The most common types of dies perform cutting and forming. Cutting dies are used to shear sheet material into what is called a blank. These blanks are then exposed to blanking dies that cut the entire perimeter of the part, or to forming dies where the blank is shaped into a part. Cutting dies are also used to trim excess metal from around a formed part. Punching is literally pushing or punching a "punch" through the blank to form a hole or slot.
Forming is a general term used to describe a stamped part whose shape and contour is reproduced usually through multiple operations within the dies set to produce the desired configuration.
The major forming operations accomplished with press-mounted dies are:
Drawing, or draw forming, involves forcing a blank deeply into a die cavity and shaping it into the shape and contour of the punch and dies faces and sides. Without sufficient formability qualities, drawn blanks are subject to folding, thinning, and fracturing.
Bending is a relatively simple forming operation that provides rigidity and shape to sheet metal parts. Similar to bending is flanging. However, a flange is significantly smaller in dimension than the rest of the part.
The functions of a flange include:
Hemming is the folding over of a short flange upon itself to form a smooth, rounded edge and to facilitate the attachment of mating parts. Multiple stamping operations may be performed within a single die, or at a number of die stations within a die set and with a single stroke of the press. Single station dies can be either compound dies or combinations dies. A compound die performs basic cutting operations such as blanking and hole punching to produce parts. Combination dies combine shaping and forming functions with cutting operation(s) to manufacture parts.