Tool selection in three-axis rough machining

An approach to tool selection and sequencing is presented for three-axis rough machining. The trade-off in the selection of tools is as follows: larger tools have reduced access while smaller tools are capable of reduced cutting speed. Furthermore, every tool change incurs a time penalty. The objective of this paper is to select a tool sequence that minimizes the total rough-machining time. In our approach, the removal volume is stratified into 2.5D machining slabs and, for each tool, the area accessible in each slab is computed incrementally, keeping in mind the cutting portion of the tool and the shape of the tool holder and spindle assembly. This reduces the three-axis problem to a series of two-axis problems with complex precedence constraints. Two models are presented to understand this new form of the problem. First, an integer linear programming formulation is discussed to show the complexity of the task. Second, a network flow formulation is presented, by which we show that it is possible to obtain efficiently an approximate solution of the problem. Examples are discussed to illustrate the algorithms discussed.