Fabrication direction optimization to minimize post-machining in layered manufacturing

Layered manufacturing (LM) can fabricate any complex 3D physical model without geometric limitations by depositing 2D layers in a given direction. However, the surface of the LM processed part is excessively rough in comparison with that of general NC machined part due to the LM process itself. Hence to improve the surface quality, additional post-machining such as coating and grinding process is required. This post-machining, however, is also detrimental to the original geometry of the part and is time consuming. To minimize the required post-machining region (RPMR) in the LM, an intelligent methodology to determine the optimal fabrication direction is proposed in this paper. An expression of the distribution of surface roughness is presented and the relation between the RPMR and fabrication direction is investigated taking real LM environments into consideration. The objective is to minimize the RPMR for general LM technology. A genetic algorithm is applied to obtain reliable solution for a complex geometry CAD model. Validity and effectiveness of the proposed methodology are tested by various experiments and applications.