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Unison Tube Bending Blog: Springback

How do you work out the Springback of a piece of material so that you can get most bend angles closer to the designed angle?

Written by Managing Director Alan Pickering.

The traditional and still the best method for doing this is by picking two bend angles and making two test bends and measuring the result.

The typical angles chosen to bend are 20 & 120 degrees, however if most of your designed bend angles fall within a smaller range eg. 30 & 90 then the calculations will work better the tighter the range.

Most modern control systems will have a Springback Calculator built in, into which you put these two designed angles and the two angles achieved.

The simple bit of mathematics behind it will give you Fixed Springback and Proportional Springback and these can be automatically added to your designed YBC / LRA part.

Fixed Springback is basically the amount of springback that will always happen what ever you do to the material.

Proportional Springback is for every degree of bend, your tube will springback by this amount.

Eg. If your fixed springback is 1.5 degrees, your proportional springback is 0.05 degrees and your designed angle is 90 degrees, that will require a bend of 90 + 1.5 + (90 * 0.05) = 96 Degrees.

Another element you need to consider, especially when you are bending high springback material such as Titanium, is Radial Growth as this will seriously effect your part geometry.

What is Radial Growth?

In essence, Springback doesn’t just come from nowhere or reappear nowhere.

Whatever you have in the Swept Length of the Springback of the bend appears in the corresponding straight.

High-end control systems such as Unibend have this feature automatically built in should you wish to turn it on, for most applications it isn’t required, but for Aerospace tube bending it is almost essential.

Got a question for our expert team? Drop us an email – sales@unisonltd.com