I recently sent a model to a company for 3-D printing. The model looks like this:

The tech at the company said there was a problem with the file because "it was not a solid part. It was all surfaces."

What I actually did was create parts like these:

And then created the requisite mates between edges and surfaces to make the final model. As you can see in the final, many of the individual parts' surfaces overlap. Then I saved this assembly as a .sldprt file and made a .stl file out of the .sldprt file. I'm guessing that I need to somehow meld the surfaces between the parts to make a solid piece. Is there anyway to do this in SolidWorks to avoid problems like this?

(These are ultimately supposed to be channels in a box. The actual model would be a box or cube, and the snaking channels would be empty space. So the printer needs to put support material where the channels are, and modeling material everywhere else.)

Thanks!

Aaron