Attribute Gage R&R with no bad samples

PastorBee13

Registered
Is it possible, practical, or worth anything to perform an attribute gage (check fixture with pins, not measurements) R&R with no bad parts put into the test? We are a stamping company and the check fixtures do not check any areas where actual variation takes place (along the outer edges of the parts).
 

Ron Rompen

Trusted Information Resource
PastorBee: The requirements for GRR (attribute) required that you use sample parts which represent the spectrum of possible outcomes (i.e. from undersize to oversize). Having worked in a stamping facility for a number of years, I understand how difficult it is to make a 'bad' part when you want one. The easiest way that I have found is to take samples from a regular run, and 'modify' them (tool room or maintenance can probably assist) to make an out-of-tolerance condition.

There is not much point in conducting a GRR study if you don't have nonconforming parts to PROVE that the gauge will detect them.
 

PastorBee13

Registered
PastorBee: The requirements for GRR (attribute) required that you use sample parts which represent the spectrum of possible outcomes (i.e. from undersize to oversize). Having worked in a stamping facility for a number of years, I understand how difficult it is to make a 'bad' part when you want one. The easiest way that I have found is to take samples from a regular run, and 'modify' them (tool room or maintenance can probably assist) to make an out-of-tolerance condition.

There is not much point in conducting a GRR study if you don't have nonconforming parts to PROVE that the gauge will detect them.

Yeah, the customer isn't interested in a common sense approach. And I can't damage the parts just enough without it being obvious to the person conducting the test. Using the parts as a hammer isn't part of the normal process.
 

Ron Rompen

Trusted Information Resource
PastorBee: You are stuck between a rock and a hard place. Forget the EXTERNAL customer for a moment, and focus on your INTERNAL customer. You need to be able to demonstrate to them that your gauging concept works to protect them.
HOW you make the 'bad' sample parts may be a challenge, but without them there is not much point in doing a GRR study.
Get some input from your toolroom/maintenance team - ask them how THEY could assist you in creating a nonconforming part that isn't visually detectable.
 
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