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?

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acgarcia over 7 years ago

Well the are different controllers also and yes they the features are diameters. The newer CMM running 2017 is much faster than the other one. I had a big probe deflection problem in the beginning when the tech was calibrating it. He had to slow down the de acceleration a bit to keep the probe from deflecting just from moving around the CMM.

I believe the touchspeed should be the same but I know the move speed varies.

I checked a master ring to both CMMs. CMM A was measuring -0.0003 under nominal and CMM B was measuring 0.0001" over nominal. This this be a cause for concern on a individual cmm basis?
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KIRBSTER269 over 7 years ago in reply to acgarcia

I'm not to sure I agree with the touchspeed thing. I myself have a 7-10-7 and a 5-4-5. The 7-10-7 clearly runs faster than the other, so I have to run it slower than the small one, but to get them to read the same, my 7-10-7 touchspeed is set at 1% and my 5-4-5 is at 2%. I still set mine up in % not mm.
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KIRBSTER269 over 7 years ago in reply to acgarcia

I'm not to sure I agree with the touchspeed thing. I myself have a 7-10-7 and a 5-4-5. The 7-10-7 clearly runs faster than the other, so I have to run it slower than the small one, but to get them to read the same, my 7-10-7 touchspeed is set at 1% and my 5-4-5 is at 2%. I still set mine up in % not mm.
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