Improving surface quality of selective laser sintered rapid prototype parts using robotic finishing

Because of `stair-step' and `shrinkage' effects, most rapid prototyping (RP) parts have need of surface finishing in post-processing to obtain good surface quality. Instead of manual operations or homogeneous polishing techniques, a robot, with its high flexibility and sophistication, can effectively finish the surfaces of selective laser sintering (SLS) parts. After the sintering process, an SLS part that requires finishing is placed on a fixture with the help of a special base fitting. By calibrating the base fitting, the position and orientation of the part relative to the robotic system are determined. The robot holds a finishing tool, which can be changed according to different materials and different surfaces, as its end-effector. Once the calibration data, finishing tool, surfaces to be finished and finishing parameters are determined, the robotic finishing path can be automatically programmed from the computer aided design/computer aided modelling (CAD/CAM) model. The robot then moves a high-speed finishing tool over the desired surfaces according to the finishing path. Some experiments have been carried out on different SLS parts using different materials. It is shown that surface quality, which includes surface roughness, dimensional accuracy as well as geometrical accuracy, can be improved using robotic finishing.