Welcome to the Onshape forum! Ask questions and join in the discussions about everything Onshape.

First time visiting? Here are some places to start:
  1. Looking for a certain topic? Check out the categories filter or use Search (upper right).
  2. Need support? Ask a question to our Community Support category.
  3. Please submit support tickets for bugs but you can request improvements in the Product Feedback category.
  4. Be respectful, on topic and if you see a problem, Flag it.

If you would like to contact our Community Manager personally, feel free to send a private message or an email.

Extruding up to surface with hidden area

gauthier_östervall
gauthier_östervall Member Posts: 99 ✭✭
edited December 2019 in Community Support
This is a minimal example: https://cad.onshape.com/documents/f2056bc8a4f21f6dc05c0aaa/w/db5173e0d0b77e5474e5fa42/e/bfaac868460e035bc6c0abf4

I have a surface with acute angles, which I project to a plane in order to extrude from the plane to the surface. The acute angle of the surface make the extrude fail, which I can understand. How would you go about making this work? Extrude all that is see-able from the plane in several steps, then fill in the gap? Isn't there a more elegant solution?



Here is where I extrude. The volume under the acute part of the surface, where there are three faces stacking up over the sketch, seems to be where the extrude fails (see Origin):

Tagged:

Best Answer

Answers

  • owen_sparks
    owen_sparks Member, Developers Posts: 2,660 PRO
    How about extruding above the surface and then use using the surface to split the part, followed by discarding the top part created by the split?
    Owen.
    Business Systems and Configuration Controller
    HWM-Water Ltd
  • NeilCooke
    NeilCooke Moderator, Onshape Employees Posts: 6,100 image
    Thanks for the image, saves me opening the doc  :) This is where your problem is:


    If you are trying to "add" these together, it will create non-manifold geometry (a solid cannot have coincident edges or vertices with zero volume).
    Senior Director, Technical Services, EMEA
  • gauthier_östervall
    gauthier_östervall Member Posts: 99 ✭✭
    NeilCooke said:
    Thanks for the image, saves me opening the doc  :) This is where your problem is:


    If you are trying to "add" these together, it will create non-manifold geometry (a solid cannot have coincident edges or vertices with zero volume).
    Thanks for the reply, you had me read about non-manifold. 
    The image shows the extrude that works, though. It stops working when I add the middle sketch face to the extrude (expecting a manifold volume). Sorry if I was unclear. 
  • gauthier_östervall
    gauthier_östervall Member Posts: 99 ✭✭
    owen_sparks said:
    How about extruding above the surface and then use using the surface to split the part, followed by discarding the top part created by the split?
    Owen.
    I like this! It's outside the box, although I expected an inside the box answer too. 
    In this very case it doesn't cut it entirely since the upper side of the surface doesn't expand to split the volume, but that might be enough for my real project. 

    I would expect the extrude to work as is, and go to the bottom of the surface. 
  • tim_hess427
    tim_hess427 Member Posts: 648 ✭✭✭✭
    edited December 2019
    The easiest method would probably be to do two separate extrudes and merge them together. Do one up to the top surface (area A), then do a second that goes up to the bottom surface (area B ) .


Categories