Linde recently announced that its collaborative project with Liebherr-Aerospace Toulouse SAS to optimise the benefits of additive manufacturing (AM) for aluminium aircraft components, has delivered definitive results in terms of improvement of product quality and production repeatability. Linde’s ADDvance® O2 precision solution gas analysis technology played a central role in the research.
As a leader in cutting-edge innovation for the aerospace industry, Liebherr-Aerospace Toulouse SAS is keen to integrate the fabrication of AM printed parts into their already established automated workflow to enhance manufacturing efficiency and reduce production surplus. As AM technology represents a new manufacturing approach for the company, a pilot project was launched in collaboration with Linde to develop aluminium components including bleed air valves. Having installed their first AM metal printer at their manufacturing centre at Campas in France, although Liebherr-Aerospace found initial results to be promising, oxygen levels were shown to fluctuate during the printing process. The variation in oxygen levels was seen to negatively impact the quality of the printed parts – particularly those made from aluminium alloys.
Linde’s solution was to employ its ADDvance O2 precision technology to provide continuous analysis of the gas atmosphere. Detecting O2 concentrations with high precision – as low as 10 parts per million (ppm) – without cross-sensitivity, the unit automatically initiates a purging process to maintain the atmosphere as pure as needed.
After the atmosphere in the AM printer chamber is purged, impurities can remain present due to incomplete purging, via access through loose connections or within the metal powder itself. Even extremely small variations in oxygen content can impair the mechanical or chemical properties of alloys sensitive to oxygen like titanium or aluminium and can affect the composition of the end product, resulting in negative physical characteristics such as discolouration and even poor fatigue resistance.
“Linde has always played a pioneering role in the development of atmospheric gas technologies,” said Pierre Forêt, Senior Expert Manufacturing, Linde. “That we were selected by Liebherr-Aerospace Toulouse to collaborate in this important project to advance the understanding of the role atmospheric gases play in additive manufacturing of critical aerospace parts, is further testament to our innovative capabilities.”
ADDvance O2 precision has given Liebherr-Aerospace Toulouse precise, granular control over oxygen concentrations in its printer chamber, enabling them to test different levels to assess how it impacts printed components. ADDvance O2 precision significantly improves monitoring and control through a feedback loop with dynamic adaptation, meaning operators can define a setpoint value and maintain purity levels at that value. An unexpected benefit that Liebherr-Aerospace Toulouse discovered is the ability of ADDvance O2 precision to also measure humidity within the chamber – another critical variable in the production process and a capability unique to ADDvance O2 precision.
“We know that gas purity during fusion has a direct impact on the mechanical and metallurgical properties we can expect to achieve – especially with aluminium alloys. So, we needed a dedicated solution to help us improve atmosphere control in the printer,” said Frédéric Letrange, AM Project Leader, Liebherr-Aerospace Toulouse. “Having looked at the various oxygen measurement and control systems available on the market, it quickly became clear to us that ADDvance O2 precision was the most mature so it was a natural step for us to expand our partnership with Linde into the additive manufacturing space.”