Calibration in the Wrong?

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  • Calibration in the Wrong?

    I have a slight calibration issue. The CMM calibrates perfectly to the calibration probe, but does not calibrate to a boring gage set to 1.5743; it always shows undersized or oversized. Is this problem fixable? If so, how?
    I feel a lot better now that I've lost my mind.


    Global Activ
    PCDMIS CAD ++3.5 MR2

  • #2
    I wouldn't compare the CMM to a bore gage. How many hits are you taking on it? How do you know you are hitting perfectly on it? How far off? What is the capability of your CMM?
    There are a number of variables that need to be looked at.
    When in doubt, post code. A second set of eyes might see something you missed.
    sigpic

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    • #3
      WJS. Especially - how far off?
      Bill Jarrells
      A lie can travel half way around the world while the truth is putting on its shoes. - Mark Twain

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      • #4
        Post the entire program into a posting here.
        sigpic

        James Mannes

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        • #5
          Originally posted by John Kingston View Post
          I wouldn't compare the CMM to a bore gage. How many hits are you taking on it? How do you know you are hitting perfectly on it? How far off? What is the capability of your CMM?
          There are a number of variables that need to be looked at.
          The CMM takes 3 rows of hits to make 3 circles; about 6 or 7 hits per circle.

          The hits are relatively evenly spaced all around the part.

          Everything else I'm not sure.
          The boring gage is 1.5743, and the boring micrometer(or whatever you call it) calibrates to the boring gage just fine. My whole thing is: If the CMM measures a different number for a boring gage(which is precisely precise), how can I be sure the CMM is giving me the correct results?
          I feel a lot better now that I've lost my mind.


          Global Activ
          PCDMIS CAD ++3.5 MR2

          Comment


          • #6
            Originally posted by operator1 View Post
            The CMM takes 3 rows of hits to make 3 circles; about 6 or 7 hits per circle.

            The hits are relatively evenly spaced all around the part.

            Everything else I'm not sure.
            The boring gage is 1.5743, and the boring micrometer(or whatever you call it) calibrates to the boring gage just fine. My whole thing is: If the CMM measures a different number for a boring gage(which is precisely precise), how can I be sure the CMM is giving me the correct results?
            Please do what James said. CMM's report what they get. They get what you tell them to get. They have some error but if you use them correct you can minimize this.

            The thing is, you don't say what kind or error you are getting. And 6 or 7 hits per row doesn't sound like a precise pattern etc.

            Please do what James says and post code.
            Bill Jarrells
            A lie can travel half way around the world while the truth is putting on its shoes. - Mark Twain

            Comment


            • #7
              Originally posted by operator1 View Post
              The CMM takes 3 rows of hits to make 3 circles; about 6 or 7 hits per circle.

              The hits are relatively evenly spaced all around the part.

              Everything else I'm not sure.
              The boring gage is 1.5743, and the boring micrometer(or whatever you call it) calibrates to the boring gage just fine. My whole thing is: If the CMM measures a different number for a boring gage(which is precisely precise), how can I be sure the CMM is giving me the correct results?
              I asked for a copy of your program for that exact reason. Your alignment and how the circles are measured are critically linked to the methodology used to align your part to the CMM.

              Have you taken my/other peoples advice and created a manual alignment that locks down the 6° of freedom cited in the papers I gave you? And then did you do this in DCC mode?
              sigpic

              James Mannes

              Comment


              • #8
                Code:
                =alignment/start,recall:, List= Yes
                            Alignment/end
                            Loadprobe/rick1
                            Tip/t1a0b0, Shankijk=0, 0, 1, Angle=0
                            Mode/manual
                            Workplane/zplus
                            Loadprobe/rick1
                            Tip/t1a0b0, Shankijk=0, 0, 1, Angle=0
                            Prehit/ 0.075
                            Retract/ 0.055
                            Check/ 0.4724,1
                            Movespeed/ 80
                            Scanspeed/ 5
                            Fly/on,0.1181
                            Workplane/zplus
                            Mode/dcc
                            Move/point,9.403,4.7804,-26.0703
                            Move/point,9.6389,4.5946,-28.3462
                Plane1     =feat/plane,rect
                            Theo/9.387,4.5542,-28.7035,0.0004049,-0.0003886,0.9999998
                            Actl/9.387,4.5542,-28.6997,0.0002327,-0.0003199,0.9999999
                            Meas/plane,5
                            Hit/basic,10.3705,4.716,-28.7039,0.0004049,-0.0003886,0.9999998,10.3706,4.716,-28.6999,use Theo = Yes
                            Hit/basic,9.862,3.8501,-28.704,0.0004049,-0.0003886,0.9999998,9.862,3.8501,-28.7,use Theo = Yes
                            Hit/basic,8.8631,3.8502,-28.7036,0.0004049,-0.0003886,0.9999998,8.8631,3.8502,-28.6998,use Theo = Yes
                            Hit/basic,8.5182,4.8233,-28.7031,0.0004049,-0.0003886,0.9999998,8.5182,4.8234,-28.6994,use Theo = Yes
                            Hit/basic,9.321,5.5315,-28.7031,0.0004049,-0.0003886,0.9999998,9.321,5.5315,-28.6993,use Theo = Yes
                            Endmeas/
                            Move/point,9.3206,4.775,-27.8987
                Circle1    =feat/circle,rect,in,least_sqr
                            Theo/9.3996,4.6063,-28.9924,0,0,1,1.5743
                            Actl/9.4192,4.6209,-28.9924,0,0,1,1.5768
                            Meas/circle,5,workplane
                            Hit/basic,10.1814,4.697,-28.9924,-0.993331,-0.1152974,0,10.2036,4.6995,-28.9924,use Theo = Yes
                            Hit/basic,9.4688,3.8221,-28.9924,-0.0878054,0.9961376,0,9.4676,3.8339,-28.9924,use Theo = Yes
                            Hit/basic,8.6214,4.4888,-28.9924,0.9887999,0.1492472,0,8.6415,4.4919,-28.9924,use Theo = Yes
                            Hit/basic,8.8771,5.195,-28.9924,0.6638055,-0.7479052,0,8.8755,5.1918,-28.9924,use Theo = Yes
                            Hit/basic,9.9109,5.2049,-28.9924,-0.649424,-0.7604265,0,9.9266,5.2244,-28.9924,use Theo = Yes
                            Endmeas/
                            Move/point,9.4911,4.9548,-28.9825
                Circle2    =feat/circle,rect,in,least_sqr
                            Theo/9.3996,4.6064,-29.352,0,0,1,1.5743
                            Actl/9.4192,4.6211,-29.352,0,0,1,1.5755
                            Meas/circle,5,workplane
                            Hit/basic,10.1829,4.6807,-29.352,-0.9955311,-0.094434,0,10.2046,4.681,-29.352,use Theo = Yes
                            Hit/basic,9.7902,3.9227,-29.352,-0.4960448,0.868297,0,9.7855,3.9237,-29.352,use Theo = Yes
                            Hit/basic,8.6354,4.4184,-29.352,0.9710249,0.2389783,0,8.657,4.4224,-29.352,use Theo = Yes
                            Hit/basic,9.0814,5.3265,-29.352,0.4042207,-0.9146615,0,9.0761,5.3302,-29.352,use Theo = Yes
                            Hit/basic,9.9153,5.2013,-29.352,-0.6550641,-0.7555733,0,9.9307,5.2203,-29.352,use Theo = Yes
                            Endmeas/
                            Move/point,9.4625,4.8422,-29.3522
                Circle3    =feat/circle,rect,in,least_sqr
                            Theo/9.3996,4.6067,-29.76,0,0,1,1.5743
                            Actl/9.419,4.6213,-29.76,0,0,1,1.5754
                            Meas/circle,5,workplane
                            Hit/basic,10.1866,4.6036,-29.76,-0.9999922,0.0039426,0,10.2064,4.6014,-29.76,use Theo = Yes
                            Hit/basic,9.7917,3.9241,-29.76,-0.4980471,0.86715,0,9.7872,3.9249,-29.76,use Theo = Yes
                            Hit/basic,8.6697,4.3118,-29.76,0.9272035,0.3745579,0,8.6913,4.3197,-29.76,use Theo = Yes
                            Hit/basic,8.9327,5.2401,-29.76,0.5934024,-0.8049059,0,8.9297,5.2385,-29.76,use Theo = Yes
                            Hit/basic,9.8794,5.2311,-29.76,-0.6092803,-0.7929549,0,9.893,5.2504,-29.76,use Theo = Yes
                            Endmeas/
                            Move/point,9.4867,4.695,-29.7627
                            Move/point,9.4867,4.6951,-26.8188
                            Move/point,9.4867,8.7528,-25.1042
                Point1     =feat/point,rect
                            Theo/10.3996,4.6063,-28.9824,0,0,1
                            Actl/10.4192,4.6209,-28.9924,0,0,1
                            Constr/point,offset,circle1,1,0,0
                Line1      =feat/line,rect,unbnd
                            Theo/9.3996,4.6063,-28.9824,1,0,0
                            Actl/9.4192,4.6209,-28.9924,1,0,0
                            Constr/line,bf,2d,circle1,point1,,
                Cyl1       =feat/cylinder,rect,out,least_sqr
                            Theo/9.3995,4.6065,-29.3712,-0.000013,0.0005203,-0.9999999,1.5743,0.7783
                            Actl/9.4191,4.6211,-29.3763,-0.0003899,0.0003382,-0.9999999,1.5759,0.7683
                            Constr/cylinder,bf,circle1,circle2,circle3,,
                A1         =alignment/start,recall:, List= Yes
                            Alignment/level,zplus,plane1
                            Alignment/rotate,xplus,to,line1,about,zplus
                            Alignment/trans,xaxis,cyl1
                            Alignment/trans,yaxis,cyl1
                            Alignment/trans,zaxis,
                            Alignment/end
                Dim Loc1= Location Of Cylinder Cyl1  Units=in ,$
                Graph=off  Text=off  Mult=1.00  Output=both
                Ax   Nominal     +tol       -tol       Meas        Max        Min        Dev      Outtol   
                X      0.0000     0.0005    -0.0005     0.0000     0.7874    -0.7775     0.0000     0.0005 ----#----
                Y      0.0000     0.0005    -0.0005     0.0000     0.7091    -0.7873     0.0000     0.0005 ----#----
                Z    -29.3692     0.0005    -0.0005   -29.3755   -28.9914   -29.7596    -0.0064     0.0069 <--------
                D      1.5743     0.0005    -0.0005     1.5759     1.5771     1.5753     0.0016     0.0011 -------->
                H      0.7783     0.0005    -0.0005     0.7683     0.7683     0.7683    -0.0100     0.0105 <--------
                End Of Dimension Loc1
                I feel a lot better now that I've lost my mind.


                Global Activ
                PCDMIS CAD ++3.5 MR2

                Comment


                • #9
                  What is it that you are measuring?
                  Is it a master of some sort or a actual part?
                  Links to my utilities for PCDMIS

                  Comment


                  • #10
                    Originally posted by cmmguy View Post
                    What is it that you are measuring?
                    Is it a master of some sort or a actual part?
                    The part is called an Idler Pulley, and I'm checking the inside diameter of a bored hole.




                    By the way, I didn't write the program. Someone else did. And we're using a completely different probe tip from before(but it calibrates fine).

                    But the program I created with the other tip (a 3by20) did the exact same thing.

                    There's a program for the ring gage. Did you need that too?
                    I feel a lot better now that I've lost my mind.


                    Global Activ
                    PCDMIS CAD ++3.5 MR2

                    Comment


                    • #11
                      And yes, the alignment is done in Mode DCC.
                      I feel a lot better now that I've lost my mind.


                      Global Activ
                      PCDMIS CAD ++3.5 MR2

                      Comment


                      • #12
                        Originally posted by operator1 View Post
                        And yes, the alignment is done in Mode DCC.
                        Unless something posted incorrectly or I am missing something your alignment is not done until after you measure your features.

                        When I want to repeat a bore gage measurement I set the machine to a ring gage. But, to get closer numbers you might want to consider measuring a Cylinder and setting algorythm to MAX Inscribe. A cylinder is not susceptible to alignment error like a circle is. Be mindful of shanking.

                        Also remember, a CMM ID (MAX Inscribe) is based on three points. Dial Bore Gage is based on two. CMM will come closer to an Intramic (3 points) but even there may be form error unless you are talking about a Calibrated Ring Gage. If you are measuring a Ring Gage your values should be MUCH closer than you reported. I would expect a few tenths.
                        Just some thought.
                        Last edited by Wingman; 08-14-2007, 09:26 AM.
                        Bill Jarrells
                        A lie can travel half way around the world while the truth is putting on its shoes. - Mark Twain

                        Comment


                        • #13
                          Originally posted by Wingman View Post
                          Unless something posted incorrectly or I am missing something your alignment is not done until after you measure your features.
                          No, you're not missing anything. He put the alignment at the end of the program. He did the same thing for the program that checks the ring gage.
                          I feel a lot better now that I've lost my mind.


                          Global Activ
                          PCDMIS CAD ++3.5 MR2

                          Comment


                          • #14
                            Originally posted by operator1 View Post
                            The part is called an Idler Pulley, and I'm checking the inside diameter of a bored hole.




                            By the way, I didn't write the program. Someone else did. And we're using a completely different probe tip from before(but it calibrates fine).

                            But the program I created with the other tip (a 3by20) did the exact same thing.

                            There's a program for the ring gage. Did you need that too?
                            With regular parts (not masters), it is always possible to get variation between a CMM and a Boregage. The geometry variation (out of round condition) will cause the different results. Bore gages are the most accurate method for non-lobed features. CMMs will give you close results but are more about feature location not size. The different methods of calculation (LSQ/MIC/etc...) can affect the results also.

                            When compared on a ring gage, then the variation you see is probing and machine caused.

                            Regarding the alignment, do that before remeasuring the bore, nto before the dimension only.
                            Last edited by cmmguy; 08-14-2007, 09:28 AM.
                            Links to my utilities for PCDMIS

                            Comment


                            • #15
                              Always level any ring gage or master to the ID and not the face of the part. Do as the others have stated, make manual alignment, then DCC, then measure you bore where you want. Use prime numbers for your bore measurement, not really necessary but I have heard that the software calculates diameters better with prime numbers for the hits taken.

                              Just my .02.

                              Duane
                              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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