Cutting edge preparation of micro end mills by PVD-etching technology

Micromilling tools face significant challenges in achieving cutting edge preparation by mechanical processes due to their small size. To address these limitations, a new approach for cutting edge preparation of micro end mills by physical vapor deposition (PVD) etching technology is presented. By adapting the etching strategy, which is conventionally used as pre-treatment process for PVD technology to clean and condition the surface of cemented carbide substrate, cutting edges of micromilling tools were successfully modified. The high-energy process variation by Advanced Arc-Enhanced Glow Discharge (AEGD) offers the possibility of achieving high material removal rates on the tool surfaces and thereby altering the cutting edge geometry. Fundamental investigations on material removal as well as on the effects on surface topography, sub-surface properties, and coating adhesion of a subsequently applied PVD coating are performed. To influence the topography and the cutting edge geometry, the preparation time t p and bias voltage U B were selected. Subsequently, the machining performance of the modified tools is evaluated in a micromilling process of the hardened powder-metallurgical high-speed steel AISI M3:2 with a hardness of 62 ± 1 HRC. For this purpose, micro end mills of cemented carbide with a diameter of D = 1 mm were conditioned, achieving asymmetric geometric properties of cutting edges with varying average cutting edges rounding of S = 5.8 … 14.8 µm and a form-factor of K = 2.0 … 2.7. Based on the application tests a positive influence on the process forces was found. Thus, an efficient approach to cutting edge preparation can be identified by specifically designing ion etching in the PVD coating process.