What if anything do you use to verify accuracy/repeatability of your cmm?

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  • What if anything do you use to verify accuracy/repeatability of your cmm?

    We are researching different ways of verifying the calibration of our CMM’s between calibration cycles. The powers at be do not seem think it is necessary to have an artifact on site to verify the calibration. Does ISO require that you have a means to do they just require you to follow your process what ever it is?
    37
    Ball Bar
    18.92%
    7
    Renishaw machine checking gage
    24.32%
    9
    Koba Step gage
    13.51%
    5
    Dont Verify
    43.24%
    16

    The poll is expired.

    Last edited by terry; 07-19-2006, 08:24 PM.

  • #2
    ISO only requires to calibrate your machine at established intervals in accordance with your procedures. The only requirement I saw in the ISO9000/2000 standard was that you have to have all your gages calibrated to NIST traceable artifact. There was another post on this, do a search on calibration to find the suggestions.
    Kevin

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    • #3
      We use what we call a baseline part--this is a part that has the tightest tolerances we generally run here, uses one of our longest tips, and uses 4 different angles of our indexing head.
      We have had this part for going on 5 years, and it was also measured by our customer on their Zeiss machine.
      Directly after each calibration, we measure this part and keep all of our reports.
      Anytime we have a concern that our machine might not be giving us good results, we plop this part up there, and compare the current report to all of our historicaly data.
      this has saved us many, many, many times, especially when I get a call at 11:30 pm and the night guy has bumped something and needs to know whether or not he needs to re-calibrate tips.

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      • #4
        We don't calibrate between the annual calibration dates, but each new CMM production program has to correlated with another third party program. Gage RR is then ran and the upshoot of this is we measure one part and keep the measured data, like yourself, and call this the "gold standard". This is kept under lock in our stds room.
        Bristol Citysigpic
        Home of the Reds

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        • #5
          I couldn't answer to the poll, as I do what Shelley does. When Hilton Roberts logs in, he is the Guru of this topic. If you search his posts here and at the other PC-DMIS sites, you will learn quite a bit on the topic.
          When in doubt, post code. A second set of eyes might see something you missed.
          sigpic

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          • #6
            I have in the past used a Renishaw MCG dumping all into stats and monitor the variation. It really did not check the machines accuracy but gave me valuable data that I could use to tell me when something was not right. I have a TP20 take a dump on me once and caught when my data showed extreme variation one morning.

            Right now I am startin to use a master part for this running the same part on all 4 of our CMMs.
            Xcel & MicroVal Pfx & Global 37mr4 thru 2012mr1sp3
            Contura Calypso 5.4

            Lord, keep Your arm around my shoulder and Your hand over my mouth. Amen.

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            • #7
              Just a noob still, but I hope to have several artifacts within the next few years.
              From what I've read on the forum it's the cat's meow for verifying accuracy. It
              seems weird that the big cmm producers haven't tried to sell us something by now but I wouldn't buy it- unless it was really cool.

              Mike
              "listening for the last trump... looking toward the eastern sky"

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              • #8
                We have 4 CMM's. I have a "Golden Part" for each CMM. I try to run at least twice monthly. Data is stored in Datapage and Csv files. I compare latest run with all runs since last calibration. Dimension does not have to be in "Spec" on original run just measure the same each time you run it. Our QS9000 Auditor asked me about 2 years ago how I knew my CMM's were running accurately. I told him we had them calibrated annually. Last calibration was 6 month's before. He asked how I knew they were still running accurately. I brought out the "Golden Part" and told what it was and that was the end of that. He was satisfied.

                It does not have to be a purchased artifact. I use a production part that has had a movable areas either welded or tapped with a screw to prevent movement or changes. I painted It white and labeled "Golden Part- Qc use only"
                Last edited by layout tech; 07-20-2006, 08:10 AM.

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                • #9
                  Well, I don't verify. I haven't had a problem with it yet.

                  I like the idea of a "golden part". I may try to find something around here to use. I assume the larger the part the better.

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                  • #10
                    I run the test block that came with the machine.
                    sigpic
                    if you had soap on a rope it would be tied to yer ankle

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                    • #11
                      Every once in a while, if things aren't checking right, I'll use gage blocks to check distances at different probe angles and on different areas of the machine. But, not very often.
                      sigpic Life is not a journey to the grave with the intention of arriving safely, but rather a skid in broadside, totally worn, proclaiming WOW What a ride!

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                      • #12
                        I have a Test part that I use, whenever I get a question about accuracy, I run it and compare it to past runs, take about 10 mins, and cuts thur the bull ****, as production will believe my results after that.
                        sigpic

                        B&S Global 544
                        Using 3.7mr3


                        Peace
                        Greg


                        Nothin left ta dew but :) :) :) !

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                        • #13
                          Any one have a spare test block?
                          DR Watson shut me down again !!!! :mad: Smoke break:eek:

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                          • #14
                            Originally posted by Jeffrey Lovely
                            Any one have a spare test block?
                            How about 2, the one for this system is long gone, would be nice for walking through some of the tutorials.

                            TK
                            sigpicHave a homebrew

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                            • #15
                              We're going through a bunch of DPD/MBD stuff with a few of our customers, mostly Boeing, and this subject has recently come up. They want our CMMs verified on a regular schedule with the results stored on file for reference. We ordered a Renishaw gauge that should be here any day now. It'll be nice, as I had a tip get bent just slightly enough to throw out precision, but wasn't visually noticible. It would be nice to run a gauge program and find that out before I measure a part.

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