Next-generation electrical discharge machining

新一代放电加工

• 批准号: RGPIN-2019-06585
• 负责人: Koshy, Philip
• 金额: $ 2.33万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=738986
• 关键词: Next; generation; electrical; discharge; machining

Electrical discharge machining (EDM) is a precision material removal process that utilizes the heat generated from controlled, rapid electrical spark discharges struck between the tool and workpiece electrodes. Until recently, the thermal nature of material removal in EDM has limited its application in the manufacture of safety-critical components like those in an aircraft engine. Recent advances in EDM machine tools to do with advanced solid-state generator technologies have however paved the way for EDM to emerge as a staple in the aerospace industry, to the extent that it is even displacing processes like broaching, in the machining of fir-tree blade retention slots in turbine disks. EDM is poised for an even more widespread application in the coming years with the advent of aerospace materials of declining thermal conductivity, which renders them extremely difficult to cut, due to the higher energy partition to the cutting tool that accelerates tool wear. Significant progress notwithstanding, EDM continues to be largely limited by a low material removal rate relative to cutting processes, and surface integrity issues referring to recast material and micro-cracks. Interestingly, these issues are interrelated in EDM, in the context of the mechanism of material removal at the scale of a single discharge. The removal of molten material is presently understood to be due to the implosion of the gas bubble that is manifest from the evaporation of the dielectric fluid following a discharge, and it is estimated that less than 20% of the molten material is removed, due to insufficient ejection forces. The rest of the material is recast back on the work surface; not only does this render the process highly inefficient in terms of material removal, it also severely affects the integrity of the machined surface, because of the micro-cracks that result from rapid solidification and shrinkage of the molten material. An improvement in the ejection efficiency would therefore bring about an increase in the removal rate and concurrently yield a better surface quality. Currently, aspects of process and generator technology are at such a sophisticated stage of development that it is imperative to gain additional fundamental physical insights into the process, and peruse outside-the-box radical ideas, to further enhance EDM performance. In this context, the long-term objective of the proposed work is to investigate the mechanism of material removal in EDM at increasingly higher spatial and temporal resolutions and in fundamental terms, with the objective of increasing the material ejection efficiency. In the short-term, the research seeks to develop novel process concepts, and pursue science-based innovative approaches to bring about a simultaneous and substantial enhancement in both the removal rate and the quality of the machined surface.

放电加工 (EDM) 是一种精密材料去除工艺，利用工具和工件电极之间受控的快速电火花放电产生的热量。直到最近，电火花加工中材料去除的热性质还限制了其在制造安全关键部件（例如飞机发动机中的部件）中的应用。然而，放电加工机床的最新进展与先进的固态发电机技术有关，为放电加工成为航空航天工业的主要技术铺平了道路，甚至在涡轮盘中枞树叶片固定槽的加工中，它甚至取代了拉削等工艺。随着导热系数下降的航空航天材料的出现，电火花加工有望在未来几年获得更广泛的应用，这使得它们极难切割，因为切割工具的能量分配较高，加速了工具磨损。尽管取得了重大进展，但电火花加工仍然在很大程度上受到相对于切削工艺的低材料去除率以及涉及重铸材料和微裂纹的表面完整性问题的限制。有趣的是，在单次放电规模的材料去除机制的背景下，这些问题在电火花加工中是相互关联的。熔融材料的去除目前被认为是由于气泡的内爆，这由放电后介电流体的蒸发所体现，并且由于喷射力不足，估计少于20%的熔融材料被去除。其余材料重新浇铸回工作表面；这不仅导致该工艺在材料去除方面效率极低，而且还严重影响加工表面的完整性，因为熔融材料的快速凝固和收缩会产生微裂纹。因此，喷射效率的提高将带来去除率的增加，同时产生更好的表面质量。 目前，工艺和发生器技术的各个方面正处于如此复杂的发展阶段，因此必须获得对工艺的额外基本物理见解，并仔细研究创新的激进想法，以进一步提高 EDM 性能。在这种背景下，拟议工作的长期目标是在越来越高的空间和时间分辨率下研究电火花加工中的材料去除机制，并从根本上提高材料喷射效率。短期内，该研究旨在开发新颖的工艺概念，并追求基于科学的创新方法，以同时大幅提高去除率和加工表面的质量。