Optimal tool replacement and resetting strategies

Abstract

In all machining processes tool wear occurs. As a result of this there will be a change in the dimensions or machined parts produced. To minimize the cost of producing parts out of specification and to minimize the overall tooling cost, the optimal tool resetting and replacement intervals need to be determined. In this thesis, optimal expected cost models are developed for tool replacement and resetting by using renewal functions. The tool life as well as tool reset times are modelled as inverted normal distributions. A computer program is developed for obtaining the generalised solutions for the models. As an application of the models, a set of experiments were conducted on a Mazak CNC machine to monitor the dimensional changes of the machined part and to monitor tool wear as a function of time. The data obtained from the experiments was used to validate the tool replacement and resetting models.