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Measuring the same part on 2 CMMs, Different Results

We have 2 4.5.4 SFs. I ran a part 5 times on CMM A and then ran the exact same part on CMM B. Got different and same results.

CMM A runs 2016 and CMM B runs 2017. Both use the same star probe build. Both checked the same features with the same parameter... number hits, prehit retract, etc..

One CMM seems to read a little larger than the other. CMM B measures one feature 0.002" smaller than CMM A and CMM A measure a feature 0.0006" smaller than CMM B. One feature was exact on both CMMS, exact nominal and deviation, 0.000.

Essentially I copied the program from CMM A to CMM B and just adjusted some movespeeds.

Is this something normal? Operators at night sometimes will fail parts on one cmm and then take them to the other cmm and it pass so they pass the part through. I know they CMM will not match perfectly but they should be closer than 0.002". I'm trying to build confidence in the CMMs for the operators as its only be a few years of having CMMS.

Any advice or ideas on this?
Parents
  • Variables as in what Josh posted earlier about? Both machines use the exact same star probe build and there are no other probes on the machines. How do I explain to operators that when one CMM barely fails a part, run it on the other and it might pass it?

    I get it, these are not supper accurate machines and the tightest tolerance on this part is ±0.001". Where do I start to eliminate some of these variables? add more points to my features? more points on probe calibration?

    In other words, how do I explain to my boss who is not a CMM dude, why these 2 CMMS that are physically identical but report different output?
Reply
  • Variables as in what Josh posted earlier about? Both machines use the exact same star probe build and there are no other probes on the machines. How do I explain to operators that when one CMM barely fails a part, run it on the other and it might pass it?

    I get it, these are not supper accurate machines and the tightest tolerance on this part is ±0.001". Where do I start to eliminate some of these variables? add more points to my features? more points on probe calibration?

    In other words, how do I explain to my boss who is not a CMM dude, why these 2 CMMS that are physically identical but report different output?
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