Innovative sensor concept for chip transport monitoring of gun drilling processes

In the past few years, process monitoring of drilling processes using force and vibration signals has successfully been established. However, only few investigations were performed in the monitoring of chip breakage and chip transportation, while in gun drilling these properties are more relevant to ensure process robustness and performance than force and vibration. This paper presents a new monitoring approach of chip frequency and transportation for gun drilling processes using infrared light reflection next to the drilling bush. Gun drilling is a high performance cutting process used for small diameter and large aspect ratio drilling operations in the field of automotive, aeronautic, power generation and medical devices. The usage of new harder materials for future products increases the challenge of proper chip transportation and raises the need of chip monitoring being able to operate with economically acceptable parameters. The approach of optical chip detection highlights the opportunity of detecting chips smaller than 1 mm and velocities in axial direction of more than 16 m/s clearly and suggests new characteristic values to be used for process validation. For implementing the measurement principle a new sensor is designed. In addition, the opportunities of future data analysis and detection of characteristic values are explained. (C) 2014 Published by Elsevier B.V.