A robotic boring system for intersection holes in aircraft assembly

Purpose The purpose of this paper is to introduce a robotic boring system for intersection holes in aircraft assembly. The system is designed to improve the boring quality and position accuracy of the intersection holes. Design/methodology/approach To improve the boring quality of intersection holes, a robot posture optimization model is established. The target of the model is to maximize the robot stiffness and the variate is location of the robot on the guideway. The model is solved by the iterative IKP algorithm based on the Jacobian matrix. To improve the position accuracy of intersection holes, a robot positioning accuracy compensation method is introduced. In the method, a laser tracker is used to measure the actual position and orientation of the boring bar. Combined with the desired position and orientation, the error can be obtained and compensated. Findings In practical case of the robotic boring system, the robot stiffness is effectively improved and the surface roughness of intersection holes achieves a grade of Ra0.8. Besides, the robot end achieves a position accuracy of 0.05 mm and an orientation accuracy of 0.05°. Practical implications The robotic boring system has been applied successfully in one of the aircraft assembly projects in northwest China. Originality/value The robotic boring system can be applied for machining intersection holes in an aircraft assembly. With the robot posture optimization method and accuracy compensation method, the boring quality and position accuracy of the intersection holes can be guaranteed.

Finite element simulation and experimental analysis of robotic boring based on an approach of equivalent stiffness

Robotic boring is an effective way to implement finish machining of intersection holes. However, to a certain extent, its application is limited due to the low rigidity of the robot, whose stiffness brings on high vibration levels. In this study, a new approach based on an equivalent stiffness is proposed to gain a fundamental understanding for the cutting mechanism and vibration performance of a robotic boring system. In the approach, the robotic boring system in one direction is regarded as a mass–spring–damping unit according to the structure characteristics of the robot. Thus, the whole robotic boring system is equivalent to a mass–spring–damping group in three-dimensional space. The stiffness and natural frequency of the robot system were measured by stiffness identification and a modal test on an ABB IRB 6600-175/2.55 robot. An equivalent three-dimensional finite element model based on this approach was established to simulate the robotic boring process, and a verification experiment was conducted to determine the accuracy of the finite element simulation. The results show that the simulated cutting force components and the amplitude in the feed direction are in good agreement with the experiment under different cutting conditions, and this proposed approach is feasible.