Do you bend sheet metal? If you do, you have likely been affected by material springback.

Springback is a natural phenomenon derived by residual elastic recover of the plate. After the bending force has been removed, the profile will tend to open and the resulting angle will be 2.5°-3° more than the expected result. When bending high-strength steels (HSS), elastic recover is often from 10° to 25°.

This effect can be compensated by overbending the profile at a sharper angle, so that springback will make it reach the desired angle afterwards.

It's a trial-and-error process: You bend a sample, measure it, correct the pressbrake setup, and then proceed to a few more pieces. After a while, you realize that the sheet metal you are now working comes from a different batch and has different properties. You have to start all the process from the beginning.

For this reason, we have developed an innovative device, named GPS4. A sensor embedded into the die mechanically measures the profile angle within the die cavity, so as to always reach the exact value.

The first advantage is the possibility to bend complex shapes, with Z-bends, or with narrow flanges. In those cases, optical sensing is either ineffective or leads to problems due to error accumulation.

Another strength point is that surface finish has no influence, while it can make some laser systems ineffective. Also setup times are reduced, because the operator does not need to know thickness, length, material or bending force.

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