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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Matthew D. Hoedeman over 11 years ago

THEO and ACTL thickness are for when you are checking the OPPOSITE side of stock from what you have cad data for. Say your part is 1mm thick, but you only have cad data for ONE SIDE of the part, and that is NOT the side you are checking.

THEO THICKNESS is for when you want the NOMINALS to reflect the side you are checking on, ACTL THICKNESS is for when you want the nominals to STAY cad nominals, but you don't what the 1mm stock thickness to screw up your checks. ACTL acts sort of like 'extra' probe comp. When used for an edge point for the edge thickness, it has the same effect, BUT (IMO) there should never BE an edge thickness value.

DEPTH: Sheet metal.... When sheet metal is stamped (cut) you get a 'shear' and a 'break' on the edge. You don't want to check the 'break', there is where the metal wasn't 'cut', but 'broke away' from the 'shear' cut that was done. You need the probe to hit on the 'shear'. Well, depending on WHICH SIDE the part was cut FROM will determine which side has the shear and which side has the break. Let's go with a 'thick' part, 6mm thick. You will have about 1mm of shear and 5mm of break on the edge of that part. If the shear is on the 'bottom' as you are checking it, you would want a 5.5mm depth so that the probe hits the shear. If the shear is on the 'top', then you would want 0.5mm of depth. A zero is BAD because you will either be hitting the break (shear on the bottom) or you WILL be hitting the curl that will be on the shear side, there is always a little bit of curl, so that's a bad place to hit as well.

Now, since Pcdmis isn't DMIS, if that thickness had been meant for the SURFACE, it should show up in the THEO_THICKNESS and not the THEO EDGE THICKNESS. This could be an issue with DMIS out / DMIS inm but IMO, there should NOT be any edge thickness value. I would guess that the metal thickness of the sheetmetal is 0.711 and that it got screwed up in the translation and put in the edge thickness.
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Matthew D. Hoedeman over 11 years ago

THEO and ACTL thickness are for when you are checking the OPPOSITE side of stock from what you have cad data for. Say your part is 1mm thick, but you only have cad data for ONE SIDE of the part, and that is NOT the side you are checking.

THEO THICKNESS is for when you want the NOMINALS to reflect the side you are checking on, ACTL THICKNESS is for when you want the nominals to STAY cad nominals, but you don't what the 1mm stock thickness to screw up your checks. ACTL acts sort of like 'extra' probe comp. When used for an edge point for the edge thickness, it has the same effect, BUT (IMO) there should never BE an edge thickness value.

DEPTH: Sheet metal.... When sheet metal is stamped (cut) you get a 'shear' and a 'break' on the edge. You don't want to check the 'break', there is where the metal wasn't 'cut', but 'broke away' from the 'shear' cut that was done. You need the probe to hit on the 'shear'. Well, depending on WHICH SIDE the part was cut FROM will determine which side has the shear and which side has the break. Let's go with a 'thick' part, 6mm thick. You will have about 1mm of shear and 5mm of break on the edge of that part. If the shear is on the 'bottom' as you are checking it, you would want a 5.5mm depth so that the probe hits the shear. If the shear is on the 'top', then you would want 0.5mm of depth. A zero is BAD because you will either be hitting the break (shear on the bottom) or you WILL be hitting the curl that will be on the shear side, there is always a little bit of curl, so that's a bad place to hit as well.

Now, since Pcdmis isn't DMIS, if that thickness had been meant for the SURFACE, it should show up in the THEO_THICKNESS and not the THEO EDGE THICKNESS. This could be an issue with DMIS out / DMIS inm but IMO, there should NOT be any edge thickness value. I would guess that the metal thickness of the sheetmetal is 0.711 and that it got screwed up in the translation and put in the edge thickness.
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