【作者】 王维；

【导师】 朱荻；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 管电极电解加工是根据阳极电化学溶解的原理,利用金属管作为阴极工具对工件进行蚀除的孔加工方法。本文针对航空航天、模具以及汽车制造业中大量存在的孔结构,对电解加工群小孔中的若干关键技术进行研究。本文首先在电解加工机床上构建了管电极电解加工监控系统。监控系统以实时采集到的加工电流作为加工间隙的反馈信号,通过监控加工中的电流信号使加工间隙处于稳定良好的状态,同时采用了电流阈值控制方案,以实施短路保护和孔出口处杂散腐蚀的控制,取得了良好的效果。对管电极电解加工工艺进行了系统研究。首先从电场和流场两方面研究了绝缘层的涂覆尺寸特征对小孔加工性能的影响,得到了理想的绝缘层厚度参数。分别针对孔电解加工的间隙电场和流场进行仿真建模,分析了加工间隙内电场分布和压强分布对管电极加工精度与过程稳定性的影响规律。设计并制作了多种单电极、阵列电极工艺装备,开展了管电极电解加工试验研究,通过对影响加工稳定性、加工精度的主要工艺参数,如绝缘层的涂覆厚度、工具进给速度、电解液供液压力等进行优化,得到了不同尺度和不同数量下的相对均匀一致的小孔/群小孔结构。本文提出了电解液抽吸反流电解加工技术并设计了相应装置。通过流场分析证明该技术可以提高管电极加工的过程稳定性,可用于大规模群孔的电解加工中。开展了抽吸式反流电解加工的正交试验,对影响孔加工定域性的各加工参数进行了优化,得到了精度较高的孔型。另外,针对采用管电极电解加工斜孔时易出现空口精度低,加工稳定性差等缺陷,提出了楔形电极加工倾斜孔的方法,该方法加工精度高,同时避免了火花短路等现象,可用于大角度倾斜孔的加工。本文最后对电解液分配腔流场进行了仿真研究和优化设计。电解液分配腔的结构是影响群电极电解加工的稳定性和成形精度的重要因素,对群孔管电极电解加工的分流/汇流腔流场进行了建模分析,得到了影响电解液分流均匀度的主要参数。基于理论分析结合试验分别得到了适合正流群电极电解加工以及抽吸式反流群电极电解加工的分配腔尺寸和相应的分流均匀度系数。采用优化的分配腔参数和加工参数进行试验,得到了尺寸精度较好的群孔结构,其加工过程稳定,没有发生短路等现象。更多还原

【Abstract】 Electrochemical drilling (ECD) is a versatile process for drilling small holes in hard-to-machine metals. The ECD process has been applied in aerospace industries as well as automotive industry to machine coolant channels on aircraft turbine blades, combustion chambers, and apertures on extrusion die mold, etc. In this dissertation, some key technologies in electrochemical drilling multiple small holes are studied.A mornitoring and control system for ECD has been developed by the author, in which the machining current is real-time monitored as the feedback signal to control the machining process with different control scheme. The threshold current method is adopted to ensure short circuit protection and stray current attack control in the hole shape.Fundermantal research on ECD process is carried out systematically. Insulation of electrodes is achieved by electrostatic spraying process with polyethylene terephthalate (PET) powder. Electric field simulation of the side gap shows that the current distribution varies remarkably with the size of insulation layer shape, and appropriate thickness of insulating layer leads to an improvement in hole accuracy and machining stability. Flow model of the electrolyte along the machining gap is also established, based on which, the influence of machining parameters on the current is analyzed theoretically. The experiments were conducted subsequently to show that the machining accuracy and stability were influenced by the process parameters such as insulation thickness, tool feed rate, and electrolyte pressure.In order to improve machining stability of ECD, an electrochemical drilling method with electrolyte extraction has been proposed. Flow distributions along the machining gap with different electrolyte flow pattern indicate that reverse flow using electrolyte extraction distributes the pressure more uniformly and hence leads to a more stable machining process. Machining characteristics of electrolyte extraction are investigated experimentally. To minimize the radial overcut of machined hole by electrochemical machining with electrolyte extraction, the orthogonal design is used to optimize process parameters such as initial machining gap, voltage, tool feed rate, and electrolyte concentration. Good results have been obtained in the experiments with optimized parameters.A method of electrochemical machining of inclined holes using wedge shaped electrode tubes is also developed. Flow simulation of the machining area with and without the wedged tip at different machining inclination angle indicates that uniformity of electrolyte flow distribution along the initial machining gap decreased sharply with machining inclination angle increasing. In the case of using wedged electrode, the flow distributes more evenly comparing to normal electrode. Wedged electrode proved its usefulness to enhance the ECD accuracy through the decrease and elimination of sparking and striated dissolution.In the last section of this dissertation, a series of research on electrolyte manofild simulation and optimization are carried out. Process stability and machining accuracy of ECD on multiple holes were affected by the size of electrolyte manifolds. Flow of the electrolyte along the manifold was modeled to analyze the main parametesrs affecting the uniformity of the electrolyte distribution. Machining tests with electrode arrays were carried out to obtain the optimal manifold structure which suits the electrochemical drilling of multiple holes. With optimized manifold structure, array holes with good uniformity and stability have been machined, short circuit was diminished during the machining process.更多还原