Texture of inclined up-facing surfaces in laser powder bed fusion of metals

Metelková, Jitka; Vanmunster, Lars; Haitjema, Han; Hooreweder, Brecht Van

doi:10.1016/j.addma.2021.101970

Cited by 11 publications

(4 citation statements)

References 23 publications

(54 reference statements)

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“…In the rest of experiments listed, only flat surfaces are used for roughness evaluation. In [18], various inclinations are used to create stair-stepped ramps with a range of roughness values. Meanwhile, flat vertical faces are measured in [10].…”

Section: Ebmmentioning

confidence: 99%

Surface Characterisation and Comparison of Polymeric Additive Manufacturing Features for an XCT Test Object

Gallardo,

Concha,

Díaz

et al. 2023

KEM

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Additive manufacturing (AM) has experimented a huge development in recent years, improving the physical properties of parts produced by these technologies to the level of being capable of fabricating end-use functional products. High performance metals are widely used and studied; however, the reduction in material costs of polymers and their acceptable properties makes them suitable for common AM purposes. The intrinsic surface roughness of AM, as a consequence of the layer-by-layer technology, remains a challenge and its characterisation is necessary for quality control. X-Ray computed tomography (XCT), as a newly adapted evaluation technology for industrial applications, sets an opportunity for the dimensional measurement of AM parts, due to its capability of characterising the complex geometries that is possible to create with this manufacturing technologies. In this paper, a first approach to a surface characterisation of polymeric AM parts is presented. Several individual objects have been designed and manufactured using various polymeric AM technologies with different manufacturing principles (FDM, Polyjet, SLS) to build ramps with a range of surface roughness created by two main parameters (angle of inclination and layer thickness). Measurements have been carried out by an optical device (focal variation microscope, FVM), and a comparison with theoretical roughness values calculated following predictive models has been made, with the objective of analysing the behaviour of each surface. Results show that the influence of the angle of inclination is higher than the influence of layer thickness; post-processing, also, affects to the trueness of the real roughness comparing to the predicted one obtaining more unpredictable results.

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Section: Ebmmentioning

confidence: 99%

Surface Characterisation and Comparison of Polymeric Additive Manufacturing Features for an XCT Test Object

Gallardo,

Concha,

Díaz

et al. 2023

KEM

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“…Hence, the parameters affect both surfaces differently. Two primary contributors to upskin surface roughness are step edges and the agglomeration of partially sintered particles [ 14 , 15 ]. Strano et al [ 16 ] examined the relationship between overhang sloping angles and upskin surface roughness and found that for lower sloping angles, the staircase effect was the main cause of surface roughness, while at higher sloping angles, partially sintered particles attached to step edges was the dominant factor.…”

Section: Introductionmentioning

confidence: 99%

Influence of Pre- and Post-Contouring Strategies to Downskin Sloped Surfaces in Laser Powder-Bed Fusion (L-PBF) Additive Manufacturing

Valiyakath Vadakkan Habeeb,

Islam,

Chou

2024

Materials

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Among various metal additive manufacturing (AM) technologies, L-PBF is known for fabricating intricate components. However, due to step edges and powder particle attachments, attaining a good surface finish is challenging, especially on downskin surfaces. Contour scanning has potential to improve surface quality because such scanning may dominate the surface formation of sloped features. This study evaluates the effects of pre- and post-contouring strategies on the sloped downskin surfaces fabricated using a commercial L-PBF system with Ti6Al4V powder. L-PBF parts printed at inclination angles 30°, 45° and 60° were investigated. A double-contouring approach with varying processing conditions was employed and surface characteristics were analyzed using data acquired by white light interferometry. The average surface roughness, Sa, surface skewness, Ssk, and percentage area of powder particles attached onto surfaces were statistically evaluated. The lowest Sa obtained for pre- and post-contoured samples is 14.08 µm and 18.88 µm, respectively. For both strategies, the combination of a low laser power and a high scan speed on the interface of downskin surface and underneath powder results in smoother surfaces. However, while comparing both strategies, pre-contouring gives better surface finish for samples built at similar processing conditions, with a difference of nearly 5 µm in Sa.

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“…The inclined sample is one of the best examples to demonstrate the complexity of the surface quality issue in the L-PBF process. Both up-facing (up-skin) surfaces and down-facing (down-skin) surfaces suffer from a much lower surface finish compared to the in-skin surface [9]. Different factors contribute to the poor surface finish for up-and down-skin surfaces and have distinctive mechanisms [9].…”

Section: Introductionmentioning

confidence: 99%

“…Both up-facing (up-skin) surfaces and down-facing (down-skin) surfaces suffer from a much lower surface finish compared to the in-skin surface [9]. Different factors contribute to the poor surface finish for up-and down-skin surfaces and have distinctive mechanisms [9]. For an up-facing surface, the shape of the step edges and the number of attached powder particles on those edges dictate the surface quality [10].…”

Section: Introductionmentioning

confidence: 99%

Surface Formation of Sloping Features in Laser Powder–Bed Fusion by Multi-Track Multi-Layer Simulations

Chou

2023

Metals

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Laser powder–bed fusion (L-PBF) metal additive manufacturing has been widely utilized in various industries. However, large variability and inconsistent quality of the built parts still hinder the full potential of this manufacturing technology. Regarding part quality, the poor surface finish of sloping features remains one of the major shortcomings of L-PBF. The process parameters and contouring strategies have been identified as the primary factors dictating the surface roughness of the inclined surfaces, both up-skin and down-skin. Experimental approaches to modify the surface roughness by tuning contouring parameters could be costly and time-consuming. In addition, such methods cannot provide adequate physical insights into the phenomenon. Therefore, this study presents a multi-physics modeling framework to simulate a multi-track multi-layer L-PBF process in fabricating an inclined sample. The established simulation provides a valuable physical understanding of the driving forces exacerbating the formation and roughness of the inclined surfaces. The simulation results imply that the voids, formed due to insufficient melting in the low-energy contouring scan, are the leading cause of higher surface roughness for up-skin regions. On the other hand, though the visualization of attached particles is challenging regarding the down-skin surface, the simulated results show a lower and abnormal thermal gradient at the melt boundary due to the poorly supported melt region. The presence of thermal gradient irregularities suggests an overabundance of powder particles adhering to the melt boundary, resulting in increased surface roughness on the down-skin.

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Texture of inclined up-facing surfaces in laser powder bed fusion of metals

Cited by 11 publications

References 23 publications

Surface Characterisation and Comparison of Polymeric Additive Manufacturing Features for an XCT Test Object

Surface Characterisation and Comparison of Polymeric Additive Manufacturing Features for an XCT Test Object

Influence of Pre- and Post-Contouring Strategies to Downskin Sloped Surfaces in Laser Powder-Bed Fusion (L-PBF) Additive Manufacturing

Surface Formation of Sloping Features in Laser Powder–Bed Fusion by Multi-Track Multi-Layer Simulations

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