Progressive die stamping is a multi-stage sheet metal forming process, where the final shape is given in two or more sequential operations. In progressive die stamping, coil is fed through all the stations and the blank is pierced and formed in the earlier stations. In the last station, the part is blanked and discharged from the skeleton. If the part cannot be formed within the metal strip (i.e., very deep drawing is present or the part size is large), transfer die stamping is used. In transfer die stamping the part is first blanked and then formed and pierced.
Since a progressive die (generally) is used in a single press, the part size is limited to small and medium parts. Larger parts may require transfer die stamping and a tandem press line. A very well known example of many parts formed by progressive dies is the soda can lid. The soda can itself is formed in a transfer die. Other examples of progressive die stampings include: electric motor laminations (stators and rotors), washers, oil filter housings among many others.
Designing progressive dies is more challenging than designing a single operation die. One has to decide the number of stations. This may be limited by the press bolster dimensions or the feeding device. After the decision, each station has to be designed. It is essential to check thinning and avoid cracking in each station. Today, Finite Element Analyzes (FEA) helps many die designers. Through FEA, it is possible to check the strain (thinning) distribution after each and every step.
Many metal forming companies offer progressive die stamping services: including the design and manufacturing of the dies and stamping of the parts. There are special presses (mechanical, hydraulic or servo driven) for progressive die stamping work. These generally have: