Differences between Sheet Metal Processing and Metal Stamping, & Various Technical Terms for Stamping Processing

Future Development Trends and Judgment of Metal Stamping Industry

Metal stamping is a way of forming a work-piece (metal stamping part) at required shapes and sizes by using an external force to a plate, a strip, a pipe, a profile, and so on by a punching machine and a stamping die to cause metal plastic deformation or separation. Metal stamping and forging are the same metal plastic processing (or pressure processing), collectively called forging. Metal stamping blanks are primarily hot and cold rolled steel sheets and strips.

Among the world's steel, 60% to 70% are sheets, and most of them are completed by metal stamping. The bodies, chassis, fuel tanks, radiator pieces of the automobile, the steam drum of the boiler, the casing of the container, the iron core silicon steel of the electric motor and the electric appliance are all metal stamping processing. In instrumentation, household appliances, bicycles, office machinery, living utensils and other products, there are also a large number of metal stamping parts.

Compared with castings and forgings, metal stamping parts are thinner, lighter and stronger. Metal stamping could produce work-pieces with ribs, undulations or flange that are difficult to make by other means to increase their rigidity. Due to uses of precision stamping dies, the precision of the work-pieces can reach micron levels, and the repeating precision is high and the specifications are the same. Metal holes and also embosses can be punched out.

Cold metal stamping parts are generally no longer machined or needed only a small amount of machining. The accuracy and surface condition of hot metal stamping parts are worse than cold metal stamping parts, but still better than castings and forgings, and the amount of cutting processing is less.

Metal stamping is an efficient production style, which adopts composite stamping dies, especially multi-position progressive stamping dies. It can complete multiple metal stamping processes on one press, which can make true unwinding, leveling and punching of strips to forming and finishing. Fully automatic production, high production efficiency, good working conditions, low production costs, normally hundreds of pieces/minute could be produced.

Types of Metal Stamping Processes:

Metal stamping is mainly sorted based on the process and is divided into two kinds: separation process and forming process. The separation process is also called punching, whose purpose is to separate metal stamping parts from the sheet along a certain contour line, and at the same time ensure quality requests of separated sections. The purpose of the forming process is to plastically deform the sheet without breaking the blank to produce a work-piece of the desired shape and size. In the actual production, multiple processes integrated into one work-piece are often the case, such as blanking, bending, shearing, drawing, spinning, correction, and so on.

The surface and intrinsic properties of metal stamping sheets have a great influence on the quality of metal stamping products. The thickness of metal stamping materials is required to be precise and uniform, and the surface is smooth, without spots, flaws, scratches, surface cracks, etc., with uniform yield strength, without obvious directionality, with high uniform elongation, low yield ratio and low work hardenability.

During the actual production, the technical test similar to the metal stamping process, such as the drawing performance test and the bulging performance test, is used to ensure the final part’s quality and high qualified rate.

The precision and the structure of stamping dies directly affect the forming and precision of metal stamping parts. The manufacturing cost and the life of stamping dies are important elements influencing the cost and the quality of metal stamping parts. The design and the manufacturing of stamping dies requires more time, which extend the production lead time for new metal stamping parts.

The standardization of die holders, die plates and guides and the development of simple stamping dies (for the small batch production), compound dies, multi-station progressive dies (for the massive production), and the development of quick change devices to reduce the workload and the metal stamping production preparation, so the advanced metal stamping technology suitable for the mass production can be reasonably applied to the small batch and the various production.

In addition to the formation of thick plate hydraulic presses, the metal stamping equipment generally uses mechanical punching machines. Centered on modern high-speed multi-station mechanical punching machines, it is equipped with unwinding, leveling, finished product collection, conveying and other machinery as well as the stamping die library and the quick change device, and can be controlled by the computer program to form a high-productivity automatic metal stamping production line.

In the case of producing dozens or hundreds of metal stamping parts/minute, the processes of feeding, metal stamping, discharging, and waste’s discharging are finished in a short time, and personal, equipment and quality accidents often occur. Therefore, the safe production in metal stamping is a very important issue.

Development of the Resistance Metal Stamping Forming Industry to Seek Breakthroughs:

According to statistics, in 2003, China produced about 2.4 million tons/800 million pieces of automotive metal stamping parts, about 280,000 tons/1.9 billion pieces of motorcycle metal stamping parts, and about 960,000 tons/710 million pieces of metal stamping parts for tractors and agricultural vehicles, 1 million tons/1.28 billion pieces of metal stamping parts for household air conditioning and refrigerator. Industry experts predict that with the rapid development of the automotive industry in the largest user market in the metal stamping and forming industry, the Chinese metal stamping industry has ushered in a period of rapid development opportunities, and can seize the opportunity to achieve new and faster development, but experts point out that there are still many obstacles to overcome and break through on the road ahead.

Obstacle 1: Mechanization, Below-normal Automation

70% of the 680 metal stamping lines in the United States are multi-station punching machines, and 32% of the 250 production lines in Japan are multi-station punching machines. This kind of the large-scale multi-station punching machine representing the current international level is not used in China. SME equipment is generally backward, high energy consumption and high environmental pollution. The head forming equipment is simple, and the manual operation is more important. The fine punching machine is more expensive, 5 to 10 times than the ordinary punching machine, so most enterprises are unable to invest to hinder the promotion and application of fine punching technology in China. Hydroforming, especially internal high pressure forming, large equipment investment, it is difficult to start in China.

Break Through Point: Speed up with Technological Transformation

It is necessary to change most of the current backward situations of manual loading and unloading, and adopt new techniques to improve the degree of mechanization and automation in light of specific situations. The metal stamping of the automobile body should be developed to the single machine connection automation and the metal stamping production line by robot, especially the large multi-station punching machine. To increase the investment and accelerate the technological transformation of the metal stamping production line, it’s much faster to reach the current international level. With the development of microelectronics technology and communication technology, the materialization and flexibility of the sheet metal forming equipment has a technical basis. It’s important