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Additive Manufacturing
Unlocking the potential of metal powder for 3D printing heat exchangers
Accurate builds allow for tightly packaged components and easy assembly of the final product .
The additive manufacturing industry is growing at a compound annual growth rate of 24.3 % [ 1 ] and by 2030 there will be over 2.7 million 3D printing devices in the world [ 2 ] . Alongside the medical sector , aerospace and automotive are amongst the top industries exploiting this rapid rise in additive manufacturing capability .
Text & images by Conflux Technology
As the top sectors that take advantage of developments in additive manufacturing continue to find new applications for 3D printing technology , the physical properties of printing materials are being pushed to their limits . Consequently , companies like Conflux are undertaking major R & D projects to discover new materials and develop techniques that can unlock performance from metallic printing powders .
How does 3D metal printing work ? There are several methods to 3D print metallic components , all of which are based on the same basic principles where a CAD model is used as a template to build up a physical component in thin layers . Laser Powder Bed Fusion ( LPBF ) is one of the most widely used techniques which utilises a laser to fuse layers of metallic powder . It is a popular method for many practical reasons , such as ease of handling and recycling of the raw materials , but for Conflux the benefits lie in the accuracy of the component builds . To achieve accurate builds with high heat transfer properties , choosing the most suitable printing powder is of paramount importance . There are a variety of metallic powders available for 3D printing , but not all can cope with the intense environment of a heat exchanger . “ For high performance heat exchangers , we are always trying to make the walls and fins as thin as possible ,”
highlights Dr Ian Fordyce , Additive Manufacturing Engineer at Conflux . “ The thicknesses we are dealing with are of the same order of magnitude as the particle diameters of the powder and the laser spot size itself . So , an error as small as 10 microns is a massive deal for us . This could cut the number of fins we can put in the heat exchanger as well as affect the surface roughness and increase wall thickness , all reducing the thermal performance of our heat exchangers .”
Metal printing powders characteristics The first stage to selecting a material is understanding its printability , which can vary hugely between powders . Printability is defined as the ability of a material to physically print geometries without causing the build to fail . Hard steels and nickel alloys for example , experience residual stress and warping during printing which causes them to lift off the build plate and crash into the recoater . While other materials will print with low density , resulting in holes that can lead to failures .
Intricate fin designs can be achieved using various printing powders ( stainless steel pictured ) with consistent particle size distribution and optimum composition .
20 Heat Exchanger World June 2024 www . heat-exchanger-world . com