Calculating Feature Depth - Fun With Angles

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  • Calculating Feature Depth - Fun With Angles

    Hello!
    Running PC-DMIS 2013 MR1 SP5
    --------------------------------------------
    11071205_AngleNotch.jpg
    This is a cylinder.
    I need to measure this parts depth (3.49)

    My process goes:
    Perform an alignment on the cylinder (Level-Rotate-Origin)
    Measure some features.
    Then I measure the angle notch location
    Next I align to the notch, offsetting the 45° and measure a plane.

    My problem comes from dimensioning the depth.
    I guess I'm having a hard time understanding what I'm trying to do?
    ---
    My original hypothesis involved an intersect point from the plane at the bottom of the notch to the top of the OD; however I could use some help!

    EDIT: I guess my real issue is how I would go about accurately representing the "point in space".
    I have measurements for the OD, of the diameter of the notch, the depth and the angle; I just need to dimension the depth
    Last edited by InspectorJester; 05-17-2018, 07:51 AM. Reason: CREATURE FROM [i]THE DEPTH[/i] OF THE ABYSS!!!

  • #2
    If you can measure the hole as a cylinder, create an ellipse (intersection of the cylinder with the plane, create a point at the small radius of the ellipse (intersect point or generic point), and dimension the distance between this point and the bottom plane.
    Another way, with a little trig (and it's not friday, even if I don't work tomorrow )
    ASSIGN/V1=CROSS(CYL1.IJK,CROSS(PL1.IJK,CYL1.IJK))
    IF/DOT(V1,PL1.IJK)<0
    ASSIGN/V1=-V1
    END IF
    ASSIGN/V2=CYL1.XYZ+CYL1.R*V1
    F1 =GENERIC/LINE,DEPENDENT,CARTESIAN,OUT,$
    NOM/XYZ,<V2.X,V2.Y,V2.Z>,$
    MEAS/XYZ,<V2.X,V2.Y,V2.Z>,$
    NOM/IJK,<CYL1.I,CYL1.J,CYL1.K>,$
    MEAS/IJK,<CYL1.I,CYL1.J,CYL1.K>,$
    DISTANCE/10,10

    Then create a pierce point between F1 and PL1
    and dimension the distance between the pierce point and the bottom plane

    Comment


    • #3
      I'll have to try that out!
      I was thinking I'd have to measure it as a cylinder as well.
      Never made an ellipse in PC-DMIS, so this'll be fun too!

      As for your math;
      I'm not sure I understand! (Typical!)

      It looks like what you're asking is for me to measure it as a cylinder, "project" that cylinder to be perpendicular with the plane (depth).
      Wouldn't the pierce point between the cylinder and the plane be at the bottom of the notch?

      EIDT:
      The notch is cut away; essentially a cylindrical hole (with depth) cut 45° relative to the OD.
      It looks like it's dimensionsed from the location, so would I pierce it from the location...?

      Last edited by InspectorJester; 05-17-2018, 08:05 AM. Reason: I need more coffee..

      Comment


      • #4
        With a little explanation :

        CROSS(PL1.IJK,CYL1.IJK) creates a vector perp to CYL1 and PL1
        so ASSIGN/V1=CROSS(CYL1.IJK,CROSS(PL1.IJK,CYL1.IJK)) creates a vector perp to this one and cyl1, so on your draw, it's in the plane of the draw !
        The cross function in PC-DMIS gives a unit vector, so you don't have to use "UNIT" function (in the real maths, you would have to divide the cross product by the length of the vector)
        IF/DOT(V1,PL1.IJK)<0
        ASSIGN/V1=-V1
        END IF
        the result of a cross product depends on the order of vectors and of their direction. The vector that you need must go towards PL1, so the if statement changes the direction if the dot ptroduct is negative.
        ASSIGN/V2=CYL1.XYZ+CYL1.R*V1 this create a "point" from the centroid of the cylinder, offset of the radius value in the right direction.
        F1 =GENERIC/LINE,DEPENDENT,CARTESIAN,OUT,$ The line is parallel to cylinder axis, and goes through the "high point" searched, so the pierce point will be the right one !
        NOM/XYZ,<V2.X,V2.Y,V2.Z>,$
        MEAS/XYZ,<V2.X,V2.Y,V2.Z>,$
        NOM/IJK,<CYL1.I,CYL1.J,CYL1.K>,$
        MEAS/IJK,<CYL1.I,CYL1.J,CYL1.K>,$
        DISTANCE/10,10

        Comment


        • InspectorJester
          InspectorJester commented
          Editing a comment
          So Cyl1 is the OD then? I was under the impression you were referring to the cylinder described to measure the notch!
          I will try with this.. I was getting numbers around 0.03, I'm looking for 3.49 lol!

        • JEFMAN
          JEFMAN commented
          Editing a comment
          No, CYL1 is the "notch", not the OD !

      • #5
        Edit: I definitely didn't think this through - ignore this...

        It is possible to create a line from a plane (it will be the normal), so if you have a reliable plane at the bottom of the notch (PL1), just do

        - construct cast line from plane PL1 (that's what PC-DMIS does if you select "Auto")
        - construct pierce point of line and cylinder (PP1)
        - distance PP1 perpendicular to PL1

        You may have to reverse the line to get the right point (construct line from another line, Auto)
        Last edited by AndersI; 05-17-2018, 10:01 AM.
        AndersI
        SW support - Hexagon Metrology Nordic AB

        Comment


        • #6
          Here :
          pierce pt.JPG

          Comment


          • #7
            11071205_AngleNotch.jpg

            Comment


            • InspectorJester
              InspectorJester commented
              Editing a comment
              I can't edit this for whatever reason.. But these are the features I have. I don't have a plane at the top of the OD; are you suggesting I make one?

            • JEFMAN
              JEFMAN commented
              Editing a comment
              The 3.49 comes from the pierce point to the bottom, no ?

            • InspectorJester
              InspectorJester commented
              Editing a comment
              Right, but it's offset 45°. Wouldn't it make a difference how far "left" it is? I'd like to account for this.
              I will come back to this; could I just use a point on top of the OD?

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