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Ask the Stamping Expert: The continuing challenge of die maintenance

Q: I have been trying to locate the die maintenance check list printed in a STAMPING Journal® article several years ago, which also included the 10 Tooling Laws. I am hoping you can lead me to it.

A: You will find the check list at the end of this article. But even with a maintenance check list like this, stampers typically don’t understand the three primary end goals of the process: consistency, documentation, and continuous improvement. This thought process is driven home with the 10 Tooling Laws. You can find them at www.thefabricator.com/article/stamping/10-design-laws-for-tool-designers. Post them in your shop.

However, following the 10 Tooling Laws and driving toward the end goals will not get you where you need to be without the 3 R’s. Be sure to consider these fundamental practices in the design phase to prevent problems in the maintenance phase:

  • Repeatability – Design components to prevent mistakes. Specify details to increase repeatability. Define springs. If pilots need to be removed for tool servicing, make sure they’ll go back in the same location. Add callouts for surface finish. Make sure components can’t be put in upside down, backwards, or in the wrong location.
  • Reliability - Tool builds that yield a lot of variation fall short on robustness. Die shoes are too thin, resulting in forming variation. Down stops are not sufficient to maintain consistent hits. The guidance pins and bushings are too small. Coil springs are used when nitrogen are required. Pressure pads are missing. There aren’t enough pilots and lifters. Stripper clamping pressure is insufficient. Slug retention is not designed into the tool.
  • Replication - Design a process or tool that is easy to duplicate. The design needs to ensure you can make multiple spares, all exactly the same. I have seen complex form inserts that required regrinding when serviced. After every service, adjustments were required. If tool builders would split the dies into two stations and wire EDM the components, it might add a few thousand dollars to the tool cost, but it would be repeatable and prevent the expense of many hours every week over the life of the program.
  • A best-in-class maintenance procedure will let you predict what needs to be serviced and when. Your quality data will be consistent, and costs will be driven down.

    20-point Tooling Maintenance Check List

    1. Before cleaning a tool, visually inspect it for slivers, sludge, and black grease.
    2. Visually inspect the last strip. Look for punch shear and brake lines, burrs, tool marks, and slivers.
    3. Inspect the slugs for correct penetration and tightness, as well as irregularities.
    4. Check and measure the die shoe guideposts. Inspect for tracking, galling, and wear.
    5. Check that all pilots are present and the right length. Always measure the first one, as it does most of the work.
    6. Check the punch length with a height gauge to make sure it is correct.
    7. Make sure the punch float and pump in the punch holder are correct.
    8. Check the height of the die inserts and forms with a height gauge.
    9. Check and confirm the strip lifter height. Springs may collapse over time.
    10. Make sure toe straps and clamps appear to be in good order.
    11. Visually inspect die sections for chips and side galling.
    12. Visually inspect the stripper face for signs of wear, hits, nicks, and other damage.
    13. Make sure the in-die stock pusher is working properly.
    14. Inspect the scrap retainers.
    15. Check all the miscellaneous items in the die maintenance card instructions, such as the lace-up starting point and concerns and tooling demagnetization. These should include general notes that toolmakers have entered regarding specific historical problems to help prevent having to reinvent the wheel.
    16. Check the safeties and air ports.
    17. Complete the maintenance check list and file it in the die maintenance card.
    18. Make sure the die maintenance card has been filled out for all work done.
    19. Tag the tool with the proper storage tag, and put it away in the designated location.
    20. Make sure all orders for spare parts are submitted.
About the Author
Micro Co.

Thomas Vacca

Micro Co.

Has a shop floor stamping or tool and die question stumped you? If so, send your questions to kateb@thefabricator.com to be answered by Thomas Vacca, director of engineering at Micro Co.