Ask the Stamping Expert: How can we minimize progressive tool development costs?

A: Sounds like you have a problem with your design process. If the design is robust, development time will be minimal. But if you don’t address these issues upfront and, for example, design your tool and safeties to prevent breakage in case of a misfeed, you will continue to spend way too much on die development.

Minimizing development time and costs is a daunting task that needs to be addressed over time; there is no quick fix. Here are seven things to take into consideration as you start to whittle away at development time. They often are overlooked in the tool design phase, and that can increase costs:

1. Stock lace-up point. The stock lace-up point should be designed so you can lace up without creating half-slugs that can get stuck in the die and cause breakage.
2. Press stroke. Have you minimized it? Running 200 strokes per minute with a 2-inch stroke is essentially the same as running 400 SPM with a 1-in. stroke.
3. Slug controls. Be sure to put appropriate slug controls—such as slug notches in the die sections, vacuums, punch rooftops, and slug darts—into the design.
4. Die features. Don’t try to skimp on die features, even if they increase cost. Sometimes beefing up the die shoe to prevent flexing, using larger-diameter guide pins, and adding some extra stations in the tool where you see significant risk is a very wise decision. It’s much better than trying to address robustness and adding a restrike station after the tool is built!
5. Tool support. Review the press the tool will go into and make sure the press bolster opening will support the tool where work is being done. A tool flex of even a few thousandths of an inch is a common problem that leads to part variation. You might need a custom support plate under your die shoe.
6. Sensors and stock support liners. These must be engineered in. Die designers often leave out feed-to-die support liners and buckle sensors and expect the pressroom to put something together. That’s a mistake. At the minimum, include a micron sensor to detect slug pulls, a misfeed sensor for stock feeding issues, a buckle sensor for stock infeed issues, and a loop sensor between the coil stock and press feed. If you can, build in part-out sensors as well.
7. Checklist. Probably one of the most important keys to success is a progressive die design checklist. This checklist is a living document that will change with every die build so you can use it to make subsequent die builds more effective. After every build, sit with the team and discuss each problem that was addressed in development. What could you do differently in the design phase to eliminate the problem before it required development time? Here are some examples:

• Verify the flat blank, bend lines, and trim geometry.
• Add undercuts to reduce material bulging at bend lines.
• Define the start strip location to prevent generation of half-slugs on lace-up.
• Add an in-tool camber corrector if you are stamping a reeled strip off the die.
• Using computer-aided design software, complete an interference check on the punch, die, and stripper assemblies.
• Complete the proper calculations for forming and make sure the springs have sufficient pressure with an added safety margin.
• Address slug retention in every trim station.
• Mark plates and components as required with numbers or as front, back, left, and right.
• At a minimum, engineer all service items so they cannot be put in backwards or upside down.
• Make sure all rails, punches, and die sections have sufficient lead-ins.
• Add a form-qualifying station if the bend angle is difficult to achieve in one hit.

Our build checklist has hundreds of “lessons-learned” items accumulated over the years, and we review it before every die build. We just completed build on five new tools from 30 tons to 160 tons; we eliminated debug time on some of the tools and minimized it on others. Are we working really hard? No, not really. Are we working smart? Yes!