Advanced laser beam forming technology improves 3D metal printing

A new laser beam shaping module has been developed at the Swiss Innovation Park Bell/Bian, which aims to solve the prevailing challenges in the LPBF process.

A major limitation of current commercial LPBF machines is the non-uniform thermal conditions caused by lasers. Current LPBF machines use Gaussian intensity distributions, which focus energy strongly at the center of the beam, resulting in excessive temperature rise and metal evaporation. In addition, the low density at the edges of the stream and the effects of thermal conduction prevent the material from reaching the melting point.

This Gaussian distribution creates a conical melt pool, which requires small aperture spacing to ensure trace overlap. However, this reduces productivity and increases the heat affected zone (HAZ) due to frequent reheating. Increasing the total energy density to increase the size of the melt pool is ineffective because after exceeding a certain energy density limit, the melting process switches from conduction to keyhole mode, resulting in process instability. The intensity gradient from the center to the edges of the beam is very challenging and results in large thermal gradients.

The research uses a spatial light modulator to shape the beam to achieve better temperature distribution control and increase the throughput of LPBF. This innovative technology enables significant improvement of the LPBF process by enabling precise control of the spatial modulation of energy deposition in the material. Thus, the melt pool geometry and temperature distribution can be tuned in three dimensions. The liquid crystal spatial light modulator used in this study serves as a highly efficient active beamformer that allows the transmittance of each pixel to be tuned to improve the spatial beam quality of laser energy.

Using this technology, 3D printing of metal parts can be performed not only with increased productivity but also with improved energy efficiency. In contrast to existing beam shaping techniques, such as ring shaping, this technology allows unlimited shapes of the laser beam to be shaped, offering numerous possibilities for different research objectives and activities.

In cooperation with an Austrian research group at Montanuniversität Leoben, known for its expertise in the field of bulk metallic glass (BMG), the application of a newly developed beam forming technique for use in the LPBF process of BMGs was investigated. High strength, large reduction of elastic deformation, low modulus of elasticity, and high resistance to wear and corrosion are the main advantages of BMGs. However, the biggest challenge in producing BMG using laser-based additive manufacturing is unwanted reheating and crystallization, which can deteriorate the mechanical properties of the final parts. Therefore, a beamforming technique was used to control the reheating and melt pool geometry, thus reducing the HAZ, leading to a change in the amorphous structure at the atomic level. Advanced material properties confirm a nearly amorphous structure with improved properties that cannot currently be achieved using state-of-the-art LPBF machines. The outline of this study has Advanced Functional Materials Magazine Cover Making.

The full work can be titled “Glass state control towards structural and mechanical reinforcement: additive manufacturing of bulk metallic glass using advanced laser beam forming technology” here It is retrieved.

The project was supported by IRPD AG (Switzerland) and the Swiss Innovation Agency (Innosuisse).