Effect of different milling strategies on the quality of specular surfaces in tool steels

ABSTRACT

Given the difficulty in machining of hardened steels and the complex geometries commonly observed in injection molds, besides the necessary surface quality to produce plastic parts without defects, an adequate milling strategy must be chosen, which consists in defining not only the cutting parameters and the tool, but also its trajectory. Thus, the present work focuses on investigating the influence of two different cutting strategies in milling process on the surface quality of a convex (constant curvature) surface on two types of material. The quality was evaluated through distinct roughness parameters, which were correlated to the perceived gloss and analyzed in combination with the characteristics of each material, such as hardness and microstructure. From the results obtained after the finishing operation, it was possible to verify the positive influence of the parallel tool path, which led to the lowest values of average Sa and maximum Sz roughness in both steels, VH13IM and VTMPlus, in comparison to the zig-zag tool path. The combination of low roughness values with a homogeneous topographic profile of the surface led to a higher gloss level and mirror effect.

Keywords
Milling; Free-form surface; Molds and dies; Gloss