Laser Powder Bed Fusion (LPBF) is a critical additive manufacturing process known for its accuracy and complexity in producing intricate parts. However, challenges like limited production speed, hot cracking, and material restrictions hinder its efficiency. This study explores the use of Multi-Plane Light Conversion (MPLC) as a beam shaping solution to improve LPBF. By applying MPLC, we achieve faster printing while maintaining high-quality parts. Comparative analysis demonstrates the superiority of MPLC-based beam shaping in enhancing process yield and manufacturing efficiency.
In recent years, Laser Powder Bed Fusion (L-PBF) has become an industrially established manufacturing technique due to the possibility to manufacture highly complex parts without additional tools. State-of-the-art L-PBF machines use single-mode fiber lasers in combination galvanometer scanners due to their broad availability, high dynamic capability and excellent focusability. To increase system productivity the manufacturing task is parallelized by the utilization of multiple laser-scanner-systems leading to increased machine costs. Alternative approaches for the scaling of L-PBF productivity such as beam shaping and variable laser beam diameters for the use of higher laser powers (PL < 400 W) are hardly used in L-PBF machines. In consequence the high peak intensities of Gaussian intensity distribution with ds = 50 – 100 μm of state-of-the-art L-PBF machines limit the usable laser powers due to the risk of part defects resulting from keyhole formation. Hence, non-Gaussian intensity distribution such as ring-mode laser beams as well as laser beam diameter variation exhibit great potential for high-power L-PBF systems. As part of the Digital Photonic Production (DPP) Research Campus funded by the BMBF L-PBF machine setups with a switchable ring-mode fiber laser and a defocused Gaussian laser intensity distribution were developed, validated and compared for the processing nickel-base alloy 625. By implementation of these approaches build-up rates up to 150% higher than those of conventional L-PBF machines were achieved while maintaining relative densities above 99.9%.
In Laser Powder Bed Fusion (LPBF), there are high demands on the cleanliness of the protective window (PW). During processing, however, process-by-products may accumulate on the PW surface and thereby change the process boundary conditions. In this work, a methodology to assess the condition of PWs in a LPBF machine using a line scan camera is presented. Image processing is used to detect the degree of contamination on the PW surface by using a thresholding algorithm. The line scan camera results are further validated by ex-situ microscopic images of the contaminated surface of the PW. The higher resolution of these images enables the quantification of particle count and size distribution. Moreover, the influence of the contamination degree of the PWs on the beam quality is investigated. A laser focus shift of up to 22.6 mm against the direction of beam propagation within a caustic measurement as well as a minor decrease in relative density of 0.08 pp in 316L samples were detected due to the contamination. Based on this work, methods for monitoring the health condition of PWs in LPBF can be derived.
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