Model of force interaction for stability prediction in turning of thin-walled cylindrical workpiece

Abstract

Turning of the thin-walled cylindrical workpiece is technologically highly demanding process due to the high flexibility of the workpiece. In this paper, a mathematical treatment of integral-based model of the cutting force which takes into account feed, cutting speed, depth of cut and tool nose radius leading to a model of tool-workpiece interaction is presented. The force interaction together with the compliant workpiece dynamics leads to a machining stability formulation. The effect of the aforementioned parameters on characteristic exponents is calculated and validated by comparison with experimentally identified exponents. One of the outputs with immediate practical value is identification of the process damping, which is in the studied case shown to be significantly higher than structural damping of the workpiece itself. This means that without loss of reliability in stability prediction the experimental modal analysis of a given workpiece may be omitted and workpiece’s dynamics may be described only by mass and stiffness matrices which can be easily and reliably obtained by a finite element analysis.