NC-Milling of pressure casting dies

High costs and long machining times are characteristical features of die and mold manufacturing processes in general. At the same time, the tendency in decreasing product cycle time demands fast response and high flexibility in die production. Currently, manufacturing of pressure casting dies is mainly covered by conventional processes, such as electrical discharge machining EDM, copy milling or a combination of both. Because of extreme material properties and surface complexity of typical casting dies, these processes are always associated with long machining times and high production costs. In addition, undesired influences on the material properties, as well as geometrical inaccuracy, result in low surface quality and, thus, demands additional manual rework. In order to reduce machining time and costs, the application of NC-milling gains more and more significance in die and mold manufacturing. The availability of highly developed CAD/CAM sytems, together with high performance tooli ng and machinary, leads to maximum flexibility. At the same time, it offers the benefits of directly milling hardened steel with wear-resistant cutting tools (e.g. coated carbides, CBN), while maintaining a sufficient process reliability. However, utilizing optimum cutting parameters and applying specific milling strategies are essential issues, particularily for critical tool engagement conditions, which mainly occure in deep slots and small curvatures. Considering those geometrical features, the use of small non-rigid cutting tools is often necessary. Consequently, dynamic effects like tool vibrations and chatter have to be taken into account. The aim of this contribution is to discuss the potentials of NC-milling for casting die manufacturing, concerning machining time, surface quality and costs, in comparison to conventional machining processes. Results of tool wear investigations, determining optimum cutting conditions for different cutting materials and various milling strategie s are presented, as well as dynamic effects, influencing the milling process and the surface quality. The manufacture of a sample part for verification purposes finally produces relevant data to evaluate the efficiency of NC-milling.