Development Of High Quality And High Efficiency Controllable Pulse Power Source For Electric Spark Deposition

As a surface strengthening technology to improve the surface properties of metal matrix,ESD is widely used in the fields of surface repair and modification of parts.Pulse power supply is the key core of ESD equipment,its performance directly affects the ESD processing efficiency and quality.The traditional deposition pulse power supply has the disadvantages of low processing efficiency and poor surface quality after processing.Aiming at this problem,this paper designed and developed a controllable ESD pulse power supply with high deposition efficiency and processing quality.Compared with the traditional pulse power supply,this power supply can realize continuous adjustment of processing parameters.Furthermore,the deposition efficiency of ESD and the surface quality of the coating after machining are improved.The main research contents of this subject are as follows:(1)Design of electric spark deposition pulse power supply circuit.The main circuit of ESD pulse power supply is composed of signal generator circuit,power amplifier circuit and transistor controlled RLC circuit.Signal generation circuit transmits signal generation and control program to AD9850 chip in parallel through STC89C51 microcontroller,and obtains the output waveform that meets the requirements of ESD.The power amplifier selects the power MOSFET as the power switch of the pulse power supply.After the input signal is amplified by the optocoupler isolation circuit composed of high-speed optocoupler 6N137,the power MOSFET is turned on and off by the special drive chip UCC37321 of power MOSFET.The transistor controlled RLC circuit can improve the efficiency of ESD pulse power supply by improving the traditional RC circuit appropriately.The control circuit is based on single chip microcomputer and programmable logic device to realize the switching between power MOSFET and transistor-controlled RLC processing and the adjustment of working parameters.(2)Design of gap detection module and test of pulse waveform.The gap detection part is based on the gap average voltage detection method.The gap voltage sampling module,threshold voltage configuration module,high-speed comparison module and output module are connected in turn to realize the detection of discharge pulse in the machining process and improve the accuracy of the gap state detection.According to the processing requirements of ESD,the technological parameters of the ESD pulse power supply were selected.The developed ESD pulse power supply was tested by oscilloscope.The circuit was adjusted by testing the output frequency of 100-800 Hz and the pulse waveform under the duty cycle of20%-80%.The waveform of the second stage can be changed according to the state change of the previous stage,and the waveform of each stage can meet the requirements of ESD processing.(3)Comparison test of power supply performance.The experimental results were compared between the developed ESD and the conventional ESD,and the deposition efficiency and the surface quality of the coating were compared.Comparison tests of power deposition under different output frequencies,deposition voltages and duty ratios of waveforms were carried out to analyze the effects of different processing parameters on deposition efficiency and coating surface quality.The performance of the developed ESD pulse power supply was verified,and the influence rules of process parameters on deposition efficiency and coating quality were obtained.