Industrial FDM 3D printing with pure copper, yes you read that right. American 3D printing machine and material manufacturer Markforged has introduced a pure copper filament (99.8% Cu by weight) for its industrial FDM metal 3D printing machines.
Copper is a much-used metal in many industrial applications, desired for its high electrical and thermal conductivity. Copper is used for example for making pipes, particularly where heat conduction is important, wires, housing, and electrical equipment and welding equipment (spot welding shanks) to name just a few common applications.
But copper is a notoriously difficult material to 3D print.
Copper filaments have been available for additive manufacturing for use in desktop FDM machines, but these are mainly used and meant for decorative projects.
These copper filaments are made of a mixture of copper powder and PLA. The ratio differs per brand from 60% copper to up to 90% percent.
Note that there are also copper-colored filaments. But these are merely mimicking the aesthetics of copper and do not contain copper.
These copper filaments are meant for use on regular desktop FDM machines with some adjusting required on the nozzle and heating settings. But as mentioned the resulting prints are mainly for decorative objects, like statues or jewelry, because the parts are very brittle
To make parts for industrial use the industry looked at Selective Laser Melting as a more serious option.
Printing with copper for industrial use: SLM
To create copper parts for industrial use, the marked looked towards a more expensive but higher quality process of Selective Laser Melting or SLM.
But for that to become an option some hurdles needed to be overcome.
The nature of copper makes it hard for the lasers to melt or sinter the powder.
A new technique developed in 2018 by the Fraunhofer institute to sinter copper using a so-called green laser (and adding pre-heating of the powder to the process) made SLM possible for copper.
Industrial FDM printing with pure copper
But maybe the time has come to have a serious look at copper for FDM. The reason being that in February of 2020, Markforged released pure copper for use in their metal FDM machines.
Markforged says it has tested its 3D printed pure copper welding parts with an automotive manufacturer with good results.
Of course, the FDM metal printers from Markforged are not to be compared to the regular FDM desktop printers, and the manufacturing process involves 3 steps to arrive at industrial quality parts.
So how do they do it?
Their copper filament contains pure copper powder contained in a plastic matrix. In the first step, the model is built up layer by layer feeding the plastic filament containing the copper powder heating and gluing the plastic-like any other FDM technology.
In the next stage of the process, the plastic binding material is dissolved and removed from the model. This is done in a washer.
In the final step, the model is placed in a furnace or sintering machine where the remaining plastic binding material is melted away and the copper is sintered together at high temperature.
CHEMICAL COMPOSITION OF MARKFORGED PURE COPPER
- Copper: min. 99.8%
- Oxygen: max. 0.05%
- Iron: max. 0.05%
- Other: bal
MATERIAL PROPERTIES OF MARKFORGED PURE COPPER
- Ultimate Tensile Strength: 193 MPa
- Tensile Yield Strength: 26 MPa
- Elongation at Break: 45%
- Relative Density: 98%
- Electrical Conductivity: 84% IACS
- Thermal Conductivity: 350 W/mK