Why is my press brake bending unevenly?
Uneven bends are most often caused by the tooling not being seated or aligned, by worn or mixed tooling segments, or by deflection across the beam that crowning is meant to correct. Machine levelling and material thickness variation are the other common causes.
Symptom, cause and fix
Work from the symptom rather than the suspected cause. The table below covers the faults seen most often in press brake work.
| Symptom | Likely causes | What to check first |
|---|---|---|
| Angle varies along the bend | Beam deflection, mixed or worn segments, uneven seating | Seat and align the tooling, then check crowning |
| One end bends more than the other | Tooling not parallel, ram out of level | Check tool alignment and machine level |
| Bend angle wrong overall | Material springback, wrong die opening, wrong depth | Measure a trial part and correct the depth |
| Cracking on the outside | Radius below the material minimum | Increase the radius or change the material |
| Marks on the part face | Punch or die contact, galling | Anti-mark film, urethane die, or polish the tool |
| Punch or die cracked | Load per metre exceeded | Compare calculated load with the tool rating |
| Flange too short to form | Below the minimum flange for the die | Narrower die or reduced-shoulder die |
| Bend opens after release | Springback not compensated | Overbend or use angle correction |
Why do I get marks on the part?
Marks come from the punch or die contact points sliding on the surface, or from the material being pressed against a sharp die shoulder. Soft materials, coated sheet and cosmetic faces show them first.
- Use a urethane or polyurethane die for a mar-free finish.
- Fit a protective film or anti-mark insert at the contact points.
- Widen the die opening to reduce the shoulder pressure.
- Check for galling on the tool and polish or replace it.
Why does the bend angle vary along the length?
The usual cause is deflection of the ram and the bed under load, which the machine's crowning system is designed to compensate. Worn or mixed tooling segments make it worse because the load is not shared evenly.
| Check | What a bad result means |
|---|---|
| Seat the punch and die and re-clamp | Loose or dirty seating spreads unevenly |
| Compare segment wear across the length | Mixed wear gives mixed angle |
| Verify crowning is set for the job | No compensation means a bowed bend |
| Check material thickness across the blank | Thickness variation bends differently |
Why did my tool crack?
Almost always the load per metre, not the machine tonnage. A narrow die opening, a thick or high strength material, or a long bend can put the tool over its rated load, and the failure is sudden.
Related technical pages
Tooling load calculator
Check the load before a tool cracks.
Regrinding guide
Wear and regrinding, and when to replace.
Anti-mark tooling
Eliminating marks on cosmetic faces.
Tooling setup guide
Seating and alignment, the first thing to check.
Next step
Describe the symptom or send a photograph of the faulty part and we will suggest the tooling change that fixes it.
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