Research On Automatic Precision Drilling Process Of Aeronautic Material

In the aircraft manufacturing process, the quality of assembly and connection will influence thelife of the aircraft directly. At present, the main way of connection during aircraft assembly is stillmechanical connection. While most of the aircraft fatigue failure occurred in the connection hole, thelife of aircraft can be improved by improving the connection hole`s quality. Compared to thetraditional manual drilling, automatic drilling system can significantly improve the accuracy andquality of the hole, so it`s more and more widely used in aeronautic manufacturing. During automaticdrilling of aeronautic material, the requirement of high efficiency, stability and continuity should bemeet. Besides, the problem of drilling aeronautic material stacks in one step should also be solved toensure accuracy and quality of the hole. In this paper, some core process problems that exist in theautomatic precision drilling of aeronautic material were studied as follows:（1） The key technical problems in automatic drilling of aeronautic materials wascomprehensively analyzed. The chip control method, the tool change strategy, the method to inhibitdrilling defects and adaptive drilling method were proposed.（2）The process assisted by pressure foot to inhibit interfacial burr was studied. The concept offlow force was proposed, and it was used to characterize the vertical force that acts on the metal sheet,which is formed by the plastic flow that caused by cutting edge extrusion. The flow force was verifiedby the finite element simulation and experiments. The superposition principle of stacks`clearanceformation was put forward. It was pointed out that the formation of interfacial burr is the result of themutual action of thrust force, compact force and flow force. The general mechanism of interfacial burrformation was got in the circumstances of unilateral compact drilling and bilateral compact drilling.The approximate value of flow was predicted to analysis the effect of pressure foot size and sheetthickness effect on the interfacial burr height.（3）The drilling process of CFRP/aluminum alloy stacks were studied through a large numberof experiments. The regulation of hole`s accuracy, roughness, aluminum alloy exit burr height andcutting force influenced by the process parameters and cutting tool was obtained. The advice to selectprocess parameters, cutting tool and the advice to improve the drill diameter size was put forward.The wear regulation of drilling CFRP/aluminum alloy stacks was studied, and a targeted tool changestrategy was put forward. The special drilling character of CFRP/aluminum alloy stacks when usingthrees awl drill was analyzed, and the drill geometric parameters optimization was conducted. Verifiedby experiments, the threes awl drill after optimization had more superior cutting performance. In this paper, some issues in automatic precision drilling of aeronautic material were analyzed.The two core problem was studied: the interfacial burr between stacks and the drilling of two or morematerials stacks at the same time. The theoretical and experimental results had high reference valuefor the engineering applications of automatic drilling in aviation manufacturing.