Microstructure of Cutting Edge Affecting Minimum Thickness of Cut in Micromachining

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At an extremely small thickness of cut, a transition takes place in chip removal process from stable to unstable. The effective thickness of cut, which is the undeformed thickness of the workmaterial effectively removed by cutting edge from the worksurface, at the transition can be defined as the minimum thickness of cut. The minimum thickness of cut determines the possible limitation of the cutting accuracy attainable. The purpose of the present work is to analyse the effects of microstructure of a diamond cutting edge to minimum thickness of cut. The results obtained in the work are shown as follows.For the analysis of micromachining phenomena, a special cutting apparatus is designed and built using an air spindle and a hydrostatic slide. It has features of high stiffness, high repeatability in motion and nanometer resolution in infeed mechanism.Cutting experiments are carried out on the cutting apparatus described above. The results show that the sharpness of cutting edge is the pri … More mary factor which affects the minimum thickness of cut and that the sharper the cutting edge, the smaller the minimum thickness of cut. The uniformity of microstructure over the effective length of cutting edge is also the important factor enabling the stable chip removal. Lack of uniformity in the edge configuration deteriorates the cutting performance in terms of minimum thickness of cut.Using a two-dimensional finite element method, the initial stage of elastic chip separation process in micromachining is analysed. When the cutting edge with a certain edge radius is indented, the workmaterial on the interface between the tool and the workmaterial tends to separate into two directions, rake face side and flank face side. The separation point on the tool egde changes depending on the thickness of cut and the interaction force between the tool and the workmaterial. By the analysis, the minimum thickness of cut is estimated to be about 0.7 of the radius of the cutting edge sharpness. That ratio tends to incease with the increase of the interaction force between the tool and the workmaterial. Less