The Research On Automatic Drilling Technology Of Oval Hole

In aircraft digital assembly field, it is the trend that the robot flexible drilling system with higher efficiency and flexibility will replace the manual work that is relatively slow and complicated. The research and exploration on multifunctional end-effector and related new technology is the key point to realize totally automation in this field. Today, some military aircraft are willing to use integrated wing to enhance its functional ability. But this structure needs to be assembled on one side using a kind of plate nut with oval head and the oval hole should be made on the framework of the wing. Traditional manual tool is very simple, the processing quality depends on the skill of the worker and has defects such as asymmetric and different in shape which decreases the reliability of the assembling. Using 6-axises industry robot with special end-effector to replace the manual work is regarded as the best solution now. But the difficult problems related to the technology are ready to be solved.This paper points out that the development and exploration on the oval hole end-effector and the manufacturing technology of oval hole is an urgent thing through deep analysis about the trend of the development on end-effectors and aviation fastens all over the world. On the basis of deeply analyze on the structure characters and the processing principles about oval hole, the idea that the relative position between the countersink and the swing center is the key factor which decides the hole’s shape is proposed, and then, the formula of the swing center is deduced. Combined with the forming principle of oval hole, the basic structure, functional character and working mechanism of the oval hole end-effector is introduced in detail. Through analyzing the influences of the machining precision which caused by the projection component of the relative angle deviation of the oval hole end effector’s component in the local coordinate system of pressure foot, it points out that the components of the end-effector should reach some relative angular deviation requirements to control the system error. LeicaAT901 laser tracker is used to calibrate the end-effector. After the calibration, the data acquired is used to figure out the theory shape parameters of the oval hole. Some shape experiments are conducted using theory computing results. After those experiments, some common deviation forms are summarized and the related compensation methods are proposed. Use NAS6 oval hole as an example to do experiments on the aluminum, which demonstrates that in order to eliminate the surface chatter of the oval hole during the processing progress, considering the specific characters of the material, higher spindle speed, lower feed speed and higher swing angle speed should be adopted. This method could decrease the peak force of the processing system effectively during the drilling of oval hole, degrade the system vibration, improve the surface quality of oval hole. Using adjusted shape parameters and optimized processing parameters to drill, the deviation of the diameter positions of oval hole could be within 0.05mm, the deviation between the end face of oval nut and the surface of workpiece could be within 0.02mm, the roughness of the oval hole could reach Ra1.6, the processing result satisfys the requirements of integrated wing assembly.