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The fast tool servo (FTS) is one of the emerging ultra-precision machining technologies for the fabrication of high-quality optical microstructural surfaces. The diamond tool is fixed on the FTS, which is activated back and forth by a stacked type piezoelectric actuator. Optical microstructures with sub-micrometre form accuracy and nanometric surface finish can be fabricated without the need for any subsequent post processing. However, current understanding of the cutting mechanics and the factors affecting the surface generation in FTS machining is still far from complete. Although there has been some research work conducted to fill the research gaps with respect to FTS machining, most of the previous studies have been focused on the design of FTS for better performance and modelling characteristic of FTS actuators. The study of the process factors affecting surface generation in FTS machining has received little attention. As a result, this paper aims to analyse the effects of process parameters on surface generation in FTS machining. The factors being studied include spindle speed, feed rate, and depth of cut. A series of cutting experiments was carried out under various cutting conditions and the surface quality of the workpiece in terms of the form error and form defects were studied. Based on the results of the investigation, some recommendations for optimizing surface quality in the FTS machining process are discussed.

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This paper presents a study of effect of cutting conditions on surface quality in FTS machining of optical microstructures such as micro-lens array. A power spectrum analysis is proposed to characterize the surface quality in FTS machining. It is found that there is a strong relationship between the surface roughness and the power spectrum of the surface profile. This provides an important means for the characterization of surface quality in FTS machining of optical microstructures.

Microlens arrays are widely used as critical components in a large number of photonics and telecommunication products. The increasing demand for high-tech products provides an expanding room for the development of the micro-fabrication technology. This study presents a tool compensation for correcting the form error of fabricated microlenses in ultra-precision machining with fast-tool-servo (FTS) system. After presentation of optimal cutting conditions deduced on the basis of cutting experiments of microlens arrays, a tool radius compensation method will be proposed and evaluated in this paper. This methodology makes use of form measurement data from a Form Talysurf system to modify the C program employed in the software of ultra-precision machining FTS system – SOP. The form error was successfully reduced after implementation of tool compensation.