Machining straight-groove-type microstructure arrays with the three-axis ultra-precision lathe assisted by a rotating stage based on the double closed-loop controller

Functional microstructure surfaces with sub-micrometric form accuracy and nanometric surface roughness are gaining wider applications due to their excellent innate properties. However, for the three-axis machine tool equipped with the X, Z, and C-axes, it is difficult to machine complex micro structures due to the interference between the tool flank and the workpiece, caused by the relative rotation of the cutting tool. In this work, an additional high-precision air-bearing rotating stage is introduced to adjust the tool posture relative to the workpiece in real time. The integrated machining system and the tool path generation considering the tool setting error in the Y direction are introduced first. Then, to achieve the high-precision tracking performance, a double closed-loop controller is designed to control the stage. The observer-based sliding mode control method is used in the speed-loop first to suppress the influence of disturbances, while the proportional-integral-derivative control method is used in the position-loop to achieve high-precision tracking. The effectiveness of the proposed control scheme is verified by trajectory tracking experiments. Finally, the experiments of cutting various straight-groove-type micro structure arrays are performed on a three-axis ultra -precision lathe equipped with the air-bearing rotating stage, and the machined workpieces are inspected with a white light interferometer. The experimental results show that the proposed method can avoid the tool-workpiece interference and improve the machining quality effectively.

Automated summary

This paper introduces a method of machining complex microstructures on a three-axis machine tool by using a high-precision air-bearing rotating stage. A double closed-loop controller is used to control the stage and achieve high-precision tracking performance. Experimental results show that this method can effectively avoid interference between the tool and workpiece and improve machining quality.