From Handbook of Die Design, Second Edition

2-1 SHEET METAL AND ITS BEHAVIOR IN METAL STAMPING PROCESS

The metal stamping process can alter the sheet-metal material in many ways. Parts may be blanked, pierced, drawn, formed, or embossed, just to name a few basic operations. Each of these processes exerts its influence upon the structure of the material: that of the part and that of the scrap.

Often, a congested piercing can cause stresses that will produce an increase in area measurements of that particular section, which is called bulging, or oilcan effect (from oilcan's snapping back and forth). Forming or drawing, on the other hand, can produce wrinkling, tearing, ironing, or undesirable folding of metal.

2-2 PLASTICITY THEORIES

During the forming or deforming process, any metal material, with all its mechanical, electrical, and other properties, will go through a transformation from its elastic state to plastic. These changes are forced upon its structure by various stresses, temperature changes, and speed of the forming application, among others. The changes may occur either along the plane of the highest concentration of potential energy, or along the plane of maximum shear stress.

Naturally, such an array of influences cannot fail to produce considerable changes in the part's structure and appearance. Some changes may have been originally planned for, and for that reason these can be considered beneficial. Unfortunately, there can be changes that are detrimental to the outcome of the performed operation and these result in a defected product.

In an attempt to control the material-related defects...

Copyright Ivana Suchy 2006 under license agreement with Books24x7

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Stamping Services
Stamping services use punches and dies to create three-dimensional parts and add surface definition such as lettering to flat-sheet materials.
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Deep drawing services form parts by using a punch to radially draw a sheet metal blank into a forming die. The part is re-drawn through a series of successively smaller dies until its depth is greater than its diameter.
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