Experimental design of EDM pulse generator based on VB and SCM

Pulse generator is the key equipment of electrical discharge machining (EDM). Considering the disadvantage of the traditional EDM pulse generator, a new pulse generator based on VB and SCM is designed. The simulation and serial communication with SCM are achieved, and the pulse width, pulse period, and phase sequence difference can be adjusted by the upper computer at a wide range. The simulation experiment results show that the pulse parameter can be adjusted conveniently, and the effects of the pulse parameter on the process performance can be understood easily. Introduction Electrical discharge machining (EDM) is a kind of machining process that removes material utilizing electrical energy and thermal energy, and it has been rapidly developed due to its huge advantage in machining hard cutting material, special and complicated parts [1,2]. Pulse generator provides energy to the discharge gap to remove material, so it is the key equipment that directly influences the machining speed, machining precision, machining stability, surface roughness of the workpiece and electrode wear ratio in EDM [3,4]. The common pulse generator in EDM is the transistor pulse generator, and the pulse signal is produced by resistors and capacitors when they charge or discharge. However, the pulse signal can only be gradually adjusted, and the pulse width and pulse period cannot be adjusted independently. Thus, it is hard to adjust each pulse parameter accurately according to the EDM request. The PWM signal, whose frequency, duty ratio and phase sequence difference can be adjusted, is produced by the AT89C52 SCM to drive the MOSFET in this paper. Furthermore, VB language is used to program the controlling interface of the pulse generator, the simulation and serial communication with SCM are achieved, and the pulse width, pulse period, and phase sequence difference can be randomly adjusted at a wide range. As a result, the pulse parameters can be adjusted conveniently during EDM, and the effects of the pulse parameter on the process performance can be understood easily. Production of PWM Signal by SCM Modular programming is used in the pulse generator in this paper, moreover, the assignment between modules is specific, the repeated design is avoided, and the relative independence between modules is built. The power system mainly contains two modules which are the PWM signal module and the serial communication module. The PWM Signal Module. In this module, three channels of PWM signals are produced from the SCM timer interrupt, and they are exported by P10, P11, and P12 of the AT89C52 SCM. T0 is used as the timer, and the minimum resolution is 0.2ms. The program flow chart of the PWM signal module is shown in Fig. 1, and the pwm, mk, aq represent the serial sequence difference, the pulse width, and the pulse period, respectively, which are transferred from the upper computer to SCM. 1060 2nd International Conference on Electronic & Mechanical Engineering and Information Technology (EMEIT-2012) Published by Atlantis Press, Paris, France. © the authors Fig. 1 The flow chart of the PWM signal module The Serial Communication Module. The flow chart of the serial communication module is shown in Fig. 2. In this module, the data is received and transmitted by a full duplex UART asynchronous serial port of the AT89C52 SCM. This module is composed of the serial reception interruption subprogram. The timer T1 is used as the baud rate generator in the serial communication. The serial initialization subprogram and the serial reception interrupt subprogram are programmed. Fig. 2 The flow chart of the serial communication module Interface Design of EDM Pulse Generator Based on VB The interface of EDM pulse generator is programmed by VB language in this paper. The pulse width, pulse period, and phase sequence difference of the PWM signal can be adjusted with the serial communication between MSComm and SCM. The interface is shown in Fig. 3. It can be seen from this figure that the theoretical duty ratio and frequency can be computed, and the theoretical wave can The serial reception interruption overflows, and the serial reception interruption subprogram begins End interrupt Query about data reception