Development Of Pressure System Of Micro Resistance Spot Welding Based On Servo Drive

Precision resistance spot welding technology is widely applied in the field of electronic information manufacturing.The miniaturization of electronic equipment has put forward higher requirements for resistance spot welding equipment,such as: more precise electrode position control,smaller welding pressure and more flexible compression process.However,the mode of pneumatic pressurization for traditional resistance spot welding is unable to meet the need of small pressure welding for micro parts because of many disadvantages,such as large impact force,high fluctuation in welding process,and unable to control electrode pressure and position,etc.This paper aims to develop a set of pressure system for micro resistance spot welding based on servo drive to meet the needs of micro parts welding,and mainly studied the hardware and software of the whole pressure system and servo motor control system,as well as the pressurization characteristics and process behavior of the developed system.A set of pressure mechanism for resistance spot welding was designed in this paper,which was mainly composed of AC servo motor,ball screw mechanism,spot welding head and pressure sensor.Through the direct connection of servo motor and ball screw,screw rod driving to make straight movement of spot welding head to provide pressure for welding and using pressure sensor to detect electrode force and feedback control in pressure process,not only the compliant,flexibility and portability of the pressure mechanism,high transmission efficiency and accuracy,small electrode pressure and "soft contact" with work piece,accuracy of electrode force detection and other functions was realized,but also the performance requirements of micro parts for small pressure welding pressure equipment were achieved as well as with high control precision of welding pressure,electrode position and pressure speed.The servo motor motion control system was designed based on DSP controller for the selected AC servo motor.According to the design scheme of the control system,the whole design and implementation of the system hardware circuit,control program and human-computer interaction system were completed.The debugging results showed that the system could control the movement of the servo motor quickly,accurately and steadily according to the control requirements,and the pressure detection and control was accurate and stable.The man-machine interface was friendly and the parameter settings were convenient.Finally,the pressure characteristics and process behavior of the system were studied.The welding experimental platform was built based on the pressure system that developed,and the characteristics of the position,velocity and pressure was researched and analyzed through the experimental,the electrode pressure curve was obtained during compression,and the stability,applicability and reliability of the system were verified by the welding experiments of thin nickel and micro copper enameled wire.The experimental results showed that the pressure system based on servo drive designed in this paper had the advantages of high accuracy of displacement control,achieving the "soft contact" between electrode and workpiece by speed control,and stable and accurate pressure control in the process of welding,which were very suitable for the precision welding of micro parts under the condition of small pressure,and could made up the shortage of pneumatic spot welding equipment.