A hardened steel contour with a sharp edge presses against plastic foil which lies on top of a hardened steel anvil plate. What would be the force required to punch through the foil?

I am familiar with the general punching/blanking formula, however, as far as I know this only applies to punching into a die i.e. the countour goes fully through the sheet. A picture is added to further clearify the question.

General blanking formula: \begin{equation} F = K*l*t*\tau \end{equation}

where $K$ is a material/safety factor, $l$ the circomference of the contour, $t$ the sheet thickness and $\tau$ the shear stress.

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  • $\begingroup$ So, you say the hardened steel tool has to go through the plastic and you state the formula is for a tool to go through material. Then why do you think it is not relevant? $\endgroup$
    – Solar Mike
    Sep 7, 2022 at 13:42
  • $\begingroup$ The formula is for full puncturing. In this case the contour cannot fully pass through the foil. It can only press against a bottom anvil with the foil in between. I can imagine this might not match the given formula but I'm more than happy to be told otherwise. $\endgroup$ Sep 7, 2022 at 14:17

1 Answer 1


Common plastic used in grocery shopping has an average shear strength of 200-500 psi. Or check the datasheet!

One could multiply this by the length of the cut, or perimeter of the circle.

A punching tool with a sharp edge and slanted strike can cut with much less force, but one has to be careful to halt the tool before it actually hard lands on the anvil!


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