How to design your own support structures for FDM printing
Like any manufacturing process, FDM comes with its own unique strengths and weaknesses. Specifically, certain geometric features require support structures to print successfully. By manually modeling in support structures in specific regions, designers can exert much more control over the support process than is typically afforded by algorithmic support techniques available in most consumer level slicers.
See below for a method to manually model support structures.
Answered with a tutorial: https://grabcad.com/tutorials/how-to-design-your-own-support-structures-for-fdm-printing