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What’s Got You Warped?

Learn techniques for preventing distortion during punching applications. 

December 6, 2019

There’s no way around it: sheet metal can be tricky. When your material is under the tool, there are countless variables that can cause imperfections like buckles, wrinkles and waves. The imperfections left behind by the oil-canning effect are not structurally harmful, yet their aesthetic leaves something to be desired.

What is Oil Canning/Distortion?

It might look like clockwork, but each punch is a dramatic event causing major stress across your material; with each hit your material becomes more vulnerable to distortion. To put it simply: fewer hits minimalizes the opportunity for distortion/oil canning.

Oil canning, also referred to as distortion, is a warping effect that takes place during the punching process. The force of the punch causes the material to distort from a flat sheet to wavy or buckled. Regardless of structural integrity, the cosmetic blemish left behind is unacceptable. 

What Can Be Done to Mitigate Oil-Canning?

There’s no cure-all and each application will have its own intricacies and challenges. Variables like clearance, number of inserts in a cluster tool, and the height of those inserts should be taken into account when trying to avoid unsightly warping. For perforating applications, Wilson Tool offers cluster tools, which allow for the maximum number of holes with the least amount of hits. Cluster tools can be designed with any hole size, shape or pattern, from 2 to 120 holes per punch. Cluster tools can be combined with a back-bending die to further defend against oil-canning.

Programming is a game-changer. Changing how and when you hit the material and how stress is distributed across the sheet can make all the difference. By starting in the middle of the sheet and working in a circular, middle-out pattern, you’ve taken a large step toward minimizing the oil-canning effect.

Need More Advice?

Following these tips will have a mitigating effect on distortion, but again, there is no cure-all solution. For help guiding you through your own application, contact a tooling technician at Wilson Tool International, where we can walk through the process, step-by-step, finding an approach that works for you.

For more information on techniques to avoid distortion, read this article or visit

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