Calibration - STD DEV

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  • Calibration - STD DEV

    I was told at the PCDMIS training that anything under 0.015" STD DEV is ok. Where is everyone's max at? What is a good STD DEV to stay under? 0.015" seems high to me.
    I used to be high on life but I built up a tolerance.

    Brown & Sharpe Global Advantage
    PCDMIS CAD++ v2011mr2
    PH10MQ/SP600M


    sigpic

  • #2
    in or mm? I hope that is mm!
    <internet bumper sticker goes here>

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    • #3
      I would say MM, NOT INCHES ("). Nowayinhell would I accept 0.015" for the STD DEV for ANYTHING. You can basically double that value to get any of the 'shape' items, ROUNDNESS, SPHERE, FLAT, STRAIGHT, etc. (at least, it will be DANG close). So, I guess it depends on WHAT that STD DEV is for? CAlibration results? NO WAY! Alignment features on a fixture? NO WAY! A measured feature of a part, well, that will depend on the tolerance of the part.
      sigpic
      Originally posted by AndersI
      I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

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      • #4
        He might of been talking mm LOL. What do you usually go with?
        I used to be high on life but I built up a tolerance.

        Brown & Sharpe Global Advantage
        PCDMIS CAD++ v2011mr2
        PH10MQ/SP600M


        sigpic

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        • #5
          That has to be MM. and that is a little high for MM for simple probes.

          Although, how many of their trainers have real world experience?
          Links to my utilities for PCDMIS

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          • #6
            What do you guys consider limits as far as calibration goes?
            I used to be high on life but I built up a tolerance.

            Brown & Sharpe Global Advantage
            PCDMIS CAD++ v2011mr2
            PH10MQ/SP600M


            sigpic

            Comment


            • #7
              On a Discovery, 5 microns on a good probe, and up to 17 microns on a bad probe.
              Good= within the Renishaw guidelines of module
              Bad = Not within the guidelines of the module

              Star probe - forget them....
              Links to my utilities for PCDMIS

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              • #8
                I have my calibration STD DEV set to give me a warning if it is greater than 0.010mm (0.0004"). Only EVER happens if I miss a piece of crap on teh tool or tip.
                sigpic
                Originally posted by AndersI
                I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

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                • #9
                  sure wish i checked sheet metal....
                  Links to my utilities for PCDMIS

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                  • #10
                    Originally posted by cmmguy View Post
                    Star probe - forget them....
                    First time I've heard anyone else say that. Now I don't feel so bad. I get a big ration here for refusing to use one. everyone whose seen a picture of a CMM sees one of those being used so they think I should use it. There is one guy here that insists I use it instead of tip rotations (he is a Ziess guy). I still refuse. I don't know why that is the most requested thing here in a plant full of people that don't know jack about CMMs. They have their place but that place is not with most of today's hardware and certainly not with most of our tolerances that is for sure.

                    Craig
                    <internet bumper sticker goes here>

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                    • #11
                      Originally posted by craiger_ny View Post
                      First time I've heard anyone else say that. Now I don't feel so bad. I get a big ration here for refusing to use one. everyone whose seen a picture of a CMM sees one of those being used so they think I should use it. There is one guy here that insists I use it instead of tip rotations (he is a Ziess guy). I still refuse. I don't know why that is the most requested thing here in a plant full of people that don't know jack about CMMs. They have their place but that place is not with most of today's hardware and certainly not with most of our tolerances that is for sure.

                      Craig
                      They work on the Zeiss head, they work very well on the SP600, they just down right suck on the TP20?
                      Links to my utilities for PCDMIS

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                      • #12
                        Originally posted by cmmguy View Post
                        sure wish i checked sheet metal....
                        What-you-talking-about, eh? This machine is 20 (or more) years old and yes, I check sheet metal. The machine (factory) specs are +/-0.0007" (linear, repeat, sqaure, etc., and I am still within them) and I use 1/2 of my machine spec as a limit for my calibration STD DEV. What gives? What does sheet metal have to do with that, huh?!

                        sigpic
                        Originally posted by AndersI
                        I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

                        Comment


                        • #13
                          I never see anything over .0002 inches so that is my limit. If it comes up .0003, I clean the tip and the calibration sphere and run again. I've never had it come up .0003 after cleaning.

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                          • #14
                            Originally posted by Goodluck View Post
                            I never see anything over .0002 inches so that is my limit. If it comes up .0003, I clean the tip and the calibration sphere and run again. I've never had it come up .0003 after cleaning.
                            Ya know, I never even look at the results of the calibration. IF it calibrates within the set tolerances (0.0004" STD DEV and 0.002" size) I never even bother, I just go on with what I am doing. If it pops-up a warning, then I will double check what I have done and do it over.
                            sigpic
                            Originally posted by AndersI
                            I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

                            Comment


                            • #15
                              Originally posted by Matthew D. Hoedeman View Post
                              What-you-talking-about, eh? This machine is 20 (or more) years old and yes, I check sheet metal. The machine (factory) specs are +/-0.0007" (linear, repeat, sqaure, etc., and I am still within them) and I use 1/2 of my machine spec as a limit for my calibration STD DEV. What gives? What does sheet metal have to do with that, huh?!

                              PLUS OR MINUS???!!! Holy cow! j/k

                              What is the tightest tolerance on your worst sheet metal part?

                              Last edited by cmmguy; 12-19-2006, 11:45 AM.
                              Links to my utilities for PCDMIS

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