How do I stop press brake tooling marking the part?
Marks come from contact pressure at the punch tip and the die shoulders. The practical fixes are a urethane die, a wider die opening, a protective film at the contact points, and a polished or coated tool.
What causes marks on a bent part?
Two mechanisms: the sliding contact at the punch tip as the material bends, and the pressure against the die shoulder. Softer and coated materials show both more readily.
| Mark | Cause | Typical fix |
|---|---|---|
| Line across the inside at the tip | Punch tip contact pressure | Larger tip radius, film, polish |
| Line on the outside at the die shoulder | Shoulder pressure | Wider die opening, urethane, film |
| Scuffing along the bend | Sliding contact and galling | Lubrication, coated tool, polished surface |
| Indentation at a point | Debris or a damaged tool | Clean and inspect the tooling |
What is anti-mark tooling?
Anti-mark tooling reduces or moves the contact pressure so the visible face is not marked. It includes urethane dies, dies with radiused or reduced shoulders, punch tips with a larger radius, and tools with a protective coating.
- Urethane die: the insert carries the contact, so steel never touches the face.
- Radiused shoulders: spread the pressure over a wider area.
- Larger punch tip radius: reduces tip pressure but increases the bend radius.
- Protective film or insert: a consumable that takes the contact instead of the part.
- Coated tool: reduces friction and galling, which limits scuffing.
When is a protective film better than a urethane die?
A film is better when the drawing specifies a tight radius, because it does not change the radius. A urethane die changes the radius to a larger, load-dependent value, which may not suit the part.
Does lubricating the material help?
It reduces sliding friction, which limits scuffing and galling, but it does not remove the pressure marks at the contact points. It also has to be cleaned off afterwards, which matters for painted parts.
For pre-painted or coated sheet, check that any lubricant used is compatible with the coating before running production.
Related technical pages
Urethane dies
Mar-free forming with an elastomer insert.
Radius dies
Radiused shoulders that spread the contact pressure.
Press brake dies
Die types and openings, and how the opening affects marking.
Troubleshooting
Diagnosing marks and the other common faults.
Next step
Send a sample of the material and a photograph of the mark and we will recommend the tooling or surface treatment that removes it.
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