leica laser tracker question on measuring sphere

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  • leica laser tracker question on measuring sphere

    I am using a leica laser tracker with t probe. I have a disk 60 in in diameter and a 281 inch spherical radius convex in face of part. I am getting readings off bout a inch on the radius. any ideas?

  • #2
    You're measuring a very, very, very small part of a large sphere, and expect it to be reliable? What about the uncertainty in each measuring point? How many points do you measure? What's the uncertainty of your measuring device?

    I did an experiment on a circle with three points, with your numbers for radii, and all that's needed to change the diameter ~1in was an error of one micron (0.001 mm) in each of the measuring points...

    (code in mm)

    Edit: My calculation is wrong - I read mm as inch. In the example the diameter difference is less than 1mm. The error in the hits must be increased to 0.03mm to generate an inch of diameter error.

    Code:
    STARTUP    =ALIGNMENT/START,RECALL:USE_PART_SETUP,LIST=YES
                ALIGNMENT/END
                MODE/DCC
                FORMAT/TEXT,OPTIONS, ,HEADINGS,SYMBOLS, ;NOM,MEAS,TOL,DEV,OUTTOL, ,
                LOADPROBE/ALLA
                TIP/T1A0B0, SHANKIJK=0, 0, 1, ANGLE=0
    PNT1       =FEAT/CONTACT/VECTOR POINT/DEFAULT,POLAR
                THEO/<7137.4,0,0>,<-1,0,0>
                ACTL/<7137.399,0,0>,<-1,0,0>
                TARG/<7137.4-0.001,0,0>,<-1,0,0>
                SHOW FEATURE PARAMETERS=NO
                SHOW CONTACT PARAMETERS=NO
    PNT2       =FEAT/CONTACT/VECTOR POINT/DEFAULT,POLAR
                THEO/<7137.4,6.093,0>,<-0.9943509,-0.1061426,0>
                ACTL/<7137.401,6.093,0>,<-0.9943509,-0.1061426,0>
                TARG/<7137.4+0.001,6.093,0>,<-0.9943509,-0.1061426,0>
                SHOW FEATURE PARAMETERS=NO
                SHOW CONTACT PARAMETERS=NO
    PNT3       =FEAT/CONTACT/VECTOR POINT/DEFAULT,POLAR
                THEO/<7137.4,353.907,0>,<-0.9943509,0.1061426,0>
                ACTL/<7137.401,353.907,0>,<-0.9943509,0.1061426,0>
                TARG/<7137.4+0.001,353.907,0>,<-0.9943509,0.1061426,0>
                SHOW FEATURE PARAMETERS=NO
                SHOW CONTACT PARAMETERS=NO
    CIR1       =FEAT/CIRCLE,CARTESIAN,IN,LEAST_SQR,NO
                THEO/<0,0,0>,<0,0,1>,14274.8
                ACTL/<-0.354,0,0>,<0,0,1>,14275.506
                CONSTR/CIRCLE,BFRE,2D,PNT1,PNT2,PNT3,,
                OUTLIER_REMOVAL/OFF,3
                FILTER/OFF,UPR=0
    SmallRad.PNG
    Last edited by AndersI; 04-17-2018, 05:15 AM.
    AndersI
    SW support - Hexagon Metrology Nordic AB

    Comment


    • MarkFeasel
      MarkFeasel commented
      Editing a comment
      I get that the reliability of the measurement is questionable. Still need to check per customer. I am going to try to take a lot more points. We are doing experiment to see the best number before we check on cmm.

  • #3
    Originally posted by AndersI View Post
    You're measuring a very, very, very small part of a large sphere, and expect it to be reliable? What about the uncertainty in each measuring point? How many points do you measure? What's the uncertainty of your measuring device?

    I did an experiment on a circle with three points, with your numbers for radii, and all that's needed to change the diameter ~1in was an error of one micron (0.001 mm) in each of the measuring points...

    (code in mm)

    Code:
    STARTUP =ALIGNMENT/START,RECALL:USE_PART_SETUP,LIST=YES
    ALIGNMENT/END
    MODE/DCC
    FORMAT/TEXT,OPTIONS, ,HEADINGS,SYMBOLS, ;NOM,MEAS,TOL,DEV,OUTTOL, ,
    LOADPROBE/ALLA
    TIP/T1A0B0, SHANKIJK=0, 0, 1, ANGLE=0
    PNT1 =FEAT/CONTACT/VECTOR POINT/DEFAULT,POLAR
    THEO/<7137.4,0,0>,<-1,0,0>
    ACTL/<7137.399,0,0>,<-1,0,0>
    TARG/<7137.4-0.001,0,0>,<-1,0,0>
    SHOW FEATURE PARAMETERS=NO
    SHOW CONTACT PARAMETERS=NO
    PNT2 =FEAT/CONTACT/VECTOR POINT/DEFAULT,POLAR
    THEO/<7137.4,6.093,0>,<-0.9943509,-0.1061426,0>
    ACTL/<7137.401,6.093,0>,<-0.9943509,-0.1061426,0>
    TARG/<7137.4+0.001,6.093,0>,<-0.9943509,-0.1061426,0>
    SHOW FEATURE PARAMETERS=NO
    SHOW CONTACT PARAMETERS=NO
    PNT3 =FEAT/CONTACT/VECTOR POINT/DEFAULT,POLAR
    THEO/<7137.4,353.907,0>,<-0.9943509,0.1061426,0>
    ACTL/<7137.401,353.907,0>,<-0.9943509,0.1061426,0>
    TARG/<7137.4+0.001,353.907,0>,<-0.9943509,0.1061426,0>
    SHOW FEATURE PARAMETERS=NO
    SHOW CONTACT PARAMETERS=NO
    CIR1 =FEAT/CIRCLE,CARTESIAN,IN,LEAST_SQR,NO
    THEO/<0,0,0>,<0,0,1>,14274.8
    ACTL/<-0.354,0,0>,<0,0,1>,14275.506
    CONSTR/CIRCLE,BFRE,2D,PNT1,PNT2,PNT3,,
    OUTLIER_REMOVAL/OFF,3
    FILTER/OFF,UPR=0
    SmallRad.PNG
    I see less than 1mm in size error.... (0.706mm to be picky) not an inch.
    sigpic
    Originally posted by AndersI
    I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

    Comment


    • #4
      Originally posted by Matthew D. Hoedeman View Post
      I see less than 1mm in size error.... (0.706mm to be picky) not an inch.

      You are absolutely right! My bad - I did the program in mm, then read the difference as inch.

      Make the error 0.03 mm to get an inch. This seems to be about the same size of error as the accuracy of an AT960 + T-Probe


      AndersI
      SW support - Hexagon Metrology Nordic AB

      Comment

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