hexagon logo

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
  • parts are about 48 lbs. valve bodies.

    This is the breakdown of the reports on both machines. We measured 5 dimensions total. Same exact part on both machines run 5 times. Using the same star build

    1 ID that is constructed with 11 vector points (Tips 2-5)

    1 auto cylinder ID, used for (xy orgin) (Tip 1)

    1 auto circle OD (Tip 3)

    1 auto circle ID (Tip 5)

    and an angle dimension

    Average Deviation Comparison

    Constructed ID on A 0.0014, B 0.0008
    auto Cylinder ID on A -0.0004, B -0.001
    Auto Circle OD on A 0.006, B 0.002
    Auto circle ID on A 0.0000, B 0.000

    Again, CMM A matches the mic measurements closer than CMM B.

    How would I begin to troubleshoot CMM B for accuracy?

    Thank you all for the info.

Reply
  • parts are about 48 lbs. valve bodies.

    This is the breakdown of the reports on both machines. We measured 5 dimensions total. Same exact part on both machines run 5 times. Using the same star build

    1 ID that is constructed with 11 vector points (Tips 2-5)

    1 auto cylinder ID, used for (xy orgin) (Tip 1)

    1 auto circle OD (Tip 3)

    1 auto circle ID (Tip 5)

    and an angle dimension

    Average Deviation Comparison

    Constructed ID on A 0.0014, B 0.0008
    auto Cylinder ID on A -0.0004, B -0.001
    Auto Circle OD on A 0.006, B 0.002
    Auto circle ID on A 0.0000, B 0.000

    Again, CMM A matches the mic measurements closer than CMM B.

    How would I begin to troubleshoot CMM B for accuracy?

    Thank you all for the info.

Children
No Data