July 05, 2018

New laser 3D printing materials research and developments

This article is a short description of the new technologies we are using at Ultimate Jets and Enata Aerospace for 3D printing.

I have worked extensively with SLA laser 3D printers for several years. As such I have developed a good knowledge of the material available on the market for UAV and RC jets use.

We have been laser printing most of our scale accessories for quite a while now, like instrument panels, antennas and probes, pitot tubes and ejection seat. However, I have also selected resins that are close to the properties of ABS for more structural components like our line of engine accessory holders or angle sensor mounts.

Over the course of the last year, I have started experimenting with glass nano fibers. I have been able to select specific resins that would mix well with these fibers and keep a good fluidity during printing. Furthermore, a 50 micron fiber size allowed to print parts at 100 micron accuracy with very good accuracy and very smooth surface finish. This process is now being used for our hatch latches, magnetic base antennas and probes, as well as SR-71 strut covers.

Finally, I have recently been able to use the ferro-magnetic 50 micron nano carbon fibers that I have been mixing in the hybrid reinforced resin before. Although quite expensive, this additive is giving a significant stiffness increase and very interesting surface finish and color.

The laser printing process is proprietary and uses the polarization principle, where an electro-magnetic field is generated around the periphery of the resin tray and influences the orientation of the nano carbon fibers. These effectively react like mini compasses in a magnetic field. This allows me to tweak the material property. As the nano carbon fiber cones align, they create a quasi continuous fiber along the field direction and strengthen. This gives an isotropic characteristic in one direction to each layer. The field can be changed from one layer to the next one, effectively crossing the isotropic direction to match. This essentially reproduces the process of FDM printing the hybrid carbon fiber filament with SLA technique.

The process can also be used without the electro-magentic field, where a layer or a succession of layers becomes anisotropic and create a more flexible material in one zone. The reason is that when the nano-cones do not align in a magnetic field, they tend organize randomly.

Here are comparative pictures of two GenTech hatch latches printed at 50 micron resolution in glass fiber and carbon fiber composite.