Investigations into peck drilling process for large aspect ratio microholes in aluminum 6061-T6.

Deep or large aspect ratio microholes are needed in products made of aluminum alloys that find applications in space, automotive, and other sectors. In the present work, microholes of 500 µm diameter are produced by mechanical microdrilling. By following peck drilling strategy, microholes having aspect ratio of 6 are drilled in 3-mm thick aluminum 6061-T6 plates. Microdrills being slender and having low rigidity, breakage of these drills is a common occurrence. Hence it is necessary to analyze thrust force as well as torque obtained in microdrilling. For reliable measurement, the thrust force from a dynamometer and torque from a torque sensor is acquired simultaneously using a novel arrangement. For comparison, another set of experiments is also performed to produce 0.5-mm diameter blind holes by direct drilling and the results are further discussed. The causes for increase in forces at some peck steps during microdrilling of holes are explained using the signals and images acquired during the process. By having a threshold on the drilling torque, it is possible to control the microdrilling process and minimize the microdrill breakages. [ABSTRACT FROM AUTHOR]