Novel tool offset fly cutting straight-groove-type micro structure arrays

Abstract

Optical micro structure arrays, with regular geometrical morphology such as micro groove array, pyramid array, triangular pyramid array, etc., are widely used in optical components due to their unique optical properties. The machining of these micro structure arrays needs the cooperation of the multi linear axes of precision machine tools, while the lack of certain linear axis (e.g. Y-axis) limits the machining of such micro structure arrays. In this paper, a novel offset-fly-cutting-servo (OFCS) machining system was developed, which can fabricate the straight-groove-type micro structure arrays under the general configuration (X-, Z-, C-axis) of commercial ultra-precision machine tools. In this paper, a mathematical model for tool arc trajectory linearization compensation was established. Then the machining scheme was designed and cutting experiments of micro groove array, pyramid array and triangular pyramid array were performed. Finally, the machined and designed morphology of the micro structure arrays were compared and analyzed. Theoretical and experimental results show that the machined and designed morphology of the micro structure arrays match well, the root mean square (RMS) value of the form error of micro groove array, pyramid array and triangular pyramid array are below 1 μm. It confirmed that the proposed OFCS is an effective machining method for the straight-groove-type micro structure arrays. It provides a technical solution for machining straight-groove-type micro structure array in the absence of linear axis of ultra-precision machine tools, also provides theoretical reference for other machining of complex micro structure arrays.