanging and bulging, etc. ), due to the isotropic yield in turn, the plastic deformation is inconsistent, which will cause uneven deformation, inaccurate forming and defective products or waste products. ④ High uniform elongation. In the tensile test, the elongation before the specimen begins to neck is called uniform elongation. In deep drawing, the deformation of any area of the sheet metal cannot exceed the uniform extension range of the material, otherwise uneven deformation will occur. ⑤ Low yield. The ratio of yield limit to strength limit of materials is called yield ratio. Low yield ratio can not only reduce the deformation resistance, but also reduce the tendency of wrinkling in deep drawing, reduce the springback after bending and improve the accuracy of bending parts. ⑥ Low work hardening. Work hardening after cold deformation will increase the deformation resistance of materials, and it is difficult to continue deformation, so plates with low hardening index are generally used. However, materials with high hardening index have good plastic deformation stability (that is, plastic deformation is relatively uniform) and are not prone to local tensile cracking. In actual production, process tests similar to stamping process, such as drawing performance test and bulging performance test, are often used to check the stamping performance of materials to ensure the quality of finished products and high qualified rate. The precision and structure of the die directly affect the forming and precision of stamping parts. Die manufacturing cost and life span are important factors affecting the cost and quality of stamping parts. Mold design and manufacture need more time, which prolongs the production preparation time of new stamping parts. The standardization of die frame, die frame and guide rail, the development of simple die (small batch production), compound die and multi-station progressive die (large batch production) and the development of rapid die changing device can reduce the preparation workload and shorten the preparation time of stamping production, so that advanced stamping technology suitable for large batch production can be reasonably applied to small batch and multi-variety production. The special stamping equipment generally adopts mechanical press except that the thick plate is formed by hydraulic press. With modern high-speed multi-station mechanical press as the center, equipped with uncoiling, leveling, finished product collection, conveying and other machinery, as well as mold base library and rapid mold changing device, controlled by computer program, an automatic stamping production line with high productivity can be formed. The press lubricates the general workpiece in the stamping process, because the temperature will rise rapidly in the stamping process, especially in the cold forging stamping process, it is necessary to add lubricating oil for lubrication. If the workpiece is directly stamped without lubrication, the life of the die will be shortened, the accuracy will be reduced, and a lot of money will be invested in the improvement of the die. It is for this reason that stamping lubrication is necessary in cold forging stamping. In the case of producing dozens or hundreds of stamping parts per minute, safety production can complete the processes of feeding, stamping, discharging and waste disposal in a short time, which often leads to personal, equipment and quality accidents. Therefore, stamping safety production is a very important issue. The safety measures for stamping are: ① Mechanization and automation of loading and unloading. ② Set mechanical protection device to prevent hand injury. Use mold protective cover, automatic material returning device and hand tools to feed and discharge. ③ Set electrical protection and power-off devices. Set photoelectric or air curtain protection switch, two-hand or multi-hand series start switch and misoperation prevention device. ④ Improve the clutch and brake structure, so that the crankshaft, connecting rod and punch of the press can stop at the original position immediately after sending out the danger signal.