Sheet marking is a common problem in sheet metal fabrication. Sometimes it is unavoidable, and in some cases it may not matter. But when it does matter, there are a variety of things you can do that will reduce unwanted marking. If you haven't tried one of the following, you may want to look into them as possible solutions for your shop.
Products
- Bonded Urethane Strippers for Thick Tooling: Hardened tool steel stripper plates that have had a layer of urethane bonded on the top surface to help reduce marking and can be used with a standard punch.
- Trumpf-Style Coated Stripper Plates: The addition of the wear-resistant Nylon-based coating helps to greatly reduce sheet marking when being used in an active stripping mode.
- Light Spring Packs: Replaces the heavy disc springs with lighter coil springs, resulting in less pressure on the sheet.
- Ball or Brush Dies: A ball riding or brush die brings the sheet up closer to the height of the forming die, allowing the sheet to move more freely through the punch press, helping to reduce sheet marking and distortion. A ball die, versus a brush die, is best for heavy or thick material applications.
- Retractable Die or Forming Station: Some machines have the ability to drop the forming die down and raise it when it is needed, essentially eliminating the cause of sheet marking.
Enhancements
- Nitrex® Heat Treatment: Nitrex high endurance surface enhancement strengthens the die cap protecting it from gouges when the sheet runs over it. This eliminates burrs on the die cap, which results in less marking on your sheet.
- Large Radius: Increasing the radius on the edge of the die cap creates edges that are more round, reducing the amount of marking on the sheet when it has to move over the die.
- Zip-Mar™ Adhesive Disks: Zip-Mar disks can be applied to your stripper plate to create a protective layer, greatly reducing, and potentially eliminating, sheet marking. Disks are simple to apply – just peel and stick – and are available in multiple sizes.
Application & Maintenance
- Place tools far apart in your machine. Punching too close to forming dies can cause sheet marking.
- Create as few motions over the forming die as possible, thus limiting the number of times the sheet has to pass over the die.
- Keep your dies and roller balls clean. A consistent cleaning schedule will prevent build-up, which can be a cause of sheet marking.
For more information on sheet marking solutions contact our Tooling Technicians.
October 02, 2020