Advancements in process monitoring and quality control for electrical discharge machining: A comprehensive review

As an unconventional machining technology, electrical discharge machining (EDM) enables the processing of any electrically conductive material through a thermoelectrically coupled material removal mechanism. With the growing demand for increasingly sophisticated and miniaturized high-end components, particularly in mold manufacturing, aviation, and biomedical sectors, EDM has become an indispensable machining solution and continues to attract significant industrial and academic attention. However, the extremely narrow inter-electrode gap and inherently complex gap conditions make discharge behavior highly stochastic and dynamic. This characteristic poses substantial challenges to machining stability, mechanism analysis, and quality improvement, hindering its efficient application and development. Addressing these problems requires robust process monitoring and effective quality control strategies to ensure the stable production of high-precision parts. Previous literature reviews have primarily focused on theoretical modeling, application, and optimization, without systematically addressing the aforementioned challenges. With the ultimate goal of enabling stable and high-performance EDM processes, this paper investigates state-of-the-art monitoring strategies and broadly explores solutions to quality control. The review begins with an overview of the fundamental principles of EDM, its process variants, and the key challenges encountered in practice. Then, a detailed examination of sensing techniques (direct or indirect monitoring) that are employed to capture machining information is provided, which can assess process condition and workpiece performance. The paper further discusses the causes of quality defects, presenting strategies for controlling dimensional accuracy and surface integrity through parameter optimization, process hybridization, and advanced monitoring methods. Finally, promising directions for potential EDM development are highlighted from the perspective of process monitoring level, quality control level, and versatility of EDM applications. This review offers valuable insights and practical guidance for advancing intelligent EDM technology, providing a roadmap for its increased industrial application.