The control plan portion of PPAP documents the methods the casting supplier has in place to ensure the things that could go wrong in the part, don’t.


results are just as important, and many times the casting supplier may not pay as much attention to those,” Helgeson said. “The yield strength, hardness, fatigue strength, excessive wear, etc., are all very critical in the application, depending on the type of metal and application.”


Roles and Review


At Caterpillar, the PPAP is evaluated by three par- ties—engineering, process engineering and quality—and each party is focused on different sections. Engineering evaluates whether the part is defined


correctly, the FMEA is current and complete and critical characteristics are appropriately defined. Engineering also checks that it can trace key elements of the FMEA and critical characteristics through to the control plan. Te process control engineer/manufacturing engi-


neer is responsible for making sure all the elements are complete and reviewed. Quality evaluates sample inspection and measurement correlation, determines whether appropriate lab tests and analysis are complete and reviews the inspection and control plans. “The earlier collaboration begins, the better,


because you can’t skip any steps,” Helgeson said. “The more surprises we can eliminate or address early on, the better. It makes things go a lot more smoothly when we are delivering parts.” Caterpillar uses PPAP for every part, but not every


part goes through the same scrutiny. Some metalcasting facilities and machining houses will charge for PPAP services, while others view it as a necessary customer service.


44 | MODERN CASTING September 2013


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