CMM to CMM Variability

[[Pr...]]

One of our DuraMax CMMs has been measuring inside diameters .0006" smaller than they actually are. We have two CMMs, so we call one "White" and the other "Red." The Red CMM is suspect. We use a 1mm star stylus system to measure the ID. I measured a part on White, and was able to confirm the measurement with pins. I took the stylus system from White, put it on Red, and qualified it. I remeasured the same part with the same program, and it was .0006" smaller. Looking at the stylus system geometry, I am seeing .02" variance in ruby location from one CMM to the other. I attached screenshots of the stylus system geometry from each CMM. On White, the +X ruby was -.0065" from zero. On Red, the same ruby was -.0266" from zero. Is it normal for the same stylus system to be .02" different on one CMM versus another? We just had a Zeiss tech calibrate the machine a few weeks ago, and it is currently in spec. Is it possible for the head to be off center and still pass calibration?

[[DW...]]

My gut says no, but try cross posting this under the "Calypso" forum for exposure.

[[To...]]

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Screenshot 2023-06-19 143729.jpg

[[Da...]]

Those positions are distance from the master probe. So, if you're using different master probes then the positions would not match exactly.

[[Je...]]

All of your reported probe radii vary by .0004" from one machine to the next. That is well beyond an acceptable amount of variation
1 - Clean your Reference Sphere and MasterProbe with alcohol
2 - Ensure the machines are at stable temperature
3 - QUADRUPLE check that your Reference Sphere properties match the Certification for that Ref Sphere SN.
4 - Repeat steps 1 -3 🙂
5 - Locate your Ref Sphere (under most robust measurement method, Passive Qual if this is XXT)
6 - Requalify all styli (Passive Qual if this is XXT)

In proper conditions, stylii radii should match under .0001" from one machine to the next.

If it still doesn't qualify properly. Repeat Step 3.
7 - Request a HW ticket poor qualification. Machine giving you highest sigma values on MasterProbe qualification is likely the culprit.

US HelpDesk : +1 800 327-9735
cic.metrology.us@zeiss.com