Copper 3D printing for e-mobility
Green lasers and mastering the challenge of thermal conductivity.
1. Introduction: Copper – The enfant terrible of 3D printing
With the electrification of industry (e-mobility, renewable energies), the need for extremely efficient copper components (coils, contact terminals, heat exchangers) is growing. Pure copper is known for its unsurpassed electrical and thermal conductivity.
But these very properties made copper an absolute nightmare for metal 3D printing (especially for selective laser melting, PBF) for years.
The physical problem
Standard PBF machines use infrared lasers (wavelength approx. 1,064 nm). At this wavelength, pure copper reflects over 90% of the laser energy like a mirror. The remaining 10% heat is dissipated by the copper so quickly (thermal conductivity) that a stable melt pool is not formed. The printed parts became porous and the reflected radiation often damaged the expensive optical systems of the printers.
2. The first compromises: copper alloys
In order to make copper printable, alloys were developed whose reflectivity was lower.
- CuCr1Zr (copper-chromium-zirconium): Can be easily processed with standard infrared lasers.
- The disadvantage: Any addition to pure copper massively reduces the electrical conductivity. This was often unacceptable for high-precision electric motor coils.
3. The breakthrough: green and blue lasers
The solution to the physical problem resulted in a shift in the wavelength.
- The Green Laser (515 nm): Companies like TRUMPF have developed machines (e.g. TruPrint 1000/5000 Green Edition) that use green laser sources. At this wavelength, liquid copper absorbs over 40% of the radiation (compared to <5% for infrared).
- Blue diode lasers (450 nm): Blue lasers (e.g. from Nuburu or Laserline for the DED process) are strongly absorbed and enable copper structures to be welded on.
- The result: A deep, stable melt pool. Components made of pure copper (Cu-OF/Cu-ETP) can now be printed with a relative density of >99.9% and achieve 100% IACS (International Annealed Copper Standard) electrical conductivity.
4. High temperature preheating
Even with a green laser, the extreme thermal conductivity of copper remains a problem: the molten pool solidifies too quickly and the component cracks (hot cracks).
- Therefore, modern machines combine the green laser with heating the build platform to 500 °C (some systems even up to 1000 °C). The reduced cooling rate reduces internal stresses and leads to perfect, crack-free structures.
5. Use cases in e-mobility and space travel
If pure copper can be printed additively, completely new (DfAM) design possibilities open up:
- Hairpin stator windings: In electric motors, copper windings must be close together to maximize the fill factor. Printed copper conductor tracks can be angularly and precisely adapted to the stator. This noticeably increases the efficiency of the electric motor.
- Induction coils: High-frequency induction is used to harden gears. Printed coils made of pure copper with three-dimensionally curved internal cooling water channels have a service life that is many times longer than manually soldered copper pipes.
- Rocket nozzles: Combustion chambers must be extremely cooled. 3D printing enables cooling channels directly in the solid copper wall through which ice-cold liquid oxygen is pumped before it burns.
6. Conclusion: A new era of design
The technology for reliably printing pure copper is now ready for series production. The biggest challenge is no longer the laser, but the engineers, who have to learn that they can now design thermal components completely free of the constraints of bent copper tubes.