Jan 2022     Issue 18
A Breakthrough on the Resolution of 3D Printing Pure Copper Components Using Highly Complex Geometries
Prof. Song Xu, Department of Mechanical and Automation Engineering

A research team led by Prof. Song Xu from CUHK Engineering recently proposed a novel method for 3D printing high-performance pure copper at a resolution of 100μm. They demonstrated that pure copper structures can be built at a high resolution and high performance using micro laser power bed fusion (µLPBF), an additive manufacturing method. This fabrication process enables the printing of pure copper under low power using a low-cost infrared laser which achieves low roughness, high physical properties, and high precision at the same time. The outcome of this research has been published in ‘Additive Manufacturing’, a prestigious journal in the manufacturing engineering field.

Pure copper is an essential material in many industries. Due to its superior electrical and thermal conductivity, it is employed in many energy-related applications such as heat transfer devices and electric motors. Although copper parts with complex geometries play key roles in numerous applications, achieving high geometric complexity and high resolution via traditional manufacturing processes can be very costly. Laser powder bed fusion, a powerful technique in metal additive manufacturing, enables the 3D printing of smooth curved surfaces and complex geometries, thanks to its high resolution and powder bed support. However, the high laser reflection and thermal conductivity of pure copper can reflect and diffuse most of the energy from the power source, leading to printing failure and low physical properties of as-printed parts. Moreover, the reflective nature of copper can also cause damage to machine optics. Recently, short-wavelength laser technology has been utilised to fabricate pure copper due to its high energy absorption rate. However, its disc-shape optics result in a large beam size that limits its resolution. In addition, these optics are more expensive than the conventional infrared laser, which is often used for material processing.

Combining the small laser spot using CU customised laser optics and the small layer thickness achieved using the CU customised recoater, Prof. Song’s team proposed the micro laser power bed fusion technique to build high-performance pure copper parts using a low-cost infrared laser. The small laser spot can direct more energy as compared to commercial systems under the same amount of power. It also enables the molten pool to achieve a higher temperature in a lower size to realise high resolution and low surface roughness at the same time. The small powders and thin layer thickness enhance the microstructure densification process and improve the bonding between layers, which is key to achieving high density and good physical properties. This technology can be applied in many industries such as thermal management and electric power transmission, where complex geometric components and structures made from pure copper material are in great demand.

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