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Booleans on parts with tangent surfaces

tony_soares459tony_soares459 Member Posts: 117 ✭✭
edited February 18 in Using Onshape
In the real world, I expect that if I lay one part on top of another so that their surfaces are tangent, then I can glue them or weld them together so that they are joined.
But this seems a difficult thing in Onshape. Much of the time, if surfaces or edges are tangent, then the Boolean fails. It seems silly to add 1/100th of an inch to artificially overlap the tangent surfaces just to get the Boolean to work.
Does anyone know why tangents are such a problem with Booleans? I avoid them where I can, but sometimes the parts to join just have to be tangent---like a panel to be welded on a beam or strut...


  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 3,186
    Simple explanation - if the parts touch at an infinitely small line or vertex, then there is no volume, so it is not a valid solid (I don't think glue would stick either). To make parts that touch behave as one part, please use Composite Parts.
  • Jake_RosenfeldJake_Rosenfeld Moderator, Onshape Employees, Developers Posts: 1,570

    Could you give an example?  If it is an edge-to-edge surface it should work.  But if they are solid parts as Neil mentions, they do need some overlap.
    Jake Rosenfeld - Modeling Team
  • tony_soares459tony_soares459 Member Posts: 117 ✭✭
    Ah! I'll try composite parts. Thanks!
  • tony_soares459tony_soares459 Member Posts: 117 ✭✭
    edited February 21
    An example of the boolean struggles I have all the time.

    The mating surfaces are coincident. I made sure of it by replacing the mating surface on one part with the mating surface on the other.
    In the real world, you can glue these parts together. In the pure geometry world, I'm sure you can do the same. A bit confused as to why booleans like this would fail.
    I can get the boolean to work by replacing the remaining surfaces, but this creates overlap with the parts that are supposed to go right behind. Plus, it changes my geometries in ways that I had not intended, which means I cede control over my model for the sake of a rote boolean operation...
    Compositing the parts together isn't ideal, since the two geometries form one continuous solid, not two solids rigidly bonded together...
  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 3,186
    Can you share the URL?
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