Design Of Spot Welding Machine Based On Servo Drive

Resistance spot welding has been widely applied in various industrial fields because of its good manufacturability.With the continuous emergence of new materials and technologies,its application area will also expand gradually.Therefore,further improving the quality of resistance spot welding is particularly important.Electrode pressure is an important parameter that affects the quality of spot welding.Whether the spot welding machine can realize the stability and real-time tunability of the welding process is very important for the quality of spot welding.At present,most of the pressure way of universal vertical spot welding machine is cylinder pressure.There are defects such as unstable pressure,large fluctuation and pressure can not be adjusted in welding process,which is not good for improving the quality of solder joints.In addition,the pneumatic compression method can not feed back the motion of the electrode,and the positioning accuracy is not high.In order to solve the above problems,this paper uses the servo motor as the driving device to design a new structure of the spot welding machine,and the main work is completed as follows:1.The working principle of the servo pressure mechanism is introduced,and the performance index of the spot welding machine is made.According to the performance requirements of the pressure system,such as responsiveness,stability and location accuracy,the driving mechanism of the pressure mechanism and the design scheme of the transmission mechanism,supporting unit,guiding device and deceleration device are determined.2.Based on determining the design scheme of the spot welding machine,starting from the maximum velocity of the electrode and the maximum designed pressure of spot welding machine,the main components of the servo pressure mechanism,such as ball screw and rolling bearings,linear guide,servo motor,coupling are selected and calculated,and the positioning accuracy and the dynamic performance of the pressurizing mechanism is verified.Then,the structure design of the support parts of the spot welding machine is completed by using the analogy design method.Finally,the servo pressure mechanism and the supporting large parts are assembled in the Pro/E,and the whole assembly of the spot welding machine is completed.3.The static analysis of electrode arm structure with bolt connection is done by using ANSYS software.In order to ensure the results more accordance with the actual conditions,the bolt pretension and contact problem is considered into the boundaryconditions.Analysis results show that the electrode arm and the connecting bolts have enough strength and stiffness,which means the design is reasonable.In addition,in order to investigate the influence of bolt pretension on the stiffness and strength of the electrode arm structure,static analysis of two kinds of bolt pretension on the electrode arm are carried out and compared.The relationship between the bolt pretension and stiffness and strength of electrode arm were determined,which provided the basis for the installation of electrode arm.4.Taking the STM32 microcontroller as the core,according to the motion parameters needed to control in the spot welding process,the working mode of the servo driver is selected,and the interface circuit between the servo driver and the controller is designed.The scheme of motor returning home is determined.The circuit for collecting encoder Z phase signal is designed.The design of the minimum working system of the controller is completed,including power supply circuit,starting circuit,reset circuit,debug interface circuit and serial port circuit that communicates with host computer.