Distance to highest point on plane

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  • Distance to highest point on plane

    Hey guys
    Ive think ive seen a couple of similar threads of this topic, but i havent really been satisfied with the responses.

    I have a cylinder, and the plane at one end is flat. the plane at the opposite end is angled 77 degrees.
    I have a couple of distances from the flat plane to the highest point at the angled plane.

    How we measured this manually was just putting the flat plane on a surface plate, then with a height guage look for the longest possible distance to the angled plane.

    Now we want to automate this process by putting it in a CMM. Is there anyway for me to measure the angled side as a plane, then finding the highest point (in Y-direction) and evaluate distance to that point from the flat plane?
    Maybe it works with assigning a high point from the plane or something similar

    Last edited by pcdmisstudent; 12-05-2019, 09:56 AM.

  • #2
    The plane would either be bounded and not extend to your high point, or unbounded and have an infinite high point. You would need to use some constructions, intersection points, etc.

    The angled plane has a specific orientation to the Datum structure? If it does, you could measure a line up the cylinder at the angle of the highest theoretical point and intersect the line and plane, then dimension the distance of the point to the flat plane. Or, use several lines offset from each other by whatever amount you think is good enough to capture the highest point, and several intersection points, and use an array to pick the highest Y value, or the highest distance value, or whatever.
    "This is my word... and as such is beyond contestation."


    • pcdmisstudent
      pcdmisstudent commented
      Editing a comment
      So maybe i can just make a intersection point where the cylinders centerline intersects with the plane. And depending on the direction of the cylinder (being y+ or y-) it would give me the highest / lowest point?

    • VinniUSMC
      VinniUSMC commented
      Editing a comment
      That would only give you the intersection points of the cylinder center-lines. So, you would know the distance to the cylinder center-line intersection with the slanted plane. I suppose you could trig it out if you find the measured angle of the slanted plane to the flat plane, and using the cylinder's measured diameter, as in the below solution by Anders.
      Last edited by VinniUSMC; 12-05-2019, 11:19 AM.

  • #3
    NOTE: My original post had an error in it, using SIN() instead of TAN(). This is now corrected.

    You could locate the hit on the slanting plane that has the highest Y value, but I don't think you will be able to measure that reliably, as that hit would need to be on the absolute edge of the surface. If you have a scanning probe, you could try "High point scan", if you only have a touch probe it's probably faster to measure it the old manual way...

    Simple geometry might be another solution:

    3D angle between the two planes gives A
    Cylinder diameter gives D (To be most accurate, the cylinder should really be calculated with the additional constraint "perpendicular to the bottom plane")
    Intersection point Cylinder / Slanting plane gives P
    Calculate distance from bottom plane to highest point of slanting surface of cylinder as: P.Y + D/2 * TAN(A)

    (JEFMAN will correct me if I have made a mistake in the above)
    Last edited by AndersI; 12-06-2019, 08:14 AM.
    SW support - Hexagon Metrology Nordic AB


    • AndersI
      AndersI commented
      Editing a comment
      NOTE: My original post contained an error - using SIN() instead of TAN(). Corrected.
      Why didn't anyone spot my mistake?
      Last edited by AndersI; 12-06-2019, 08:14 AM.

    • JEFMAN
      JEFMAN commented
      Editing a comment
      Because it's friday ?
      Because when A is little, in rad, A=sin(A)=tan(A) ?
      Because I didn't readd carefully ?
      Because I didn't draw a scheme ?

      Or just because you have all our confidence...

      Happy week-end, all !

    • VinniUSMC
      VinniUSMC commented
      Editing a comment
      Ah, right, I see what you're saying.

      I can't believe we all overlooked SIN/TAN... lol. Missing the forest for the trees.

  • #4
    You can also :
    ASSIGN/V1=CROSS(PL1.IJK,CROSS(CYL1.IJK,PL1.IJK)), which gives the vector parallel to the longer radius of the constructed ellipse (intersection angled plane / cylinder = ellipse)
    Then, construct the pierce point between the cylinder and the plane.
    Construct a generic line through this point using the vector above.
    Create the pierce point between the line and the cylinder : it will give the upper or the lower point, depends on the diredtion of the vector... (using +/- in this case)


    • pcdmisstudent
      pcdmisstudent commented
      Editing a comment
      Hey Jeff
      Ok sorry for my lack of knowledge, but i dont got much experience with neither generic elements nor assign.

      So i have my elements:

      I then construct elipse thru intersection with my plane_angle and cylinder.
      I write the assign command you wrote above with plane_angle and cylinder_straight
      I insert a generic line (with measured values and put on dependent) and in the dialog with IJK and XYZ I replace the IJK values with V1.
      i then create pierce point between the generic line and the cylinder_straight.

      Is this correct?

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