Fabrication and milling performance of micro ball-end mills with different relief angles

Micro ball-end milling is an efficient and feasible method for the fabrication of microlens array molds which are widely applied in the aerospace, mechanical electronics, optics, and optoelectronics fields. The geometric structure of the micro ball-end mill plays an important role in micro dimple milling performance. The relief angle, as one of the major geometric parameters of the micro ball-end mill affects the sharpness of the cutting edge and determines friction between the tool and the workpiece. To investigate effective fabrication of a micro ball-end mill with different relief angles, this paper proposes a practical grinding method for the relief face validated by a grinding experiment, in which micro ball-end mills with relief angles of 10°, 20°, and 30° are fabricated. Furthermore, to analyze the influence of the relief angle on milling performance, micro dimple milling experiments on die steel material H13 with fabricated mills are carried out. The milling force, tool wear, and machining quality are measured and analyzed. The experimental results show that the micro ball-end mill with a 20° relief angle is more appropriate for micro dimple milling compared to the other two mills.