Rmeas help

I've been trying to figure out what PC-DMIS does with the RMEAS statement with the different numbers of Hits. I found some info that refers to the Rmeas with 3 hits as the "Flush/Gap" measurement. Can anyone explain the difference between the RMEAS with 1 hit versus the RMEAS with 3 hits? From analyzing the data I believe it has to do with the vector that is used when it takes the actual measurement. From what I've seen looking at data is the single hit RMEAS would be considered a "Surface/Edge" measurement where the edge is too thin to consider it having any thickness/depth.

From my own analysis it appears that the single hit version uses an approach vector that is perpendicular to the reference points vector. The vector I believe is derived by the unit vector of (|V1| X |V2|) X |V1|, where V1 is the vector on the surface point and V2 is the vector on the point being measured with RMEAS. The X represents the Cross Product function. The first cross product is done between the 2 vectors to obtain a vector normal to the 2 vectors. The cross product of the resulting vector & the surface vector then gives you a vector that is perpendicular to the surface vector V1, but in the same plane as V2.

Does anyone know what the 3 hit version does?

F(F0954M009B) = FEAT/POINT,CART,2531.99,860.834,605.15,0.0437,0.9651,0.2584
  MEAS/POINT, F(F0954M009B), 1
  ENDMES
 T(XTOL_4)=TOL/CORTOL,XAXIS,0.0,0.0
 T(YTOL_4)=TOL/CORTOL,YAXIS,-0.15,0.15
 T(ZTOL_4)=TOL/CORTOL,ZAXIS,0.0,0.0
 T(VECTOL_4)=TOL/PROFP,0.0,0.0
 TEXT/OUTFIL,'F0954M009B - POINT - INSP=D METAL=0.686'
 OUTPUT/FA(F0954M009B),TA(XTOL_4),TA(YTOL_4),TA(ZTOL_4),TA(VECTOL_4)

  GOTO/2536.032,864.531,605.704
F(G0954M009B) = FEAT/POINT,CART,2524.03,857.084,605.007,0.9667,-0.2002,-0.1595
  RMEAS/POINT, F(G0954M009B), 1, FA(F0954M009B)
  ENDMES
 T(XTOL_5)=TOL/CORTOL,XAXIS,-0.15,0.15
 T(YTOL_5)=TOL/CORTOL,YAXIS,0.0,0.0
 T(ZTOL_5)=TOL/CORTOL,ZAXIS,0.0,0.0
 T(VECTOL_5)=TOL/PROFP,0.0,0.0
 TEXT/OUTFIL,'G0954M009B - HEDGE - INSP=D METAL=0.686'
 OUTPUT/FA(G0954M009B),TA(XTOL_5),TA(YTOL_5),TA(ZTOL_5),TA(VECTOL_5)
  GOTO/2536.032,864.531,605.704

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mjdevries over 11 years ago

Thanks again for the great response.

I just hopped on here to ask about the depth setting of 0. What does PC-DMIS do with that? Do they offset the gap nominal by the 'edge theo_thickness' along a vector perpendicular to the Edge point surface vector? If so that could actually explain part of what I am seeing.

Do you know what effect the edge theo_thickness has?

From looking at the CAD. If I offset the nominal point by the theo thickness along the gap point surface vector it give me a point on the opposite side of material. If I then offset that point along the vector that is perpendicular to the edge surface vector, then it gives me a point that is in line with where all the data is after I remove the surface point deviation from it. I will need to try to get a graphic of this.
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mjdevries over 11 years ago

Thanks again for the great response.

I just hopped on here to ask about the depth setting of 0. What does PC-DMIS do with that? Do they offset the gap nominal by the 'edge theo_thickness' along a vector perpendicular to the Edge point surface vector? If so that could actually explain part of what I am seeing.

Do you know what effect the edge theo_thickness has?

From looking at the CAD. If I offset the nominal point by the theo thickness along the gap point surface vector it give me a point on the opposite side of material. If I then offset that point along the vector that is perpendicular to the edge surface vector, then it gives me a point that is in line with where all the data is after I remove the surface point deviation from it. I will need to try to get a graphic of this.
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