Chinese additive firm prints pure copper structures using fibre lasers

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Farsoon Technologies, a Chinese manufacturer of industrial-grade plastic and metal laser melting systems, has developed an additive manufacturing process capable of printing structures made entirely out of copper using standard fibre laser wavelengths.

The firm recently displayed a part made with the process at TCT Asia, one of the largest industrial additive manufacturing shows in the Asia-Pacific area.

Pure copper is notoriously difficult to process using fibre lasers due to its over 90 per cent reflectance rate, which prevents the lasers from being used to continuously and regularly melt it in powder form without causing issues such as interface failure and thermal cracking. Pure copper also oxidises very easy when exposed to air, which reduces the properties of the parts made using it. It also requires special handling processes for storage, delivering and cleaning.

Alternative additive processes have therefore been developed using a large range of copper alloys since the turn of the century, which according to Farsoon have been achieving stable and high-quality results since 2015. These are being used to build parts such as heat exchangers, moulds and electrical components in the aerospace, automotive, shipbuilding and electronics industries.

Being able to print using low-oxygen, pure copper however unlocks a number of additional applications due to its exceptional thermal and electrical properties, which are diminished when the copper is mixed with other metals to form alloys. Existing structures such as the heat exchangers, electronic components and moulds being made with copper alloys could also be produced with improved properties if pure copper was used.

Farsoon's application team therefore joined hands with industrial partners in 2017 to begin developing an additve process with optimised parameters and scanning strategies that could print pure copper components using standard fibre laser wavelengths.

‘For developing the pure copper, we conducted a large number of tests to obtain the best parameters, especially on laser power, fill scanning speed and fill scanning line spacing,’ Farsoon told Laser Systems Europe. ‘These parameters minimise the adverse effects of high laser reflectance of pure copper, in order to achieve the perfect part density, an optimised 3D printing process, and excellent performance.’

At present, all of Farsoon’s metal laser sintering systems can be used to produce high-quality, cost-effective pure copper parts.

The part displayed by the firm at TCT Asia was a pure copper heat exchanger (see image), with complex spiral geometry and a wall thickness of only 0.5mm, this part was printed as a single piece using Farsoon’s new sintering process. The pure copper structure offers a far more efficient heat exchanger than one made by a traditional brazing process. The lightweight design also reduces weight by over 30 per cent and cost by 35 per cent. The heat exchange performance of the pure copper is also better than that of any other copper alloys, according to Farsoon.

Although challenges still exist concerning the oxidation of pure copper parts, Farsoon told Laser Systems Europe that it is now intensively working on this issue with its partners. 

Going green

Printing structures from pure copper has also been explored by laser manufacturer Trumpf, who at Formnext last year premiered a new pulsed green laser, the TruDisk 1020, which when combined with the firm's TruPrint 1000 3D printer is able to print pure copper and precious metals such as gold. The firm explained that the materials’ absorbance of the green wavelength is far better than that of infrared, enabling it to be used to process copper and gold without experiencing the difficulties faced by standard fibre lasers.

Image caption: Farsoon Technologies displayed a pure copper heat exchanger at TCT Asia that was printed using standard fibre lasers. 

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