Research Of Gap Flow And Servo Control System For Electrical Discharge Small Hole Drilling

With the continuous development of the mechanical industry and aerospace industry, the strength, hardness and density of materials have been put forward higher requirements. As a sort of EDM machining, EDM small hole machining have an advantage in high precision and no characteristics of cutting force and widely used in the fields of Aerospace, precision components and instrumentation. Owing to chip discharge and stability of the discharge condition, there are shortcomings such as low processing efficiency, difficult to control the processing aperture and so on. Therefore, researching on distribution of working fluid flow field in the gap of EDM with different flushing fluid and proposing a servo feed control strategy for small hole machining, promoting machining efficiency and quality have a great significance.The thesis established the theoretical model of electro discharge machining holes, and EDM gap was estimated, on the basis of it, the flushing fluid and liquid hole machining are modeled and simulated. The pressure and velocity distribution at the bottom of the hole and the side of the hole in the internal and external flushing fluid are analyzed, which provides the guidance for the experimental study.By means of experiment, get depth and time relations of different flushing under the condition of small hole machining, studies the internal and external flushing of the aperture, conducted electrode wear rate experiment and take photo of holes on the Digital microscope, to verify the simulation results is right.Designed EDM holes of the servo control system, including the gap voltage detection circuit and the frequency conversion type servo controller, the frequency of short circuit pulse range from 10 Hz to 300 Hz, the frequency of open circuit pulse range from 10 Hz to 5KHz. Designed voltage frequency converter, when the gap voltage is 3.6V~10V, the pulse frequency is 0Hz~mHz, the value of m as needed can adjust from 12 to 17 to meet the control requirements of different machining rules.Based on the frequency conversion servo control system, studied frequency conversion servo controller. Explores which voltage frequency conversion ratio to get the optimum processing efficiency under the different depth, and formulated with control strategy based on machining depth, the machining time of using strategy is 13.96% lower than that of not using the strategy. According to different machining rules, the experiment is carried out with different strategy, The results show that to achieve the highest machining efficiency, we need to use different voltage frequency conversion ratio. Conducted the experiment of different machining materials, The results show that the optimal voltage frequency conversion ratio are related to the material properties.