Measuring the perimeter of an organic shape

anp1994 over 1 year ago

I need to measure the perimeter of a shape that is a combination of an ellipse and a rounded slot accurately on the CMM. If I try measuring the feature as an ellipse or rounded slot, it will best fit the points, which will not give me the dimension I need to capture.

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Neil Challinor over 1 year ago

Create a scan or measure points and put them into a set and then construct a curve ( https://docs.hexagonmi.com/pcdmis/2020.2/en/helpcenter/index.htm?rhcsh=1&rhnewwnd=0#t=mergedProjects%2Fco re%2F16_const_topics%2FConstructing_a_Curve.htm). You should be able to report the length of the curve.

SCN1       =FEAT/SCAN,LINEARCLOSE,NUMBER OF HITS=164,SHOW HITS=NO,SHOWALLPARAMS=NO
            MEAS/SCAN
              BASICSCAN/LINE,NUMBER OF HITS=164,SHOW HITS=NO,SHOWALLPARAMS=NO
              ENDSCAN
            ENDMEAS/
CRV1       =FEAT/CURVE,DEPENDENT,98,164,TOLERANCE,0.01
            THEO/81.195
            MEAS/81.195
            CONSTR/CURVE,SCN1,,
DIM LOC1= LOCATION OF CURVE CRV1  UNITS=MM ,$
GRAPH=OFF  TEXT=OFF  MULT=10.00  OUTPUT=BOTH  HALF ANGLE=NO
AX    NOMINAL       +TOL       -TOL       MEAS        DEV     OUTTOL
L       81.195      0.050      0.050     81.195      0.000      0.000 ----#----
END OF DIMENSION LOC1

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Neil Challinor over 1 year ago

SCN1       =FEAT/SCAN,LINEARCLOSE,NUMBER OF HITS=164,SHOW HITS=NO,SHOWALLPARAMS=NO
            MEAS/SCAN
              BASICSCAN/LINE,NUMBER OF HITS=164,SHOW HITS=NO,SHOWALLPARAMS=NO
              ENDSCAN
            ENDMEAS/
CRV1       =FEAT/CURVE,DEPENDENT,98,164,TOLERANCE,0.01
            THEO/81.195
            MEAS/81.195
            CONSTR/CURVE,SCN1,,
DIM LOC1= LOCATION OF CURVE CRV1  UNITS=MM ,$
GRAPH=OFF  TEXT=OFF  MULT=10.00  OUTPUT=BOTH  HALF ANGLE=NO
AX    NOMINAL       +TOL       -TOL       MEAS        DEV     OUTTOL
L       81.195      0.050      0.050     81.195      0.000      0.000 ----#----
END OF DIMENSION LOC1

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Benedictj1 over 1 year ago in reply to Neil Challinor

number of hits x point spacing will not report the same number? just curious
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JEFMAN over 1 year ago in reply to Neil Challinor

Benedictj1 : changing the tolerance to 0.00001 should give the same number of hits.
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BIGWIG7 over 1 year ago in reply to Neil Challinor

dangnabit, i dont know if ive needed to measure using Curve before. Gonna have to experiment with this one. I like it.
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Neil Challinor over 1 year ago in reply to Neil Challinor

@Benedictj1
Yes, obviously the point density and the curve fitting tolerance will have an effect. The denser the scan and the more closely the curve is fitted to the points, the more accurate the result will be.
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