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Lofting Errors

paul_ardenpaul_arden Member, Developers Posts: 80 ✭✭
I have spent hours trying to get a successful loft with no luck. I have tried simplified cases which end up being hit and miss but for the one I am actually trying to do I haven't been able to get anything to work. The failed loft is at the bottom of the feature list in this document:

https://cad.onshape.com/documents/6b0496e855682661004f9ecd/w/5d467c03d1f0b17cef7cd0c3/e/5ed83894eac9e781203c43aa

Here's what it looks like:



And here's the top and bottom profile:




I've put each guide into it's own sketch and added pierce constraints to all of the end points however I still get loft errors. I have tried each guide individually and I also have the same issue. I've been through the forum looking at quite a few other peoples problems with lofts but haven't found any of those solutions to work.

Any bright ideas?
Tagged:

Comments

  • philip_thomasphilip_thomas Member, Moderator, Onshape Employees, Developers Posts: 1,205
    edited July 2018
    @paul_arden - you were close! :)

    #1 problem - guides must be tangent continuous
    #2 lofts are just plain fiddly in any system - sometimes just playing with extra sections and start/end conditions will get you better results.

    This document contains a couple of itterations
    Hope this helps :)




    https://cad.onshape.com/documents/8f9a97f07eb330531a392528/w/6bd39b5084aea70644f4c269/e/8acf96caf9e86aabed042a97


    ps - totally fine to loft to a point, you did not need to make the tiny circle.
    Philip Thomas - Onshape
  • paul_ardenpaul_arden Member, Developers Posts: 80 ✭✭
    Awesome, thanks! The tangent continuity was key, re-reading the documentation I see it does say it, though given how critical it is to success I think it would be great to emphasise it even more.

    Thanks for the top on lofting to a point as a profile, that saves a lot of messing around. In the end the other issue I had was the paths were just not structured well enough to line everything up nicely so I redrew them and ensured the tangent constraints were there. Giving me:



    I added some additional profiles to keep it cylindrical in the center and it's finally looking exactly as intended. One question I did have is how did you make the 'Selections' that are in your loft, when I use the 'Create Selection' and add them it just adds the individual items. In the end I used Composite Curves instead to create the subsets of curves to use as guides, just curious how you did that.

    Thanks for the help!
  • brucebartlettbrucebartlett Member, OS Professional, Mentor Posts: 1,787 PRO

    Paul, I think you will find if you click the little arrow next to the selection you can expand it to select multiple selections rather than using a compound curve. 
    Engineer ı Product Designer ı Onshape Consulting Partner
    Twitter: @onshapetricks  & @babart1977   
  • paul_ardenpaul_arden Member, Developers Posts: 80 ✭✭
    @brucebartlett ah, thanks got it now.
  • brucebartlettbrucebartlett Member, OS Professional, Mentor Posts: 1,787 PRO
    No Worries!
    Engineer ı Product Designer ı Onshape Consulting Partner
    Twitter: @onshapetricks  & @babart1977   
  • philip_thomasphilip_thomas Member, Moderator, Onshape Employees, Developers Posts: 1,205
    edited August 2018
    ^^^^Love it Paul! :)
    (also clears up some debate around here as to 'what the hell is that?' :))
    Philip Thomas - Onshape
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