3D printing a complex heat sink in copper
Renishaw has demonstrated an intricate heat sink built in commercially pure copper using 3D printing.
Pure copper is a highly desirable material for heat exchangers and electrical components due to its excellent thermal and electrical properties. While these properties are beneficial for the application, they also turn the process of using copper in additive manufacturing into a challenge.
Traditionally, a heat sink is built from thin sheets of material that are welded together but the complex geometry of the designm can make production challenging and time-consuming. Additive manufacturing (AM) systems build parts layer-by-layer, only adding material where needed, to produce lightweight yet complex components, making this process attractive for manufacturing heat exchangers.
While its high thermal conductivity makes copper the ideal material for a heat sink, the properties of the material can create challenges when using an AM system. The laser sintering of copper powder with an infra-red laser at a wavelength of 1070 nm is difficult, because copper is very reflective at that wavelength. Therefore, only a small amount of the laser energy is absorbed into the powder, and absorption is required to melt the powder together. Combining the high conductivity of copper and the laser energy required, leads to instability and often results in poor mechanical properties of the finished part.
Renishaw has worked with software developer nTopology to demonstrate the manufacturer of such systems, says Kenneth Nai, Principal Engineer at Renishaw
Combining Renishaw’s RenAM 500S additive manufacturing system and nTopology software demonstrated an easy method for designing intricate structures that are suitable for use in heat exchangers and how it can be integrated with Renishaw’s build preparation software, QuantAM.
The RenAM 500S system, with a single 500 Watt laser and 70um laser spot size, was loaded with 99.9% pure copper powder supplied by Carpenter Additive.
Next: Copper heat sink with 0.35mm walls
The system was able to manufacture thin walls with a thickness of 0.35 mm and solids with a density over 98 per cent, prior to heat treatment in 30 micron layers.
nTopology software was used to generate triply periodic minimal surfaces (TPMS) that are ideal for a heat sink design as they generally require the amount of surface area within a given volume to be maximised. The design critieria for the TPMS gyrold structure was for a wall thickness of 0.35 mm and cell sizes of 2 and 5 mm. The nTopology software was used to slice the design into 30 micron layers and export the boundaries and hatches as CLI files. These were then imported into Renishaw’s QuantAM software to generate the build file for the AM process. Using CLI files removes the need for the traditional STL file format which has many disadvantages when used to describe complex intricate structures like these.
www.renishaw.com/en/metal-3d-printing
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