Stamping is mainly classified according to 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 (Table 1). 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. Punching, bending, shearing, stretching, bulging, spinning and correction are the main punching.

separation process

(blank)

This is the basic stamping process of separating materials with 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 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. forming process

Bending: 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.