Uniform metal droplet ejection 3D printing technology is a promising space-based metal Additive Manufacturing (AM) technology. Understanding the gravity sensitivity is the premise to realize its application in space. Under ground condition, it is able to intuitively exhibit the gravity effects on printing processes by overturning the ejection and deposition direction to a horizontal state. Here, toward the challenge of realizing the stable horizontal ejection of metal droplets, a fluid dynamics model and a kinetic model of piezoelectric vibrator during the process of droplet horizontal ejection are established. The mechanisms on unstable ejection are experimentally investigated, the vibration characteristics of different ejection behaviors are ascertained, and the regulation law of stable horizontal ejection is unveiled. The results show that the vibration characteristic of the vibrator rod depends on the drive signal (pulse duration, amplitude) of piezoelectric module. With the growth of the amplitude or pulse duration, the vibrator travel increases at first, but then decrease. In addition, the diameter, initial velocity, and injection stability of the droplet can be effectively tailored by modulating the vibration characteristic of the vibrator rod. The droplet diameter decreases with the increase of the amplitude, and the droplet velocity is both positively correlated with the amplitude and pulse duration. Based on these findings, uniform metal droplets are experimentally obtained, and structures that agreed with the designed models are printed through droplets horizontal deposition.
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