Stamping and stretching is a common processing form, and it is also common in the industrial industry. Stretch forming is a stamping method that uses a die to form a flat blank into an open hollow part. As one of the main stamping processes, drawing is widely used. Thin wall parts with cylindrical, rectangular, stepped, spherical, conical, parabolic and other irregular shapes can be made by drawing process. If combined with other stamping processes, parts with more complex shapes can also be made. So what are the types of metal stamping and stretching parts processing?

Use stamping equipment for stretch forming of products, including stretch processing, re stretch processing, reverse stretch and thinning stretch processing.

Drawing processing: use the pressing plate device and the punch pressure of the punch to pull part or all of the flat plate into the cavity of the concave model to form a container with a bottom. The processing of the side wall of the container parallel to the stretching direction is a simple stretching processing, while the stretching processing of cone (or corner cone) descriptors, hemispherical descriptors and parabolic containers also includes expanding processing.

Re stretching: for deep stretched products that cannot be finished in one stretch process, it is necessary to stretch the formed products again to increase the depth of the formed container.

Reverse stretching processing: reverse stretching the stretched workpiece in the previous process, turning the inner side of the workpiece into the outer side, and reducing its outer diameter.

Thinning and stretching: use punch to squeeze the formed container into the concave model cavity slightly smaller than the outer diameter of the container, so as to reduce the outer diameter of the container with bottom and thin the wall thickness, which can not only eliminate the wall thickness deviation, but also make the surface of the container smooth.

When using stamping equipment for metal stamping and stretching, it includes the following 16 types:

1. Cylinder drawing

Stretching of flanged (flanged) cylindrical products. Both the flange and the bottom are in plane shape, the side wall of the cylinder is axisymmetric, the deformation is evenly distributed on the same circumference, and the blank on the flange produces deep drawing deformation.

2. Elliptical drawing

The deformation of the blank on the flange is tensile deformation, but the deformation amount and deformation ratio change accordingly along the contour shape. The greater the curvature, the greater the plastic deformation of the blank; On the contrary, the smaller the curvature, the smaller the plastic deformation of the blank.

3. Rectangular drawing

A low rectangular part formed by one-time drawing. When stretching, the tensile resistance at the fillet of the flange deformation area is greater than that at the straight edge, and the deformation degree at the fillet is greater than that at the straight edge.

4. Mountain drawing

When the side wall of the stamping part is an inclined plane, the side wall is suspended in the stamping process and does not stick to the mold until the end of forming. The deformation characteristics of different parts of the side wall are not exactly the same during forming.

5. Hill drawing

The blank deformation of dome shaped cover plate in the forming process is not a simple tensile deformation, but a composite forming with both tensile deformation and bulging deformation. The deformation of the blank on the pressing surface is tensile deformation (tensile stress in the radial direction and compressive stress in the tangential direction), while the deformation of the blank inside the contour (especially in the central area) is bulging deformation (tensile stress in both radial and tangential directions).

6. Hemispherical drawing with flange

When the spherical part is stretched, the blank is in local contact with the spherical top of the punch, and most of the rest are in a suspended and unconstrained free state. Therefore, the main technological problem of drawing such spherical parts lies in the serious thinning of local contact parts or the instability and wrinkling of curved surfaces.

7. Flange stretching

The flange part of the stretched product is processed by shallow stretching. The stress-strain condition is similar to that of compression flanging. Because of the tangential compressive stress and easy wrinkling, the forming limit is mainly limited by compression wrinkling.

8. Edge stretching

The material of the flange with good plastic shape before the drawing process.

9. Deep drawing processing

Stretching products that exceed the limit of stretching can only be completed after more than two times of stretching. The products that have been stretched in the depth direction of the front station shall be re stretched in the depth direction. The wide flange stretching part is stretched to the required flange diameter at the first stretching, and the flange diameter remains unchanged at the subsequent stretching.

10. Conical drawing

h/d>0.8、 α = For deep conical parts with a depth of 10 ° ~ 30 °, due to the large depth and large deformation degree of the blank, the forming force is transmitted only by the local area of the blank in contact with the punch, which is very easy to cause local excessive thinning and even fracture of the blank, which needs to be formed gradually after many transitions. The step drawing method is to draw the blank into a step transition part, the step shape is tangent to the inner shape of the conical part, and finally expand to form a cone. The stretching times and process of step transition parts are the same as those of step cylindrical parts.

11. Rectangle re drawing

The deformation of high rectangular parts formed by multiple drawing is not only different from that of deep cylindrical parts, but also very different from that of low box parts. Figure 1-46 shows the changes of the shape and size of the workpiece with the stretching height during multiple stretching when the multi station automatic conveying press is used to process high rectangular boxes.

12. Surface forming

Surface stretch forming is a stamping forming method of hollow products with non straight wall and non flat bottom surface shape, which reduces the outer flange part of metal plate blank and elongates the inner flange part.

13. Step drawing

Re stretch the initially stretched product on the left to form a stepped bottom on the right. The deeper part deforms in the early stage of drawing forming, and the shallower part deforms in the later stage of drawing. The side wall of the changing part of the step is easy to induce shear stress and deformation.

14. Reverse stretching

Reverse stretching is a method of re stretching the workpiece processed by stretching in the previous process. The reverse stretching method can increase the radial tensile stress and get a good effect on preventing wrinkling. It is also possible to increase the tensile coefficient of re stretching.

15. Thinning drawing

Different from ordinary drawing, thinning drawing mainly changes the thickness of the cylinder wall of the drawing part in the drawing process. The gap between the male and female dies is less than the blank thickness. When the blank straight wall passes through the gap, it is under a large uniform compressive stress. When 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 accuracy and strength are improved.

16. Panel stretching

Panel products are sheet metal stamping parts with complex surface shape. In the drawing process, the deformation of the blank is complex, and its forming property is not a simple drawing forming, but a composite forming in which deep drawing and bulging exist at the same time.