Design and Manufacturing Guides

Four Tips for Avoiding Sheet Metal Deformation

Laser-Cutting
28 Nov

Sheet metal can be surprisingly unpredictable. Bend it in a press brake and it may distort in unexpected directions. To minimize this deformation the sheet metal fabricator needs to know and work with his material.

1.

Work-hardening

Bending metal makes the crystals side over one another. In some grades of some materials they move easily but in others they quickly lock together. This has the effect of increasing the metal’s hardness. If you look at aluminum sheet as an example, the 3000 series grades work-harden very little while the 7000’s demonstrate significant hardening.

Work-hardening increases the bending force needed, and also the chance of cracking. One way of reducing the effect of work-hardening is to bend faster.

2.

Grain direction

Rolling metal into sheet form at the mill elongates the metal crystals and gives it a grain. When bending metal along this grain there’s an increased risk of cracking, especially when putting-in a tight radius. It’s always best to bend across the grain.

sheet metal fabrication
3.

Hardness and thickness variation

Specifications for sheet metal allow for a range of hardness and thickness. As a result, two supposedly identical sheets may show differing degrees of springback. If the press brake operator isn’t alert to this he could end up with some parts that don’t assemble as easily as they should.

4.

Hole positions

A hole near a bend changes how the metal stretches and compresses, and that gives rise to deformation. A good rule of thumb is that any holes should be at least three times the material thickness away from the start of the bend.

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