Analysis of multi-axis milling in an anthropomorphic robot, using the design of experiments methodology

Currently, the concept of advanced machining technologies (AMT) includes different processes such as high-speed machining, multi-axis machining, etc. The common characteristic between these technologies is that they aim to improve the cutting process. Research done in the past has mainly concentrated on metal machining. In this present research, efforts are made to apply these techniques to the ceramic industry. This work forms part of the ongoing research at Staffordshire University into the application of CNC machining techniques in the production of models and moulds, with regards to the production of tableware and sanitaryware items. This paper focuses on the analysis of multi-axis milling using an anthropomorphic robot to produce near net shape plaster parts. The robotic system was run based on a specific set-up that allows multi-axes toolpaths and avoids “Gimbal Lock” singularity. The milling tests were carried out on plaster using conventional cutting tools (slot-mills). The design of experiments (DoE) was implemented using factorial techniques. The surface quality and geometric accuracy of the plaster parts were the response variables used to characterise the part quality and test the levels of acceptability of lead/lag angle, feed-rate and robot arm-extension. A mathematical equation based on the geometric accuracy was developed and used to plot flatness contours. Through these plots it is easy to define other possible combinations of feed-rate and robot arm-extension that can be used.