Thomas Vacca
Director of Engineering

Tips for Maximizing Tooling Life

I receive many questions on how to improve high-speed progressive-die hits per service, otherwise known as “tooling life.” How can I get more parts per service? How can I run the tool longer and faster?  

The most immediate answer: Add coatings to the tooling. But first, ensure that the stamping process is predictable and repeatable, and resulting in perfect part quality—that starts with a robust die design. If the tool design lacks robustness, then investing in coating is like throwing good money after bad.  

Among the most common design shortcomings I’ve seen: 

• Too-thin die shoes that sit over large openings in the press bolster without proper support. This results in flexing during the stamping process, which not only impacts part quality by increasing dimensional variation, but also severely negatively impacts the cutting edges on the tooling. This causes the cutting edges to break down prematurely due to increased vibration.  
• Undersized guide pins and ball cages, which allow for some lateral flex during cutting and forming, and result in increased vibration. This leads to premature degradation of the tooling.  
• Poor or spotty inconsistent lubrication of the base material during stamping. I have seen felt pads held in place by clothespins and oil being dripped only on the top of the strip. This yields a very inconsistent lube spread. The strip must be evenly coated with the right amount of lubricant applied to the top and bottom—excess lubricant can cause as many problems as too little lubricant. Invest in a quality lubrication system. 
• Designs that lack the proper slug retention, part ejection and sensors needed to prevent tool damage from miss hits. I confidently can state that more than half of the causes of inefficiency and maintenance in stamping operations are due to these issues. Once a shop has achieved a predictable and consistent stamping process, tooling service life should be repeatable to within ±10% every single time. Then and only then can you take tooling service life to the next level by using tool coatings. If tooling service-life repeatability exceeds 10%, take the time to understand why. If a tool lasts 100,000 hits today and 50,000 hits tomorrow prior to performing required maintenance, tooling coatings will not help.

Now let’s focus on coatings. As an example, consider a die running at 1000 strokes/min., using carbide tooling to form and coin simple flat blanks from thin-gauge copper and stainless steel (0.004 to 0.012 in. thick). The metal stamper developed a robust tool design and fabricated a solid die that consistently achieves 18 to 20 million hits between service. Taking the time to re-engineer the tooling to allow for coatings likely would provide minimal benefit, perhaps another week or two of run time between service.

Note, however, that for more extreme stamping applications, such as forming and extruding tough and abrasive materials such as Inconel, the stamping process might not run at all without the proper tool coatings.