Press Mold Special Edition: Mold Maker Column - What is the Hull Bottom Phenomenon?

In the mold shop column, we will continuously share various topics about molds! (We also publish the mold shop column on our company Instagram.)

In this column, I will introduce the "boat bottom phenomenon"! When you want to punch out terminal shapes like those in the icon diagram, processing them at every pitch, as shown in Figure A, results in a reduced area for holding during the punching process. This can lead to situations where the punch comes down with such force that the stripper plate cannot hold the product securely, causing it to tilt over. This is known as the boat bottom phenomenon. The tilted product resembles a boat bottom, hence the name. To avoid this, changes in layout are necessary. For example, one solution could be to use multiple pitch feeding as shown in Figure B. In the case of multiple pitch feeding, a single group is punched out in one go (all punches come down simultaneously), leaving no room for the product to tip over, thus preventing such issues. However, on the other hand, this will narrow the spacing between the dies, which raises concerns about die strength. It is essential to determine specifications based on strength calculations.

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