Iterative alignment question

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  • Iterative alignment question

    I need some clarification how the coordinates of target points should be given on the drawing. When creating drawing customer rotated CAD model. It is irregular shape and the views on the drawing do not match views from CAD anymore. I want to get to the same part orientation as on the drawing. How do I get to this point using target points? Do target points on the drawing have to have coordinates after part was already rotated? Thanks for any help.

  • #2
    Just use the customer provided numbers. The views on the drawing are not definitive. The DRF doesn't care about the orientation of the views of the drawing, unless there are basic angles defining it as such.
    "This is my word... and as such is beyond contestation."


    • #3
      I attached an extract from one of our GD&T training courses that talks about datum targets and how they should appear on a drawing.
      Attached Files
      Neil Challinor
      PC-DMIS Product Owner

      T: +44 870 446 2667 (Hexagon UK office)
      E: [email protected]


      • #4
        Drawing is not finalized yet. They just sent me preliminary version for review and comments. The moment they rotated CAD for the drawing purposes they introduced new coordinate system. Distances on the drawing are based on this rotation. If target points on the drawing are given in original car coordinate system how do I get to their rotation so I can measure those distances correctly?


        • VinniUSMC
          VinniUSMC commented
          Editing a comment
          If it doesn't have a Feature Control Frame that tells you what the DRF is, then the coordinate system is whatever it needs to be to get that dimension, and for many feature types is unrelated to any coordinate system.

          If it does have a FCF, the basic dimensions on the print can be anything, as long as it relates the feature to the datums.

          Rotating a drawing view does not introduce a new coordinate system. The coordinate system is CAD, or DRF defined.

      • #5
        I guess the reason I am talking about new coordinate system is because when I am checking CAD outside CMM I am using CAD viewer and in order to get what I see on the drawing and verify some nominals I am actually changing original alignment. Attached is example of what I am after. I just came up with the shape, it is not the actual part. Shape on the left is one of the CAD views when part is in car coordinates. On the right is view from the drawing which shows part rotated. This view has basic of 2 marked where the section should be done. Based on this section some distances are presented on the view of the section which are to be measured in the new X, Y, Z directions. Those new X,Y,Z directions in relation to the part are not the same X,Y,Z directions as in CAD.
        Attached Files


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