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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
  • Movespeed can significantly affect diameter sizes.
    Try getting both machines to move as close as you can to exactly the same speed.
    You may see closer results.

    Also, make sure you are running programs at exactly the same speeds that you are calibrating at.

    Check for size accuracy by measuring standards, ring gages, jo-blocks, etc.
Reply
  • Movespeed can significantly affect diameter sizes.
    Try getting both machines to move as close as you can to exactly the same speed.
    You may see closer results.

    Also, make sure you are running programs at exactly the same speeds that you are calibrating at.

    Check for size accuracy by measuring standards, ring gages, jo-blocks, etc.
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