Atomized Dielectric-Based Electric Discharge Machining for Sustainable Manufacturing

电火花加工技术已成功地应用于航空航天、汽车等行业，用于制造各种材料、不同硬度的高精度微细零件。然而，由于单个放电能量低以及电极间间隙中堆积的碎屑颗粒，加工效率很低，尤其是在加工微尺度特征时。此外，电火花机器使用压力冲洗技术，导致比有效放电过程所需的电介质消耗量高得多的电介质。该奖项支持研究一种雾化的基于介质的电火花加工工艺，该工艺可以将介质的消耗减少10-20倍，并有助于实现环境可持续的加工工艺。新工艺将提供制造复杂几何形状的高精度零部件和设备的独特能力。此外，对流动液体中等离子体放电的定量了解将有助于从水净化到等离子体医学的许多等离子体应用。本研究的总体目标是通过减少有害介质的消耗来提高微细电火花加工工艺的效率，并生产出环境可持续的加工工艺。方法是将电介质雾化，产生一层薄的移动薄膜，填充电极间的缝隙，有效地冲洗碎片。这项研究有四个具体目标：(1)了解薄膜形成、流动特性、熔池形成和碎屑清洗；(2)了解等离子体在液体介质中的形成、崩溃和放电；(3)建立碎屑轨迹和介质速度之间的关系；以及(4)建立加工参数和加工特征(放电能量、材料去除和碎屑清洗)之间的关系。为实现这些目标，将利用喷雾中电介质液滴的质量和动量传递建立一个成膜模型；将使用基于流体的方法建立一个空间分辨的三维等离子体模型；以及将利用电极间间隙中流动的碎片颗粒的力平衡建立碎片冲洗模型。为了验证这些模型，实验测量的数据将与模型预测进行比较。使用高速相机测量薄膜厚度，使用光谱学测量等离子体温度和电子密度，并使用扫描电子显微镜测量不同尺寸的碎片颗粒，确定放电位置周围的碎片颗粒分布。

Electro discharge machining process has been successfully employed in aerospace, automobile, and other industries to manufacture high-accuracy micro-parts with range of materials irrespective of their hardness. However, the efficiency of the process has been low due to low energy of individual discharges and accumulation of debris particles in the inter-electrode gaps, especially, when machining micro-scale features. Further, the electro discharge machines use pressure flushing techniques that result in consumption of significantly higher amount of dielectric than needed for an effective discharge process. This award supports research to study an atomized dielectric-based electro discharge machining process that can reduce the consumption of the dielectric 10-20 folds and helping to achieve an environmentally sustainable machining process. The new process will offer unique capabilities of manufacturing high-accuracy components and devices with complex geometries. In addition, the quantitative understanding of plasma discharges in flowing liquid will be useful in a number of plasma applications ranging from water purification to plasma medicine. The overall goal of this research is to improve the efficiency of the micro-electro discharge machining process and produce an environmentally-sustainable machining process by reducing the consumption of hazardous dielectric. The approach is to atomize dielectric and produce a thin moving film that fills inter-electrode gap and flushes out the debris efficiently. This research has four specific objectives: (1) to understand film formation, flow characteristics, melt-pool formation, and debris flushing; (2) to understand the formation, collapse, and discharge of plasma in liquid medium; (3) to establish the relationship between the trajectory of the debris and the dielectric velocity; and (4) to establish relationships between process parameters and machining characteristics (discharge energy, material removal, and debris flushing). To achieve these objectives, a film formation model will be developed using mass and momentum transfer from the dielectric droplets in the spray; a spatially-resolved three-dimensional plasma model will be developed using a fluid-based approach; and the debris flushing model will be developed using the force balance at the flowing debris particle in the inter-electrode gap. To validate these models, experimentally measured data will be compared to model predictions. Film thickness will be measured using high-speed camera, plasma temperature and electron density will be measured using spectroscopy, and debris particle distribution around the discharge location will be determined from the measurements of different sized debris particles using scanning electron microscope.