【作者】 王少华；

【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】 微细电解线切割加工技术是以微米尺度线电极作为工具阴极,利用金属在电解液中发生电化学溶解的原理,结合多轴数控运动,对金属材料进行加工成形的一种电解加工新方法。基于原理上的优势,线电极加工过程中不发生损耗,可采用数微米直径金属丝作电极,加工出小至数微米尺度的复杂微结构件。该技术在航空航天、精密仪器、生物医疗等微细制造领域具有广阔的应用前景。本文的主要研究工作内容如下:1.提出了三种强化传质的方案。讨论了微细电解线切割加工的原理和特点,分析了脉冲电流微细电解线切割加工的定域蚀除特性。基于微细电解线切割加工自身的特点,提出了三种强化传质方案:线电极轴向微幅振动方案、线电极轴向冲液方案和环形线电极单向走丝方案。2.完善了微细电解线切割加工的试验系统。改进了运动系统、超短脉宽电源、加工检测系统、加工控制系统,建立了电解液循环系统。根据不同的强化传质方案,分别设计了轴向微振动线电极系统、轴向冲液线电极系统和单向走丝线电极系统。3.进行了轴向微幅振动微细电解线切割工艺试验研究。实现了直径2μm线电极的在线制作。分析了线电极轴向微幅振动加工间隙流场特性,建立了线电极轴向微幅振动加工间隙理论模型。通过大量的对比试验,研究了线电极轴向微幅振动对加工稳定性、加工效率、加工精度以及电参数工艺规律的影响。比较了不同工件材料、不同线电极直径对加工工艺的影响。在镍、高温合金和不锈钢材料上加工出多个复杂微结构,其中微螺旋结构切缝宽度为8μm。4.进行了轴向冲液微细电解线切割工艺试验研究。对引流道流场进行了仿真和优化,采用增加牺牲阳极的方法改善了出液面切缝边缘圆角现象。根据所建立的理论模型,研究了不同工艺参数对加工效果的影响。选择合适的工艺参数,采用直流电源在5mm厚的不锈钢板上加工出了深宽比高达30的微缝等结构;采用脉冲电源在厚100μm不锈钢板上加工出了微缝、微探针和直角等典型微结构。5.提出了环形线电极单向走丝电解线切割加工新方法。建立了单向走丝电解线切割加工间隙流场的数学模型,从理论上分析了走丝机构上的导轮回转精度对电极丝振动的影响,通过增加辅助阳极消除了切缝周围非加工区的点蚀现象,探讨了加工中断丝的原因并提出了有效的解决措施。设计了单向走丝机构,实现了环形线电极的无缝对接。通过大量的对比试验,分析了走丝速度、进给速度、电解液浓度、工件厚度和辅助阳极等因素对加工的影响。进行了单向走丝电解线切割典型结构加工试验,实现厚度为20mm的不锈钢板的切割,加工出的切缝结构深宽比达66.7。6.将微细电解线切割技术应用于某新型传感器关键弹性敏感元件的研制。针对该弹性敏感元件加工精度要求高且凹槽壁厚只有0.01mm,试验中采用了超声振动消除工件材料内的残余应力,线电极对刀法确定工件平行度和找正凹槽位置以及通过设定线电极轨迹重复两次切割凹槽成形等有效工艺方法。在分析了钴基弹性合金材料的电化学特性的基础上,进行工艺参数优化,最终成功加工出满足要求的完整弹性敏感元件。更多还原

【Abstract】 Wire electrochemical machining (WECM) is a new method of electrochemical machining (ECM) process. WECM uses a thin metal wire as the tool, combining multi-axis numerical control to cut the work-piece. The micrometer scale metal wire can be used as the tool by WECM for no electrode wear in the processing. The micrometer structures with complex shape can be fabricated by WECM. The technology has broad application prospects in the field of aerospace industry, precision instruments, biomedical, and so on. The main research work as follows:1. Three schemes of mass-transfer enhancement were investigated. Firstly, principle and characteristics of micro-WECM were summarized. Secondly, the influence of nanosecond pulse electricity on electrochemical reaction region was investigated. At last, for enhancing mass-transfer in machining gap, schemes of axial tool micro-vibration, axial electrolyte flow and unidirectional wire drive were adopted in this paper.2. The micro-WECM machining system was improved. The motion system, high-frequency short-pulse power supply, control and measuring system were improved. Wire electrode system and electrolyte circulation system were designed. According to different methods of enhancing mass-transfer in the machining gap, wire electrode system was divided into axial tool micro-vibration system, axial electrolyte flow system and unidirectional wire drive system.3. The technology of micro-WECM with low frequency and small amplitude tool vibration was experimentally investigated. Firstly, a wire electrode with the diameter of 2μm was machined. Secondly, the theoretical model of micro-WECM’s machining gap was founded based on flow field characteristics of axial tool micro-vibration. The influence of the tool micro-vibration on processing stability, feed speed, machining accuracy and technology law of electrical parameters were experimentally investigated. The impacts of work-piece material and the diameter of wire electrode on the machining process were experimentally compared. At last, the various micro-structures in thin nickel, stainless-steel and superalloy were obtained. And a micro helix with the slit width of 8μm was fabricated.4. The technology of micro-WECM with axial electrolyte flow was experimentally investigated. Flow field of auxiliary channel was simulated and analyzed. The method of sacrificial anode was used to improve the rounded edge on outflow surface. Effects of process parameters on the machining process were investigated.Finally, by using DC, micro grooves with the aspect ratio of 30 were obtained in 5mm-thick stainless steel. And by using pulse power, structures of micro-slit, micro-probe and rectangular structure were fabricated in 100μm-thick stainless steel.5. In order to machine high-aspect-ratio structures in 20mm-thick stainless steel, WECM with unidirectional wire drive was adopted. The theoretical model of machining gap flow field was founded. The influence of idler pulley precision of the unidirectional wire drive device on wire electrode vibration was investigated. The additional anode was used to improve the processing quality of non-processing zone. The reasons of broken wire were discussed and the effective solution measures were proposed. The unidirectional wire drive device was designed, and the seamless ring wire electrode was achieved. The influence of several process factors, such as wire drive speed, feed speed, concentration of electrolyte, work-piece thickness and additional anode, on the machining process was investigated. Structures with high-aspect-ratio were fabricated, and the aspect ratio of the slits in the 20mm-thick stainless steel was nearly 66.7.6. Micro-WECM was applied to fabricate a key elastic sensitive element of acceleration sensor. Because of the high requirement of machining accuracy and the special thin thickness of groove wall, the ultrasound was adopted to eliminate the residual stress in the work-piece material, and the tool positioning was proposed to exactly measure the parallelism and the groove position of work-piece. Moreover, the machining precision of groove was improved by repeating process twice through setting tool track. Based on the electrochemical property of co-based elastic alloy analysis, the process parameters were optimized. Finally, the full elastic sensitive element which meets the processing requirements was successfully manufactured.更多还原