How to use the sheet metal springback calculator
Bend a part to 90 degrees on a press brake and it always opens up once the punch lifts, because the elastic portion of the deformation recovers. Enter the punch radius, sheet thickness and material properties and this tool returns the springback angle plus the overbend angle the tooling needs to land on your target.
The calculation uses the standard metal forming relation Ri/Rf = 4(Ri Y / E t)^3 - 3(Ri Y / E t) + 1, where Y is yield strength and E is elastic modulus. Holding the neutral axis length constant then converts the radius change into an angle change, giving both the formed radius and the degrees of recovery.
Aluminum springs back far more than steel for the same geometry because its modulus is roughly a third as high, and high strength or spring steels behave the same way through their higher yield point. Tightening the punch radius lowers the R over t ratio, raises the plastic share of the deformation, and shrinks springback.
Watch the lower limit though: once R over t falls below about 1 the outer fiber can crack, so check the minimum bend radius published for the alloy and temper. Treat these numbers as a tooling design starting point, since rolling direction, coining pressure and lot to lot variation all shift the real result, and confirm with a test bend.
Frequently asked questions
Springback scales with yield strength divided by elastic modulus. Aluminum has roughly a third the modulus of steel, so the same thickness over the same punch radius springs back noticeably further.
Tightening the punch radius lowers the R over t ratio and cuts springback. Coining at the bottom of the stroke to force plastic deformation, or building the overbend angle straight into the tooling, are the other common fixes.