Performance-based predictive models and optimization methods for turning operations and applications: Part 1 - Tool wear/tool life in turning with coated grooved tools

Tool wear/tool life is an important aspect commonly considered in evaluating the performance of a machining process. The advent of new grooved tools with complex chip-groove geometry has required a better understanding of their effects on tool wear/tool life. This paper presents an overview of research at the University of Kentucky on extensions to the conventional tool wear and tool life methodologies when machining with grooved tool inserts resulting from the more complex wear features observed and the more subtle failure criteria applied. The influence of cutting conditions including the cutting speed, feed and depth of cut on the tool life was studied experimentally using tools with chip-groove geometries and different tool coatings. It was shown that the slope and intercept of the log-log plot of tool life versus feed, for example, change considerably for different chip-groove geometries or different tool coatings. An empirical tool-life equation to consider the effects of these parameters was proposed. The approach described required that 11 tool wear/tool life tests be conducted for every tool insert. In a comparison between predicted and experimental tests involving 200 production trials, this approach predicted tool life within 24% of the results encountered, while tool-life estimations using conventional approaches yielded results that gave an error of more than 300%. Furthermore, an 'equivalent toolface (ET)' model was developed to orrelate progressive tool wear to changes in chip formation with corresponding predictability of the dominant wear modes in turning with grooved cutting tools.