| Wired Electrical Discharge Machining(WEDM) is referred to as the wired cutting. It is anew processing method developed on the basis of Electrical Discharge Machining (EDM).WEDM uses a thin metal wire (molybdenum wire or copper wire) moving continuously as thetool electrode. When the high frequency pulse voltage is loaded between the electrode wire(connected with the negative of the high frequency pulse power) and the workpiece (connectedwith the anode of high frequency pulse power), the metal was removed by the sparkdischarging from the workpiece and parts are formed. At present, WEDM is one of the mostwidely used special processing methods. Medium-speed Wired Electrical DischargeMachining (WEDM-MS) is actually High-speed Wired Electrical Discharge Machining(WEDM-HS), which have the repeatedly cutting function. By inheritance of the WEDM-HSand configuring a new generation of pulse power supply, improving the electrical system of themachine tool, improving the machine precision and the wire conveying mechanism, the cuttingprecision of the WEDM-MS is improved by repeatedly cutting.Based on the analysis and research of the research status and the development trend ofcurrent pulse power supply used by WEDM at home and abroad, the basic principles of theWEDM and the mechanism of spark discharge is researched in this thesis. Analysis andresearch of the influence of the electrical parameters on the cutting processing quality andcutting speed are carried out. The research shows that the cutting speed increases with thehigher average current. The surface roughness decreases with the decreasing of the peakcurrent, pulse width and the open circuit voltage in the processing. In the case of fixed peakcurrent, the increasing of open circuit voltage benefits to improve the working stability and therate of pulse utilization.The main circuit structure based on the PWM control of DC/DC transformer is putforward in this thesis. Some important power conversion technology, such as DC/DCtransformer, high frequency PWM technology, is used in this design. The main circuit ofvoltage-adjustable pulsing power source based on DC/DC converter is designed and simulated.The simulation circuit mainly includes AD conversion module, a microprocessor, a switchingdevice, the power driving device, and so on. The simulation results show that the voltage of thevoltage-adjustable pulsing power source based on PWM control and DC/DC transform can beadjusted independently along with the no-load voltage, breakdown voltage, processingmaintenance voltage. Therefore the machining accuracy can be greatly improved by choosingthe adaptation machining voltage, depending on the thickness of the workpiece. The regulatingprecision of the voltage-adjustable pulsing power source is good enough to meet therequirements of the subject. The pulse power system uses the master-slave level controlling structure. The upper PCcomputer and lower89C51MCU control module are used. As a pulse generator, MCU alsocontrol the pulse width and pulse interval, connect the digital display circuit. Using theRS232C serial port realizes the communication among PC and the lower position machine.Host control software is developed using the Visual Basic advanced language, which realizethe data pretreatment and human-computer interaction and other functions. The systemachieves more intelligent.Through the simulation, the design scheme of the main circuit power circuit and thecontrol circuit is identified. On the basis of the schematic design, the real circuit is produced.The pulse power supply is tested, and the waveform of the circuit is drawn. According to thetest, the output waveform of the design in this thesis is good enough to meet the expectedpurpose of the topic. |
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