Investigation of porosity behavior in SLS polyamide-12 samples using <i>ex-situ</i> X-ray computed tomography

Ziółkowski, Grzegorz; Grochowska, Emilia; Kęszycki, Dawid; Gruber, Piotr; Hoppe, Viktoria; Szymczyk‐Ziółkowska, Patrycja; Kurzynowski, Tomasz

doi:10.2478/msp-2021-0035

Cited by 3 publications

(3 citation statements)

References 21 publications

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“…Pore sphericity is defined as the aerial ratio of the sphere to the pore where the sphere outlines the pore. The closer the value to one, the higher the pore sphericity is [29]. The results of the data from the individual series and between all the processes coincide with each other.…”

Section: Porositysupporting

confidence: 71%

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Influence of the AlSi7Mg0.6 Aluminium Alloy Powder Reuse on the Quality and Mechanical Properties of LPBF Samples

et al. 2022

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Additive manufacturing (AM) is dynamically developing and finding applications in different industries. The quality of input material is a part of the process and of the final product quality. That is why understanding the influence of powder reuse on the properties of bulk specimens is crucial for ensuring the repeatable AM process chain. The presented study investigated the possibility of continuous reuse of AlSi7Mg0.6 powder in the laser powder bed fusion process (LPBF). To date, there is no study of AlSi7Mg0.6 powder reuse in the LPBF process to be found in the literature. This study aims to respond to this gap. The five batches of AlSi7Mg0.6 powder and five bulk LPBF samples series were characterised using different techniques. The following characteristics of powders were analysed: the powder size distribution (PSD), the morphology (scanning electron microscopy—SEM), the flowability (rotating drum analysis), and laser light absorption (spectrophotometry). Bulk samples were characterised for microstructure (SEM), chemical composition (X-ray fluorescence spectrometry—XRF), porosity (computed tomography—CT) and mechanical properties (tensile, hardness). The powder was reused in subsequent processes without adding (recycling/rejuvenation) virgin powder (collective ageing powder reuse strategy). All tested powders (powders P0–P4) and bulk samples (series S0–S3) show repeatable properties, with changes observed within error limits. Samples manufactured within the fifth reuse cycle (series S4) showed some mean value changes of measured characteristics indicating initial degradation. However, these changes also mostly fit within error limits. Therefore, the collective ageing powder reuse strategy is considered to give repeatable LPBF process results and is recommended for the AlSi7Mg0.6 alloy within at least five consecutive LPBF processes.

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Section: Porositysupporting

confidence: 71%

“…Pore sphericity is defined as the aerial ratio of the sphere to the pore where the sphere outlines the pore. The closer the value to one, the higher the pore sphericity is [ 29 ].…”

Section: Resultsmentioning

confidence: 99%

Influence of the AlSi7Mg0.6 Aluminium Alloy Powder Reuse on the Quality and Mechanical Properties of LPBF Samples

et al. 2022

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“…The novelty of this work is the detailed characterisation of voids' shape, such as voids' 3D dimensions, aspect ratio, and orientation, inside the manufactured polymeric lattice structure. As discussed earlier, process-induced voids within the 3D printed samples have typically been represented as spheres in prior research and therefore, the effects of geometric parameters of voids on the mechanical properties of lattice structures under various load scenarios have been rarely investigated [106][107][108]. Although this study solely focuses on characterising void shapes through image processing techniques, the methods of defects characterisation and the subsequent findings will be applied to explore the effects of void shapes on the mechanical properties of additively manufactured lattice structures in future studies.…”

Section: Scope Of the Present Studymentioning

confidence: 99%

Characterisation of process-induced defects in polymeric strut-based lattice structures produced by powder bed fusion additive manufacturing process

Amirian,

Battley,

Amirpour

2024

Preprint

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Additive manufacturing processes can be utilised to fabricate lattice structures with robust mechanical performance and high energy-absorbing capacity, which have garnered significant attention in various sectors, such as aerospace, automobile, and bioengineering industries. Despite the advantages of 3D printing technologies, such as fabricating highly complex workpieces at low costs, additive manufacturing processes can cause defects and imperfections in final products that might degrade the desired mechanical properties. To gain insights into the effects of process-induced defects on the mechanical performance of lattice structures, and to optimise the printing parameters and lattice design for obtaining structures with minimum imperfections, detailed characterisation of manufacturing-induced defects is necessary. This study investigates the characteristics of process-induced defects in a polymeric BCC lattice structure created via the powder bed fusion process. X-ray computed tomography (CT) techniques are used to scan the printed lattice. Then, image processing methods, utilising MATLAB scripts, are developed to extract the characteristics (morphology and distribution) of imperfections. The image processing results reveal that geometry-related defects (i.e. thickness variation and the deviation of strut cross-sectional shape) and internal voids exist in the 3D-printed sample. The distribution patterns of defects indicate that geometric imperfections are more pronounced near the strut junctions. Detailed characterisation of internal voids’ shape, including 3D dimensions, aspect ratio, and orientation, which have been rarely investigated in previous studies, are explored in this research. The morphology of internal voids and the correlation between the size of voids and powder particles suggest that lack of fusion has led to void formation.

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Influence of bioactive metal fillers on microstructural homogeneity of PA12 composites produced by polymer Laser Sintering

Gruber

Ziółkowski

Olejarczyk

et al. 2022

Archiv.Civ.Mech.Eng

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In this paper, polyamide 12 (PA12) blends with three types of metallic fillers are tested, which differ in the type of material and its’ morphology. Low content mixtures are taken into consideration (0.5, 1.0, 2.0, 5.0 wt%), since a low impact on mechanical properties along with obtaining antibacterial properties are desired. The investigation focuses on filler distribution as well as the influence on microstructural homogeneity of the base material after processing with polymer Laser Sintering. Moreover, the influence of the filler content on the mechanical properties and fracture behaviour were examined. Processability PA12 with bioactive metal fillers was confirmed, and no significant changes in ductile behaviour of PA 12 were observed. An in-depth analysis of the effect of the filler on microstructural homogeneity was conducted. Graphical abstract

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Investigation of porosity behavior in SLS polyamide-12 samples using ex-situ X-ray computed tomography

Cited by 3 publications

References 21 publications

Influence of the AlSi7Mg0.6 Aluminium Alloy Powder Reuse on the Quality and Mechanical Properties of LPBF Samples

Influence of the AlSi7Mg0.6 Aluminium Alloy Powder Reuse on the Quality and Mechanical Properties of LPBF Samples

Characterisation of process-induced defects in polymeric strut-based lattice structures produced by powder bed fusion additive manufacturing process

Influence of bioactive metal fillers on microstructural homogeneity of PA12 composites produced by polymer Laser Sintering

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