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leica laser tracker question on measuring sphere

MarkFeasel
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?
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  • 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. 

    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[COLOR=#FF0000]-0.001[/COLOR],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[COLOR=#FF0000]+0.001[/COLOR],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[COLOR=#FF0000]+0.001[/COLOR],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>,[COLOR=#FF0000]14275.506[/COLOR]
            CONSTR/CIRCLE,BFRE,2D,PNT1,PNT2,PNT3,,
            OUTLIER_REMOVAL/OFF,3
            FILTER/OFF,UPR=0


Reply
  • 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. 

    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[COLOR=#FF0000]-0.001[/COLOR],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[COLOR=#FF0000]+0.001[/COLOR],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[COLOR=#FF0000]+0.001[/COLOR],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>,[COLOR=#FF0000]14275.506[/COLOR]
            CONSTR/CIRCLE,BFRE,2D,PNT1,PNT2,PNT3,,
            OUTLIER_REMOVAL/OFF,3
            FILTER/OFF,UPR=0


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