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Rmeas help

mjdevries
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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  • Matthew,
    Where did you go?

    Do you know what the theo thickness and edge theo thickness are when you use the edge measurement? I'm assuming they are perpendicular to each other. See my image and let me know if it makes sense what I labelled as the Theo Thickness and the Edge Theo Thickness.

    I have a few things wrong with the measurement I think. The Indent is wrong I believe. When I measure from the Surface point to the edge point on the wrong side of material perpendicular to the surface normal I get what they have in the CMM Program as the Indent. I believe the indent should be the distance from the surface point to the edge point on the correct surface. This error gives me the 0.711 mm material thickness shift.

    If the Edge Theo Thickness is actually the thickness of the part in the direction that would be tangent to the edge surface (perpendicular to the edge surface normal vector), then that woud be the other 0.711 shift I am seeing in the target point that PC-DMIS is taking the hits on.

    Now the target point is on the wrong side of material so I also have that shift to along the measurement direction that also needs to come out of the data.

    It is crazy how much can be wrong with one stinking dimension when someone really screws it up. Unfortunately they use some offline programming here and some automation to create the cmm programs. I believe I will find that we have this issue in a couple hundred CMM programs. Yippee!

Reply
  • Matthew,
    Where did you go?

    Do you know what the theo thickness and edge theo thickness are when you use the edge measurement? I'm assuming they are perpendicular to each other. See my image and let me know if it makes sense what I labelled as the Theo Thickness and the Edge Theo Thickness.

    I have a few things wrong with the measurement I think. The Indent is wrong I believe. When I measure from the Surface point to the edge point on the wrong side of material perpendicular to the surface normal I get what they have in the CMM Program as the Indent. I believe the indent should be the distance from the surface point to the edge point on the correct surface. This error gives me the 0.711 mm material thickness shift.

    If the Edge Theo Thickness is actually the thickness of the part in the direction that would be tangent to the edge surface (perpendicular to the edge surface normal vector), then that woud be the other 0.711 shift I am seeing in the target point that PC-DMIS is taking the hits on.

    Now the target point is on the wrong side of material so I also have that shift to along the measurement direction that also needs to come out of the data.

    It is crazy how much can be wrong with one stinking dimension when someone really screws it up. Unfortunately they use some offline programming here and some automation to create the cmm programs. I believe I will find that we have this issue in a couple hundred CMM programs. Yippee!

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