A geometric algorithm for selecting optimal set of cutters for multi-part milling

For the manufacture of milled parts, it is well known that the size of the cutter significantly affects the machining time. However, for small-batch manufacturing, the time spent on loading tools into the tool magazine and establishing z-length compensation values is just as important. If we can select a set of milling tools that will produce good machining time on more than one type of parts, then several unnecessary machine-tool reconfiguration operations can be eliminated. This paper describes a geometric algorithm for finding an optimal set of cutters for machining a set of 2½D parts. In selecting milling cutters we consider both the tool loading time and the machining time and generate solutions that allow us to minimize the total machining time. Our problem formulation addresses the general problem of how to cover a target region to be milled with a cylindrical cutter without intersecting with the obstruction region; this definition allows us to handle both open and closed edges in the target region. Our algorithm improves upon previous work in the tool selection area in following ways: (1) in selecting cutters, it accounts for the tool loading time, and (2) it can simultaneously consider multiple different parts and select the optimal set of cutters to minimize the total manufacturing time.