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What effect does toolroom management have on tooling life?

Extend the life of metal stamping tooling

The progressive die operation by making the sheet metal parts for automotive industry.

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Q: We know that tooling life can be improved by using the right material, coating, lubricant, and press. Are there any other factors that can extend the life of stamping tooling?

A: Yes. One big, and rarely addressed, factor is toolroom management. To really have a best-in-class stamping shop, you need to implement four fundamental practices.

1. Zero First-off Part Quality Failures

On every new tool setup, it usually is standard practice to do a complete dimensional readout on the part. This takes some time and labor. If the part fails, you have to go back, adjust, and repeat the cycle, and that’s a total waste.

Before your first-article inspection (FAI), know what you need to look at. Some features generally don’t change, like trim dimensions, while others are subject to variation, like forms and true positions. Take the time to know your part is good before moving to FAI. Track the number of failures versus passes. The goal is 99% passing.

2. Zero Unscheduled Die Pulls for Service

Don’t wait until your tool has to be pulled for service. Schedule service based on the expected number of hits you know you can get repeatably. Unscheduled die pulls cause chaos; multiple tools often are pulled at the same time, and some have to wait because of labor availability.

Also, consider the length of the stamping run. If you expect a service at 300,000 hits and the total run is 500,000, service the tool around 250,000 hits. This allows the pressroom planners to manage their labor by knowing ahead of time what is running and what isn’t.

Track the unscheduled die pulls. The goal is zero.

3. Proactive Tooling Component Changeouts

With tools that do a lot of forming, the forms do not all wear at the same rate. Usually, a particular part feature goes out of spec, and then we pull the tool and replace it.

This practice can be complicated by a few factors, however. First, multiple forms in the die are interdependent when forming part features; if a new form is working with an old, worn form to produce the part features, the results might not be to spec.

Second, some form tools are so complex that it can be very challenging to get the exact same results with a replacement spare. Be sure to identify these tools in advance and start replacing them one at a time on your standard end-of-run service. Don’t wait for a part failure.

After replacement, if the next part run is good, wrap up the replaced form; label it with the date, number of hits, and condition; and store it as a spare that is good to go. If the next part run is not good, drop in the tool you removed and figure out the problem at the end of the production run. Do this for all the critical forms, one at a time, until you have a complete set of proven forms in your spare tools inventory. The goal is zero unscheduled die pulls during production runs.

4. Root Cause Discovery and Documentation

Any time you experience an unscheduled die pull, take some time to determine the root cause:

  • How many hits did the tool get as compared to expected service life?
  • Did the failure happen on lace-up or while the tool was running?
  • Is this a new lot of raw material?
  • Are there anomalies in the run data?
  • Based on the lead hit, is the press ram setting correct?
  • Do the slugs in the tool and scrap bin show evidence of the problem?

Keep a record of every unscheduled die pull and fill out a corrective action sheet. As your base of data grows, these records will be a great resource when future problems arise. This documentation process also forces the team to really look for a cause instead of just replacing the broken punch and moving on. Remember, Tooling Law No. 4 states, “If nothing changes, then nothing will change.”

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.