Linde is collaborating with Liebherr-Aerospace Toulouse SAS to optimise the benefits of additive manufacturing (AM) for aluminium aircraft component.

The two companies have been working on a project which 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

Liebherr-Aerospace is keen to integrate the fabrication of AM printed parts into its 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.

Liebherr-Aerospace installed its first AM metal printer at its manufacturing centre at Campas in France and although the company 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 at 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.”

“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 at 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.”