An investigation into tool dynamics adaptation for chatter stability enhancement in the turning of flexible workpieces

Abstract

It seems a universally accepted doctrine that chatter resistance of a machining system can be improved with increasing stiffness of its components. However, the viewpoint that the tool stiffness reduction would be beneficial to cutting stability of flexible components has been demonstrated by the compliant tool-workpiece chatter model. This paper presents a comprehensive investigation of the dynamic interaction between the tool and the workpiece during turning operations and its effect on the cutting stability. Following the formulation of the chatter model, the effect of the coupling dynamics of the cutting system on the limiting depth of cut (doc), a conservative but reliable indicator for evaluating the stability level of the machining process, is highlighted. It is shown that stability can be enhanced by judicious increase of the tool flexibility and/or the workpiece damping. Also, an inflexion point generally exists on the cutting position-dependent limiting doc stability curve, revealing that the stability appears to be unchanged once the stiffness of the tool or workpiece is increased to a certain degree. As a result, the analysis results lay the foundation of a tool dynamics adaptation (TDA) approach to machining chatter control. It suggests an adaptive adjustment of the tool dynamics to the machined workpiece to enhance stability. The proposed approach was validated through turning experiments, in which the tool shank was installed parallel to the length of the flexible workpiece. The experimental results have shown an effective extension of the chatter-free cutting margin when tuning dynamics of the compliant tool-workpiece system. Given the reality that there is no absolutely rigid workpiece or tool in industrial applications, the proposed chatter control strategy can be adopted as a generic approach for the turning or boring processes.

Experimental Study on Entropy Features in Machining Vibrations of A Thin-walled Tubular Workpiece

“…It is concluded that the dominant vibration frequency as well as the energy distribution shifted with the transition of machining status during machining of Tube A, leaving distinct chatter marks on the machined surface. The physical mechanism behind these phenomena could be that the moving contact point between the cutting tool and the workpiece in operation leads to time-varying and position-dependent dynamics of the machining system, which critically determines the chatter stability of machining processes [24][25][26].…”