冷等离子体射流中的微细电火花加工机理与方法

Micro electrical discharge machining (EDM) is one of important micromachining methods to process difficult to cut alloys. In EDM, the instability of process is caused partially by the electrical discharge medium such as mineral oil, deionized water or gas. In this project, the low temperature plasma is proposed to be used as discharge medium in micro EDM to improve the stability of process and surface quality in machining difficult to cut alloys. In this project, the generation and control method of low temperature plasma jet are studied based on the requirements of micro EDM. The material removal mechanism of micro EDM in low temperature plasma jet is revealed. The relationship between tool wear, discharge gaps and machining parameters is also studied, and corresponding theoretical models are developed. The minimum dimension of feature and the surface roughness are explored. The parameters of micro EDM in low temperature plasma jet are optimized. As the result of this project, the proposed process of micro EDM in low temperature plasma jet is studied theoretically and experimentally. The results are published in journals and presented in conferences.

微细电火花加工是对难加工合金材料进行微细加工的重要手段，但无论采用电火花油、去离子水还是常规气体作为放电介质，都存在各种各样的不足，并使加工过程难以稳定。本项目所提出的冷等离子体射流中的微细电火花加工方法，以冷等离子体射流作为放电介质，既可继承现有各种微细电火花加工方法的优点，又能很好解决上述不足，提高难加工合金材料微细电火花加工的稳定性和表面加工质量。本项目将针对微细电火花加工的要求，研究冷等离子体射流的获取方法与控制工艺，揭示微细电火花在冷等离子体射流中材料去除机理、电极损耗规律和放电间隙与放电介质特性等加工条件的关系，并建立相应的理论模型，探索其微细加工的极限尺寸和表面粗糙度，优化在冷等离子体射流中的微细电火花加工工艺。研究的最终结果是提出系统性的难加工合金材料的微细电火花加工新方法，推动微细电火花技术的发展，并通过国际交流和论文发表，使我国在微细电火花加工领域占据领先地位。

本项目针对微细电火花气中放电加工过程不稳定问题，提出了采用冷等离子射流为介质进行放电加工的新方法。研究结果表明电极间的击穿距离增加，排屑容易，提高了加工过程稳定性。在项目执行过程中，研制了冷等离子射流的卧式微细电火花加工实验装置，并进行了加工参数与加工性能关系的大量实验，同时与其他气体介质和去离子水中的加工性能进行对比研究。在此基础上，进一步提出了采用超声波振动辅助，并以冷等离子体射流和雾气混合为介质，进行微细电火花加工的新方法，研制了相应的实验装置。研究结果表明，在冷等离子体射流和雾气混合为介质的微细电火花加工中的电极损耗接近于零，其材料去除率大于在去离子水中的材料去除率。这为电极无损耗加工微细三维形状提供了可能性。