Toward the Automation of the Plunge Milling Strategy for Roughing Sculptured Surfaces from Stl Models

Part with sculptured surfaces is obtained in three stages: roughing, semi-finishing and finishing. The roughing operation consists in using flat end tools or fillet end tools on sequential horizontal cutting planes to remove the most material from the raw part as rapidly as possible using “Parallel Planes” or “Offset Contours” machining strategy. When roughing deep parts, radial cutting forces, vibrations and tool bending are important. To avoid these disadvantages, the “Plunge Milling” strategy is developed. The complex geometry of sculptured surfaces makes the tool path generation without interferences and collisions a very difficult task. In this paper, an automated methodology is proposed for roughing any part with sculptured surfaces from its STL model using “Plunge Milling” strategy on 3-axis CNC milling machines. After the specification of the principal parameters (stock allowance, radial cutting depth, radial step, tool diameter and sweeping mode), the methodology determines: 1) intersection contours, 2) machined segments, 3) plunging positions without interferences, 4) plunge depth for each valid plunging position, 5) minimum tool length avoiding collision and finally tool path in « One-Way » or « Zig-Zag » mode.