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In comparison to laser additive manufacturing, metal droplet deposition technology presents substantial cost benefits by obviating the necessity for costly metal powders and high-power lasers. Nonetheless, prevalent metal droplet deposition methodologies often grapple with challenges such as intricate drive architectures, substantial droplet volumes, and diminished jetting frequencies. This paper proposes an ultrasonic vibration micro-jet ejection technique and constructs a prototype for metal additive manufacturing. Utilizing ultrasonic vibration of a tool rod, the technique generates a high-frequency acoustic pressure field within the crucible, which facilitates the ejection of molten metal from the nozzle. The study explores two operational modes: continuous jet and on-demand jet. It was determined that the tool rod's amplitude must exceed a certain threshold to initiate metal ejection. As the amplitude further increases, the droplet jetting behavior transitions from uniform to non-uniform ejection states. To enhance formability quality, the study examined the influence of various process parameters on single-pass and three-dimensional forming. The examination of jetted parts revealed that both uniform and non-uniform jets provide satisfactory formability and mechanical performance. This research presents a new direction for achieving efficient metal droplet jetting forming.

In one-side welding with full penetration, the use of backing strips helps support molten weld metals, but increases manufacturing cycle time and cost. The backing-free welding technology is under investigation for medium-thickness structural components in the aerospace industry. Its crucial challenge is ensuring complete joint penetration and maintaining a suitable and stable backside bead width. This paper presents an innovative method of controlling weld formation based on weld-face vision sensing in arc welding. A standard laser triangulation setup is used to obtain images of weld pool, and a new weld-face feature ‘depression degree of the weld pool’ is proposed. An image processing procedure is developed to extract the depression degree of the weld pool from images in real-time. The depression degree of the weld pool is found to correlate closely with the backside bead width, and is a better indicator of the backside bead width than the weld pool width, with a higher consistency and a smaller time lag. Employing the depression degree as a feedback signal, a backside bead width control method is developed and implemented. Welding experiments on 6-mm-thick aluminum alloy 2219 plates show that the presented method is remarkably effective in achieving full penetration and keeping backside bead width constant.