Burr height monitoring while drilling CFRP/titanium/aluminium stacks

Abstract

In the aerospace industry, deburring operations are often difficult to achieve and can be very costly. Hence, burrs generated during the machining should be studied. In this research, the drilling operations were performed and analysed for a stack composed of carbon fibre reinforced polymer (CFRP), titanium and aluminium alloys, using three cutting feeds and three cutting speeds for each material. A monitoring method is presented to predict the burr heights in the titanium and aluminium layers. The cutting force signals obtained during the drilling of the CFRP layer were analysed using the regularization fractal analysis, resulting in an estimation of the fractal dimension. This fractal analysis was optimized in order to monitor the clearance tool wear and the burr heights. The burr heights, measured at the outlet of the titanium and aluminium alloys, were observed in terms of the thrust force, the torque, the hole diameter and circularity, and the clearance tool wear. This fractal analysis technique can be implemented for an on-line control to predict the generated burr heights in the metallic layers while drilling the previous CFRP layer.