So I recently attempted to 3D-print a part I created in solidworks (printer: Airwolf 3D). The part printed, but it appears that everything that I *thought* would be solid was printed as a hollow shell with support material inside, which is not acceptable for my application. So the individual rings with 3mm height around the main body of my part (solidworks .part file attached) were printed as hollow rings, and the main cylindrical body itself was printed as two thin shells with support material in the middle. I only used "boss/extrude" followed by an "extruded cut" to make each of my components individually, followed by assembling them, mating them, creating a part out of the assembly, and intersecting the bodies. At no point did I indicate I wanted the thing to be hollow (yes, I understand the thing has a giant hole in the middle, but I mean between each of the surfaces the part was printed hollow). How do I go about fixing this? What caused it?

This is an image of my finished part in SolidWorks: