%0 Journal Article
%T Experimental investigation of dynamic instability of the turning process
%A J. Kopa£¿
%A A. Stoi£¿
%A M. Luci£¿
%J Archives of Computational Materials Science and Surface Engineering
%D 2009
%I 
%X Purpose: Purpose of this paper is consideration of dynamic instability in turning process. There are several sources which lead to instability in turning process (cyclic variation of depth of cutting, inadequate rigidity of machine tool, high passive force component Fp, small tool nose radius and small tool/workpiece contact length, non-uniform stress distribution over contact length). In hard turning, when depth of cutting and feed have low values, lead edge angle and passive force Fp are strongly depend on real time value of depth of cutting.Design/methodology/approach: Experimental tests and numerical modeling of tool /workpiece contact line have been done to evaluate the rate of cutting instability while using and comparing different process monitoring sensors, and acquisition techniques. This data can be used for prediction and compensation of machining errors.Findings: It was found that high chip thickness alteration occurs because of cutting depth vary for a value of some 60 %. Even higher alteration of Fp force signal is recorded when machine tool has inadequate stiffness.Research limitations/implications: Results and findings presented in this paper are qualitative and might be slightly different in other cutting condition (e.g. if wiper inserts are used). Also there are no experiences with coated workpieces or with workpiece material with low deformation energy.Practical implications: Assuming that a hard turning is a semi finishing or finishing process, surface finish is of big relevance. Surface roughness is a consequence of both cutting instability and of tool/workpiece loading condition. Results of test indicates an optimal cutting depth for final pass when minimum surface roughness can be achieved what can be valuable for cutting regime determination. Furthermore, more effective use of the machine tool performances might be achieved.Originality/value: Originality of the paper is in analysis of sources of turning instability (variable depth of cutting combined with lead edge angle and tool nose radius) which lead primary to condition where Fp sensing data does not fit to the normal distribution and secondary to cyclic push-offs of the edge.
%K Machining
%K Mechanical properties
%K Dynamic properties
%K Depth of cutting
%U http://www.archicmsse.org/vol09_2/0923.pdf