Metal Stamping Process & Capabilities
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As described earlier, the metal stamping process places compressive forces on the raw material. As the top edge is rolled into the cut, the bottom edge tends to turn slightly also. This distortion at the edges affects the flatness of the finished part, being minimal in thinner or milder materials, but becoming severe in heavier stock or tougher materials such as stainless steels and highength alloys. When flatness is critical, tooling can be designed to minimize distortion but may require extra stations or secondary operations.
For the same reason, perforated or trimmed features that are placed too close to each other or the material edge tend to roll the material between, producing a distorted or thinned edge. The rule of thumb in stamping design is to leave a minimum of 1-1/2 times material thickness between trimmed or perforated features. Also, the stretching and compression of forming can distort holes adjacent to a form or bend. Holes are best kept at least 2 times material thickness beyond the radius of a formed feature. If this is not possible, the hole should be designed with sufficient clearance to allow for distortion.