A simulation-based analysis on the cooling effect and the tool temperature distribution in modulated turning (MT)

Abstract

Modulation assistance is widely used for breaking chips of highly ductile materials in turning. This process is also known as the “modulated turning” (MT) or the “modulation assisted machining (MAM)”. The process transforms continuous single point turning into an intermittent cutting process where the tool tip briefly disengages from the workpiece generating discrete short chips. Resembling the milling process mechanics, periodic tool disengagements in modulated turning introduces cyclic cool-down periods and thus it can potentially attenuate tool-tip temperatures. It has been hypothesized that this effect can greatly lower maximum and the average tool-tip temperatures improving wear resistance of the process. This paper presents a thermal model to predict the tool-tip temperature distribution in modulated turning. A generalized chip formation formulation is first developed to predict the uncut chip thickness variation, cutting forces and the tool engagement/disengagement phase durations. Thermomechanical behavior of tool-chip contact is then modeled to predict the rake face temperature distribution. Simulation studies are presented to analyze the temperature distribution and understand peak temperature (hot) spots on the rake face. It has shown that the phase angle parameter – the frequency ratio between workpiece rotation and tool modulation– of MT plays a key role in controlling the hot spots on the rake and can be used as a tool to influence the wear regime.