Metal 3d Printing

Fused Layers Deposition (FLD) 3d printers have been defined “glorified glue guns” and indeed, conceptually, this is what they are!

If you have something that can spit out in a controllable way some material that you can stack up, you have the basis for 3d printing. This can be chocolate, Concrete or even biological materials….

And what if we were spitting out electrons?… Well…. They don’t exactly stack up nicely… unless those electrons cause some positively charged metal ion in a solution to reduce to solid metal depositing on the cathode…

The holy grail of 3d printing (or the Pandora Box, depending on your point of view) is the ability to print in metal at room temperature without the need for an highly controlled environment as in 3d laser syntering.

The idea is to use a modified electrodeposition system, with water based bath (e.g. Copper Sulphate) and a very sharp cathode  perpendicular and very close to a large flat anode.

Figure 1: A conceptual schematic of the idea, the specifics of the chemicals are just for indication and will need to be adapted and optimized.

However, due to the formation of a limiting layer at the interface between liquid and solid, this process is inherently slow 

The solution is to replace the sharp tip with a charged liquid jet that closes the circuit between a solid anode and the solid cathodic plate

Fig. 2 A jet of positively charged electrolyte impacts on a metallic cathode causing localized metal deposition (insert)

Replacing the extruder of a low cost FDM printer with a glass nozzle, and adding copper anode, pumps, filters and a programmable signal generator with a current amplifier, a simple 3d printing setup was created.

Electrolyte is copper sulphate and sulphuric acid, resulting in a bright copper deposition with current densities (in proper jet conditions) up to 23 A/cmq.

Fig. 3 different views of the 3d printer mounted nozzle and it actual printing process.

Deposition speeds up to (stationary) 25 microns/sec can be reached with the realization of extremely high aspect ratio structures as in Fig. 4 

Fig. 4 Pillars of 400 microns diameter have been easily extended to 25 mm length.