Microgravity Space Manufacturing: Droplet-Based 3D Printing Shows Great Potential

In the recently published ‘Suppression of gravity effects on metal droplet deposition manufacturing by an anti-gravity electric field,’ researchers from Northwestern Polytechnical University explore greater complexity in metal 3D printing.

Droplet-based 3D printing is a technique offering great potential, but fabrication in space takes the challenge to an undeniably extreme level. This study offers great relevance to the issue of part maintenance in space and specifically at the International Space Station. Many parts are required to be replaced there, but obviously this is not an easy feat in such isolation.

Realistically, the better idea is to either make parts in space (here’s where 3D printing comes into the picture) or maintain them indefinitely. A variety of different 3D printers have been used in space, although the researchers remind us that powder is not a suitable material as the particles would simply float away. They also state that a new type of 3D printing is necessary for space as none have been extremely successful so far.

(a) Droplet charging and deflection setup; (b) flight trajectory of a droplet under charging voltage Uc = 951 V, and deflection voltage Ud = 1250 V.

With droplet-based printing, there is a wide selection of materials available, to include:

• Functional ink
• Wax
• Tin solder
• Aluminum
• Copper
• Gold

Processes can be tested in normal gravity ahead of time, but the researchers had to mimic an anti-gravity state.

Schematic diagram of (a) experimental system; (b) the detail sketch of a solidified droplet.

“Depositing droplets perpendicularly on vertical substrates could be an effective approach because the impact velocity of the droplets is separated from the gravity in the horizontal direction. In other words, the droplets do not respond to gravity in the direction of deposition,” stated the researchers.

“There were still challenges, however, as the droplets were projected horizontally due to gravity, spreading, and even slipping. It was necessary for the researchers to manipulate the flight trajectory further, creating an anti-gravity electric field for proper substrate impact, with droplets made via a horizontal generator.”

Physical properties of Sn63%Pb37%

The researchers explain that the best place for a droplet, ultimately, is the inflection point of its trajectory—allowing velocity to slow to zero, with any effects from inertia eliminated.

Theoretical and experiment trajectories under (a) charging voltage 951 V and deflection voltage 1200 V–1500 V; (b) deflection voltage 1700 V and charging voltage 517–951 V. The symbols represent the experimental data (abbreviated as Exp), the curves represent the theoretical data (abbreviated as Model), and the short dot-dot curves represent the mean trajectory (abbreviated as Mean).

“… this work proves that droplets could impact on a vertical substrate that is far from the nozzle against gravity under the manipulation of the electric force. This finding would be valuable for the simulating of droplet deposition under microgravity,” conclude the researchers.

“These experimental results pave the way for an applicable additive manufacturing approach in space. The present work is a pioneering work for the droplet-based space manufacturing, printing a part with high forming accuracy, good surface roughness, and low porosity under vacuum and microgravity will be the aim in our future research.”

3D printing in space is becoming the concern of many researchers today, from scientists who are bioprinting in space to 3D printing with magnets, and even ceramics. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

Solidified droplets on a vertical solid surface: (A)–(F) solidified morphologies; (a)–(f) contours of the droplets in (A)–(F) respectively.