Scheduling with tool changes to minimize total completion time under controllable machining conditions

Abstract

In the literature, scheduling models ignore the unavailability of the cutting tools. Tool management literature considers tool loading problem when tools change due to part mix. In practice, tools are changed more often due to tool wear. The studies on tool management issues consider machining conditions as constant values. In fact, it is possible to change the processing time and tool usage rate of a job by changing the machining conditions. However, the machining conditions, such as cutting speed and feed rate e ect the processing time and usage rate of the tool in opposite directions. Increasing the usage rates of jobs will lead to an increase in number of tool switches. Processing times and number of tool switches are two components of our ob jective function. This two-side e ect creates a tradeo between processing time and tool usage rate. Therefore machining conditions should be selected appropriately in order to minimize the total completion time. We proposed a set of single-pass dispatching rules and a local search algorithm to determine the machine conditions for each job and to schedule them on a single CNC machine simultaneously to minimize the total completion time.