Evaluation of critical parameters in micro machining of hardened tool steel

Abstract

Micro mechanical milling plays a significant role in fabrication of miniature features in a variety of materials with capability for producing three dimensional (3D) freeform surfaces. A major challenge for micro machining of hardened material is a high tool wear rate and unpredictable tool life. In addition, surface roughness and burr formation are factors to be closely controlled. In this paper, the statistical analysis of critical parameters for micro milling of hardened tool steel is presented. The parameters included spindle speed, depth of cut, ratio of undeformed chip thickness to cutting edge radius and lubrication/environment conditions. The significance of these parameters on surface finish, burr formation and tool wear are reported. The study shows that machining environment is the most significant factor in controlling surface finish and tool wear. While, selection of appropriate spindle speed and the ratio of undeformed chip thickness to cutting edge radius is more critical in limiting burr size. The work reported in this paper is important, because industry needs to know key process variables (KPVs) that are critical in the control of micro machining performance. Additionally, the methodology enabled identification of optimum cutting values for these cutting parameters within the identified process window.