3D printing is an advance technology that have changed many industries and the way of producing the products, and in the foreseeable future 3D printing will be a major contributor in most of advance industries such as medical and aerospace industries. In the future, 3D printing will play a significant role in most industries and will advance many fields. However, 3D printing technologies are considered by many designers as good and valid technology in which most of geometries can be produced without considering the limitation of the technology which makes it a problem in the final stages of the process. FDM is one of the most popular 3D printing technologies, however the designers are unaware of the process limitations and design rules the process. This research aims to address the absence of awareness in such designs, by developing a set of design rules so the design can be more reliable, predictable and gives the required results when making parts.