Monitoring process stability in GTA additive manufacturing based on vision sensing of arc length

Gas tungsten arc additive manufacturing (GTA-AM) is a highly promising technology to produce large-scale components. Monitoring and control of process stability are key challenges that hinder the wholesale industrialization of this technology and lack thorough investigation. A vision sensor is employed to directly monitor the arc length which can reflect the forming height stability with little detection hysteresis. Arc images are captured under two different brightnesses, and corresponding image processing algorithms are designed to detect the arc length under strong arc and weak arc. Thin walls are deposited to reveal the effectiveness of both detection methods. The results show that the detected arc length under weak arc fluctuates less than strong arc and is almost the same as the actual value, and the maximum error is less than 0.03 mm. This study will lay a solid foundation for the future control of process stability in GTA-AM.