In a perfect world, at least from a manufacturer’s standpoint, metal 3D printing would be as cheap, easy, and efficient as printing with thermoplastics on a desktop machine. We are still at a very early stage of research and development within the entire 3D printing space, much less the metal 3D printing space, but researchers around the world are working diligently to improve efficiencies of such technology.
One body of research, which was recently outlined in a paper titled ‘Toward 3D Printing of Pure Metals by Laser-Induced Forward Transfer,’ and published in Advanced Materials, takes an entirely new approach to printing with metals. The new process, which relies on a technique called Laser-Induced Forward Transfer (LIFT), requires no metal powders, and functions unlike anything we’ve seen before.
The team of researchers behind this process includes Claas Willem Visser, Ralph Pohl, Chao Sun, Gert-Willem Römer, Bert Huis in‘t Veld, and Detlef Lohse. They realized that, for the most part, metal printing has been limited to those materials which have lower meting points. Using currently available technology, it’s either very difficult or incredibly expensive to fabricate objects additively from metals such as copper or gold. That’s until now…
The Laser-Induced Forward Transfer process utilizes a high powder pulse laser and a metal film suspended from a clear substrate. The laser pulse is then focused onto the film, which liquifies upon being struck by the laser. When the heat of the laser makes contact with the metal film, the metal rapidly heats up and a phase change occurs. This phase change provides the propulsion necessary to rapidly propel the liquified metal towards a receiving substrate or build platform below.
Layer-by-layer, the researchers were able to construct incredibly fine towers of both copper and gold using this process. Just how small were these micropillars? One such tower was printed which was 2 millimeters tall and had a diameter of just 5 micrometers in size.
There are two main issues researchers have to deal with when printing with this LIFT method, which they summarized below:
“3D metal printing using LIFT has been limited to low aspect ratio pillars, perhaps since at least two challenging requirements have to be simultaneously fulfilled. First, good adhesion between stacked drops is required, but the deposited drops generally solidify in a spherical or torus shape. This unavoidably results in porosity and limited drop-to-drop contact when the drops are stacked on top of each other. A second requirement is that the landing position of a single drop has to be limited to the previously deposited drop’s impact area. This is nontrivial for the relatively large donor–receiver distances required for 3D printing, but was achieved for a narrow range of ﬂuences.”
Researchers were able to meet the first requirement by using a high energy laser within their process. In past research, lower powered lasers were utilized, resulting in smaller drops, but they were more spherical in shape once hardened. By using the lower energy laser, researchers in this study were able to achieve droplets which were disk shaped, allowing for better layer stacking and bonding, and equating to a lower porosity.
Researchers were also able to control, quite precisely, the deposition of each layer. However, there still is much room for improvement in this area, and several droplets landed away from their intended target. When dealing with builds as thin as 5 micrometers in diameter this should be somewhat expected.
It will be interesting to see how quickly this research is able to progress, and what may eventually come out of it for the 3D metal printing space. Let’s hear your thoughts on this research in the LIFT 3D Printing forum thread on 3DPB.com.