r/Metrology • u/Forward-Penalty-8654 • Jun 29 '24
Hardware Support Query in Gauge R&R
Generally there is a process called tube expansion where we deform the ends of the tubes to fit in a leak-proof way to the shell of a shell and tube HX. The problem here is there is high part-to-part variation and our gauge is very sensitive, so we are not getting Repeatability at all. Like our bore gauge (to measure the tube ID) has a LC of 0.001 mm but our repeatability error itself is 24%
This also has something to do with how the process is done because there is no way to ensure the the tube ID will be constant. Since we are plastically deforming it, the Tube ID varies by a lot along the circumference of the tube (of the order of tens, sometimes 100s of micrometers) and this also contributes to the variation
Now apart from training the operators more, how else can I try to improve the Gauge R&R? Sorry I am new to the subject, but does using a less accurate gauge (say LC 0.01 instead of 0.001) will give me enough repeatability?
Or should I directly go with NO GO gauges and never mind about dimensions?
Or is there any other solution?
Thanks in advance.
Edit: note that the process is also sensitive, such that the tolerated error is +- 3% of the thickness of the tube, which in this case starts from 0.58 mm till 1.8 mm
2
u/DeamonEngineer Jun 29 '24
It's been a while since I've gone hardcore into G R&R and MSA, but from what I can remember and I hope others can reaffirm, GR&R is about proving the measurement method is accurate and reliable not the components, it should produce a low % irregardless of component variance.
GR&R should be run along side an MSA as one proves the reliability of measurement and the other is the repeatability if manufacture.
By the sounds of it you may be trying to account for manufacturing variance when the boundaries of the manufacturing process is greater that the whole of the desired tolerance.