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Measuring the same part on 2 CMMs, Different Results

acgarcia
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.


    Actually just touch speed, make sure both machines are in absolute with the same exact touch speed, make sure both machines have the same exact touch speed used when qualifying with your artifact as you do when you measure your parts, make sure both machines are using the exact same probing down to the module force and tip size, make sure both machines have been recently certified to be within spec by the manufacturer. Depending on who is doing your sticker and how long since the last cal between both machines, it could just as easily be a simple squareness error between the machines.
Reply
  • Movespeed can significantly affect diameter sizes.


    Actually just touch speed, make sure both machines are in absolute with the same exact touch speed, make sure both machines have the same exact touch speed used when qualifying with your artifact as you do when you measure your parts, make sure both machines are using the exact same probing down to the module force and tip size, make sure both machines have been recently certified to be within spec by the manufacturer. Depending on who is doing your sticker and how long since the last cal between both machines, it could just as easily be a simple squareness error between the machines.
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