Abstract
Tool replacement models for automatic machining centers are developed. If a tool fails during the cut, the workpiece become defective and the down time for system adjustment and the cutting of another workpiece occurs. Two models introducing a tool life distribution are formulated from a statistical point of view using the minimum-production time and cost criteria. Numerical results show that the economical tool replacement for the tool with large life-variance requires earlier replacement than that of a tool with small variance.
