The splat morphology of 3D printed metal and solder jetting

New research from the University of Texas looks at liquid metal and the findings have interesting applications for metal additive manufacturing. The study focuses on, “splat morphology.”

Splat morphology refers to the “study of the overall splat shape, spreading on the substrate surface and the splat thickness.” In other words, the way liquid particles (in this case liquid melt) behave when hitting a surface. The paper explains, the “desired splat properties depend on the particular application.” Since for coating purposes, greater spreading and small thickness is desirable, “while a bump characterized by a higher thickness is needed for additive manufacturing processes.”

Advancing 3D printing with metal

This work expands the growing body of knowledge around how better use 3D printing metal can be made. Other researchers at Lawrence Livermore National Laboratory (LLNL) have looked at ways to improve porosity and repeatability when working with direct metal laser sintering (DMLS).  3D Printing Industry has also spoken to NIST who are working to improve understanding about the metrology found in DMLS build chambers.

This particular research from the University of Texas takes a different approach, with its focus on, “solder jetting, microcasting, sputtering and 3D printing.”

Xjet nano-particle ink. Image via Xjet.
Xjet nano-particle ink. One approach to 3D printing with jetted metal. Image via Xjet.

Metal inkjet 3D printing research

The scientists, Vimal Ramanuj and Albert Y. Tong, embarked on the project with plans to identify a numerical model to predict splat behavior, and thus advance manufacturing methods.

The model is applied to study the splat morphology and solidification characteristics of the process with particular focus on the convective effects, thermo-solutal coupling and eutectic formation. 

The specific process evaluated is a liquid metal printing technique. Metal inkjet 3D printing is still at a relatively earlier stage when compared to 3D printing techniques such as FDM or SLA. There are a variety of approaches taken by commercial 3D printing enterprises including XJET’s NanoParticle Jetting technology, Nano Dimension’s Dragonfly 2020 and Vader Systems with their magnetojet liquid metal 3D printing system.

An example of a completed metal 3D print using a jetting technique from XJET. Photo by Michael Petch.
An example of a completed metal 3D print using a jetting technique from XJET. Photo by Michael Petch.

Impact velocity an important factor

The UT model, “comprises of three governing equations: continuity, momentum and energy.” While it is of course apparent that temperature is absolutely vital to the 3D printing of metal, the team found that velocity was also very important. As they say in their conclusion,

The splat morphology is highly dependent on the impact velocity and droplet temperature.

The full paper, published in the Journal of Materials Science, can be viewed here.

Don’t forget that nominations for the 1st Annual 3D Printing Awards are closing soon, let us know if this research into 3D printing metal or other any work should be included in our shortlist.

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Featured image shows Visualization of liquid metal. Image via JK Studios.