Real-time visual monitoring and control of molten pool width for geometric consistency in electron beam freeform fabrication

Electron beam freeform fabrication (EBF3) technology has attracted considerable attention due to its unique high-vacuum environment, high deposition efficiency, and exceptional space adaptability. However, the multi-parameters complexity and time-varying deposition conditions usually make it difficult to ensure the stability of the molten pool width, which in turn imposes a huge burden on the geometric consistency of the thin-wall part. Therefore, this study presents a real-time vision-based monitoring and control system designed to regulate the molten pool geometry for enhanced precision. The results show that the developed image processing subsystem can quickly and accurately extract the molten pool width. The processing time for a single frame is approximately 17.65 ms, and the extraction accuracy is less than 0.2 mm. Based on the developed closed-loop control subsystem, the molten pool width can be stably and effectively controlled at the target value within ±0.5 mm, and the need for post-machining was largely eliminated. Moreover, variable speed and heterogeneous substrate deposition experiments demonstrate that the system developed in this study can effectively resist disturbances and exhibits good robustness. This work demonstrates a robust and cost-effective strategy for high-precision AM, representing a significant advancement towards intelligent and reliable manufacturing systems for the aerospace industry.