气液两相介质电火花微小孔加工工艺及其伺服策略研究

发布时间：2018-03-04 06:31

  本文选题：微小孔　切入点：电火花　出处：《哈尔滨工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着微机电系统的不断发展,机电产品日趋复杂化、精密化和高性能化,在航空航天、医疗设备、电子工业和国防装备等领域小孔结构的应用日益增多,且广泛采用高性能材料,这使得微小孔的加工面临极大的挑战。电火花加工(EDM)作为一种微小孔加工的常用方法,传统上多采用液体工作介质,加工稳定性好,但电极损耗偏大。国枝正典等学者用压缩气体作为工作介质,创造性的提出了气中电火花加工,显著降低了电极损耗,甚至出现了负损耗。由于气体中放电间隙小,存在加工稳定性差,效率低等问题。本文综合液体和气体介质的特点,研究不同气液混合比下电火花加工的特点,以期获得更快的加工速度和更低的电极损耗。从气体和液体的放电击穿特性入手,分别分析了以气相为主相和以液相为主相的两相介质的放电特性。根据气液两相介质电火花微小孔加工工艺实验的需求,搭建了加工平台,可以提供不同去离子水和空气体积比的工作介质。最终选用去离子水,去离子水体积比10%的雾以及去离子水体积比90%的气泡水作为工作介质。为进一步分析工作液供给系统的冲液效果,以实际加工参数为边界条件,对放电间隙流场进行了仿真,证明放电加工在两相介质中进行。以加工时间、电极损耗和小孔质量为评价指标,通过实验研究了电容、充电电流和伺服参考电压对电火花微小孔加工的影响。为了对不同介质进行合理的比较,设计了正交试验,分析各因素的影响程度,探求各介质中最优的参数组合。采用定加工时间和定进给深度的方式,探讨了不同介质中加工速度和电极损耗与加工深度的关系。相比去离子水,雾中电极损耗低,最多降低27%,气泡水中加工时间短,最多缩短17%,去离子水中孔锥度小。针对气液两相介质电火花微小孔加工的特点和机床控制系统本身的不足,引入PID控制对机床的伺服控制系统进行了改进。通过工艺实验,验证了PID控制的有效性。针对PID控制的不足,引入模糊控制,对PID参数进行在线整定。通过实验,与原系统相比,加工时间最多可缩短38%,取得了较好的加工效果。
[Abstract]:With the continuous development of MEMS, electromechanical products are becoming more and more complex, precision and high performance. The applications of orifice structure in aerospace, medical equipment, electronic industry and national defense equipment are increasing day by day. The high performance material is widely used, which makes the machining of micro hole face great challenge. As a common method of micro hole machining, EDM has traditionally used liquid working medium, so it has good processing stability. However, the electrode loss is on the high side. By using compressed gas as the working medium, some scholars creatively proposed EDM in gas, which significantly reduces the electrode loss and even results in negative loss. Because of the small discharge gap in the gas, There are some problems such as poor processing stability and low efficiency. In this paper, the characteristics of EDM under different gas-liquid mixing ratios are studied by synthesizing the characteristics of liquid and gas media. In order to obtain faster processing speed and lower electrode loss, starting with the breakdown characteristics of gas and liquid discharge, The discharge characteristics of two-phase dielectric with gas-phase and liquid-phase are analyzed, and the machining platform is built according to the requirement of the experiment of gas-liquid two-phase dielectric EDM micro-hole machining. Can provide different deionized water and air volume ratio of the working medium. Fog with deionized water volume ratio 10% and bubble water with deionized water volume ratio 90% are used as working media. In order to further analyze the efflux effect of working fluid supply system, the discharge gap flow field is simulated under the boundary condition of actual machining parameters. It is proved that the electric discharge machining is carried out in two phase medium. The capacitance is studied experimentally by taking the processing time, electrode loss and hole quality as the evaluation indexes. The effect of charging current and servo reference voltage on EDM. In order to compare different media reasonably, orthogonal test was designed to analyze the influence of various factors. The optimum parameter combination in each medium is explored. The relationship between machining speed and electrode loss and machining depth in different media is discussed by means of fixed processing time and fixed feed depth. Compared with deionized water, the electrode loss in fog is lower than that in deionized water. The maximum reduction is 27%, the processing time of bubble water is short, the maximum is 17% shorter, and the hole taper in deionized water is small. In view of the characteristics of micro-hole machining of gas-liquid two-phase dielectric EDM and the deficiency of the machine tool control system itself, The PID control is introduced to improve the servo control system of machine tools. The effectiveness of PID control is verified by technological experiments. In view of the deficiency of PID control, fuzzy control is introduced to set the parameters of PID online. Compared with the original system, the processing time can be shortened by 38%, and good processing effect has been achieved.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG661;TH-39
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本文编号：1564523