Atomized Dielectric-Based Electric Discharge Machining for Sustainable Manufacturing

放电加工工艺已成功应用于航空航天、汽车和其他行业，可制造各种材料的高精度微型零件，无论其硬度如何。然而，由于单个放电能量低以及电极间间隙中碎片颗粒的积累，该过程的效率较低，特别是在加工微尺度特征时。此外，放电机使用压力冲洗技术，这导致消耗的电介质量明显高于有效放电过程所需的电介质量。该奖项支持研究基于雾化电介质的放电加工工艺，该工艺可以将电介质的消耗减少 10-20 倍，并有助于实现环境可持续的加工工艺。新工艺将提供制造具有复杂几何形状的高精度组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理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。这项研究的总体目标是提高微放电加工工艺的效率，并通过减少有害电介质的消耗来产生环境可持续的加工工艺。该方法是将电介质雾化并产生一层薄薄的移动薄膜，该薄膜填充电极间间隙并有效地冲洗掉碎片。这项研究有四个具体目标：（1）了解薄膜形成、流动特性、熔池形成和碎片冲洗； (2) 了解等离子体在液体介质中的形成、塌陷和放电； (3)建立碎片运动轨迹与介电速度的关系； (4) 建立工艺参数和加工特性（放电能量、材料去除和碎屑冲洗）之间的关系。为了实现这些目标，将利用喷雾中介电液滴的质量和动量传递来开发成膜模型；将使用基于流体的方法开发空间分辨的三维等离子体模型；利用电极间间隙中流动的碎屑颗粒的力平衡来建立碎屑冲刷模型。为了验证这些模型，将实验测量的数据与模型预测进行比较。将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通过测量不同尺寸的碎片颗粒来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.