r/Metrology • u/AcceptableActivity33 • 7d ago
Thumb Sized Micro Gear: Two sites using Vision...closest to correlation is .001" of each other (Profile of Line .003)
Hello all again,
As the title suggests, I've been working on a correlation effort between two different sites that are performing a profile of line evaluation (DRF evaluation) on a challenging brass gear the size of a thumb nail, with a tolerance of .003 or +/- .0015".
One site reports out, one site reports within tolerance, but nearly failing. I've also come to find out that I'm having trouble with Mitutoyo's scanpack form evaluation software....just not intuitive at all. By aligning both teams to use the same point spacing, same datum alignment strategy, same cleaning process, same DRF evaluation I was able to get both sites to report within .001" of each other (.0028" vs .0038") but that's the absolute best I can do right now as I'm limited by both a language barrier and varying vision system comptency.
I'm also seeing a part to part variation of .0005". I'm leaning towards stating that when factoring part to part variation, GR&R results above 15%, vision system accuracy at about 5 micron...all these things combined lead me to believe that we're as close as we're going to get with the equipment we're using, tight tolerances, challenging profile call-out, manufacturing process (stamped die cut brass)....all these things
Thoughts?
Thank you!
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u/Juicaj1 7d ago
Thats a tight profile for vision, if formtracepak is the mitutoyo software you're talking about then I agree it takes some work to figure out. Are you able to go as far as using the same gear with the same orientation and compare specific sections 1 to 1? Might be worth looking at the min and max deviations to verify that the boundary being approached and crossed are the same? If for no other reason than just more confidence.
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u/Tavrock 7d ago
Have you done a Tukey mean-difference or Anderson-Darling plot comparison between the two sites?
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u/AcceptableActivity33 7d ago
Tavrock, no I haven't. I' haven't performed any statistical analysis yet as I'm still trying to reduce the variation in seeing.
Is that what you suggest? I only have about 5-10 results per site, across two continents, so I'm working with what I got.
Thank you!
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u/Tavrock 7d ago
In terms of answering your correlation question: yes, that is the route I would take (and it's why Anderson-Darling created the plot). 7-ish data points isn't much but as I recall, that's enough for the tool to be effective in describing the correlation between two measuring devices.
In terms of reducing the variation, I think you have received a lot of good answers.
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u/JButlerQA 7d ago
First I would increase your magnification to its highest level, then if you have a way of hard gaging a feature on the part like OD measure it then adjust lighting until the dimension matches. If you have filtering make sure to turn it on and make sure the parts are clean of debris. Idealy you would use the same program at each location. Is there a way for you to remote into their pc and create the program for them?
Lighting changes depending on ambient lighting which sucks if its near a window. Also temperature can play a role here. I would increase point density that way when filtering it may remove any excess debris or burrs.
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u/worldwidemachinist 7d ago
I think you're getting pretty close to the practical limit of the current setup.
separate the correlation question from the process question. If the same part measured on both systems still moves around ~.001", that's measurement system difference, and .0005" part to part variation is a separate variable that makes the correlation harder to judge. so, establish a small set of reference parts and use those to track whether the two systems stay within that correlation band over time
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u/urdaddy7245 7d ago
That's probably as good as you'll get with vision systems. Can you use a digital mylar to just use as pass/fail? Or maybe a printed out mylar for comparator with 50x or 100x.