Guide

Deep drawn metal stampings can be classified into 3 categories, simple, average & difficult. Simple drawn parts usually have the following characteristics; Straight one diameter shell, no critical visual requirements, corner radius equal to 3 times material thickness or greater, an overall length of 1 ½ to 2 ½ times the diameter of the part, an overall length tolerance of plus or minus .005, a wall thickness of .010 – .020 and a tolerance for the outside or inside diameter of the part of plus or minus .002.

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Deep drawn metal stampings have basic dimensional characteristics. The first of these would be in regard to material thickness. The bottom of the shell tends to remain the same thickness as the original starting material since this area is not affected by the draw process. This area does not see a change in temper as well since it is not being worked unless it is being coined or flattened.

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As we continue forward in understanding the deep draw process, let’s look at the different stations that we can have in the press and their functions. As mentioned previously, the first station is the blanking station. The blank is pierced out of the metal strip and then forced down to the transfer slide which moves the blank to the next station. The second station is called the cupping station. This is where the blank is first reduced. The reduction of the blank should not be any more than 45% of the blanks diameter which will avoid any tearing of the material. Following the second station or cupping station are a series of deep drawing stations. Depending on the press it is common to have up to 12 to 15 stations to form a finished part.

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Continuing from last week’s post, the blank for the part to be drawn is removed from the strip and moved into the transfer slide. The transfer slide carries the blank to the first draw operation or station. At this station the blank is drawn to its first shape. The transfer slide then returns to its original position and is now ready to accept the next blank.

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