To 3D Print Copper, Green Means Go

Copper is a shining example of a metal that’s resistant to 3D printing—because it is shiny. Its reflectivity is a problem for laser metal fusion (LMF), the most common method of 3D-printing metal. LMF systems use a laser to heat and sinter successive layers of powdered metal to build up a 3D structure. But copper, even in powdered form, is so reflective that much of the laser beam’s energy simply bounces off.

Another reason it is difficult is that copper is thermally conductive—so conductive that whatever amount of laser beam energy that doesn’t bounce off the powder because of its reflectivity passes through it without the buildup of heat needed for sintering.

The usual laser for an LMF system, including the TRUMPF (trumpf.com) TruPrint system, produces an infrared beam to heat and sinter the powdered metal.

But according to Thomas Fehn, TRUMPF’s general manager for additive manufacturing , the infrared laser has a wavelength that is too long for sintering “highly reflective materials such as copper.”

However, according to Fehn, the company has found that it can be done with laser light in the green wavelength spectrum. When the shorter-wavelength green laser beam hits copper, the metal absorbs rather than reflects most of the energy—and absorbs it faster than it can conduct it away—causing heat to build up and the melting to proceed as required.

The company first developed its green TruDisk disk laser line as a solution to the challenge of laser welding copper. In late 2018, the company demonstrated that when the new TruDisk 1020 is used as the beam source in a TruPrint 1000 3D printer loaded with copper powder, 3D printing of pure copper workpieces is enabled. The same approach works for the printing of gold and other highly reflective metals, Fehn says. He believes the process “opens up new possibilities for 3D printing, particularly in the electronics and automotive industries.”