OPTIMUM CUTTING SPEED AND TOOL REPLACEMENT POLICY WITH VARIABLE TOOL L

A theoretical analysis is made to determine what is the optimum cutting speed, considering variable tool life at any one speed, for each of three common tool replacement policies. It is found for the models studied that (1) for replacement upon failure, the conventional ecnomical tool life (CETL) gives the lowest probable cost, (2) for a scheduled tool replacement with no penalty for unscheduled replacement, CETL is best. The same is true for a decreasing failure rate. For an increasing failure rate, the optimum cut speed is some multiple of the conventional, (3) for block replacement with penalty, CETL does not appear to be a valid criterion in many cases.