The high thermal conductivity of copper makes it difficult to maintain needed temperatures during SLM. Also, copper is prone to oxidation at high temperatures, further complicating (thermal based) laser melting 3D printing techniques. It’s more typical to print copper alloys than pure copper.

Those are solved issues.

> oxidation at high temperatures

SLM machines typically use an Argon gas chamber. DED machines use an Argon gas shield.

> It’s more typical to print copper alloys than pure copper.

In the context of modern SLM, it depends on your definition of "pure" and "alloy". During the process, a bit of resin to is mixed into the powder and heat treated in a final step to get to 99.9% pure copper.

edit: Just fixed up my knowledge. Indeed alloys are typically used (99% copper with things like Chrome added on depending on use-case), tough the pure copper can be used with higher laser power.

Printing pure copper (99.9%) is possible since years with SLM process using lasers with an appropriate wavelength

Any references for 99.9% density with SLM copper? My understanding is that pure copper SLM printing is less frequently done as doesn’t work well with the infrared lasers on most machines, requires high heat & speed, and has more porosity than other alloys. It’s also hard to print so that it’s strong, conductive and heat stable.

I think there’s still quite active research in the area, though, and no doubt there’s a lot going on that I don’t know! https://www.sciencedirect.com/science/article/pii/S026412752...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10861549/

Sorry I wasn't talking about density but the copper content of a powder which is printable. Googling a bit I found this presentation from 2022 showing that a density of 99.5% for pure copper is possible although at half the productivity of a copper alloy https://www.coppercouncil.org/wp-content/uploads/2022/02/TS2...

> doesn’t work well with the infrared lasers

The copper use-case is what kick-ed off an industry-wide race towards offering blue laser as an option. There is more than just wavelength that goes into printing good copper results, but that is a major factor.