Abstract
Free form surfaces offer an excellent modeling capability of product design in automobile, aerospace, and air-conditioning industries. For example, one critical component in the industries, turbine blade, often contains such complex geometries. Its manufacturing process involves 5-axis CNC machining, in which the crucial task is tool path planning of the blade surface. Despite of previous studies concerning this problem, most of them independently adjusted individual tool positions for educing the machining error. Very few studies investigate optimization of the total deviation on the entire surface in an integrated fashion. To overcome this deficiency, this work aims at reducing the total machining error in 5-axis flank milling of ruled surfaces. Two novel methods based on dynamic programming techniques are proposed for generation of the optimized tool path. The machining problem is thus transformed into a mathematical programming task. The influences of important parameters: tool radius, the number of the discrete number on the boundary curves, the maximal span over the discrete points, the surface extension ratio, and the maximal tool contact length, are examined. This research discusses how the intrinsic properties of the surface affect the optimized tool path. In addition, three error evaluation criteria: approximating tool envelop, best matching of the curve tangents, and grid-height based volumetric error, with an increasing degree of simplification, are tested. The corresponding estimated errors are compared with the simulation results generated from commercial software to verify their practicality in the tool path optimization. A ruled-surface part is used as an example in 5-axis milling tests with the tool paths computed by different methods. The machining error is measured using a CMM for each finished part. The measure result indicates that the proposed method produces the best machining quality. It shows that this work provides effective methods for automatic generation of optimized tool path and improving the machining quality in 5-axis flank milling. The machining technology of complex geometries is thus enhanced.