Hi Guys

I created a simple Box in 123D design.
I then imported the box and another STL file into Meshmixer to combine the two objects. When I Boolean Union the two objects to make one object to print, the Box comes out very bad.
The edges are not straight, they get flattened etc Looks like the edges have been cut off. Looks terrible. What could I be doing incorrect not get clean part.

Thanks
Vaughan

I'm not familiar with meshmixer. I have it on my PC but I've never invested the time to learn it.

The first question I'd have to ask, though, is what is the condition of the two input objects? Are they manifold? If they are not, that might be the cause of your problems.