BIZOMAT MAKEOS · Fabrication
Sheet and Plate Bend Feasibility (Radius Limits, Springback, Press Force)
Can this material be bent to my inside radius without cracking or springing back flat, what angle must I bend to, and is the press brake big enough?
Feasibility check of a press-brake bend: the smallest inside radius the material takes without cracking from its tensile reduction of area, and the largest radius beyond which the bend stays elastic (as the bend radius limits tool), the radius and angle after springback and the angle to bend to (as the bending springback tool), and the air-bending force for the bend length and V-die against the press capacity (as the press brake force tool).
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Material thickness | mm | Thickness of the sheet or plate. |
| Planned inside bend radius | mm | Inside radius you want after bending. |
| Final bend angle | ° | Angle the finished bend must have. |
| Reduction of area in a tensile test | % | Reduction of area from the material’s tensile test (a measure of ductility). |
| Yield strength | MPa | Yield strength. |
| Tensile strength | MPa | Tensile strength. |
| Elastic modulus | GPa | Elastic modulus. |
| Press brake | ||
| Bend length | mm | Length of the bend line. |
| V-die opening | mm | Opening of the V-die. |
| Die factor | Die factor for air bending. | |
| Press brake capacity | kN | Rated force of the press brake. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Material thickness
- What it is
- The thickness of the sheet or plate being bent.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Press force rises with the square of thickness.
What this means: Planned inside bend radius
- What it is
- The inside radius the bend is formed to under load in the press; the tool treats it as the radius before springback and works out the larger radius left after release.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.01 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the inside radius, not the radius to the centre line; the radius limits are checked against this value.
What this means: Final bend angle
- What it is
- The bend angle the finished part must have after springback: how far the flange is turned from flat.
- Units and format
- Enter a number in °: degrees of angle. The form accepts 1° to 179°. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 90° as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Check whether your drawing gives the bend angle or the included angle between flanges; this tool uses the bend angle.
What this means: Reduction of area in a tensile test
- What it is
- The reduction of area at fracture in a tensile test of the material, a measure of its ductility, from the material certificate.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 1% to 99%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 40% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Higher reduction of area allows a smaller inside radius without cracking.
What this means: Yield strength
- What it is
- The yield strength of the sheet or plate material, from the material certificate; it sets springback and the largest radius that still yields.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 3000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 250 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Tensile strength
- What it is
- The tensile strength of the material, from the material certificate; used for the press brake force.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 3000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 450 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Press force is proportional to tensile strength.
What this means: Elastic modulus
- What it is
- The elastic modulus of the material, from its data sheet; it sets springback and the largest radius that still yields.
- Units and format
- Enter a number in GPa: gigapascals (1 GPa = 1000 MPa). The form accepts 0.000001 GPa to 1000 GPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 200 GPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Enter GPa, not MPa: the tool multiplies by 1000 internally.
Press brake
What this means: Bend length
- What it is
- The length of the bend line along the part.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1000 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Press force is proportional to bend length.
What this means: V-die opening
- What it is
- The width of the V-die opening across the top of the die.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 24 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Press force is inversely proportional to the die opening.
What this means: Die factor
- What it is
- The die factor in the air-bending force formula, from the press brake or tooling maker.
- Units and format
- Enter a plain number with no unit. The form accepts 0.5 to 10. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.33 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Press brake capacity
- What it is
- The rated force of the press brake, from its nameplate or manual.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.000001 kN to 1000000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1000 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Method and formulas
- Smallest radius = t (50 ÷ r − 1) with r the reduction of area %; largest = t E ÷ 2S_y (as the bend radius limits tool).
- Springback from R S_y ÷ (E t); final radius and bend-to angle (as the bending springback tool).
- Force = k L t² UTS ÷ V (as the press brake force tool).
- Example: radii from 0.75 to 1,200 mm are workable; bend to 90.329° for 90°, needing 224.44 kN.
Limitations
- Bend across the rolling direction; bends along the grain need a larger radius.
- Air bending; bottoming and coining need more force.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a tight bend in plate before trying it
- Choose a radius for a high-strength steel
- Set the press brake for a new material
Who it is for
- Press brake operators
- Fabrication engineers
- Sheet-metal designers
What you get
- Smallest and largest workable radius
- Radius after springback and angle to bend to
- Bending force and press use
Interpreting the result
- High-strength steels need both a larger minimum radius and much more overbend for springback.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1346–1353. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
Bending plate past yield
In Yield and Plastic Flow by the Numbers
What it covers: What happens through the thickness of a bend, the tightest radius a plate takes without cracking, how much it springs back, and why a punch change and a nesting change cracked a batch of brackets.
BIZOMAT tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Sheet and Plate Bend Feasibility (Radius Limits, Springback, Press Force) calculator