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A1 (0,0,1) + A3(0,0,1) a headache about plane vector

RobOntario
Hello all.

I will be given a part (a very complicated part ) next week, so I am programing on cad model the last two days. Since I can not get right alignment, I looked back, found a problem on plane vector. I got 8 points for datum A1, the vector is (0,0,1), got 8 points for datum A3 same vector (0,0,1). Since A1 and A3 had different on Z AXIS, I formed A3 points to be at same level with A1. I verified them, PLN_A1 and PLN_A3 vector still (0,0,1). That is common sense. But when I added all 16 points together, the vector changed, I attached the program.
Please help... Any command is welcome...

Attached Files
  • hi,

    your "PLN_A1" is wrong

    your Points A1_1 to A1_8 have completely different values ​​than PLN_A1 
    your:
PLN_A1         =FEAT/PLANE,CARTESIAN,TRIANGLE,NO
               THEO/<45.252,-412.068,-35.499>,<-0.0000019,0,1>
               ACTL/<45.252,-412.068,-35.499>,<-0.0000019,0,1>
               CONSTR/PLANE,BF,PT_A1_1,PT_A1_2,PT_A1_3,PT_A1_4,PT_A1_5,PT_A1_6,PT_A1_7,PT_A1_8,,
               OUTLIER_REMOVAL/OFF,3
                FILTER/OFF,WAVELENGTH=0

it should be:
PLN_A1         =FEAT/PLANE,CARTESIAN,TRIANGLE,NO
               THEO/<59.256,1.931,24.618>,<0,0,1>
               ACTL/<59.256,1.931,24.618>,<0,0,1>
               CONSTR/PLANE,BF,PT_A1_1,PT_A1_2,PT_A1_3,PT_A1_4,PT_A1_5,PT_A1_6,PT_A1_7,PT_A1_8,,
               OUTLIER_REMOVAL/OFF,3
                FILTER/OFF,WAVELENGTH=0


    If I simply type your points into my program, it even works.
    I have to guess, well, that means the points you gave us aren't the same as the ones you used to create the planes.
    maybe you should recreate all points and i advise you use cad for that.
  • hi,

    If I simply type your points into my program, it even works.
    I have to guess, well, that means the points you gave us aren't the same as the ones you used to create the planes.
    maybe you should recreate all points and i advise you use cad for that.

    I agree with Henniger, the numbers don't add up. I also see that The vectors for PNT_A3_1 - PNT_A3_8 are all <-0.0000019,0,1>, the same as your constructed PLN_A1.
    while the vectors for PNT_A1_1 - PNT_A1_1 are all <0,0,1>. Either those planes are not parallel, or something got changed in the measuring routine that doesn't match the model.

    Also, it is more accurate to construct an offset plane directly from all the the measured points from both surfaces, rather than constructing offset points and then constructing a plane from those. Offsetting each point separately will shift each point based on the current alignment, which might have a slightly different vector than the plane constructed from points on both surfaces, especially if the two surfaces are not manufactured truly parallel or the offset distance between the two are not manufactured perfectly to nominal. Constructing an offset plane directly from the points will help compensate for this and offset the points in a direction that is truly perpendicular to the final constructed plane.




  • hi,

    your "PLN_A1" is wrong

    your Points A1_1 to A1_8 have completely different values ​​than PLN_A1 
    your:
PLN_A1 =FEAT/PLANE,CARTESIAN,TRIANGLE,NO
THEO/<45.252,-412.068,-35.499>,<-0.0000019,0,1>
ACTL/<45.252,-412.068,-35.499>,<-0.0000019,0,1>
CONSTR/PLANE,BF,PT_A1_1,PT_A1_2,PT_A1_3,PT_A1_4,PT_A1_5,PT_A1_6,PT_A1_7,PT_A1_8,,
OUTLIER_REMOVAL/OFF,3
FILTER/OFF,WAVELENGTH=0

it should be:
PLN_A1 =FEAT/PLANE,CARTESIAN,TRIANGLE,NO
THEO/<59.256,1.931,24.618>,<0,0,1>
ACTL/<59.256,1.931,24.618>,<0,0,1>
CONSTR/PLANE,BF,PT_A1_1,PT_A1_2,PT_A1_3,PT_A1_4,PT_A1_5,PT_A1_6,PT_A1_7,PT_A1_8,,
OUTLIER_REMOVAL/OFF,3
FILTER/OFF,WAVELENGTH=0


    If I simply type your points into my program, it even works.
    I have to guess, well, that means the points you gave us aren't the same as the ones you used to create the planes.
    maybe you should recreate all points and i advise you use cad for that.

    Thank you. That is the reason. I created all those points on CAD, it had something wrong when I created datum A which I believed should be around (0,0,1), but had 10 degrees off .


  • I agree with Henniger, the numbers don't add up. I also see that The vectors for PNT_A3_1 - PNT_A3_8 are all <-0.0000019,0,1>, the same as your constructed PLN_A1.
    while the vectors for PNT_A1_1 - PNT_A1_1 are all <0,0,1>. Either those planes are not parallel, or something got changed in the measuring routine that doesn't match the model.

    Also, it is more accurate to construct an offset plane directly from all the the measured points from both surfaces, rather than constructing offset points and then constructing a plane from those. Offsetting each point separately will shift each point based on the current alignment, which might have a slightly different vector than the plane constructed from points on both surfaces, especially if the two surfaces are not manufactured truly parallel or the offset distance between the two are not manufactured perfectly to nominal. Constructing an offset plane directly from the points will help compensate for this and offset the points in a direction that is truly perpendicular to the final constructed plane.






    My situation is that auto parts have A1 A2 A3.. for datum A. Which is better way to form datum A: 1, from datum A1 datum A2 A3 to form Datum A or 2: from points PNT_A1_1 PNT_A1_2...PNT_A1_8 PNT_A2_1 PNT_A2_2 ...PNT_A2_8... PNT_A4_1..PNT_A4_8?

    They should have some different, which is more accurate ?

    Thanks

  • in reply to Henniger123
    I started to run the program, then realized PLN_A1 on different alignment.

    PLN_A1_TEST =FEAT/PLANE,CARTESIAN,TRIANGLE,NO
    THEO/<59.255,1.931,24.618>,<0,0,1>
    ACTL/<59.256,1.932,24.583>,<-0.009438,-0.0028905,0.9999513>
    CONSTR/PLANE,BF,PT_A1_1,PT_A1_2,PT_A1_3,PT_A1_4,PT_A1_5,PT_A1_6,PT_A1_7,PT_A1_8,,
    OUTLIER_REMOVAL/OFF,3
    FILTER/OFF,WAVELENGTH=0.
    The issue was still there. I believed there are some bugs.

    PLN_A =FEAT/PLANE,CARTESIAN,TRIANGLE,NO
    THEO/<6.668,-218.433,-5.597>,<0.0455623,-0.1415901,0.9888763>
    ACTL/<6.302,-220.283,-6.921>,<0.0463451,-0.1462774,0.9881574>
    CONSTR/PLANE,BF,PT_A1_1,PT_A3_1F,PT_A3_2F,PT_A3_3F,PT_A3_4F,PT_A3_5F,PT_A3_6F,PT_A3_7F,PT_A3_8F,PT_A1_2,PT_A1_3,PT_A1_4,PT_A1_5,PT_A1_6,PT_A1_7,PT_A1_8,PLN_A2,,
    OUTLIER_REMOVAL/OFF,3
    FILTER/OFF,WAVELENGTH=0
  • Thank you all.

    I found the reason. I mixed up 2 coordinate systems. Offset was wrong.
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