Free Engineering Tool
Estimate springback and the overbend angle to hit a target bend. Enter the sheet thickness, inside bend radius, target bend angle and material properties (Young's modulus E and yield strength σy) — the calculator returns the press-brake overbend setpoint, the springback angle it will recover, and the final (relaxed) radius.
Based on the ASM springback-ratio model (Ks = 4x³ − 3x + 1) for air/V bending. Our tooling engineers use this estimate before writing press-brake programs and designing bending dies, then confirm the exact compensation with a first-article part. Use the material quick-reference to auto-fill E and σy, or enter your own values from a material certificate.
Large springback — high-strength or low-modulus material with a generous radius. Increase overbend and verify with a first-article part.
ASM springback-ratio model (ASM Handbook Vol. 14B): Ks = 4x³ − 3x + 1 with x = σy·R/(E·t). First-order estimate — real springback also depends on tooling, friction, strain hardening and material-lot variation. Use the overbend angle as a starting setpoint and fine-tune with a first-article bend.
When a sheet-metal part is bent, only the outer fibres yield plastically; the material near the neutral axis stays elastic. When the tool is released, that stored elastic strain recovers and the bend opens up — the part “springs back” to a larger radius and a smaller bend angle than the tool formed. Springback grows with yield strength and bend radius, and shrinks with elastic modulus and thickness — which is why aluminium (low E) springs back far more than steel.
This calculator uses the ASM springback-ratio model (ASM Handbook Vol. 14B — Metalworking: Sheet Forming). To hit a target angle you overbend: form the part past the target by the springback amount so it relaxes onto the specification.
Units: σy in MPa, E in GPa (converted to MPa), R and t in mm, angles in degrees. The Ks = 4x³ − 3x + 1 relation assumes elastic-dominated bending and is most accurate for r/t ≥ 2.
| Material | E (GPa) | σy (MPa) | Note |
|---|---|---|---|
| Mild / Low Carbon Steel | 207 | 200–300 | Most common for brackets, housings and structural parts. |
| High Strength Steel (HSS) | 207 | 450–650 | Higher springback — plan for over-bending or bottoming. |
| Stainless Steel 304 | 193 | 250–350 | Work-hardens quickly; springback rises with prior forming. |
| Aluminium 5052-H32 | 70 | 180–210 | High springback relative to its strength due to low E. |
| Aluminium 6061-T6 | 69 | 240–290 | Strong and springy — trial parts recommended. |
| Copper (soft) | 117 | 60–90 | Low springback; easy to form. |
| Brass 70/30 (soft) | 105 | 110–150 | Moderate springback, good formability. |
E and σy are nominal values. Actual values depend on temper, direction (rolling direction) and prior cold work — use certificate values when available.
Aluminium 6061-T6 (σy = 276 MPa, E = 69 GPa), 1 mm thick, 10 mm inside radius, 90° target. x = 276·10 / (69000·1) = 0.04, so Ks = 4(0.04)³ − 3(0.04) + 1 ≈ 0.880. Overbend to 90 / 0.880 ≈ 102.2°, giving about 12.2° of springback and a final radius near 10 / 0.880 ≈ 11.4 mm. Compare with mild steel (E = 207 GPa, σy = 250 MPa): x = 0.018, Ks ≈ 0.946, overbend ≈ 95.1° — only about 5° of springback, confirming that aluminium needs roughly 2–3× the compensation of steel.
Springback is the elastic recovery of the sheet after the bending load is removed. The bent part partially returns toward its original flat shape, so the final angle is larger than the angle set by the tooling. The amount depends mainly on the material's yield strength relative to its Young's modulus (σy/E), the bend radius to thickness ratio (r/t) and the bending method.
This calculator uses the ASM springback-ratio model (ASM Handbook Vol. 14B): compute the dimensionless group x = σy·R/(E·t), then the springback ratio Ks = R_i/R_f = 4x³ − 3x + 1. The overbend angle (press-brake setpoint) is the target angle divided by Ks, the springback angle is the difference between overbend and target, and the final radius is the loaded radius divided by Ks.
Materials with a high yield strength and low elastic modulus spring back most. Aluminium alloys and stainless steel typically spring back more than mild steel of similar strength because their E values are lower. High-strength steels also show large springback because σy is high.
A larger inside radius relative to thickness (higher r/t) means more of the bend zone stays elastic, so springback increases. Small radii (r/t close to 1) push more material into plastic deformation, reducing springback. This is why tight-radius bends are easier to hold to angle.
The overbend angle is the press-brake setpoint: the angle you form the part TO so that, after springback, it relaxes to the target angle. It equals the target angle divided by the springback factor Ks. For example, a 90° target with Ks = 0.88 means you bend to about 102.2°. The springback angle is the difference between the two — it is the recovery, not the setpoint.
Ks is the ratio of the loaded (tooling) radius R_i to the final relaxed radius R_f: Ks = R_i / R_f = 4x³ − 3x + 1, where x = σy·R/(E·t). A Ks near 1 means little springback — thick stock, tight radius, low strength. A Ks well below 1 signals aggressive springback — high-strength or low-modulus material with a generous radius.
Common methods: (1) over-bending — set the press-brake angle to target / Ks so the part relaxes to spec; (2) bottoming or coining — press the sheet fully into the die to flatten the elastic zone and nearly eliminate springback; (3) radius compensation — divide the punch/die radius by Ks when the drawing specifies a formed radius; (4) multi-stage forming when the required overbend exceeds 180°. Always confirm with a first-article bend.
The Ks = 4x³ − 3x + 1 model is the standard first-order estimate and is accurate for elastic-plastic bending of common sheet alloys, but real springback also depends on tooling geometry, friction, strain hardening and material-lot variation. Use the overbend angle as a starting setpoint and fine-tune with a first-article bend measured on the same press and material that will be used in production.
Send your drawing to shawn@balford.net — our tooling engineers will confirm the springback compensation, die design and pricing within 24 hours.