Fraunhofer ILT develops laser beam shaping platform to optimize PBF-LB process

Recently, the German research institution Fraunhofer ILT team is collaborating with the Department of Optical Systems Technology (TOS) at RWTH Aachen University to develop a testing system aimed at studying complex laser beam profiles using a new platform. This platform can construct customized beam profiles for laser powder melting (PBF-LB) 3D printing, thereby improving part quality, process stability, and productivity, while minimizing material waste to the greatest extent possible. This new beam shaping method will help additive manufacturing become more flexible and efficient.

Numerous studies have confirmed that beam shaping in PBF-LB can improve the efficiency and productivity of this additive manufacturing process. The new testing system developed by Fraunhofer ILT enables flexible research on complex laser beam profiles with power levels up to 2kW. This innovation can be used to customize solutions for industrial partners, aiming to more efficiently and robustly integrate PBF-LB process into industrial production to meet their growing needs.

1. The drawbacks of Gaussian distribution
Currently, in many PBF-LB processes, the laser power is typically between 300 and 400 watts. However, the standard Gaussian laser beam used has significant drawbacks: the power at the center of the beam is highly concentrated, which can cause local overheating, poor material evaporation, and process instability, both of which may damage component quality due to splashing and porosity. These issues severely limit the scalability of the process, which means that the available laser power of up to 1 kW in PBF-LB systems cannot be used for most materials.

Marvin Kippels, a doctoral student in the Fraunhofer ILT Laser Powder Bed Melting Department, said, "One way to accelerate this process is to use multiple lasers and optical systems simultaneously. However, the cost is at least proportional to the number of systems installed. In addition, these systems are not always evenly utilized in practical applications, which results in productivity not increasing proportionally with power. Therefore, improving the productivity of single beam processes is a promising method that can also be applied to multi beam systems.

2. Exploring new possibilities through beam shaping
Previous studies have shown that even simple beam shapes such as rectangles, rings, or combinations of two Gaussian distributions can produce satisfactory results in terms of component quality and processing speed. Due to the lack of necessary system technology, the potential of more complex beam shapes has not yet been fully explored. As researchers at Fraunhofer ILT begin conducting comprehensive research, this situation is changing.

Kippels explained, "Due to the highly dynamic nature of the interaction between laser beams and materials during this process, simulations can only serve as indicators of actual melt pool behavior." He is currently building a new system using LCoS-SLM (silicon-based liquid crystal spatial light modulator), which will enable researchers to study almost any beam profile during PBF-LB processes.

Due to its laser power of up to 2kW, this innovative system has become a platform for testing new beam shapes at extremely high power levels in PBF-LB processes, enabling the determination of suitable system technologies for individual PBF-LB tasks. Kippels explained, "We are able to optimize the PBF-LB process in a targeted manner." He specifically mentioned that by adjusting the geometry of the melt, material evaporation can be reduced, splash formation can be minimized, melt pool dynamics can be reduced, the melt surface can be made smoother, and process efficiency can be improved.

3. Flexible beam profiles that meet specific needs
Currently, system technology is often claimed to generate specific beam shapes, such as circular or hat shaped contours. However, the selection of these beam shapes is not based on a deep understanding of the underlying process mechanisms, as reflected in the conflicting literature on this topic. Only by fundamentally understanding the process can research clearly determine which adjustments can achieve established goals, such as specific melt track geometries.

This means that it is necessary to develop and optimize the beam shape for the application before it can be ideally implemented within the company without the need for LCoS SLM technology. With this research platform, Fraunhofer ILT's industrial customers and project partners can benefit from unprecedented flexibility in researching laser beam tools.

Marvin Kippels said, "Although we are still in the early stages, we have seen the enormous potential of beam shaping for PBF-LB processes. Each application has its own requirements, so there is no perfect beam shape. Thanks to our flexible beam shaping, we are able to find the ideal distribution for each process and the optimal process parameters for related tasks.

Source: Yangtze River Delta Laser Alliance