Forces vibration assistance for TA6V/CFRP drilling 2019-01-1874
For aircraft structures, mechanical assembly using fasteners remains the most common technology. The setting of the numerous fasteners requires a large number of drilling operations. In the case of CFRP/TA6V stacks, the drilling still remains a technological challenge. Indeed the high-quality requirements by the aeronautic standards are limited by the fast damaging drilling tool phenomena. For TA6V, the forced assisted drilling provides a breakthrough technology. An axial forced oscillating displacement on the feed direction of the tool allows the creation of segmented chips. Those small chips are then easily evacuated from the cutting area using a vacuum device. This allows the improvement of the hole’s roughness and mastering the burr creation at the exit of the hole. The lubrication process is also enhanced during the exit sequence of the tool. For the CFRP/TA6V configuration, the segmented geometry of the chip avoids the roughness degradation on the composite part of the stack. This parameter can modify the cyclic bearing performance of the assembly. In this paper, the different forced drilling industrial solutions are analyzed. More specifically, the mechanical solution today applied to the automotive drilling unit is investigated. This forced drilling process needs the setting of two extra parameters: the amplitude and the frequency of the forced oscillation. Those parameters are related to the feed speed and the cutting tool geometry. Oversizing the amplitude leads to the increase of axial forces that can damage both the cutting tool and the drilled material (delamination of the composite). Therefore, it is mandatory to optimize those parameters considering the drilling configuration. In this study, a new methodology based on drilling test with cutting force measurement is also presented for the optimization of the parameters of the vibration process. To demonstrate the efficiency of the proposed methodology, the quality requirements on the drilled hole are then validated with respect to the aeronautical criteria.