Stamping and stretching forming is a technological method to form flat blank into open hollow parts by using dies. According to the actual situation of equipment and personnel, the stamping and drawing process should select and design an advanced, economical and reasonable process scheme with safe and reliable use. As one of the main stamping processes, deep drawing can be used to manufacture irregular thin-walled parts such as cylinder, rectangle, step, sphere, cone and parabola. If it is combined with other stamping processes, parts with more complicated shapes can be manufactured. The following briefly introduces the types of stamping and drawing processes:

I. Types of stamping process

(1) divided by the workpiece. Stamping process can be roughly divided into two categories according to the workpiece: separation process and forming process (bending, stretching and forming).

(2) According to the temperature during stamping. According to the temperature of hot stamping, there are two ways: cold stamping and hot stamping. It depends on the strength, plasticity, thickness, deformation degree and equipment capacity of the material, and also considers the original heat treatment state and final use conditions of the material.

(2) According to the mold structure. Stamping die is a tool for separating or deforming metal plates, which consists of an upper die and a lower die. According to the structure of stamping die, the process can be basically divided into three types: simple stamping, continuous stamping and composite stamping.

Second, the type of painting process.

Drawing process of (1) panel

Panel is a kind of sheet metal part with complex surface shape, and the deformation of blank is complicated in the process of deep drawing. Its forming nature is not simple drawing, but a compound forming with both drawing and bulging.

(2) Curved surface forming process

Curved surface stretch forming makes the outer flange part of metal flat blank shrink and the inner flange part extend, which becomes a hollow stamping forming method with non-straight wall and non-flat bottom curved surface shape.

(3) Edge stretching process

Angular redrawing of the product flange drawn in the previous procedure requires the material to have good plasticity.

(4) Deep drawing process

Workpieces that exceed the stretching limit need to be stretched for more than two times to complete. After stretching in the depth direction of the previous station, the re-stretching process is performed in the depth direction.

(5) Refining and stretching process

Different from ordinary drawing, thinning drawing mainly changes the wall thickness of the drawn parts during the drawing process. The gap between the punch and the die is smaller than the thickness of the blank, and the straight wall of the blank is subjected to greater uniform compressive stress when passing through the gap. While the wall thickness becomes thinner in the drawing process, the deviation of the container wall thickness is eliminated, the smoothness of the container surface is increased, and the precision and strength are improved.

(6) Reverse stretching process

Reverse stretching of the workpiece stretched in the previous process is a kind of re-stretching. Reverse stretching method can increase the radial tensile stress, obtain better crease-resistant effect, and may also increase the tensile coefficient of re-stretching.

Third, the selection of stamping and stretching equipment

(1) Selection of stamping equipment According to the nature of the stamping process to be completed and the force and energy characteristics of various stamping equipment, the main factors such as deformation force and work required for stamping, die closing height and outline size are comprehensively considered, and the equipment type and tonnage are reasonably selected in combination with the existing equipment situation.

② Common stamping equipment includes crank press, hydraulic press, etc. Crank press is the most widely used. The stamping process is mostly carried out on a crank press, and there is generally no hydraulic press; The forming stamping process can be carried out on a crank press or a hydraulic press.

Fourthly, the choice of precision stamping drawing oil.

Stamping and drawing oil plays a key role in stamping and drawing process. Good cooling performance and extreme pressure wear resistance have brought a qualitative leap for the service life of the die and the improvement of workpiece precision. According to the different materials of workpiece, the performance emphasis of stamping drawing oil is different when it is selected, which is usually determined according to the difficulty of stamping process, oil supply mode and degreasing conditions.

(1) For materials that are easy to die-cut, generally, in order to make the finished workpiece easy to clean, low-viscosity stamping drawing oil will be selected on the premise of preventing stamping burr.

(2) For materials that are easy to harden, it is required to use stamped drawing oil with high oil film strength and good sintering resistance. Generally, stamping drawing oil containing sulfur and chlorine compound additives is used to ensure extreme pressure performance and avoid burr and fracture of the workpiece.