Investigations on the automatic precision polishing of curved surfaces using a five-axis machining centre

Polishing is usually indispensable process when better surface roughness is required for the parts such as injection mold. However, polishing process is often performed by manual operations. In this paper, an automatic polishing method for the metal parts with curved surfaces is proposed based on a machining centre. In order to realize the control of contact force, the relationship between the displacement of polishing disk and the force impacted on the polished part is first established. Then, within the contact zone between the polishing disk and the polished part, a pressure distribution model is derived for planar and curved surface polishing according to the specific process parameters. On this basis, the model of removal depth distribution along the vertical direction of feed is built for each polishing pass, and thus a suitable stepover size is further obtained so as to reduce the fluctuations of remove depth to most extent. Finally, an effective planning algorithm of cutter location data in polishing is proposed for a given CNC machine tools, and validation experiments are performed on planar and curved parts. The results show that the proposed automatic polishing scheme is able of achieving a mirror effect surface and keep a good global uniformity, at the same time it improves the polishing efficiency and realizes the integration with milling process.