German research organization Fraunhofer Institute for Laser Technology ILT will showcase its new 3D printing beam shaping technology at Formnext 2024.
Working with the Chair of Technology of Optical Systems (TOS) at RWTH Aachen University, the new platform, the Fraunhofer team is developing a test system for investigating complex laser beam profiles.
This platform can create customized beam profiles for laser powder bed fusion (LPBF) 3D printing, enhancing part quality, process stability and productivity, while minimizing material waste.
Fraunhofer ILT’s new system uses Liquid Crystal on Silicon – Spatial Light Modulators (LCoS-SLMs) to selectively bend the phase front of the laser beam during 3D printing. It can reportedly achieve more complex profiles than the basic ring and rectangular shapes achieved in previous research. This will allow researchers to investigate almost any beam profile used in LPBF. The complex profiles can then be matched with specific industrial 3D printing applications to unlock optimal results and address production demands.
“We can optimize the LPBF process in a targeted manner,” explained Marvin Kippels, a PhD student in the Laser Powder Bed Fusion Department at Fraunhofer ILT. He noted that the new platform will enable less material evaporation, reduce splatter formation, improve melt pool dynamics, smoothen melt track surfaces, and enhance process efficiency.
The new LPBF beam-shaping system, currently under construction, will be presented for the first time later this month at Formnext 2024, located in Hall 11.0, booth D31.
What is laser beam shaping?
Laser powers of 300 to 400 watts are used in many LPBF 3D printing processes. The standard Gaussian profile of these lasers presents challenges for industrial applications where quality, efficiency and reliability are key.
Philipp Kohlwes, the Head of L-PBF at Fraunhofer IAPT, previously told 3D Printing Industry that the high power concentration of Gaussian lasers creates uneven energy distribution with too much energy in the middle. This can cause local overheating, unwanted material evaporation, and process instability, leading to spatter and pores which damage part quality. These issues limit the scalability of LPBF 3D printing, restricting the maximum laser power which can be used for most materials.
According to Kippels, one way to overcome this is through the use of several lasers and optical systems in parallel. “However, the costs scale at least proportionally to the number of systems installed,” he stated. Additionally, these systems cannot always be used homogeneously, limiting their scalability for industrial applications.
To overcome these challenges, Fraunhofer IAPT is investigating laser beam shaping to increase the productivity of single lasers which can also be used in multi-beam 3D printers. In this process, the laser’s Gaussian profile is manipulated into different shapes before sintering the metal powder. These shapes can facilitate even energy distributions, translating to more energy in the melt pool. Kohlwes claims this homogeneity can increase metal 3D printing productivity by up to 2.5 times, and improve process stability by 40%.
Previous studies have demonstrated that simple beam shapes like rings, rectangles, or a combination of the two can enhance part quality and process speed. However, the creation of more complex beam shapes remains largely unexplored due to limitations in the existing technology.
Fraunhofer IAPT’s new platform reportedly overcomes these limitations, representing a new step for more complex shapes that can be customized to meet production needs.
The potential value of this capability was heralded by Kohlwes during last year’s interview. “The better the laser beam profile is matched to the respective application, the better the energy input and the associated process stability,” he emphasized. Similarly, Kippels explained that “There is no one perfect beam shape; every application has its own requirements.”
Fraunhofer’s new LPBF beam-shaping platform
The team’s new platform leverages LCoS-SLMs to unlock virtually any laser beam profile for LPBF 3D printing. With a maximum laser power of 2 kW, the test system can also assess beam shapes at high power levels, allowing the ideal profile to be matched for specific applications.
According to the Fraunhofer researchers, previous studies in beam shaping have not been based on an in-depth understanding of the underlying process mechanism. This has sometimes created ‘contradictory literature on the subject.’
Therefore, a more fundamental understanding of processes is needed before researchers can effectively determine laser characteristics, like melt track geometry. To achieve this, beam shapes need to be optimized for specific applications before being adopted by manufacturers. Fraunhofer IAPT’s new platform reportedly allows customers and project partners to access its flexibility for researching laser beam shaping to optimize LPBF 3D printing.
“We are still at the very beginning, but we can already see the enormous potential that beam shaping can offer for the LPBF process,” added Kippels. “Thanks to our flexible beam shaping, we can find the ideal distribution for each process, the best process parameters for the task in question.”
Advancing laser beam shaping 3D printing
Given its notable advantages for industrial metal 3D printing, beam shaping capabilities are being developed and commercialized by several players in the research and LPBF 3D printing spheres. Semiconductor and fiber laser specialist nLight is one such company. It agreed to supply Munich-based 3D printer manufacturer EOS with its AFX programmable beam-shaping lasers earlier this year.
The joint strategic cooperation made the lasers available on EOS’s metal 3D printers, while also implementing other complementary laser-based technologies to enhance their light engines for industrial applications. nLight’s AFX laser technology had previously been made available on metal 3D printers from AMCM, an EOS Group company.
Elsewhere, Equispheres and Aconity3D used laser beam-shaping 3D printing to achieve build rates nearly nine times higher than industry norms. Equispheres’ NExP-1 aluminum powder was used with Aconity3D’s AconityMIDI+ LPBF 3D printer to unlock speeds exceeding 430 cm3/hr for a single laser.
The system was modified to employ a PG YLR 3000/1000-AM laser with beam-shaping capabilities. By using a shaped beam over a zoomed Gaussian profile, the team reduced overheating and mitigated spatter formation during high-speed 3D printing.
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Featured image shows Fraunhofer ILT’s new laser beam-shaping platform. Photo via Fraunhofer ILT.
