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Characteristics of metal wire drawing molds:

1、 Stretch concept

1. Stretching: Press the board into hollow parts (with the wall thickness remaining basically unchanged).

2. Stretching process: Transfer the material on the flat surface (flange) to the cylindrical (box shaped) side wall, so the overall size of the flat surface will undergo significant changes.

3. Stretching coefficient: the ratio of the stretched diameter to the blank diameter "m" (the degree of deformation from the blank to the workpiece).

2、 The main factors affecting the tensile coefficient are:

1. Material mechanical properties (reduced strength - elastic deformation; tensile strength - plastic deformation; elongation coefficient; reduced area).

2. The relative thickness of the material.

3. Number of stretches.

4. Stretching method.

5. The fillet radius of convex and concave molds.

6. The smoothness, lubrication, clearance, etc. of the stretched working surface.

7. Stretching speed.

3、 Stretching process arrangement:

1. Parts with thinner materials and deep drawing larger than the diameter: reducing the diameter of the cylinder and increasing the height can gradually reduce the fillet radius.

2. Parts with thicker materials and similar deep drawing and diameter: The fillet radius can be reduced while maintaining the same height, and the diameter of the cylindrical shape can be gradually reduced.

3. Large flange with small radius: It should be achieved through multiple shaping processes.

When the flange is too large: expansion method should be used if necessary.

In order to embody the principle of "unchanged flange", the flange formed by the first stretching does not participate in subsequent stretching deformation. The material used for the first time in the concave mold (i.e. the material that forms the wall and bottom) for wide flange stretching should be 3-10% more than the actual material required to complete the stretching after *.

Note: When calculating the number of stretching times based on area, the upper limit should be taken; otherwise, the lower limit should be taken. These excess materials will return to the flange in each subsequent stretching and cutting step, which will cause the flange to thicken but prevent the head from cracking. Localized thinning areas can be corrected through plastic surgery. Therefore, it is very important to strictly control the height of each stretch during the stretching process.

4、 Box shaped component stretching

The corner is equivalent to the stretching of the cylindrical part, and the straight wall is equivalent to the bending deformation;

5、 Stretch lubrication

During the stretching process, there is friction between the material and the mold, so there must be a dedicated stamping and stretching lubricant. High friction not only increases the tensile coefficient and tensile force, but also wears and scratches molds and tools. Therefore, the intermediate surface is harmful. Therefore, by utilizing lubrication conditions, the deformation of the transmission zone can be exerted, and unevenness can be compensated for. This can not only improve the load-bearing capacity of the transmission zone, but also promote smooth plastic deformation of the entire deformation zone. Therefore, lubrication conditions are essential during stretching.