KEVOS® MAKEOS · Fabrication
Bent Bracket Plan (Flat Blank, Bend Force, Springback)
For this bent sheet-metal bracket, what flat blank do I cut, what press brake force do the bends need, and to what angle must I bend to allow for springback?
Plan for a press-braked bracket with one or two bends: bend allowances, setbacks, bend deductions and the flat blank length from the outside flange dimensions (as the sheet-metal flat pattern tool), the air-bending force for the bend length in your V-die against the press capacity (as the press brake force tool), and the angle to bend to so the bend springs back to the drawing angle (as the bending springback tool), with blank mass.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Thickness | mm | Sheet thickness. |
| Inside bend radius | mm | Inside radius of the bends. |
| K-factor | K-factor locating the neutral axis in the bend. | |
| Flanges (outside dimensions) and bends | ||
| Flange 1 | mm | First flange, outside dimension. |
| Bend 1 angle | ° | Angle of the first bend. |
| Flange 2 | mm | Second flange, outside dimension. |
| Bend 2 angle (0 = one bend) | ° | Angle of the second bend (0 for a single bend). |
| Flange 3 | mm | Third flange, outside dimension (used with two bends). |
| Bend length (part width) | mm | Length of the bend line (the width of the part). |
| Material and press | ||
| Tensile strength | MPa | Tensile strength of the sheet. |
| Yield strength | MPa | Yield strength of the sheet. |
| Elastic modulus | GPa | Elastic modulus. |
| Density | kg/m³ | Density of the sheet. |
| 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. |
| Least end flange for the die | mm | Shortest flange that sits across the V-die. |
| Least inside radius (× thickness) | Smallest inside radius the material bends to without cracking, as a multiple of thickness. | |
Method and formulas
- Bend allowance = θ (R + K t); setback = (R + t) tan(θ ÷ 2); deduction = 2 × setback − allowance; flat length = Σ flanges − Σ deductions (as the sheet-metal flat pattern tool).
- Force = k L t² UTS ÷ V (as the press brake force tool).
- Springback ratio from R S_y ÷ (E t); bend-to angle = final angle ÷ K_s (as the bending springback tool).
- Example: cut the blank 101.94 × 300 mm (0.48013 kg); each bend needs 44.888 kN; bend to 90.382° for 90°.
Limitations
- One radius and K-factor for all bends; air bending in a V-die.
- Springback from elastic–plastic theory; confirm with a trial bend.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Prepare a blank and brake set-up for a bracket
- Check a press brake can bend a part
- Set the overbend for springback
Who it is for
- Press brake operators
- Sheet-metal designers
- Fabrication supervisors
What you get
- Flat blank length and mass
- Bend force and press use
- Angle to bend to for springback
Interpreting the result
- A wider V-die lowers the force but raises the inside radius and springback.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1346–1353. Topic reference; no source tables or recommended settings are reproduced.
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Open the Bent Bracket Plan (Flat Blank, Bend Force, Springback) calculator
