Abstract: To avoid interference and to keep smooth tool movement in four-axis machining of free-form surface, a critical constraint based tool orientation optimization method is presented. According to the geometric relationship between the cutting tool and the constraint surface, critical tool orientation for every cutter contact point is determined by using point searching algorithm, then the tool orientation feasible region can be determined based on the critical tool orientation. When tool orientation feasible region for every cutter contact point is generated, an optimization model is built in order to get interference-free and smooth tool orientation. With the presented method, smooth and interference-free tool orientation along tool path in four-axis machining can be generated. To demonstrate the validation and advantages of this innovative approach, examples of four-axis milling bilks are rendered, and the results are compared to those obtained by existing method. This approach can improve machine tool movement and avoid tool interference, thus to improve machining quality of free-from surface.

Key words: 4-axis machining, Critical constraints, Freeform surface, Tool orientation optimization