Optimal Rastering Orientation in Freeform Extrusion Fabrication Processes

Many researchers have tried to optimize the build direction of additively manufactured parts to minimize the vertical staircase effect. However, the horizontal staircase effect should also be considered when fully dense parts are to be fabricated. In this paper, part inaccuracy due to the horizontal staircase effect is considered in order to determine the optimal rastering orientation in building the part. An algorithm is developed to estimate this inaccuracy and a technique is proposed to minimize it. The effect of rastering orientation on staircase errors is examined, and the particle swarm optimization method is used to determine the optimum rastering angle that leads to minimum errors for each layer. Several case studies are considered where the staircase errors are calculated with and without optimizing the rastering orientation. The results show that the errors can be reduced considerably when using the optimal rastering orientation. To verify the analytical results, parts are fabricated using a freeform extrusion fabrication process at various angles and the errors are compared