Research On Modeling Of Machining Error And Its Experimnet Of Milling Robot

Nowadays,large-scale CNC machining center is still popular in industry for overall manufacturing of large parts.This method is discredited by its high cost,degraded flexibility and low efficiency.The milling robot,on the other hand,has advantages of large working range,low cost and strong expansibility,which is one promising option for the overall machining of large parts.However,this strategy is limited in medal cutting as a result of its poor precision and stiffness.In order to solve the aforementioned problem,a localization error model of the robot is first established in this thesis based on kinematics.An experiment is designed to identify all parameters in the model.The strategies for localization error compensation and milling scheme planning of the milling robot are then proposed to increase the precision level through machining.This thesis starts with a theoretical analysis of robot kinematics.The mechanical structure of IRB 2400 industrial robot is investigated and a D-H kinematic model is obtained.Forward and inverse kinematics as well as the Jacobian matrix are derived concretely.All major specifications of the robot performance are then tested.In the second part of the thesis,the model of robot localization error during milling process is established and all parameters are identified via experiment.The factors that affect machining precision are analyzed in a steady-state-machining perspective,and the cutting force model is then obtained and investigated.The localization error of robot is the major factor that compromises the machining precision.This thesis establishes the model for robot machining error,including both geometric error model and joint error model,based on differential analysis.All parameters in this model are identified through experiment.The compensation strategy for geometric error is introduced afterwards.In the last part of this thesis,the milling scheme for the robot is proposed and the machining experiment is designed.The machining process along with the cutting tool initialization are determined based on the error model and corresponding experiment analysis.The spindle speed is selected by the modal analysis of the robot,and the cutting force model is verified with experimental measurement.All major cutting factors are investigated through experiment to see how they will make an impact on the roughness of the workpiece.It is corroborated by experiments that the proposed method is able to reduce the machining error.