Thomas Vacca
Director of Engineering

Where to Begin Continuous Improvement of Stamping-Tool Design?

At the end of every tool build and in the final development cycle, the design team should hold a formal closure meeting to review what went well and build on those strengths. But more importantly, the team should address every detail that did not go well, including every development issue. Minimally, the team must include the designer, development engineer, quality engineers and the toolmakers.

So where to begin with continuous improvement? Start with a checklist of items to confirm, with an explanation of the problems and the plan to fix them. Use this checklist at the tool-concept review and again after the final design is completed to ensure that nothing gets missed. Also update it after the final tool-development review at closure for every new tool build with suggestions for actions to reduce development time on the next tool build. 

Over time, the list will grow long, but spending a few hours in the conference room specifying every detail beats spending weeks redesigning and redeveloping in the toolroom and pressroom.   

Sample Continuous-Improvement Checklist

1. Confirm that the new tool can be laced up under power using a designated starting point. Design in a strip start button to prevent a half slug from emerging on lace up. Remove anything that might inhibit the strip from progressing through the tool. Confirm that all guide rails, lifters and forms have the proper lead-ins to facilitate smooth travel through the tool. 
2. Verify that the press stroke complies with the quoted workcenter. Usually, a stamping’s price varies based on the size and speed of the workcell it is slated to run in. Confirm that the tool will fit in the quoted cell.
3. Confirm that the tonnage required to stamp the component does not exceed that of the workcell capacity. Add a minimum of 33% to the tonnage calculated to ensure that the workcell will have the proper stability to support the job’s needs. 
4. Verify that the design will facilitate the quoted run rate. Review the design to ensure proper part ejection, slug removal/containment, minimal stripper lift, stripper travel and press stroke—all of which directly impact the speed at which the tool can run.   
5. Confirm that the parts will meet quality requirements. As a rule of thumb, if the part print stipulates a process capability index (CPK) of 1.33 or greater, this translates to about a 50% tolerance reduction. Achieving this may mean supplementing with additional trims, forms and qualifiers in the design.
6. Make sure to address slug retention. Review every trim and develop specific solutions, such as spring pins, vacuums, bazookas and slug darts, for even the slightest possibility of slug pulls.
7. Check that a solid bolster supports the tool wherever heavy work is executed. When performing heavy coining or forming in an area that has a large opening for scrap, the bolster may not adequately support the bottom of the die. You may need to design in and add a support beam, thicken the bottom die shoe, add a subplate or even change out the bolster completely.
8. Confirm that the setup document has been drafted and completed prior to the initial tool setup. The document should include detailed, specific, clear instructions for press setup, including shut height, tool location and speed. It also should include the feed pitch and pilot release, air-line pressures and locations, and the number of sensors and their locations. Most importantly, the document should describe how to verify that everything works as intended—and how to facilitate replacement. This should be marked up as needed during the first setup and then updated once all setup parameters are defined.  
9. Be sure that a tooling log accompanies the job before it goes to the press. This log should document everything done to the tool, including—but not limited to—setup, adjustments and all development activities. It will serve as a living document for every setup, tool service and production run for the life of the tool. 
10. Tooling component drawings must be clear, with 100% of the requirements defined. Have on hand a tool register of every component print and cross-section prints of every station in the die for the tooling group. Begin measuring the stamped strip only when the tool group feeds the first strip through the tool and is running at speed and stabilized. Check that every station performs as the design intended, from the first to the last. Make sure that if any discrepancies to the design exist, they will be adjusted, corrected and documented in the tool register until the entire progression meets design intent and debugging is completed.  
11. At the closure meeting, discuss all issues with the entire team to facilitate the learning curve, and update all CAD files accordingly. Remember that the goal is to design, build, run and produce a part to print the first time. Create a checklist for all future setups to ensure that:

1. All air lines are connected, pressure-checked and tested for leaks.   
2. Mounting clamps and screws are defined for the tool.  
3. All sensors are mounted and tested.  
4. Misfeed punch, buckle sensors, payout and take-up sensors are set up properly and checked as required.  
5. All auxiliary equipment, including part and scrap chutes, liners, subplates, scrap shields, and alignment pins, is defined and marked with the job number.