# Sheet Metal Springback and Overbend Calculator

> Source: https://netray.co/tools/sheet-metal-springback-overbend-calculator
> Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems.
> Section: Free Tools

## Short answer

Estimate how far a bend relaxes after the punch retracts and what tool angle to program to land on the target angle.

## Category

manufacturing

## Industry

Sheet Metal Fabrication

## Audience

- Press brake programmer
- Process engineer
- Tooling engineer

## Tool

**Kind:** calculator

**Currency:** $

**Inputs:**

#### Inside bend radius under load

**Key:** ri

**Type:** number

**Default:** 4

**Min:** 0.1

**Step:** 0.1

**Unit:** mm

#### Material thickness

**Key:** t

**Type:** number

**Default:** 2

**Min:** 0.1

**Step:** 0.1

**Unit:** mm

#### Yield strength

**Key:** y

**Type:** number

**Default:** 250

**Min:** 50

**Step:** 5

**Unit:** MPa

**Help:** Typical: mild steel 250, stainless 304 about 290 annealed, aluminium 5052-H32 about 195.

#### Elastic modulus

**Key:** e

**Type:** number

**Default:** 205000

**Min:** 10000

**Step:** 1000

**Unit:** MPa

**Help:** Typical: steel about 205000, stainless about 193000, aluminium about 70000.

#### Target final bend angle (deflection)

**Key:** target

**Type:** number

**Default:** 90

**Min:** 1

**Max:** 170

**Step:** 1

**Unit:** deg

**Outputs:**

#### Relaxation parameter (Ri x Y / E t)

**Key:** x

**Expr:** ri * y / (e * t)

**Format:** decimal

**Description:** Dimensionless group that drives springback.

#### Radius ratio Ri / Rf

**Key:** ratio

**Expr:** 4 * x * x * x - 3 * x + 1

**Format:** decimal

**Description:** Pure bending relation. Values below 1 mean the radius grows after release.

#### Final inside radius

**Key:** rf

**Expr:** if(gt(ratio,0.05),ri / ratio,ri * 20)

**Format:** decimal

**Description:** Radius after springback, in mm.

#### Tool angle to program

**Key:** tool

**Expr:** target * (rf + t / 2) / (ri + t / 2)

**Format:** decimal

**Primary:** true

**Description:** Deflection angle to form so the part relaxes to the target.

#### Overbend needed

**Key:** over

**Expr:** tool - target

**Format:** decimal

**Primary:** true

**Description:** Extra degrees beyond the target angle.

**Chart:**

#### Overbend needed vs inside radius

**Type:** line

**X:** ri

**From:** 1

**To:** 20

**Steps:** 20

**Series:**

- over

**Disclaimer:** The model assumes pure bending with a neutral axis at mid thickness. Real air bending springback also depends on die opening, tooling and material batch. Always confirm with a test bend.

## Content

**Intro:** After the punch lifts, elastic stress releases and the bend opens slightly. This calculator uses the classic pure-bending springback relation to estimate the final radius and the extra angle to program so the part lands on its target.

**Sections:**

#### How to use it

**Body:** Enter the bend radius, thickness, yield strength and elastic modulus for your material, then the angle you want after springback. The calculator gives the tool angle to program and the number of degrees of overbend. Higher strength, larger radius relative to thickness and lower modulus all raise springback. That is why aluminium and high strength steel need more compensation than mild steel at the same radius. Use the chart to see how quickly the overbend grows as the radius increases.

#### The relation used

**Body:** The model uses Ri / Rf = 4 (Ri Y / E t)^3 - 3 (Ri Y / E t) + 1, where Ri is the radius under load and Rf is the final radius. The bend length on the neutral axis is assumed unchanged, so angle times (R + t/2) is conserved. Solving for the angle that relaxes to the target gives tool angle = target x (Rf + t/2) / (Ri + t/2). It is a textbook estimate for pure bending, a good starting point for programming and a useful sanity check.

**Bullets:**

- Ri / Rf = 4x^3 - 3x + 1 with x = Ri Y / (E t)
- Angle x (R + t/2) is held constant
- Tool angle = target x (Rf + t/2) / (Ri + t/2)

#### Common mistakes

**Body:** Do not use the radius you want after bending as Ri. Use the radius the tool forms under load. Do not rely on handbook yield values for coil you have not tested, since mill variation can shift springback by a degree or more. Press brake controls often include their own angle measurement and correction, so treat this tool as a planning estimate and log the final compensation used in your setup sheet for repeat jobs.

**Cta:** Setup sheets that record actual compensation by material and lot are valuable. We can help link that history to your ERP routing so programmers start from proven values.

**Faq:**

#### Why does stainless spring back more than mild steel?

**Answer:** Stainless 304 has a higher yield strength at a similar modulus, so the elastic recovery is larger. Work hardening during forming adds to the effect.

#### Is the model valid for air bending?

**Answer:** It is derived for pure bending and is only an approximation for air bending, where the die opening also influences the result. Use it as a starting estimate and verify on a test part.

#### How many degrees of springback is typical?

**Answer:** Mild steel with a low radius to thickness ratio often shows well under a degree to about two degrees. Aluminium alloys and high strength steels can need several degrees. Always measure.

#### Can I enter inches and psi?

**Answer:** Yes, if you use consistent units. Radius and thickness must share one unit, and yield strength and modulus must share another pressure unit. The relation is dimensionless.

## Search terms

springback calculator sheet metal, overbend angle calculator, springback formula, press brake springback compensation, springback factor stainless steel, bend angle compensation, sheet metal springback aluminium

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