Micro Machining Using the Electrochemical Discharge Assisted Cutting

electrochemical discharge;micro machining;Mechanical Engineering;Engineering;Mechanical Engineering

Jiang, BaoyangMazumder, Jyotirmoy ;

University of Michigan

关键词: electrochemical discharge;    micro machining;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/138746/byjiang_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The desirable physical and mechanical properties and the low machinability of glass have attracted many studies toward micro-machining of non-conductive materials. Recently electrochemical discharge machining is considered to have good potential in processing non-conductive materials. Material removal in the process utilizes the electrochemical discharge effect, in which high thermal energy is released through electric discharging. However, electrochemical discharge machining has not been adopted in the industry so far. The major challenges include slow material removal, low surface quality, and lacking in geometric accuracy. In this study, a hybrid machining process combining electrochemical discharge and mechanical cutting is presented, under the name ;;electrochemical discharge assisted cutting (EDAC)”. Mechanical cutting can be very effective as the material is softened by the high heat generation in electrochemical discharging. The material removal rate is boosted significantly with the hybrid process.The experimental investigation of the EDAC includes both drilling and milling processes. A machining system is designed and fabricated to enable the EDAC. Experiments are conducted to validate the feasibility of the concept, as well as to explore the boundary of the machining performance in terms of material removal rate, geometric accuracy, and surface finish. By using micro drill bit or flat end mill as the tool electrode, electrochemical discharge can be incorporated into mechanical cutting and significantly increases the material removal rate. Surface finish of the EDAC milling is around Ra 4 µm. Overcutting can reach hundreds of microns, but compensation is possible by appropriate tool path control since overcutting can be quantified. Models are created to simulate the electrochemical discharging and the material removal processes. A physics-based model is derived for gas film dynamics and electrolysis to correlate film characteristics with various process parameters. Meanwhile, the mechanisms of the discharging phenomena are revealed through modeling and experimentation, including the process of bubble growth and the criterion of the transition from bubbles to gas film.The energy and spatial distributions of sparks are determined both empirically and mathematically. The energy level of each spark generated is measured and is fit in a stochastic model with a two-component mixture log-normal distribution. The energy distribution proves that conic tool improves the consistency of spark generation and suppressed the generation of minor discharges. The proposed process model is capable of predicting temperature profile and the corresponding material properties, as well as the cutting forces in the machining process. The electrochemical discharging, as the heat source in the process, is modeled analytically and is followed up with finite element simulations to determine the heat distribution on the tool electrode. The temperature profile can therefore divide the material into three zones: thermally removed, softened, or solid. A cutting force model is created to estimate the overall cutting force that addresses the thermal removal and the thermal dependent mechanical behavior. It is found that amorphous materials can be softened significantly at much lower temperature than the melting point. Mechanical cutting can therefore be effective in removing the softened material and preserving surface quality.