When exporting a 3D model to a .stl file for 3D printing its important to make sure you model meets certain requirements. Most important is following the laws of physics. On the screen a model does not necessarily need to follow the laws of physics, but a 3D print must. I have found using the repair tools in the software netfabb allows you to fix many common model based issues you may encounter when trying to with 3D print. Thinks such as overlapping triangles, intersections, center of gravity issues, holes, etc can be fixed with the Semi-Automatic Repair tests in netfabb. The software has a Basic free version ….
Although netfabb can not solve design issues – like “chicken-like proportions” – where you have a large body supported by thin legs – I have found it can solve many issues that can come up with a less than perfect 3D model.