Determination of the optimal build direction for different rapid prototyping processes using multi-criterion decision making

Rapid prototyping (RP) is an emerging technology for creating physical prototypes from three-dimensional computer aided design models using the additive process with layers. In order to use the process efficiently, several important factors must be considered. The ability to select the optimal orientation of build-up is one of the critical factors since it affects the part quality, build time, and part cost. This study aims to determine the optimal build-up direction of a part for different RP systems. The revised average weighted surface roughness, which considers stair stepping effect, build time calculated by laser/knife/nozzle travel, and part cost calculated by build cost rate, labor cost rate, material cost, etc., are considered. Among the orientation candidates chosen from the convex hull of a model, the best orientation is selected using the simple additive weighting method, a widely used multi-criterion method for decision making. The best orientation is also identified for each criterion. The validity of the algorithm is demonstrated by several examples. The algorithm can help RP users select the best build-up direction of the part and create optimal process planning.