The prediction of dimensional errors and machining planning for sculptured surface productions using ball-end milling.

摘要

Ball-end milling process is used extensively to obtain the primary dimensions for sculptured surfaces. The final dimensions are then achieved by removing the excess material using grinding process. By improving the accuracy of the end milling process, primary dimensions can be designed to be close to the final dimensions so that the machining time and costs in the subsequent grinding process can be reduced. The variations of cutting forces and dimensional errors in sculptured surface productions are complicated due to the varying cut geometries. A means to improve the productivity by optimizing cutting conditions is also important.; In this research, a surface generation model is developed for the prediction of dimensional errors due to tool deflection in ball-end milling process. The components of this surface generation model are a chip geometry model, two choices of mechanistic models (a rigid force model and a flexible force model), a tool deflection model and the deflection sensitivity of the designed surface. The dimensional errors due to the thermal growth of the machining center along tool axis are also studied. The ability of this surface generation model in error predictions was verified experimentally.; A machining planner is also developed based on the developed surface generation model to improve the dimensional accuracy and the productivity of sculptured surface productions. Cutting-path/Adaptive-feedrate Strategy is used to reduce machining time by optimizing cutting directions and feedrates using the information of a Maximum Feedrate Map. Control-surface strategy with Direct Compensation Approach and Sensitivity Function Approach is used to compensate anticipated dimensional errors before actually machining the surface. This machining planner is then applied to the production of a turbine blade die. It is shown that machining time can be reduced by using a Multiple-feedrate/Multiple-cutting direction strategy. The dimensional accuracy of the machined die is improved to {dollar}pm{dollar} 10 {dollar}mu{dollar}m after error compensation.