Sheet Metal Springback: V-Die Bending Simulator

Blank & Tooling

Material Mild Steel

Sheet thickness t 1.5 mm

Die bend radius R_i 6 mm

Die bend angle θ_i 90°

Flat blank — ready

Live Readouts

R/t ratio

4.0

K-factor R_i/R_f

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Final radius R_f

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Final angle θ_f

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Springback angle Δθ = θ_i − θ_f

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How it works

When a punch forms sheet metal over a die radius R_i to a bend angle θ_i, the outer fiber of the bend yields plastically but the material near the neutral axis stays elastic. The moment the punch retracts, that stored elastic strain relaxes and the part "opens up" — the bend radius grows and the included angle decreases. This is springback, the single hardest thing to predict in stamping die design.

This simulator uses Gardiner's classic closed-form springback equation, still the standard first-pass estimate in press-shop practice:

x = Ri·σy / (E·t)
Ri/Rf = 4x³ − 3x + 1

Ri = die (initial) bend radius
Rf = free (final, sprung-back) radius
σy = material yield strength
E  = Young's modulus
t  = sheet thickness

Because the neutral-axis arc length is conserved during the elastic recoil (no further plastic flow, no stretching), the swept bend angle scales with the same ratio:

θf = θi · (Ri/Rf)
Δθ = θi − θf   (the springback angle)

Higher σy/E (e.g. spring steel) → larger x → more springback. Steel dies for spring-steel parts are cut with a deliberately over-bent angle to compensate.
Larger R/t (thin sheet, gentle radius) → more springback, because a smaller fraction of the cross-section reaches yield.
Aluminum springs back more than mild steel at the same R/t despite its lower yield strength, because its modulus E is roughly a third as stiff — the σy/E ratio is what matters, not σy alone.

Press the button to watch the sequence: punch descends and bends the blank to the die angle, punch retracts, and the strip elastically relaxes to the predicted final shape.

Sheet metal blank Punch / die tooling

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