Research On Stiffness And Machining Performance Of Multi-position Milling Robot

With the continuous promotion and implementation of the concept of intelligent manufacturing,the development and application of industrial robots in the manufacturing industry is becoming more and more in-depth,and its high flexibility,high automation and low price have significant advantages in the manufacture of large size and complex components.However,the flutter generated by the low stiffness characteristics of this type of industrial robot will affect its accuracy and dynamic performance,and then cause processing instability and other problems,which not only seriously affects the processing surface quality of the processed material,but also aggravates the wear of the tool and affects the service life of the robot.The second joint angle and the third joint angle of industrial robots have a great influence on the stiffness performance of the robot,and the fourth joint angle and the fifth joint angle have little effect on the stiffness performance of the robot,that is,the position change of the end of the robot is an important reason for the stiffness change of the industrial robot.Therefore,this thesis analyzes the influence of the stiffness difference of the multi-pose milling robot on the processing quality of the milling robot in different postures,processes the workpiece posture based on multiple different planes,studies the stiffness distribution and processing performance of the milling robot under multiple postures,and designs a comparative experiment to match the theoretical analysis.The main contents are as follows:Firstly,build milling robot processing system.For the milling robot processing system design and selection,design spindle clamp and switching plate,processing workpiece,processing platform,and including motorized spindle,milling cutter,sensor and other equipment selection.Secondly,the kinematic analysis of the milling robot is carried out to evaluate the stiffness performance of the milling robot in multi-position and explore its stiffness distribution in multi-position.The structure characteristics of MOTOMAN-MA1400 industrial robot were analyzed,the kinematics model of Yaskawa robot was established by substituting the improved D-H parameter table,and the kinematics model of the milling robot was obtained by coordinate transformation between the end of Yaskawa robot and the cutting tool tip.The stiffness evaluation experiment of milling robot was designed.A stable load was added to the end of the milling robot,and the load and deformation data of the end of the milling robot were obtained by force sensor and laser displacement sensor,and then the stiffness performance of the milling robot was evaluated under different poses.The stiffness distribution of milling robots in different working planes was analyzed,which laid a foundation for exploring the degree and range of influence of stiffness differences on machining performance,and provided a reference for selecting regions with better stiffness performance of milling robots in multi-position.Thirdly,data such as milling force,machining surface quality and vibration signal are collected and analyzed in the process of machining.From these information,the influence of posture and stiffness changes on machining performance of milling robot is explored.A milling experiment was designed,and three groups of aluminum alloy workpiece in different working areas were milling.Data such as milling force,machining surface quality and vibration signal were collected to obtain the machining performance of the milling robot in multi-position.Combined with the stiffness distribution of the milling robot,the experimental results showed that: Milling load,surface machining quality and vibration signal of machining system are all affected by the change of stiffness to some extent,but the change of milling load is the same as the stiffness distribution in a certain range,while the change of surface machining quality and vibration signal of machining system is not consistent with the stiffness distribution,and the influence of the change of milling robot stiffness is small.