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Old 09-04-2009, 07:58 PM
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tdoty tdoty is offline
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I love a heated debate! Even when subjects get intertwined and somewhat confusing. Besides, it was my day off and I really had nothing better to do

John, drawing as a manufacturing process is indeed "performed by placing a piece of sheet metal over a die cavity and then pushing the sheet into the opening with a punch."

Drawing as a side effect (or even an intention, I guess) is pulling in metal from an area outside what is being worked.

Without firing up the debate again (unless we want to), I think I may have figured out a way to clarify my statement. I still say that stretch does not cause the tucks to form at the edge. However, most processes we use to stretch metal will also draw in material from other areas of the panel. That drawing in of material is what causes the tucks to form. In general use, it may not be at all practical to stretch without the drawing in to occur, but it is that drawing in of material, not the stretch, that causes the tucks to form.

On another note: The classic paper example was brought up. The problem with that theory, for a lot of metalshaping issues, is that cured paper does not have a plastic or elastic state - it doesn't stretch and it doesn't shrink. Steel and aluminum (as particular examples) DO posses plastic and elastic characteristics. In the die drawing example, the stretch and the shrink, to a very large extent, cancel each other out. The result is that, although shrinking and stretching have both taken place, the net surface area remains the same.

Once we got both subjects involved at the same time, and went back and forth between the two, references to drawing became interchangeable. That really was not the intent. Though there are some serious parallels between the drawing process and the "drawing effect", they are not exactly the same thing.

Now, my way of thinking may not work for everyone, but it helps me understand what is going on with the metal. I feel you have to understand what is happening in order to get the metal to do what you want...or what you think you want. At the end of the day, you really want to convince the metal that what it wants to do is the same as what you want it to do

Tim D.
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