3D PRINTING/ADDITIVE MANUFACTURING FEATURE URING CONTRIBUTE TO THE Maintaining the quality of resourcematerials


with Linde’s ADDvance powder cabinet can help avoid re-work, saving energy and waste


feedstock. This is especially the case when using metal powders in laser powder-bed fusion (L- PBF), for example. The quality ofmetal powders used is critically important as it can impact on the physical and chemical properties of the finished product, including tensile strength, brittleness, impact resistance, heat tolerance and resistance to corrosion. Powder quality also plays a vital part in consistency and production repeatability. High sphericity of themetal particles is needed


so that the metal powder flows smoothly and evenly inside the printer and gas atomisation is the most effective approach to metal powder production due to the superior geometrical properties achieved. It requires not only a large supply of inert gases such as argon and nitrogen, but the gas molecule expertise to help manufacturers fine tune the atomisation process to further improve powder characteristics and eliminate rejects. Additionally, to protect themelt during atomisation, blanketing with liquid argon will protect the metal powder from oxidisation, reducing scrap and the need for expensive crucible maintenance. When considering these various gas atomisation applications, it is important to work with a specialised partner, such as Linde, with extensive know-how in high pressure gas supply solutions. The choice of gas and the supplymode are also


crucial ingredients to the success of your process and can affect the atomising flow and melt rates, pressure and overall batch time – impacting on both quality and productivity. Once themetal powders have been produced,


it is essential tomaintain the correct atmosphere during their storage in order to avoid humidity. While this is less important when powders are first delivered in their hermetically sealed packaging, once opened, the powder can be at risk of exposure to oxygen which can age the powder, reducing its quality or rendering it unusable. Linde has developed an innovative and


very compact solution to resolving this storage challenge – the ADDvance powder cabinet. The powder cabinet works with amoisture control and monitoring unit to continuouslymeasure humidity levels, triggering a high-volume purge gas flow as soon as the doors are closed to rapidly remove moisture in the air. It then applies a lower stream of gas to ensure a consistently low level of humidity, ensuring the quality of the valuable, sensitive metal powders is retained. Beyondmetal powder storage optimisation,


atmospheric gases play an evenmore important role in the core printing process. While additive manufacturing can optimise


production of printed parts, ensuring high- quality repeatability of the process and requiring less post-print finishing, the atmosphere in the printing chamber needs to be optimal and reproducible. Although the atmosphere in the chamber is


purged with high-purity inert gases such as argon and nitrogen to rid it of oxygen, impurities can still remain present due to incomplete purging, via loose connections or even within the metal powder itself. Even extremely small variations in oxygen content can impair the mechanical or chemical properties of metals sensitive to oxygen – such as titanium and aluminium alloys – and can affect the composition of the end product resulting in negative physical characteristics such as discolouration and even poor fatigue resistance. Linde is dedicated to developing pioneering


technology to overcome these atmospheric impurities in order to give manufacturers optimal printing conditions. The result – ADDvance O2


maintain the atmosphere as pure as needed. Linde is also a leader in the research,


development and supply of bespoke gases uniquely tailored to a customer’s specific AM process and project application. This includes its advanced argon-hydrogenmixture, ADDvance Sinter250, to optimise atmospheric conditions in sintering furnaces; and itsmost recent argon- heliumtestmixture to optimise the production of complex, latticed parts during L-PBF.


THE END GAME As we shift from conventional manufacturing methods to additive manufacturing, we also need to shift from a linear to a circular economy. Although waste from additive manufacturing is significantly less than from subtractive manufacturingmethods, it still generates some waste. This is now being addressed by innovative start-ups developing processes for melting and atomising scrap metal into suitable metal powders which can be re-used. It is thought that, in principle, these small recycling facilities could be distributed across the globe, situated in additivemanufacturing hubs to give scrapmetal new life as additivemanufacturing feedstock. While itmay be coincidence that these two


precision – provides continuous


analysis of the gas atmosphere, detecting oxygen levels with high precision without cross-sensitivity. Recognising O2


concentrations


as low as 10 parts per million (ppm), the unit automatically initiates a purging process to


Linde www.linde-gas.com/am


NOVEMBER 2021 DESIGN SOLUTIONS 39


individual butmajormanufacturing themes have emerged and become key concerns independently of each other, it is clear that given the opportunity to coalesce, they present a significant ability to re-enforce each other’s potential. As demand for more sustainable products continues to grow, the manufacturing landscapemust adapt. As additive manufacturing becomes increasing scalable, more localised, resource-efficient and circular, it is not impossible for it to make a significant contribution to the sustainability agenda in the not too distant future.


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