Cutting-tool reliability assessment in variable machining conditions

It is a common industrial practice to use the same cutting tool for different operations and on different part types to minimize cutting-tool change-overs and the number of cutting-tools required, and to increase part-routing flexibility. This paper derives a recursive formula to calculate the cutting-tool reliability in variable conditions if the failure-time distribution of the cutting-tool can be represented by the accelerated failure time model (AFTM). The formulae for the cutting-tool reliability when the processing time for each operation is random are also derived. The unknown parameters in the reliability function can be estimated from cutting-tool life-data obtained under either fixed conditions or variable conditions by using the method of maximum likelihood. Two examples based on real cutting-tool life-data demonstrate the computational results.