【作者】 张雷；

【导师】 王振龙；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2011， 硕士

【摘要】 随着特殊材料的发展和复杂型腔结构的需求日益增多,微细电火花加工技术应用于越来越多的场合,而且成为目前制作大深径比微小孔的一项主要的工艺手段,在航空航天、模具制造等领域应用十分广泛。在电火花加工过程中,电蚀产物排出不畅等因素严重限制了圆柱电极加工小孔的深径比,导致加工不能满足工业生产的需求。因此有学者提出利用削边电极代替圆柱电极进行加工,或在原来加工方法的基础上复合抬刀等方法来增大深径比。这些方法都能在一定程度上增加孔的深径比,但是其原理尚没有明确的解释。由于在整个加工过程电蚀产物都是存在于间隙流场中的,因此对间隙流场的研究是探讨削边电极和抬刀控制增大深径比原因的关键。本文从有限元仿真着手,利用CFD软件,首先对微细电火花圆柱电极加工过程进行了仿真模拟,得出圆柱电极加工过程中间隙流场的运动状态为层流的结论,并通过工艺实验得到加工时间与孔深关系曲线以及深径比与加工速度的关系曲线。通过采用对可动区域进行模拟的方法,建立了削边电极电火花加工过程的间隙流场。与圆柱电极进行比较可以发现,削边电极的间隙流场中存在竖直方向分速度。这个速度会使电蚀产物随着流场运动到放电间隙之外,因此能够改善放电状态,增大孔的深径比。本文还通过相应工艺实验说明了削边电极的削边量对加工过程的影响,并验证了削边电极电火花加工模型的正确性。在电火花加工过程中,采用抬刀控制也能够增大孔的深径比,而此过程可以用动网格技术来模拟实现。文中建立了抬刀控制过程的仿真模型,也能发现其间隙流场有竖直方向分速度的存在。结合具体的工艺实验,说明了抬刀控制也能增大孔深径比的原因。本文所建立的仿真模型可作为后续的电火花流场仿真模型的基础。更多还原

【Abstract】 With the development of exotic materials and growth of demand in complex cavity structures, micro Electrical Discharge Machining (micro-EDM) is used in more and more occasions, currently has become one of the main methods in high aspect ratio micro hole machining, and is used widely in aerospace, die making, etc.In the process of EDM machining, because the particles emit difficultly from the gap in cylinder electrode machining, the discharge condition would become worse and restrict micro hole’s aspect ratio, which couldn’t meet the industry command. Then the methods of using flatted electrode instead of cylinder electrode or compounded with jump control are proposed. Although both the methods can increase the aspect ratio in a certain degree, the mechanisms are indistinct. In the whole machining process, particles are in the zone of gap flow field, thus the research of gap flow is the key of increasing the aspect ratio.The paper based on Finite Element Method (FEM) simulation, used Computational Fluid Dynamics (CFD) software to simulate the flow field of cylinder electrode machining of micro EDM, and made the conclusion that the gap flow was laminar flow in cylinder electrode machining process, and got the relationships between time and depth, also aspect ratio and efficiency through experiments.The method of simulating dynamic zone was used to get the flow field of flatted electrode. Compared to cylinder electrode, there were vertical velocities in the flow field, which could cause the particles move out of discharge gap and improve the discharge condition, and then, enlarge the aspect ratio. Relevant experiments were made to illustrate the influence of flatted level in flatted electrode machining, and proved the validity of simulation models.In EDM process, jump control could also enlarge the aspect ratio, which could be simulated with dynamic mesh method. The simulation model of jump control was established, and the vertical velocities were found. The reasons why jump control could enlarge the aspect ratio were explained with experiments. The simulation models could be the foundation of other models in EDM.更多还原