Design And Analysis Of An Automatic Tapping Robot System For Thin Plate Workpieces With Complex Distributed Holes

With the development of industry,the machining accuracy of the internal thread of parts is becoming higher and higher.Due to the complex assembly requirements of some parts,the thread holes are not only complex,but also often distributed in different planes.Although the traditional manual tapping processing has strong flexibility and can complete the processing of complex distribution thread holes,its processing efficiency is low,and the operation cannot leave the manpower.At the same time,its processing accuracy cannot meet the production needs of most enterprises.Although the existing combined drilling machine has high efficiency,it can only complete the internal thread processing of holes in the same plane,and it needs to move the workpiece to complete the internal thread processing of complex hole distribution parts.The range of motion of the joint robot is large,and the working area is generally spherical,rather than surface.The robot technology used in the internal thread processing has the advantages of wide processing range,high precision and manpower saving.One clamping can complete the internal thread processing of parts with complex hole distribution on different surfaces.Based on the analysis of the traditional hole tapping technology and process flow of thin plate parts,this paper proposes a robot automatic tapping system based on the commonly used six-degree-of-freedom KUKA industrial robot in industry,combined with the supporting end-effector tools,adaptive workbench and other peripherals to replace the traditional automatic and non-automatic tapping equipment,and complete the automatic tapping of thin plate parts with complex distribution holes,which greatly improves the automation level of enterprises in this field and the accuracy and processing efficiency of hole tapping of parts.The main research contents are as follows :(1)Structure design of automatic tapping robot systemAccording to the structure and shape of the thin plate parts to be processed and the action requirements of the internal thread processing,an overall structure of the automatic tapping robot system is proposed.Combined with the supporting terminal execution tools and the adaptive size of the workpiece,the worktable can be adjusted.With the coordination of the 6-DOF Kuka robot and the rotary positioner,the tapping processing of the thin plate parts with different sizes and different surfaces to be processed can be realized by one clamping.Based on the electromagnetic principle,a fast switching end actuator is designed to process the internal thread of the holes with different apertures.Based on Solid Works software,the structure is designed in detail and the digital prototype is obtained.(2)Theoretical analysis of automatic tapping robot systemOn the basis of the force analysis of the tapping robot system,the static analysis of the workpiece is carried out by Ansys Workbench software to obtain the stress and strain.The results show that the maximum strain and stress are 0.016 mm and 29.692 MPa,and the deformation meets the design requirements.The modal analysis of the end effector and the adaptive workbench is carried out to obtain its vibration characteristics.The results show that the first-order natural frequency of the end effector and the adaptive workbench is greatly different from the excitation frequency of the tapping spindle,so there is no resonance,which verifies that the structural design of the automatic tapping robot system meets the dynamic performance requirements.(3)Process design and simulation of automatic tapping robotBased on the analysis of the material of sheet parts to be processed,the structural distribution of holes to be processed and the manufacturing information,the internal thread processing technology and process flow of automatic tapping machine were formulated,and the optimal process parameters of internal thread processing were determined.On the basis of preliminary planning of tapping trajectory,the minimum path is obtained by greedy algorithm,and the tapping process is simulated based on Sprutcam software platform.In the simulation process,there are no phenomena such as unreachable position,collision and singularity of the manipulator,which verifies the feasibility of the machining process and the machining trajectory.(4)Control system design of automatic tapping robot systemAccording to the motion requirements of the part tapping,the overall framework of the tapping robot control system is built,and the hardware of the control system is selected.The hardware platform of the control system is established with Siemens S7-1200 Smart as the main controller.In order to realize the data communication between the control components and the controller,the control signals of the servo motor and the solenoid valve are transmitted through the I / O module of PLC.The communication between PLC,robot Kuka KRC4 controller and PC is established according to Profinet protocol.Finally,the software system of tapping robot is developed based on Via Portal V15.1,and the motion control of each motion module is realized.(5)Testing of solid function prototype machine of automatic tapping robot systemAccording to the design drawings,the mechanical parts are processed and the assembly of the functional prototype machine is completed.Taking the fixture and tool in the prototype machine as the controlled object,the internal thread machining experiment is carried out according to the position point set of the experimental thin plate to be machined hole.The machining efficiency and machining accuracy of the prototype are obtained,and the rationality of its structural design,process parameter setting and trajectory planning is verified.