Collaborating for success: inside Linde’s 3D printing lab

In Linde’s Additive Manufacturing lab, Pierre Forêt and his colleagues drive innovation in 3D printing every day – thus helping industry partners to improve process stability and productivity.

Pierre Forêt is coordinating Linde’s Global Development Centre Additive Manufacturing.

Bio

Since 2015, Pierre Forêt has been coordinating Linde’s Global Development Centre Additive Manufacturing. The team has built up a lab with highly valuable, state of the art 3D printers. Their daily research focuses on developing gas-based technologies that can be used in each step of the Additive Manufacturing value chain, from powder production, to printing to post processing like heat treatment and hot isostatic pressing. “We are part of an ecosystem with leading companies and universities that are working together to push this technology further,” says Forêt. In this interview, Forêt talks about the results of their research and what lies ahead for them.

Question: 3D printing is an industry megatrend. Why is it so significant?

Answer: Additive Manufacturing is a technology that makes a solid object of almost any shape from a digital model. The layer by layer process and the design flexibility open up new ways of designing and manufacturing parts. Companies can make their products lighter and faster to produce or more economical. 

Question: What fascinates you about the topic?

Answer: The technology has great potential and the level of innovation in this eco-system is simply fantastic. While the principles of 3D printing are more than 20 years old, the most significant developments have happened over the last five years. And even more productivity increases are expected over the next five years. Gas molecules have an invisible but important role in this development and our goal is to support the industry with cutting-edge gas technologies.

Question: Why is reproducibility sometimes an issue in 3D printing?

Answer: Today, you can print metal parts with a high quality and a density above 99.5%. The aerospace, medical and automotive industry – even Formula 1 racing cars – are already using the technology with success.  However, the process is more complex than it seems and more than 200 parameters can influence the final part’s quality. The printer, the material – in our case a very fine, highly spherical, expensive metallic powder produced by gas atomization, the laser parameters but also the gas molecules used have an influence. It’s key to monitor and control those parameters to ensure a continuous quality level. This is where we can support the industry with our gas know-how. An example was the development of the ADDvance O2 precision which can measure and control the atmosphere inside a 3D printer at an unmatched precision level. This is used by some of our key customers in the aerospace and automotive industry.

Question: The AM team of experts and PhD students are working on developing new gas mixtures per material to be used in a 3D printing chamber. What is the goal behind that?

Answer: Each material, from basic steel to high-end titanium alloy, needs a different residual oxygen level during the process. The team is working on defining this process window for each material. First, we want to offer a high process stability by controlling the level of impurities in the process chamber. The argon or nitrogen used in this industry is of very high quality. For instance, leakages from the print chamber, or impurities in the powder can influence the atmosphere composition inside the printer.

Our second goal is to develop gas mixtures that increase the productivity of the process. We have molecules in our portfolio like helium that prove already to have a very positive effect on the process. With an argon-helium mixture we can reduce the formation of fumes and spatters and increase the process stability. This allows us to increase the laser scanning speed and produce parts faster. One of our PhD students, Camille Pauzon, is investigating this process under the supervision of Professor Eduard Hryha at Sweden’s Chalmers University.

Question: What does your research process look like?

Answer: We conduct complex large-design experiments in our lab in Munich and study which gas parameter has which influence on the process. A good example is the work of our PhD student Kai Dietrich together with Professor Gerd Witt at University Duisburg-Essen. He is investigating how the residual oxygen level in the printer (from 10 to 1,000 ppm) influences the process and more precisely the meltpool dynamic. Oxygen is known to have an effect on the surface tension of fluids. The surface tension on the meltpool is known to create a so-called Marangoni flow that will influence the formation of porosity. It is therefore crucial to control the residual oxygen inside the printer with precision to stabilize the Marangoni flow and the porosity formation. We are currently proving this theory through experimental work, soon we will be able to combine it with simulation results. In 2019, we will start a project with the Technical University Munich and Professor Michael Zäh to combine simulation and experimental work to better understand what happens in the meltpool which has the size of just a few microns.

Linde’s Global Development Centre Additive Manufacturing features state-of-the-art technology.
Additive manufacturing facilitates customization and on-demand production.

Question: Cooperations seem to be an important part of your work.

Answer: Definitely. We believe that this technology can only become mature in the next five to 10 years if the industry, academics and politics team up through partnerships. We share a lot of our know-how and sometimes even technology secrets in scientific journals and conference papers so that the community can build up on our specific expertise. We have put in place an eco-system with customers and partners along the complete value chain. We work together with powder producers, OEMs, end users and leading academics.

Question: How will your work affect Linde’s ability to innovate?

Answer: A positive development over the last months has been the enthusiasm from colleagues of different market segments to re-design their products by using the possibilities of Additive Manufacturing. We support them with design guidance and part production. An interesting example comes from our colleagues of the Lindoflamm product line. Those burners use acetylene to create a flame that is then used to pre-heat a metallic object. They are highly customized and complex to manufacture with many single parts that need to be assembled manually. The new burner currently in development is printed in one piece and has integrated cooling channels.

Question: What’s next for you?

Answer: The year 2019 will be exciting with the launch of new products and the start of new cooperations. We plan, for example, to kick-off a groundbreaking project where, together with partners, we will develop a new alloy, light and strong, that will be printable only with a specific gas mixture. There are today only 20+ materials available in AM against more than 500 in the powder metallurgy. We will help to change this with customized gas technologies.

Question: What is the biggest hurdle that Additive Manufacturing still faces?

Answer: Education. If people know when and how to use this technology, it will spread much faster. It’s very important that we spread the know-how in companies, in universities, schools, even kindergartens. People need to learn that there is this new way to design and manufacture parts. Why shouldn’t there be a small 3D printer in every school in Germany? For engineers, it’s still often not part of their university curriculum. I hope that will change.