MSA (Measurement System Analysis) for a .0003" tolerance feature

Z

z28tt

We've been performing MSA's on various gages, and our customer uses the standard <10% is good, <20% is acceptable, <30% needs justification, and >30% needs parts to be submitted on a non-conformance waiver. My latest MSA was for an indicating micrometer used to measure an OD of a dowel pin that has a total of .0003" tolerance. It's over 100% using Avg & Range, and the 2nd Edition factors (customers spreadsheet, ya know!). My inspectors were interpolating past the 50 millionths marks to get it as much resolution as possible.

Is it even possible to get a <10% GR&R on a feature this tight? I'm thinking laser mics, super mics, etc... These pins are just used on two parts, and less than 100 per year, so it's not easy justifying $5k of equipment for $50 of pins. Alternative may be an attribute study using go-nogo ring gages?
 
A

alspread

Re: MSA for a .0003" tolerance feature

Not impossible, but pretty near.
It sounds like you would be better off using an attribute device even if it means 100% (or even 200%) inspection.
At less than 100 per year, just make or buy an attribute gage and move on.

Good Luck
 
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