4 Replies Latest reply on Jul 21, 2016 2:59 PM by Vincent Haley

    Surfacing Quandrey - Removal of Undercuts

    Scott Boerman

      I have a surfacing situation that I've not been able to overcome.  In a piece of tooling, there is a sculpted contour that has 3 small undercut areas.  The goal is to remove material such that the undercut surface become purely vertical.  The undercut starts in the middle of a surface, so initial efforts at creating surfaces/cuts bases on vertexes and lines in the model have not been successful.  I've thought about a 3D sketched line to sweep along a path, but am unable to create the proper path as I'm not aware of any method to find the tangency of the surfaces where the undercut begins.  Does anyone have any suggestions?  (SW2015 file attached, also have SW2016)

      Thanks in advance for the suggestions!



      Undercut Image 01.JPG

      Undercut Image 03.JPG

        • Re: Surfacing Quandrey - Removal of Undercuts
          Mike Price

          Hi Scott,


          I'm running 2014 so I'm unable to open your part, but a couple approaches would be:


          First, try to get rid of the radii.  Drafting exercises hate fillets.  If you can suppress one, fine.  If it's going to cause your model to blow up, try to delete faces and use the delete and patch.  In many cases, this will give you your corner back and drafting or surface construction will be much easier.


          Then either


          - Use draft tool and use a "parting line" draft.  In case you didn't know, your "direction of pull" is the plane for which you are doing the draft analysis and the parting lines would be the lower edges of the faces you want drafted.




          -Create a sweep ruled surface using an edge perpendicular to the pull plane as the direction.  This will be straight forward if you have been able to get rid of your fillets.  If not, you'll notice that you are undercut below the tangency of your fillets.  You will have to work with that and there are several ways to do that, but ultimately, it creating new surfaces to get rid of fillets and then re-filleting once you have a properly drafted wall.


          Please see if this helps and ask any additional questions if needed.

          • Re: Surfacing Quandrey - Removal of Undercuts
            Vincent Haley



            I took a look at your surfacing quandary. I used several techniques to create a patch in one of the regions that gets rid of the undercut. Have a look and see if this is what you are after.  I've attached a SW 2016 version of the model for you to study.





            • Re: Surfacing Quandrey - Removal of Undercuts
              Scott Boerman

              Thank you Mike and Vince for the replies and effort.  The geometry was offset from supplied step file, so there is not way to remove the radii cleanly unfortunately.

              Using tips from both of the replies, I found success using the parting line function - I had not thought of it earlier.  The parting line was very simple to make, I could select only the surfaces needed then a clean split line was put onto the faces.  From there, 2 of the 3 areas were remedied with a 3D sketch converting the split lines, then extruding a surface from the 3D sketches, and cut-with-surface.  The third area was a bit messier, but with the split lines in place, delete faces and making new surfaces achieved the final result needed.  I attached the file for others' reference also.

              Thank you!