Grid Marking

Circular Grid Systems

A KEY WORD in describing the production of successful stampings is formability. The term, which denotes the ability of metal to be developed to be deformed into desired shapes, is a communication link between the user and supplier of sheet metal. The fabricator attempts to specify desired levels of formability for each application and then makes quality control checks on incoming material. The producer wants to tailor his production practices to impart the specified level of formability into his products. Both agree that sheet metal should possess maximum formability.

Formability, however, is an elusive quality to measure. While our understanding and techniques are by no means complete, recent advances have greatly reduced the problem. One of the current attempts to measure formability is the grid analysis system in which grids are composed of very small diameter circles (0.25  0.05 in.) are used. This system was first proposed in May 1965. (1)* At that time very limited press shop experience with the technique had been obtained: the bulk of the results had been derived from laboratory experiments. Now, after more than two years of production trials, a reexamination of the technique is in order. Our goals, therefore, are to:

1. Briefly review the evolution and mechanics of the technique.
2. Critically access the present state - of - the - art.
3. Suggest areas of application.

A paper by G. M. Goodwin (2) examines specific case histories of applying a circular grid system.