Ultra-precision machine tools are capable of machining complex free-form surfaces with multi-axis simultaneous control. However, it is both complex and challenging to verify the accuracy of multi-axis simultaneous control. The real-time position capture system (RPCS) proposed by the authors was used to verify the accuracy of multi-axis simultaneous control trajectories for machining non-axisymmetric aspheric shapes and to compare the accuracy of machined workpieces. The method was used to compare a ball screw-driven four-axis ultra-precision machine tool with a linear motor-driven five-axis ultra-precision machine tool. The trajectory deviation of both machine tools and the form accuracy of the workpieces were evaluated by non-axisymmetric aspheric lens machining experiments. The shape error curve was strongly correlated with the trajectory deviation curve, indicating that the method is effective for predicting the workpiece shape error. Furthermore, differences in control performance between machine tools could be identified using this method.

This study was performed to clarify the performance of mist cutting fluid required for end milling of nickel-based superalloys (Inconel 625) additively manufactured by laser metal deposition (LMD). The cutting performances of dry, water-insoluble cutting fluid mist, water mist, and highly osmotic water mist were compared by side cutting experiments using square end mills. Under low-speed conditions (cutting speed of 40 m/min), with the water mist, the cutting edge was not chipped until a cutting distance of 1800 mm, and machined surface roughness was the lowest. This indicated that the cooling property is more important than the lubricity and permeability of the cutting fluid under low-speed conditions. Under high-speed conditions (cutting speed of 120 m/min), with the highly osmotic water mist, it was possible to cut a distance of 1800 mm with almost no tool damage. This indicated that high permeability is required to cut Inconel 625 additively manufactured by LMD under high-speed conditions.