3D Printing with Copper

Additive_Manufacturing_copper

Traditionally, copper is a very popular material due to its thermal and electrical conductivity. Recent developments have opened new possibilities in additive manufacturing.

Copper is an extremely interesting material due to its conductivity properties and for being highly malleable. 

These very same properties hindered its success as a feasible option for 3D printing. However, that has changed.

The most common technique for 3D printing copper is Powder Bed Fusion. It uses electronic beams to melt material powders and “glue” the material. When the temperature drops, the material consolidates together. 

The most popular processes of Powder Bed Fusion are known as Selective Laser Sintering (SLS), for plastics, and Selective Laser Melting (SLM), for metals. 

Despite SLM being an excellent printing process for many metals, there was a particular challenge when it came to 3D printing with copper. 

The conductivity properties of the material cause the heat of the electronic beams to be reflected instead of absorbed. 

Another reoccurring problem was the fact that the printed part would crack when the temperature would drop too fast and/or too low.

Towards a solution: green laser and pre-heating

Last year, researchers from the Fraunhofer Institute in Germany defied the status quo and developed a technique that made 3D printing high-quality copper parts possible.

Their solution consisted of switching the infrared laser from an SLM machine with a green laser. It sounds simple, right?

It is a bit more complex than that. A quick search on Wikipedia teaches us that laser is an acronym for Light Amplification by Stimulated Emission of Radiation. In short, lasers are light sources characterized by their wavelength in a vacuum. Each type of laser projects a concentrated beam that is amplified using stimulated radiation.

The light from this green laser for SLM printers developed by the German institute is better absorbed by copper which facilitates the melting of the material.


But the issue of cracking due to temperature drops was still there. The solution was to pre-heat the material before starting the printing process, which is sufficient to avoid a huge temperature drop.

This technique comes as the first real alternative for copper 3D printing, presenting a fantastic opportunity for manufacturers.

Machine manufacturer TRUMPF has applied these technologies in its new machine, the TruPrint 5000

The machine uses TruPrint Laser Metal Fusion (LMF), a green laser, and preheats to material to 500 °C.

The TruPrint 5000 was demonstrated at the Formnext, 3D print fair in Frankfurt in November 2018. 

The machine also prints with other precious metals – not only copper.

green laser

Layer of powdered Copper is exposed to a green laser during the SLM 3D printing process. Source: Fraunhofer ILT

Copper Powder

If the challenges for printing with copper are indeed overcome, copper has the potential to be widely adopted in additive manufacturing. 

As pointed out: copper has interesting thermal properties and together with the advantages of AM, particularly the design freedom, makes the additive manufacturing process beneficial for many thermal applications.

To anticipate the demand for copper in AM, different companies are developing special copper and copper alloy powders for the 3D printing market, notably Heraeus, Oerlikon and Stratasys.

Heraeus

Heraeus is a German technology group with a focus on precious and special metals, copper among them. Their additive manufacturing division is working on a portfolio of precious metals for 3D printing

The group developed a highly conductive copper powder with 99.8 percent density of solid copper and conductivity of about 95 percent IACS (International Annealed Copper Standard. Around 85 percent IACS is customary in the market.)
Heraeus presented  its highly conductive 3D-printed copper components at At the Formnext 2018.

Oerlikon

Oerlikon is a listed technology group headquartered in Pfäffikon, Switzerland, they are a manufacturer of materials for the aerospace, automobile, energy and tooling industries. The last few years they started developing metal powders for additive manufacturing at their subsidiary Oerlikon AM. In their material portfolio are nickel alloys, cobalt-chrome alloys and steel alloys. CuNi2SiCr is their thermally curable copper alloy developed specifically for AM applications.

Stratasys

Machine and material manufacturer Stratasys is also offering copper as a 3d print material: Copper (C18150), a chromium zirconium copper (CuCr1Zr) alloy.
The material has been tested with aerospace companies.

Applications

Copper is a soft, malleable, and ductile metal. Copper is a native metal with a has an orange-red color. It has very high thermal and electrical conductivity.

Applications for copper are:

  • electrical wiring (copper is a conductor of heat and electricity,
  • building material for roofing, plumbing, decorative elements and sculptures (for ex the Statue of Liberty is made from copper). The copper oxidizes and becomes a light green color.
  • constituent of various metal alloys, such as bronze (a copper-tin alloy) and brass (a copper-zinc alloy) and Sterling silver (silver-copper alloy)
  • machinery and motors
  • marine applications: copper is biostatic, bacteria or other live forms  will not grow on it. It was used in shipping to prevent growth on hulls.
  • sinks, faucets, doorknobs, handrails etc. Because copper is biostatic it is used (in various alloys) in appliances that are handled by many people, to avoid spreading bacteria.

Conclusion

In summary 3D printing with copper is fast becoming a reality. Technical hurdles are being overcome, and large companies are developing copper alloys in anticipation of market demand.

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