Do you know the methods of stretch forming?

Stretch forming is a stamping process that forms a flat plate into an open hollow part using a processing method. As one of the main processes of stamping, stretching has been widely used. The stretching process can be used to manufacture thin-walled stamping parts with irregular shapes such as cylindrical, rectangular, trapezoidal, spherical, conical, parabolic, etc. If combined with other stamping processes, more complex parts can also be manufactured.

The metal stamping system is used to perform deep drawing on the product, including deep drawing, re-drawing, reverse drawing and thinning drawing. Deep drawing is to use a stamping device to use the pressure of the punch to pull part or all of the flat plate into the concave mold cavity to form a container with a bottom. The processing of the container side wall parallel to the drawing direction is a simple deep drawing process, and the stretching process of conical containers, hemispherical containers and parabolic containers also includes unfolding processing.

Re-stretching method: In order to increase the depth of the formed container, the formed product that cannot be completed by one drawing must be processed to increase the depth of the formed container.

Reverse stretching method: The workpiece stretched in the previous step is stretched in reverse, so that the inside of the workpiece becomes the outside and its outer diameter becomes smaller.

Thinning and stretching method: Use a punch to extrude the molded container into a concave die cavity slightly smaller than the outer diameter of the container, so that the outer diameter of the bottom container is smaller and the wall thickness is thinner, which not only eliminates the wall thickness deviation, but also makes the container surface smooth.

When using metal stamping dies for metal stamping and stretching, there are usually the following:

1 Panel stretching method

Panel products are all flat stamping parts with complex surface shapes. During the drawing process, the rough deformation is complex, and its forming performance is not only stretching forming, but also deep drawing and expansion composite forming.

2 Elliptical stretching method

The deformation of the blank on the flange is tensile deformation, but the deformation amount and deformation rate vary accordingly along the contour shape. The greater the curvature, the greater the plastic deformation of the blank; conversely, the smaller the curvature, the smaller the plastic deformation of the blank.

3-step stretching method

The initial drawing product on the left is re-stretched to form the stepped bottom on the right. The deeper part is deformed at the beginning of drawing, and the shallower part is deformed at the end of drawing. The side wall of the stepped part is prone to shear stress deformation.

4. Elliptical stretching method

The deformation of the blank on the flange is tensile deformation, but the deformation and deformation rate vary with the change of the profile shape. The greater the curvature, the greater the plastic deformation of the blank. On the other hand, the smaller the curvature, the smaller the plastic deformation of the blank.

5. Cylindrical stretching method

The stretching of a cylindrical stamping part with a flange , the flange and the bottom are flat, the side wall of the cylinder is axisymmetric, the deformation is evenly distributed on the same circumference, and the blank on the flange undergoes drawing deformation.

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