Progressive tool-wear mechanisms and their effects on chip-curl/chip-form in machining with grooved tools: An extended application of the equivalent toolface (ET) model

Chip-form/chip-breakability and tool-wear/tool-life are two important aspects 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 the curling behavior of the chip for effective curling and breaking of the chip. This paper presents a methodology for modeling chip-curl in machining with progressively worn grooved tools from measured cutting forces by using the equivalent toolface (ET) model. The ET is an imaginary flat toolface formed by effective inclination and rake angles to represent a grooved tool. This is achieved by iteratively changing the effective angles to match the flat-faced forces, calculated from a predictive cutting force model, with the measured grooved tool forces. The variation of the ET orientations resulting from the combinations of the effective angles shows a good correlation with the chip-curl ratio (ratio of up-curl to side-curl calculated from the twist angle), defined to indicate the curling pattern of chip. In this paper, this methodology is extended to correlate chip curling when machining with progressive tool-wear mechanisms in grooved tools. Experiments have been performed to measure the cutting forces at varying stages of progressive tool-wear, and chips are collected for a range of cutting conditions. The anticipated chip-curl/chip-forms and the associated dominant tool-wear patterns from the use of the predictive ET model are correlated well with the experimental observations.