Study On Wave-control System Of High-speed CO₂ Arc Welding Based On DSP

The welding speed of normal CO2 arc welding is within 0.3~0.5 m/min, when it further increases, the stability of welding process and weld appearance become bad. Some defects such as undercut and"humped bead"may appear in the weld. In order to settle the defects in high-speed welding process, a current waveform control method was designed by controlling energy of metal transfer, which takes advantages of the characteristics of waveform control inverter power source that more parameters can be controlled and response is quick.The design of the current waveform control system for CO2 arc welding was introduced in this paper. The main circuit is consist of full-bridge inverter with IGBT, and the control circuit is based on the digital signal controller dsPIC30F6010, which can control the inverter power source accurately and quickly. The chip gives four independent pulses which drive IGBT to control power output. The control system is consist of A/D sample circuit, welding current and arc voltage feedback circuit, scheduling circuit, judge-sign circuit for short or arc, PWM DAC circuit and wire feed circuit.Through analyzing the short circuiting transfer process of CO2 arc welding, a waveform control method which was fit for high-speed welding middle sheet metal was put forward. The control process was divided into short circuiting period and arc period which were controlled separately. The method can solve the questions which include big splash and bad weld appearance by accurately controlling the arc energy in metal transfer. The initialization program, striking program, short and arc control program, retractile arc control program and faults interruption program were designed based on the waveform control method.The wave-control system was tested. The process of metal transfer was analyzed with HANNOVER analyzer and MATLAB software. The experiment results show that the design of the system is credible and reliable. The weld appearance is improved by controlling with the current waveform of CO2 arc welding process.