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Using reasonable cutting parameters of machining process is an effective and convenient means of improving the topography of the machined surfaces. In this study, the methods to find optimised cutting parameters can be obtained by studying the relationship between the cutting parameters and the micro-topography of frequency features in the machined KH2PO4 surfaces. Using the power spectral density and continuous wavelet transform methods, the 2D micro-topographies of frequencies corresponding to different cutting parameters are extracted from the machined KH2PO4 surfaces. The results for the extracted micro-topography are used to analyse the influence of cutting parameters on the spatial frequency feature which consists of the wavelength and amplitude. The middle-frequency feature reflects the variations of depth of cut and spindle speed, and the amplitude of it is directly proportional to depth of cut and spindle speed. The low-frequency feature reflects the variations of the feed rate and decreases to a smaller value when the feed rate increases. The high-frequency feature is mainly affected by the material properties and the vibrations that occur during processing. Comparing the micro-topography of frequencies under different cutting parameters, the depth of cut (3 μm), the spindle speed (400 r/min) and the feed rate (8 μm/r) are the optimised cutting parameters for the machine tools used in this article. In the process of reconstructing the arbitrary frequency topography, the continuous wavelet transform method can compensate for the deficiencies of the power spectral density method for extracting frequencies.

This article presents an extraction and reconstruction method for arbitrary two-dimensional and three-dimensional frequency features in precision machined surfaces. A combination of power spectrum density and continuous wavelet transform is used to analyze the potassium dihydrogen phosphate crystal surface topography. All frequencies involved in sampling area of measuring instrument are distinguished by power spectrum density method. Compared to discrete wavelet transform used to decompose frequency features, continuous wavelet transform method can extract and reconstruct two-dimensional profile and three-dimensional topography of arbitrary frequency features from original precision machined surfaces. Analysis results show that amplitude and distribution of different frequency features in two-dimensional profile or three-dimensional surface topography are fully restored by continuous wavelet transform. The effects of different factors in machining process on precision machined surface topography may be discovered. Furthermore, the extraction and reconstruction method is generally applicable for the analysis of all precision machined surfaces.

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