Research On Micro Wire Electrochemical Cutting And Its Application

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.