Stamping is mainly classified by process, which can be divided into separation process and forming process. The purpose of the separation process is to separate the stamping parts from the sheet along a certain contour line and ensure the quality requirements of the separation section. The purpose of forming process is to make the sheet metal plastic deformation without breaking the blank, and to make the required shape and size of the workpiece. In actual production, it is often a variety of processes applied to a workpiece. Punching, bending, shearing, stretching, bulging, spinning and straightening are the main punching separation processes.
Blanking is a basic stamping process that uses die to separate materials. It can be directly made into flat parts or prepare blanks for other stamping processes such as bending, drawing, forming, etc., or cut and trim the formed stamping parts. Blanking is widely used in automobile, household appliances, electronics, instruments, machinery, railway, communication, chemical industry, light industry, textile, aerospace and other industrial sectors. Punching process accounts for about 50% - 60% of the whole stamping process.
Bending: the plastic forming method of bending metal plates, pipe fittings and profiles into a certain angle, curvature and shape. Bending is one of the main processes widely used in stamping production. In fact, the bending of metal materials of automotive stamping parts is an elastic-plastic deformation process. After unloading, the workpiece will produce elastic recovery deformation in the direction, which is called rebound. Springback affects the accuracy of workpiece, which is the key technology to be considered in bending process.
Drawing: drawing, also known as drawing or calendering, is a stamping process that uses a die to turn the blank of a flat plate obtained after blanking into an open hollow part. The thin-walled parts with cylindrical, stepped, tapered, spherical, box and other irregular shapes can be made by drawing technology. If it is matched with other stamping processes, it can also produce parts with extremely complex shapes. In stamping production, there are many kinds of deep drawing parts. Because of the different geometrical features, the position of deformation area, the nature of deformation, the distribution of deformation, the stress state and distribution law of each part of billet are quite different, even essential. Therefore, the determination methods of process parameters, process number and sequence, and the principles and methods of die design are different. According to the characteristics of deformation mechanics, all kinds of drawing parts can be divided into four types: straight wall revolving body (cylindrical part), straight wall non revolving body (box part), curved surface revolving body (curved surface part) and curved surface non revolving body.
Drawing is to apply tension to the sheet metal through the drawing die, so that the sheet metal will produce uneven tensile stress and strain, and then the joint surface of the sheet metal and the drawing die will gradually expand, until the automobile parts and the drawing model surface fully fit. The main object of stretch forming is to make hyperbolic skin with large surface area, moderate and smooth curvature change and high quality requirements (accurate shape, smooth streamline and stable quality). Due to the simple process equipment and equipment used in the drawing, the cost is low and the flexibility is large, but the material utilization rate and productivity are low.
Spinning is a kind of metal rotary processing technology. In the process of machining, the blank rotates actively with the spinning die or the spinning head rotates actively around the blank and the spinning die, and the spinning head feeds the core die and the blank, so that the blank produces continuous local deformation and the required hollow rotating body parts are obtained.
Reshaping is to make use of the fixed shape of the grinding tool to finish the product's shape. Mainly reflected in the pressure plane, spring feet, etc. For some materials that are elastic and cannot guarantee the quality of one-time forming, the reprocessing is adopted.
Bulge forming is a processing method which uses die to make sheet metal stretch thin and increase local surface area to obtain parts. Commonly used are undulating forming, cylindrical (or tubular) blank bulging and flat blank tension forming. Bulging can be realized 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 edge of sheet metal or the narrow-band area of preformed hole edge of sheet metal into vertical edge along a curve or a straight line. Flanging of automobile sheet metal parts is mainly used to strengthen the edge of parts, remove the cutting edge and make the parts assembled and connected with other parts or the three-dimensional parts with complex and special shape and reasonable space on the parts, at the same time, improve the rigidity of parts. In large-scale sheet metal forming, it can also be used as a means to control cracking or wrinkling. Therefore, it is widely used in automobile, aviation, aerospace, electronic and household appliances and other industrial sectors.
Necking is a kind of stamping method to reduce the diameter of the open end of the flangeless hollow part or tube blank which has been stretched well. Before and after necking, the change of the end diameter of the workpiece should not be too large, otherwise the end material will wrinkle due to the severe compression deformation. Therefore, it is often necessary to shrink the neck from a larger diameter to a smaller one.