Abstract: Metal stamping is a method of forming a workpiece (metal stamping part) with a desired shape and size by applying an external force to a sheet, strip, pipe, and profile by means of a punch and a stamping die. . Metal stamping and forging are both plastic processing (or pressure processing), collectively called forging. There are many kinds of blanks for metal stamping: ordinary hot-rolled and cold-rolled steel plates and strips; various types of stainless steel, such as: SUS201, 202, SUS301, 304, 316, SUS430, 439, etc .; copper alloys such as brass, phosphor bronze, etc. Pure aluminum and aluminum alloys; with the trend of lightweight automobile bodies, various high-strength alloy steels are used for automotive stamping materials.

       After the steel plate is hot rolled and cold rolled, the thickness of the plate gradually changes from thick to thin. The car body, chassis, fuel tank, radiator fins, steam drums of boilers, shells of containers, iron core silicon steel sheets of motors, and electrical appliances are all processed by automotive stamping dies. Instruments, household appliances, bicycles, office machinery, household utensils and other products are also processed with metal stamping dies.

      Compared with castings and forgings, metal stampings are thin, uniform, light and strong. Metal stamping can make workpieces with stiffeners, ribs, undulations or flanging that are difficult to manufacture by other methods to improve its rigidity. Due to the use of precision stamping dies, the precision of the workpiece can reach micron level, and the repeatability is high, and the specifications are consistent. The holes and bosses can be punched out by hardware.

       Cold stamping hardware stamping parts generally no longer undergo cutting or require only a small amount of cutting. The precision and surface condition of hot stamping hardware stamping parts are lower than cold stamping hardware stamping parts, but they are still better than castings and forgings, and the amount of cutting is less.

Metal stamping is an efficient production method. Using a compound die, especially a multi-stage progressive die, multiple metal stamping processes can be completed on a single punch to achieve unwinding, leveling, blanking, forming, and finishing of the strip. Fully automated production. High production efficiency, good labor conditions and low production costs, generally hundreds of pieces can be produced per minute.

Types of metal stamping process:

       Metal stamping is mainly classified according to technology, which can be divided into two categories: separation process and forming process. The separation process is also called blanking, and its purpose is to separate the hardware stamping parts from the sheet along a certain contour line, while ensuring the quality requirements of the separation section. The purpose of the forming process is to plastically deform the sheet material without breaking the blank to produce a workpiece of a desired shape and size. In actual production, multiple processes are often applied to a workpiece. Punching, bending, shearing, deep drawing, bulging, spinning, and correction are several major metal stamping processes.

       The surface and intrinsic properties of the metal stamping sheet have a great impact on the quality of the metal stamping product. The thickness of the metal stamping material is required to be accurate and uniform; the surface is smooth, no spots, no scars, no abrasions, no surface cracks, etc .; uniform yield strength , No obvious directionality; high uniform elongation; low yield ratio; low work hardenability.

In actual production, technological tests similar to the metal stamping process are commonly used, such as deep-drawing performance test and bulging performance test to check the metal stamping performance of the material to ensure the quality of the finished product and a high pass rate.

      The precision and structure of the stamping die directly affect the forming and precision of the hardware stamping parts. Stamping mold manufacturing cost and life are important factors affecting the cost and quality of metal stamping parts. Designing and manufacturing stamping dies requires more time, which prolongs the production preparation time for new metal stamping parts.

Standardization and development of mold bases, mold bases, guides, simple stamping dies (for small batch production), compound dies, multi-stage progressive dies (for large-scale production), and the development of rapid die change devices can reduce metal stamping production preparations The workload and shortening the preparation time can make it suitable for reducing the preparation workload and shortening the preparation time of metal stamping production, and can make the advanced metal stamping technology suitable for mass production reasonable to apply to small batch multi-variety production.

       Except for the forming of thick plates with water presses, metal stamping equipment generally uses mechanical punches. Centering on modern high-speed multi-station mechanical punches, equipped with uncoiling, leveling, finished product collection, conveying and other machinery, as well as stamping die library and quick die changing device, and using computer program control, it can form a highly productive automatic metal stamping production line.

In the case of producing dozens or hundreds of metal stamping parts per minute, the processes of feeding, metal stamping, output, and waste discharge are completed in a short time, and personal, equipment and quality accidents often occur. Therefore, safety production in metal stamping is a very important issue.

Seeking breakthroughs in the development of metal stamping forming industry:

      According to statistics, in 2003 China produced about 2.4 million tons of 800 million pieces of stamped parts for automobiles, about 280,000 tons of 1.9 billion pieces of stamped parts for motorcycles, and about 960,000 tons of 710 million pieces of stamped parts for tractors and agricultural vehicles. Air-conditioning and refrigerator hardware stamping parts 1 million tons / 1.28 billion. Experts in the industry predict that as the largest user market in the metal stamping and molding industry, the automotive industry, continues to grow rapidly in the future, the Chinese metal stamping industry has ushered in a period of rapid development opportunities, but can it seize the opportunity to obtain new and faster development? Experts point out that there are still many obstacles and obstacles to be overcome and breakthroughs on the way forward.

Resistance one: low degree of mechanization and automation

      70% of the 680 hardware stamping lines in the United States are multi-station punches, and 32% of the 250 domestic production lines in Japan are multi-station punches. However, such large-scale multi-station punches, which represent the current international level, are infrequent in China. SME equipment is generally backward, energy-consuming materials are high, and environmental pollution is serious; head forming equipment is rudimentary and manual operation is significant; precision punching machines are expensive, 5-10 times that of ordinary punching machines, and most enterprises' inability to invest hinders them The promotion and application of fine blanking technology in China; hydraulic forming, especially internal high pressure forming, and large equipment investment make it difficult to start in China.

Breakthrough point: speed up technological transformation

       It is necessary to change the current backward situation where most of them are manual loading and unloading. In combination with specific conditions, adopt new processes to improve the degree of mechanization and automation. The stamping of automobile body cover parts should develop towards the single-machine connection automation and robot hardware stamping production lines, especially the large-scale multi-station punching machine. Strive to increase investment, accelerate the technical transformation of the automotive stamping parts production line, so as to reach the current international level as soon as possible. With the development of microelectronics technology and communication technology, the automation and flexibility of sheet metal forming equipment has a technical foundation. The development of digital flexible forming technology, hydroforming technology, high-precision composite forming technology, and profile bending forming technology and related equipment adapted to the new generation of lightweight body structures should be accelerated. At the same time, the old domestic equipment was transformed to make new production capacity.

Resistance 2: Low concentration of production

     Many automobile groups are large and complete, forming closed internal facilities, leading to various types of metal stamping parts, low concentration of production, small scale, easy to cause low-level repeated construction, difficult to meet specialized division of production, and weak market competitiveness; The motorcycle hardware stamping industry is facing fierce market competition and is in a state of "excellent but not inferior"; head manufacturing enterprises are small and scattered with a concentration of only 39.2%.

Breakthrough point: take the road of specialization

      Quickly change the current "large and complete" and "scattered poor" pattern, separate metal stamping parts from the automobile group as soon as possible, and classify the large, medium and small parts of the automotive stamping parts into several large metal stamping parts. Manufacturing supply centers and dozens of small and specialized parts factories. Only through specialization can we make metal stamping parts bigger and stronger and become an internationally competitive metal stamping parts supplier.

Resistance 3: The self-sufficiency rate of metal stamping plates is insufficient, and the specifications are not matched

       At present, China's automobile sheet can only meet about 60%, and steel plates for high-end cars, such as high-strength plates, alloyed galvanized plates, ultra-wide plates (above 1650mm), and so on, rely on imports.

Breakthrough point: materials should be coordinated with the industry

      The variety of steel plates for automobiles should be more reasonable, develop towards high strength, high corrosion resistance and thin steel plates of various specifications, and improve the stamping performance of hardware. Aluminium and magnesium alloys have become the rational materials for lightweight vehicles, and it is now inevitable to expand applications.

Resistance 4: Slow transformation of scientific and technological achievements

       In China, many new technologies of metal stamping and processing have not started late, and some have reached the international advanced level, but it is often difficult to form productivity. There are not many applications of advanced metal stamping technology, and some are only in the trial stage, and the speed of absorption, transformation and promotion is slow. The low investment in technology development has led to the slow application and application of advanced technology by enterprises and insufficient development and innovation capabilities. The gap between SMEs in this area is even greater. At present, most domestic enterprises still use traditional metal stamping technology, and lack of research and technical reserves for the forming technology required for the next generation of lightweight automotive structures and materials.

Breakthrough point: the road of combining production, learning and research

      Compared with Europe, the United States, and Japan, the biggest gap between our country and China is that there is not yet a consortium of production, learning, and research. It is difficult to make scientific research larger, and the results cannot be transformed into productivity as soon as possible. Therefore, we should focus on large-scale development and industrialization projects, with universities and scientific research units as technical support, and enterprises as application bases to form a joint entity of products, equipment, materials, and technology to form a benign that can both develop and innovate and rapidly industrialize. cycle.

Resistance 5: Large, precision stamping dies rely on imports

At present, the materials, design and manufacture of metal stamping dies cannot meet the needs of domestic automobile development, and the degree of standardization is still low, about 40% to 45%, compared with about 70% internationally.

Breakthrough point: improve the level of informatization and standardization

Information technology must be used to reform the stamping die company. The development focus is to vigorously promote the integrated CAD / CAM / CAE technology, especially the computer simulation analysis and optimization technology (CAE) of the forming process. Accelerate the standardization process of stamping dies in China and improve accuracy and interchange rate. Strive to reach a 60% coverage rate for stamping die standard parts in 2005 and 70% or more in 2010 to basically meet market demand.

Resistance six: lack of professional talents

     High-quality talents with advanced design analysis technology and digital technology in the industry are far from meeting the rapid development needs of the metal stamping industry, especially the professionals in the motorcycle industry with metal stamping knowledge and technology and skills are scarce and exodus. In addition, many joint ventures have engineering design by foreign parties and have the right to design and invest. It is difficult for our metal stamping technicians to truly grasp the true meaning of metal stamping technology.

Breakthrough point: improve the quality of industry personnel

This is an urgent task and a long-term and systematic task. The revitalization of China's hardware stamping industry requires a large number of high-level scientific and technological personnel, a large number of entrepreneurs familiar with domestic and foreign markets, modern management knowledge and capabilities, and a large number of high-level technical personnel with advanced technology and processes. We must be willing to spend a lot of energy and cultivate in a planned and hierarchical manner.