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Can't thicken a face

wei_xunwei_xun Member Posts: 9
I am unsure why I am unable to thicken the side faces of the mouse. It highlights the point in the back. I think it may have to do with the sharp corner.

Does anyone have any ideas why this is happening and what I should do differently?

link to file. https://cad.onshape.com/documents/1392ec3fbe4e01fa3557168e/w/3f2b3fb3761f8d05c197a118/e/9c54e6778c2df5de24db2065


  • john_mcclaryjohn_mcclary Member, Developers Posts: 3,877 PRO
    edited May 2020
    You are correct. that point is too sharp for some reason.

    If you add a small fillet to the front and rear edges then it thickens

  • Evan_ReeseEvan_Reese Member Posts: 2,055 PRO
    edited May 2020
    This has to do with what's called a degenerate point. Under the hood, every surface is 4-sided. For example, if you make a pentagon, it's really a 4-sided surface with some of it trimmed away to make a pentagon. The loft tool doesn't make trimmed surfaces so every loft has 4 sides. The way you created your surface (with profile curves touching at the ends) means that 2 of your 4 sides are actually points. When Onshape (or any NURBS based software) tries to figure out which way is normal to that surface, the calculations get wonkier and wonkier the closer you get to that infinitely small edge. the Thicken operation needs to know which way is normal to the surface to work correctly and not intersect with itself which is tricky to do at a degenerate point. All CAD has precision limits and these little imprecisions become amplified at these points. The fillet gets rid of that point so it works. At least that's how I understand it.

    Tip: typically avoid degenerate points where you can, and if you have them, put them in relatively flat areas, like this

    Evan Reese / Principal and Industrial Designer with Ovyl
    Website: ovyl.io
  • wei_xunwei_xun Member Posts: 9
    Thank you both for explaining. That makes a lot of sense! Really appreciate the help!
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