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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
  • The CMMs are about 10-12' apart on the shop floor. There is a large cnc lathe in between them. Hex Tech said vibration is going to be an issue with our newer CMM as there are more CNC machines around it than the older 1. I haven't checked on any AC vents.

    My scenario is that these SF CMMs are integrated into cells. Both cells make the exact same part, our highest selling part. One is a little older and the other is newer. CMM A inspects cell A parts and CMM B inspect CMM B parts. Operators place the parts in a fixture and hit execute and walk away. They figured out that the CMM report slightly differently so they are using that to their advantage as in when 1 CMM fails a part, CMM B might pass it and vice versa.

    I'm just trying to get these too a little more close so the operators wouldn't have to move parts around. I've gotten a quote for 120K for a vibration system but I don't think management is going for it.
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  • The CMMs are about 10-12' apart on the shop floor. There is a large cnc lathe in between them. Hex Tech said vibration is going to be an issue with our newer CMM as there are more CNC machines around it than the older 1. I haven't checked on any AC vents.

    My scenario is that these SF CMMs are integrated into cells. Both cells make the exact same part, our highest selling part. One is a little older and the other is newer. CMM A inspects cell A parts and CMM B inspect CMM B parts. Operators place the parts in a fixture and hit execute and walk away. They figured out that the CMM report slightly differently so they are using that to their advantage as in when 1 CMM fails a part, CMM B might pass it and vice versa.

    I'm just trying to get these too a little more close so the operators wouldn't have to move parts around. I've gotten a quote for 120K for a vibration system but I don't think management is going for it.
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