Clamping Force Research On Robot Drilling

It is an important part for aircraft digital assembly in aircraft manufacturing.The quality of hole plays an important role in assembly accuracy and quality.With the improvement of performance indicators,such as aircraft life and aerodynamic efficiency,accuracy and efficiency of traditional hand-made drilling could not meet the requirements of aircraft assembly.Robot drilling technology is gradually replacing the hand-made drilling technology and becoming the main way of aircraft drilling,due to high precision and high efficiency.The stiffness of robotic end-effector is weak,prone to deformation and flutter.The presser foot is integrated on end-effector to suppress vibration.This paper establishes the stiffness model.Analyze the pneumatic relations about the presser foot,treat the workpiece as a rigid body,and simplify the robot into a mass-spring-damping model.The kinematic relationship between robot displacement and gas pressure is established.The transfer function and dynamic stiffness expression of robot drilling system are deduced.The natural frequency and damping ratio of the robot system are measured by the hammering method,and the transfer function of the system is calculated to simulate the dynamic response curves under different clamping forces.Analysis shows that the clamping force can effectively increase the dynamic stiffness of the robot drilling system,and enhance the rigidity and damping performance of the system.In order to suppress the growth of interlayer burrs,clamping force is applied during robot drilling process to suppress the interlayer gap.Analyze the principle of interlayer burrs,and establish the relationship between interlayer burrs and interlayer gap.The workpiece is reduced to a beam model.Considering the thickness and the clamping force factor,the response surface experiment is carried out.The interlayer gap is obtained by finite element simulation.The clamping force prediction method is put forward based on finite element analysis,and achieves a fast and accurate prediction,which provides the theoretical basis for clamping force selection.The experimental result shows that,with the clamping force prediction method,interlayer burr is less than 0.1mm,which satisfy the requirements of aircraft hole.