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Need help Circular Pattern generating copy that is invalid for Boolean. Am I doing something wrong?

Lyle_WalshLyle_Walsh Member Posts: 28
I will try to paste the link to the part studio where I think the problem lies.  Strangely, it was working, now a piece seems to randomly disappear after re-opening my document.  I am making cutouts in the wall of a threaded cylinder with 6 circular copies of tilted rectangular blocks.  The last block in the group of 6 seems to go in and out of existence and I really don't have any idea why.

https://cad.onshape.com/documents/88e7c1789a53f86b24afc175/w/d6e3312c1431eddf480347a6/e/160bc58d408105f30b26ce3d

Best Answers

  • john_mcclaryjohn_mcclary Member, Developers Posts: 439 PRO
    Accepted Answer
    There seems to be a problem with your axis of your pattern.

    Get rid of your "Center" sketch/extrude and bring your derived threads above the pattern, and redefine the axis to the cylinder face of the thread part.

    I couldn't find any reason the edge of the "Center" extrude was failing, but it may be some sort of bug. So far I've only patterned around cylinders and haven't run into this before.




  • Lyle_WalshLyle_Walsh Member Posts: 28
    Accepted Answer
    Thanks for your great help.  I moved up 'derived' and used its internal face as center as you suggested and that worked.  I left my 'center' object in place and its mere existence didn't seem to cause any errors.  Not having a selectable origin axis as a center is a limitation with onshape IMHO.  I'll report it as a bug, who knows, I might be making some other simple mistake but I'll take the chance of looking foolish.
  • Lyle_WalshLyle_Walsh Member Posts: 28
    edited May 20 Accepted Answer
    NO {I can't reproduce this in a simplified test.  Frustrating but I may just have to start this one over.}

    I spoke too soon, here it is duplicated, my hunch is that cutting out a threaded cylinder can result in unattached bits and that is too much for onshape to resolve.

    https://cad.onshape.com/documents/162393589dea2e68f93b9fc2/w/d7580b6c017828fdb47d9093/e/67d3ddea2f52545877ed99d1



  • Lyle_WalshLyle_Walsh Member Posts: 28
    Accepted Answer
    Thank you all for the help.  I have confirmed that if I generate loose parts with Boolean subtract and then reference back to the modified part (it was my center of axis for circular pattern) this seems to cause random errors such as not generating all the parts on circular pattern.  If I modify my subtracting part to not make loose parts then the error resolves.  this has been reported in a real bug report.

Answers

  • john_mcclaryjohn_mcclary Member, Developers Posts: 439 PRO
    Accepted Answer
    There seems to be a problem with your axis of your pattern.

    Get rid of your "Center" sketch/extrude and bring your derived threads above the pattern, and redefine the axis to the cylinder face of the thread part.

    I couldn't find any reason the edge of the "Center" extrude was failing, but it may be some sort of bug. So far I've only patterned around cylinders and haven't run into this before.




  • Lyle_WalshLyle_Walsh Member Posts: 28
    Accepted Answer
    Thanks for your great help.  I moved up 'derived' and used its internal face as center as you suggested and that worked.  I left my 'center' object in place and its mere existence didn't seem to cause any errors.  Not having a selectable origin axis as a center is a limitation with onshape IMHO.  I'll report it as a bug, who knows, I might be making some other simple mistake but I'll take the chance of looking foolish.
  • john_mcclaryjohn_mcclary Member, Developers Posts: 439 PRO
    Right, the existance of your 'Center' object wasn't a problem, but it wasn't being used any more so I suppressed it. The center object was straight and centered on the origin, but using the edge as an axis made the pattern unstable for some reason. I don't think you did anything wrong.
  • Lyle_WalshLyle_Walsh Member Posts: 28
    Its back and my booleans are bad because of this I think.  [my goal: First I use circular pattern to make cutout blanks for a boolean subtract, then add parts into the cutout holes using a boolean union.]  Is a threaded part too complex to use??   The cutouts do leave some dangling bits that I manually removed 

    https://cad.onshape.com/documents/88e7c1789a53f86b24afc175/w/d6e3312c1431eddf480347a6/e/160bc58d408105f30b26ce3d


  • Lyle_WalshLyle_Walsh Member Posts: 28
    edited May 20 Accepted Answer
    NO {I can't reproduce this in a simplified test.  Frustrating but I may just have to start this one over.}

    I spoke too soon, here it is duplicated, my hunch is that cutting out a threaded cylinder can result in unattached bits and that is too much for onshape to resolve.

    https://cad.onshape.com/documents/162393589dea2e68f93b9fc2/w/d7580b6c017828fdb47d9093/e/67d3ddea2f52545877ed99d1



  • Lyle_WalshLyle_Walsh Member Posts: 28
    Accepted Answer
    Thank you all for the help.  I have confirmed that if I generate loose parts with Boolean subtract and then reference back to the modified part (it was my center of axis for circular pattern) this seems to cause random errors such as not generating all the parts on circular pattern.  If I modify my subtracting part to not make loose parts then the error resolves.  this has been reported in a real bug report.
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