Study On Milling Process System Based On Industrial Robot

In the context of rising labor costs and structural adjustment of the manufacturing industry,tandem six-degree-of-freedom industrial robots can be used as intelligent processing equipment to replace traditional mechanical processing units with the advantages of low cost,high degree of automation,good flexibility,and small installation space.Compared with CNC machine tools,robot cutting is easier to meet the modern production requirements of multiple varieties,small batches,and on-site processing.Due to the tandem structure characteristics,the stiffness of the robot is low,which affects the processing quality and stability of the robot,and limits the application range of the robot cutting process.To this end,this paper studies the stiffness characteristics of the robot,and improves the machining performance of the milling process system by optimizing the stiffness during the milling process of the robot.The main research contents are:Taking KUKA KR60-3 robot as the research object.The robot kinematics model was established by D-H method,and the forward and inverse motions were solved and verified.The Jacobian matrix was solved by the vector product method,and the equivalent coordinate transformation of force and displacement was derived by using the differential operator.The stiffness of the robot is modeled,and the joint stiffness coefficient is identified using the static load test method.The stiffness performance index was defined by the force ellipsoid at the end of the robot to realize the quantitative analysis of stiffness.By using an algorithm that can filter the poses with the best stiffness in a single space point,the optimal milling poses and corresponding stiffnesses of each point in the milling plane are obtained.By analyzing the stiffness distribution of the milling plane in the working space,the milling position and height of the workpiece are optimized.In addition,it was found that within a certain range,the distance from the end of the robot to the origin can be used as a new method to quickly estimate the stiffness of the robot.It is also pointed out that the feed direction is also one of the process parameters that affect the milling performance of the robot.The optimal rigidity direction and expression method during the robot milling process are analyzed,and a vector diagram of the optimal rigidity direction of the milling plane is made.According to the law of pointing,a more universally applicable cutting path optimization strategy is proposed.In addition,it was found that the optimal stiffness direction is also consistent with the direction of the robot’s end to the origin.Therefore,the vector of this connection line can be used as a parameter for quickly analyzing the stiffness characteristics of the robot.Its length reflects the magnitude of the stiffness and the direction reflects the direction of the optimal stiffness.Designed a PLC-based robot milling experimental platform.In order to meet the requirements of milling experiments,the system hardware design scheme and work flow ofthe experimental platform were formulated,the parameter performance of the main hardware was briefly introduced,and the electrical design and hardware communication network design of the platform were completed.By writing the main program and subroutines of PLC,the frequency conversion speed regulation of the electric spindle and the pneumatic tool change are realized;the motion control of the robot;the real-time monitoring and overload protection of the milling force;and the interactive control of the HMI human-machine interface.Finally,the construction of the experimental platform is completed.