Design for Manufacturing: Sheet Metal Bending Maximums

This rule provides instruction on maximum bend angles associated with stamping operations.

Each time a part is bent, it requires tooling to do so. The processes where bending is accomplished such that a particular angle must be greater than 90 degrees is called over-bending. Unfortunately, over-bending is not a desirable trait for a part to have. Over-bending significantly complicates the required tooling as at least two bending operations will be required. Generally, this is accomplished by first bending the part to 90 degrees then bending to the remainder of the way in a separate operation.




Some commercial options are available that can accomplish this in a single operation; however, they are proprietary and must be individually licensed. These methods typically involve special rocker arms and roller assemblies which allow the part to be manipulated while being pressed.

If

(a) While designing a product which will utilize sheet metal…
(b) If bending operations are to be performed

Then

(a) Avoiding bend angles of over 90 degrees should be prioritized whenever possible
(b) If bend angles of over 90 degrees are required, multiple bending operations will be necessary
(c) The first bending operation is called the pre-bend and should allow for spring-back considerations

By following this rule, product designers will require less costly tooling in order to produce sheet metal parts which incorporate bending operations. Flow time will also be reduced as fewer operations are required if there are no bends greater than 90 degrees in the final product.

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