| With the development of technologies recently, titanium alloy, as the typical example of difficult-to-cut materials, has such excellent material properties of high specific strength, high wear resistance, high tenacity, and has been widely applied in the important and key micro parts for the fields of the aerospace, energy and power, national defense, biomedical, vehicle engineering, which stimulates the innovation on new micro machining and precision machining approaches with high machining efficiency and quality. Micro-electrical discharge machining (micro-EDM), because of such advantages as simple electrode shape, contact-less process, no cutting force, low cost, and wide materials suit to fabricate, has been widely used in the manufacturing of geometrically complex and hard material microstructures. At present, it has been recognized as one of the most valuable techniques for micro machining. In the process of titanium alloy micro-groove with high-aspect-ratio machining, due to the micro electrode dimension, high-aspect-ratio and difficult to exclude of discharge debris, the electrode wear is serious and the processing efficiency is low with the traditional layered milling method, which hinder the development of micro-EDM milling. Therefore, to enhance the overall processing level of micro-EDM, it is inevitable to study the electrode compensation method and improve the processing efficiency and processing quality. This paper mainly includes the following.(1) In this paper, based on the self-established3-axis micro-EDM tool, the electrical control system, the pulse power supply system, servo control system and PID parameters are redesigned and debugged. Micro groove and micro cavity are machined in this experimental platform, and the machining experiments demonstrate that the tool is stable and reliable and the performance of the tool can satisfy the requirement of high precision and high sensitivity.(2) A coarse and fine layered milling method base on electrode side discharge is proposed with respect to the problem of serious electrode wear and low processing efficiency of the traditional layered milling method in high-aspect-ratio micro-groove machining on difficult-to-cut materials. Thereafter, the electrode wear volume, wear volume of micro-groove, bottom and side discharge gaps and electrode initial feed are amended according to experiments and the linear electrode compensation model for electrode side discharge machining is established. Titanium alloy micro-groove machining experiments indicate that the electrode wear under the electrode side discharge and linear compensation is still a kind of uniform wear, and the proposed method has a higher accuracy and processing efficiency.(3) Polar effect, non-discharge parameters and discharge parameters are selected as experiment parameters, then, single factor and orthogonal experiments of micro-hole and micro-groove machining on titanium alloy are carried out. Moreover, the influences of these processing parameters on machining characteristics are analyzed, which provides an experimental basis for reasonable choosing processing parameters.(4) Bottom and side discharge gaps are important parameters for executing exactly electrode compensation, for convenience of guiding practice, the discharge gap predicting model based on support vector machine is established. Thereafter, the bottom and side discharge gaps of the optimized processing parameters are obtained according to the predicting model. Consequently, the compensation parameters are calculated according to the linear electrode model proposed in chapter3. Finally, the micro-grooves on titanium alloy with high aspect ratio are carried out, and the experiments demonstrate that the present technology can achieve good accuracy on micro-groove machining and the processing efficiency is improved as much as6times comparing with the traditional layered milling method. |
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