Thomas Vacca Thomas Vacca
Director of Engineering

Q: How Do I Reduce My Stamping-Die-Maintenance Costs?

June 5, 2024

Normally, a stamper’s largest cost (after raw material) is the labor required to service and maintain the die. This is a major reason why a lot of tool-and-die work has gone overseas. It’s not because overseas workers are smarter, faster or have access to cheaper steel, but because the labor cost, relative to that in the United States, is so cheap. How can we compete with that? By minimizing the labor required to maintain the tooling.  

Putting Real Numbers to Downtime

The cost of die maintenance is not based only on the toolmakers’ time and replacement components. Actually, time and components can cost much less than the overall maintenance. In calculating die-maintenance costs, look at the total cost—including the revenue losses incurred when the press is down unexpectedly; other employees’ labor to inspect the parts for defects; the need to reset the job; and management oversight, engineering and planning resources.  

For example, if a die is scheduled to run for 6 hr. but the stamper pulls the die out halfway through the run for a broken punch, the firm incurs uplanned downtime costs not included into the sales price. Also, cost estimates often are based on a best-case scenario. Assuming that the punch costs $25 and the toolmaker takes 1 hr. to replace it at a rate of $25 an hour, then the total cost for this unplanned down time is $50, right? Not really; consider other costs, too.

It takes the setup person 1 hr. in labor to pull the tool and 1 hr. to reset it. In addition, it takes 30 min. of quality-lab time to confirm that the part meets spec. A number of parts will be scrapped and quarantined, garnering scrap costs. The operator will be paid to be idle while the press sits idle, and some management time is required to ensure that all procedures and documentation requirements are followed. 

So, accumulatively, the actual maintenance cost for this single issue nets $50 plus 3 hr. of press time at your calculated rate, 2 hr. of setup labor, quality-assurance labor, scrap costs, the loss of the margin on the parts not produced and 3 hr. of overhead. The maintenance cost for this one small issue of unplanned downtime exceeds $500. 

Conversely, if the downtime had been planned and all tooling problems had been addressed and serviced offline, maintenance costs would have been substantially less. Unplanned maintenance can be four times more expensive than planned maintenance. Look at all of the costs that would have been nonexistent if the tool had not been in production.

Eliminate Unplanned Maintenance

Start by engineering out unplanned maintenance. Usually, the largest waste factor is in the stamping tooling. Develop a plan based on the assumption that the tool’s condition must be able to support running the required number of parts without stoppage. Optimally, a stamper can match the run quantity to the tool’s service life. The plan must address and contain specific action items for the tooling service tech to achieve peak performance. 

For example, when servicing a die fully, what actions can the technicians take to guarantee that no slugs pull during coil threading? What is the risk mitigation plan to move to full production without anything going wrong?

As I’ve said in my 10 Tooling Laws, “Nothing can change unless something changes.” If nothing changes then nothing will change—for better or worse! If you have completed a perfect stamping run, how will you guarantee that nothing changes during the service? Do you have a checklist of every item that must be inspected for wear? Have you developed a process as to how to inspect in measurable detail that takes the human guesswork out of what needs to be done? If it must be done, it must be on the print. Define and document everything.  

Good luck, and happy stamping. MF

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Industry-Related Terms: Die, Run, Scrap
View Glossary of Metalforming Terms

Technologies: Tooling


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