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Stretch forming

Stretch forming is stamping process where by means of pressure, tensile stress and a locking mechanism, sheet metal is changed into a curved body.

Illustration of Stretch forming

The process

The method uses rigid tools such as punch [1], and die [2] and holder [3]. The blank is placed and locked between the die and the holder and then deformed as the punch presses the plate into the die. Only the portion of the blank that is in direct contact with the stamp is deformed, stretched and becomes thinner.

Stretching changes metal sheets into curved parts or create curved parts with smaller diameter from already curved details.

Advantages and disadvantages
In comparison with alternative methods
Large and easily contoured products from thin sheets can be created
Tight tolerances
Suitable for small series production
High cost
Requires preparation of edges before processing
Can not be double curved surfaces