Lore Thijs

Manager @ Direct Metal Printing (DMP) engineering

During her engineering studies at the university KU Leuven (Leuven, Belgium), Lore Thijs got intrigued by how much processing conditions can induce large variation in microstructure and consequently in the resulting material properties of metals that start off with the same chemical composition. Unraveling the relation between the microstructure and the processing condition of Ti grade 23 processed via Laser Powder Bed Fusion (L-PBF) in her master thesis only increased this fascination and led to the start of a doctoral research in metal Additive Manufacturing (AM) at the same university. Guided by Prof. Jan Van Humbeeck and Prof. Jean-Pierre Kruth, Lore studied the influence of the L-PBF process on the microstructure and more specifically morphological and crystallographic texture of various metals hereby looking for the similarities and dissimilarities between these materials’ response to the L-PBF process.

After obtaining her PhD in 2014, she joined the spin-off company LayerWise nv (Leuven, Belgium) which was one of the first and largest metal AM companies focusing on serial manufacturing activities in many high end industries such as medical device, semiconductor and aerospace component production. Lore started as the first materials engineer in the research and development division supporting both the serial manufacturing activities of as well as developing L-PBF process for new materials. After the acquisition by 3D Systems, the LaserWise’s own developed  printing  machines as well as the material developments  were  not  only  used  internally  for  serial  parts  manufacturing,  but  were  also commercialized as the ProX™ DMP 320 and LaserForm® material products and introduced into the market in January 2016. Since then, Lore is managing a team of materials and process development engineers fully focussing on the study and development powder specifications, L-PBF process parameters, fine-tuning heat treatments as well as characterization of new materials. Through various research projects with both academic as well as other industrial partners, she is also promoting several PhD students focusing on various aspects of metal AM.

Contribution:

Title:

Metal Additive Manufacturing, from a scientific to an industrial point of view.

Abstract:

Metal Additive Manufacturing and more specifically Laser Powder bed Fusion (L-PBF) is combining very unique process conditions resulting in fascinating microstructures. The very high energy density of the laser leads to very high melt pool temperatures and high cooling rates causing ultrafine and often supersaturated and metastable unique microstructures. The additive nature of the process adds an additional dimension that will greatly determine the directionality of the physical phenomena such as solidification and grain growth. Given the digital control of the laser path and its settings, nowadays even a localized control is possible enabling location specific microstructures and further customizable for different locations within a single part.

However, because the material and the product shape are created simultaneously and that often complex shapes are printed, process conditions vary depending on the local geometric complexity and size of the part. These changes in process conditions can alter the physical behavior of the meltpool leading to various defects such as porosities. Also the dimensions of the printed parts can be effected by these local differences in process conditions through for example a change in shrinkage behavior and/or inhomogeneity in the residual stresses build up. Proper CAD/CAM file preparation of both the shape and orientation of the parts as well as the specific L-PBF process parameters is therefore of paramount importance to minimize (unintended) local process variations and increase the production‘s success rate. In addition to the file preparation, proper heat treatments needs to be selected to first of all relieve the residual stresses and depending on the constitution of the alloy also further strengthen or soften the material.

Finally, from economic point of view, further optimization of the L-PBF process and post treatment parameters towards low run times is often needed. This gives an interesting balancing exercise between economics, part’s shape and dimension and microstructure optimization.

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