Union problem

 From: Sean (REGULATORJOHNSON) 27 Nov 2016  (1 of 7)
 Hello I am having no end of trouble getting these 2 parts to union They are both solids, but every time I try to merge them I get a joined SRF with no obvious flaws. When I try to expose naked edges nothing shows up. I have tried to accomplish this many different ways and always get the same result. What rules am I breaking? I appreciate any input! Attachments:

 From: BurrMan 27 Nov 2016  (2 of 7)
 8201.2 In reply to 8201.1 """"""""""""""""What rules am I breaking?""""""""""""""" Here's the one... Attachments:

 From: Sean (REGULATORJOHNSON) 27 Nov 2016  (3 of 7)
 8201.3 In reply to 8201.2 You seem to be correct, thanks for the tip. I am figuring out 3d modeling as I go, so please excuse any stupid questions. Why cant MOI make that shape? I could make it with a mill, 3d printer, or by gluing 2 pieces of material together.

 From: Michael Gibson 27 Nov 2016  (4 of 7)
 8201.4 In reply to 8201.3 Hi Sean, that's called a non-manifold juncture and yes you generally need to avoid that in many CAD programs. Solids in MoI are expecting to have an outer skin where each edge is joined between 2 surfaces. A juncture like that would break this rule, you'd have more than 2 surfaces trying to share a single edge. > I could make it with a mill, 3d printer, or by gluing 2 pieces of material together. Often times they won't be able to be 3d printed either. But none of this really makes any difference, non-manifold junctures just add a lot of complexity to CAD calculations. They can be ok to be present temporarily during some early stages of the boolean calculation, just as long as the final results are able to be sorted into volumes that do not have any self intersections. A non-manifold area of a single volume is basically a type of self intersection. - Michael