Dimensioning Difficulties

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  • Dimensioning Difficulties

    I am attempting to dimension the few cylinders on this door that are cut with a 15 degree angle on them and then welded to the bent plate. Previously, I had intersected the cylinder and the large plane (plane 2), created a point and then dimensioned to the end of the part. They have dimensioned now to be measured from the center of the cylinder to the intersecting line of plane 2 and plane 3 rather than the edge (plane 3). When I program it on the CAD, the measurement comes out correct. When I actually run it, the cylinder is down and to the right by .100 or so. We have verified using hand tools that it is pretty close to where it should be.

    My first plane is off the top of the cylinder. Even that shows off center. If I do not use the CAD drawing and simply check the part, the X dimension is off between .035 and .050 (depending on which cylinder I check). The Zaxis (normally the X (it's the way he created the alignment before I got the cad)) is nearly perfect. Is there a certain order I should be creating my alignment? I'm creating a plane on the small cylinder, leveling it, creating the line, rotating it, and then doing the rest. Is there something else, I'm not considering?

    Thanks for any help or suggestions at all.
    Attached Files

  • #2
    I think it's not very accurate to level a long part on "a plane on a small cylinder"...
    The draw should help you to create the right alignment...


    • #3
      Thanks, but that didn't help.


      • #4
        What features are you using for your origin?
        Have you tried creating a circle at the top and one at the bottom of the cylinder to look at the individual location?

        I agree with JEFMAN, that the small plane is not ideal to use for your alignment. I would suggest trying to set a good stable and repeatable alignment on the plate first then come back to the cylinders after that.

        I can't quite figure out what is exactly "out" but when you come across this its usually in an unstable alignment. Just looking at where your origin is, I would bet it has something to do with it.


        • #5
          Same part. Different issue. As of now, I'm not using the CAD.

          I level off the plate, rotate to a line created on the side of the part and then create X (one side of the part), Y (the edge where the end of the plate meets the top of the plate) and Z (top of plate). When I get to the posts that are cut on a 15 angle, I rotate Y 15 degrees about X and it works fine. Except when they were not cut at a 15 degree angle (I've seen 14, 14.5, 15.5). Also the weld may have pulled the post in the other axis (X) a half degree or so. This throws my X or Y out of tolerance, depending on which way the post is leaning, but if I create a separate alignment using one of the above angles, it comes in tolerance.

          Since they don't care that the post is leaning a degree or less, the parts are fine, but is there a way I can take the leaning of each post into consideration when checking them? Simply rotating everything 15 degrees works for most, but not all. I thought it may be possible to create a plane off the top of each post and create an alignment for each post, but that doesn't seem to work.


          • #6
            Since cylinders are 3D features, you shouldn't have to rotate your alignment by entering the value. If you need to rotate for dimensioning purposes, you need to use the cylinder you created.

            Not seeing a drawing makes it a little difficult to help provide guidance. If you are using X and Y values for your dimensions than your alignment is absolutely critical. Rotating your alignment will obviously change you locations. So take your cylinder and rotate it Y plus or Y minus about Z Plus (Axis used based on the previous picture you supplied. Just be cautious of the direction of your cylinder. For repeatability, make sure you take your cylinder the same each time (hits around the top of the post first, then hits around the bottom of the post).


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