A Reliability Based Approach for Predicting Optimal Tool Replacement Time

Turning can be classified as both rough and finishing process. Any failure during this process will cause a huge loss in terms of raw materials cost. In machining operation, to avoid failures and related consequences, tools are often replaced well before the end of their useful life time. Only 50-80% of the expected tool life is typically used. This is especially the case of production systems where process robustness is critical. Unfortunately, such a strategy leads to increased tool costs. Even though the cost of the tools is often assumed to be only 2-4% of the manufacturing costs, there are studies suggesting that tool costs can be much higher. The main objective of this paper is to outline a procedure for estimating the optimal tool replacement time based on the tool performance calculated using reliability function. This paper includes the selection of a suitable tool life distribution, modeling of reliability functions of cutting tool based on the flank wear as the major failure criteria, Experimental study to validate the reliability function developed for cutting tool, Development of total time on test (TTT) transformation to give brief idea regarding the failure rate of cutting tool.