alignment help needed

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  • alignment help needed

    print attached.

    This will probably seem awfully elementary to most of you here, but this is messing with me head.

    The primary datum A is a stud cylinder.
    The secondary datum B is a plane.
    The tertiary datum C is a line.

    I've measured all the features, now to what do I 'level', 'rotate' TO and ABOUT? and which features should I use as origins?

    It seems yo me that on the drawing, that the basic dimensions are all zeroed and centered on the datum A cylinder. So it would seem to follow that I'd need to level to A and origin on A, right? but the rotate thing has me perplexed. If I level to A, and then try to use B as a rotate, then aren't those basically the same features? I mean if I make cyl A the level to Z plus, then choose B as my rotate feature, it is also a Z plus feature. Can you rotate TO Z plus ABOUT Z plus, after I've already leveled Z plus? That seems illogical. Then C is sitting down there as a Y origin feature, but none of the basic dimensions reference that line.
    I am confused. help.
    Attached Files
    Last edited by d.evans; 09-06-2007, 01:53 PM. Reason: Capitalization
    ** "Well, ain't this place a geographical oddity. Two weeks from everywhere!"~ Ulysses Everett McGill **

  • #2
    Measure A as a cylinder, B as a plane and C as a line.

    Just follow the FCF. Fix as many DOF's as possible with the primary datum. Then fix as many DOF's as possible with the secondary datum. Then fix the remaining DOF's (hopefully) with the tertiary datum.

    This one is going to be a little different because of the way PC-DMIS works.

    Level A to z-plus (assuming back side is on the table)
    Rotate C to x-plus
    translate z orgin to B
    translate x and y orgins to A

    I know that isn't exactly as they are called in the FCF but you should always rotate before you translate.

    Comment


    • #3
      Originally posted by d.evans View Post
      print attached.

      This will probably seem awfully elementary to most of you here, but this is messing with me head.

      The primary datum A is a stud cylinder.
      The secondary datum B is a plane.
      The tertiary datum C is a line.

      I've measured all the features, now to what do I 'level', 'rotate' TO and ABOUT? and which features should I use as origins?

      It seems yo me that on the drawing, that the basic dimensions are all zeroed and centered on the datum A cylinder. So it would seem to follow that I'd need to level to A and origin on A, right? but the rotate thing has me perplexed. If I level to A, and then try to use B as a rotate, then aren't those basically the same features? I mean if I make cyl A the level to Z plus, then choose B as my rotate feature, it is also a Z plus feature. Can you rotate TO Z plus ABOUT Z plus, after I've already leveled Z plus? That seems illogical. Then C is sitting down there as a Y origin feature, but none of the basic dimensions reference that line.
      I am confused. help.
      Looking at what you have for a print, this is what I see:

      Datum A is the cylinder
      Datum B is the face of the raised portion
      Datum C is the flat edge of the part

      I do not think this print is correct and I would 'fight' it.

      Level to A datum
      Rotate to C datum
      Set 2 axis origin to A datum cylinder (making it 0,0), set the third to the B datum.

      This is what I think they were trying to say with the print, they were just unable to do it correctly.
      sigpic
      Originally posted by AndersI
      I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

      Comment


      • #4
        thanks

        Originally posted by Goodluck View Post
        Measure A as a cylinder, B as a plane and C as a line.

        Just follow the FCF. Fix as many DOF's as possible with the primary datum. Then fix as many DOF's as possible with the secondary datum. Then fix the remaining DOF's (hopefully) with the tertiary datum.

        This one is going to be a little different because of the way PC-DMIS works.

        Level A to z-plus (assuming back side is on the table)
        Rotate C to x-plus
        translate z orgin to B
        translate x and y orgins to A

        I know that isn't exactly as they are called in the FCF but you should always rotate before you translate.
        I actually wrote a program to measure this part a while back, and we just got some newly made parts in again that must be inspected. I always make a point to go back and check myself on how I interpreted at the time the program was written. The way you described is the way I wrote it originally, but today, I stopped and realized that the print was a little different. I appreciate all of the responses. It confirms that I was not out on a limb on this one when I originally wrote the program.
        ** "Well, ain't this place a geographical oddity. Two weeks from everywhere!"~ Ulysses Everett McGill **

        Comment


        • #5
          Originally posted by Goodluck View Post
          Measure A as a cylinder, B as a plane and C as a line.

          Just follow the FCF. Fix as many DOF's as possible with the primary datum. Then fix as many DOF's as possible with the secondary datum. Then fix the remaining DOF's (hopefully) with the tertiary datum.

          This one is going to be a little different because of the way PC-DMIS works.

          Level A to z-plus (assuming back side is on the table)
          Rotate C to x-plus
          translate z orgin to B
          translate x and y orgins to A

          I know that isn't exactly as they are called in the FCF but you should always rotate before you translate.
          what is a DOF?
          ** "Well, ain't this place a geographical oddity. Two weeks from everywhere!"~ Ulysses Everett McGill **

          Comment


          • #6
            Degree Of Freedom.

            3 rotational and 3 translational = 6 total

            Comment


            • #7
              Originally posted by Goodluck View Post
              Degree Of Freedom.

              3 rotational and 3 translational = 6 total
              DOH!!!!

              thankyaverymuch.
              ** "Well, ain't this place a geographical oddity. Two weeks from everywhere!"~ Ulysses Everett McGill **

              Comment


              • #8
                Originally posted by d.evans View Post
                DOH!!!!

                thankyaverymuch.
                No, DOH belongs in the beer thread.

                Degree
                Of
                Hammeredness

                There are only four of those:

                Hammered
                Not Hammered
                Hammered but claims to be Not Hammered
                Not Hammered but claims to be Hammered

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