Improving the surface finish in high speed milling of stamping dies

The high speed milling (HSM) of GG25 grey iron castings and GGG70L ductile iron casting stamping dies has proved its feasibility when it comes to finishing operations, giving an important cost reduction when compared with traditional manual polishing associated with conventional milling. However, a number of problems still remain unresolved, improvements in these subjects will undoubtedly lead to an optimum machining situation. In this paper, a systematic description of the main industrial problems is given, as a major step towards a stable and optimum industrial application of this technique. Thus, an important part of the study is devoted to the optimisation of tools to be used, from the point of view of their geometry, base material and coatings. Testing has been carried out using coated carbide tools and PCBN (polycrystalline cubic boron nitride) tools. The importance of the use of optimum machining strategies for roughing and finishing operations of stamping dies is then analysed. Finally, the problem of tool deflection when machining deep cavities is studied.