Yannis Kinds's scientific contributions

Publications (6)

Article
Full-text available
Insufficient surface quality is one of the common issues encountered in laser powder bed fusion (LPBF). In order to meet the industrial requirements, it is typically necessary to proceed to expensive and time-consuming post-processing. Improving surface quality during the building process would hence be very beneficial. However, in situ remelting (...
Article
In this article, the laser-based powder bed fusion (L-PBF) processing behavior of pure copper powder is evaluated by employing a conventional infrared fiber laser with a wavelength of 1080 nm, a small focal spot diameter of 37.5 µm, and power levels up to 500 W. It is shown that bulk solid copper parts with near full density (ρ Archimedes = 99.3 ±...
Article
Full-text available
Surface quality of parts produced by laser powder bed fusion (LPBF) is often insufficient for their final application. Up-facing inclined surfaces are among the major challenges, due to the combination of elevated edges (edge effect) and the staircase effect. This work presents a novel methodology to enhance the quality of inclined surfaces using a...
Conference Paper
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Multi kilowatt single mode lasers are increasingly being used in Selective Laser Melting (SLM), typically with the aim of improving productivity. However, the high power densities present in the optical path lead to a thermally induced focal shift i.e. thermal lensing. Whilst thermal lensing has been studied for many processes, its impact on parts...
Article
Full-text available
Despite its many benefits, Selective Laser Melting's (SLM) relatively low productivity compared to deposition-based additive manufacturing techniques is a major drawback. Increasing the laser beam diameter improves SLM's build rate, but causes loss of precision. The aim of this study is to investigate laser beam focus shift, or “defocus” using a dy...
Article
Full-text available
Powder bed preheating is a promising development in selective laser melting (SLM), mainly applied to avoid large thermal stresses in the material. This study analyses the effect of in-process preheating on microstructure, mechanical properties and residual stresses during SLM of H13 tool steel. Sample parts are produced without any preheating and a...

Citations

... This transition plays a vital role in LPBF processing of highly reflective materials such as copper. Jadhav et al. [84] have used the melt pool aspect ratio to determine the laser power and scan speed values where the keyhole mode of heat transfer can be achieved in LPBF processing of pure copper. ...
... Commonly such lasers have been employed for processing Cu alloys, glass, and ceramics in ablation-based micromachining applications [15][16][17]. The ns-pulsed lasers are generally characterized by high peak powers (P pk > 10 kW) and are not suited for LPBF as they induce severe powder ejection and powder bed instability due to the shockwave generated during ablation [18]. Such laser sources have been used in the early LPBF research [19] and successively abandoned as the CW fiber lasers became commercially available. ...
... Compared with the pulsed laser, the continuous wave (CW) laser has a higher energy and a long action time, which could remelt metal superficial layer more sufficiently and increase the depth of the molten pool, and then a surface with higher quality finish and better mechanical properties could be obtained (Nesli and Yilmaz (2021) and Yung et al. (2019). To improve the laser polishing quality of AM parts, a dual laser beam polishing method was proposed by Metelkova et al. (2020Metelkova et al. ( , 2021a recently. Firstly, the pulsed laser was used to generate laser-induced shock waves on the metal surfaces to remove the powder on the surface. ...
... An example of a frequent machine-related systematic variation is when gaseous byproducts (soot) released from powder fusion builds up on the laser optical window. The soot absorbs a portion of the laser energy which causes localized heating and thermal expansion of the optical window, changing the focal length of the optical system (known as thermal lensing) [12][13][14]. These anomalies in the laser focus often lead to poor material consolidation, which in turn results in lack-of-fusion porosity [14]. ...
... The cross-sectional area of the laser beam varies with height, and thus the laser spot size refers to the size of the laser beam when in focus. Some of the studies have reported a productivity increase of about 840% by using dynamic laser units to control the laser focus-defocus [68]. Laser spot size diameters for most of the AM techniques range between 50 and 600 µm. ...
... In particular, the H13 high strength steel is widely used as structural steels, tool steels and/or mold steels due to its high strength, good machinability and temper resistance [35][36][37]. For the SLM-fabricated H13 high strength steel, its microstructure, microhardness, mechanical properties and structural performance at the cross-section level have been widely investigated [34,[38][39][40][41][42][43]. A fundamental understanding of residual stresses within the SLM-fabricated H13 high strength steel hollow sections, however, is still lacking. ...