scholarly journals The Effects of Virgin and Recycled PA12 Powders in SLS Processes on Occupational Exposures

2021 ◽  
Vol 12 (11) ◽  
pp. 339-345
Author(s):  
Amir Abdullah Muhamad Damanhuri ◽  
◽  
Azian Hariri ◽  
Sharin Ab Ghani ◽  
Mohd Syafiq Syazwan Mustafa ◽  
...  
Keyword(s):  
Ultrafine Particles ◽  
Selective Laser Sintering ◽  
Occupational Exposures ◽  
Post Processing ◽  
Polyamide 12 ◽  
Total Particle ◽  
Personal Air Sampling ◽  
Working Practices ◽  
Particulate Concentration ◽  
Respirable Particulate

Particulate matter and ultrafine particles are emitted during the pre-processing and post-processing activities of selective laser sintering (SLS) processes, which is major concern to operators exposed to the powders. This study aims to determine the occupational exposure (in terms of the total particle concentration and respirable particulate concentration) during the pre-processing and post-processing activities of SLS processes using virgin and recycled polyamide 12 (PA12) powders. Personal air sampling was performed for each activity according to the NIOSH 0500 and NIOSH 0600 methods. Based on the results, both powders were uniform spheres with a particle size of 40–60 μm. The total particulate concentration was most significant during the following pre-processing activities: 1) pouring powder into the mixing machine and 2) transferring the powder to the SLS AM machine. The total particulate concentration and respirable particulate concentration were slightly higher for the virgin powder for these activities. In conclusion, the virgin and recycled PA12 powders were both inhalable and respirable, which poses serious health hazards to the SLS AM operators. Hence, it is essential for operators to use suitable personal protective equipment (including respirators) and the working practices need to be improved by automating

Study in performance and morphology of polyamide 12 produced by selective laser sintering technology

2018 ◽  
Vol 24 (5) ◽  
pp. 813-820 ◽  
Author(s):  
Junjie Wu ◽  
Xiang Xu ◽  
Zhihao Zhao ◽  
Minjie Wang ◽  
Jie Zhang
Keyword(s):  
Selective Laser Sintering ◽  
Polarized Light ◽  
Chain Scission ◽  
High Energy ◽  
Laser Sintering ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Content Type ◽  
X Ray ◽  
Polyamide 12

Purpose The purpose of this paper is to investigate the effect of selective laser sintering (SLS) method on morphology and performance of polyamide 12. Design/methodology/approach Crystallization behavior is critical to the properties of semi-crystalline polymers. The crystallization condition of SLS process is much different from others. The morphology of polyamide 12 produced by SLS technology was investigated using scanning electron microscopy, polarized light microscopy, differential scanning calorimetry, X-ray diffraction and wide-angle X-ray diffraction. Findings Too low fill laser power brought about bad fusion of powders, while too high energy input resulted in bad performance due to chain scission of macromolecules. There were three types of crystal in the raw powder material, denoted as overgrowth crystal, ring-banded spherulite and normal spherulite. Originality/value In this work, SLS samples with different sintering parameters, as well as compression molding sample for the purpose of comparison, were made to study the morphology and crystal structure of sintered PA12 in detail.

scholarly journals A Comprehensive 3D-Molded Bone Flap Protocol for Patient-Specific Cranioplasty

2021 ◽  
Author(s):  
Raphael Bertani ◽  
Caio Moreno Perret Novo ◽  
Pedro Henrique Freitas ◽  
Amanda Amorin Nunes ◽  
Thiago Nunes Palhares ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Low Cost ◽  
Selective Laser Sintering ◽  
Operating Time ◽  
Ct Scanning ◽  
Patient Specific ◽  
Manufacturing Cost ◽  
Post Processing ◽  
Cross Sectional ◽  
Cranial Defect

Abstract We present a detailed step-by-step approach for the low-cost production and surgical implantation of cranial prostheses, aimed at restoring aesthetics, cerebral protection, and facilitating neurological rehabilitation. This protocol uses combined scan computed tomography (CT) cross-sectional images, in DICOM format, along with a 3D printing (additive manufacturing) setup. The in-house developed software InVesalius®️ is an open-source tool for medical imaging manipulation. The protocol describes image acquisition (CT scanning) procedures, and image post-processing procedures such as image segmentation, surface/volume rendering, mesh generation of a 3D digital model of the cranial defect and the desired prostheses, and their preparation for use in 3D printers. Furthermore, the protocol describes a detailed powder bed fusion additive manufacturing process, known as Selective Laser Sintering (SLS), using Polyamide (PA12) as feedstock to produce a 3-piece customized printed set per patient. Each set consists of a “cranial defect printout” and a “testing prosthesis” to assemble parts for precision testing, and a cranial “prostheses mold” in 2 parts to allow for the intraoperative modeling of the final implant cast using the medical grade Poly(methyl methacrylate) (PMMA) in a time span of a few min. The entire 3D processing time, including modelling, design, production, post-processing and qualification, takes approximately 42 h. Modeling the PMMA flap with a critical thickness of 4 mm by means of Finite Element Method (FEM) assures mechanical and impact properties to be slightly weaker than the bone tissue around it, a safety design to prevent fracturing the skull after a possible subsequent episode of head injury. On a parallel track, the Protocol seeks to provide guidance in the context of equipment, manufacturing cost and troubleshooting. Customized 3D PMMA prostheses offers a reduced operating time, good biocompatibility, and great functional and aesthetic outcomes. Additionally, it offers greater than 15-fold cost advantage over the usage of other materials, including metallic parts produced by additive manufacturing.

scholarly journals Selective laser sintering of copper filled polyamide 12: Characterization of powder properties and process behavior

2018 ◽  
Vol 40 (5) ◽  
pp. 1801-1809 ◽  
Author(s):  
Lydia Lanzl ◽  
Katrin Wudy ◽  
Sandra Greiner ◽  
Dietmar Drummer
Keyword(s):  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Polyamide 12 ◽  
Process Behavior ◽  
Powder Properties

scholarly journals Hybrid Approaches for Selective Laser Sintering by Building on Dissimilar Materials

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5285
Author(s):  
Babette Goetzendorfer ◽  
Thomas Mohr ◽  
Ralf Hellmann
Keyword(s):  
Substrate Surface ◽  
Selective Laser Sintering ◽  
Dissimilar Materials ◽  
Polyamide 6 ◽  
Laser Sintering ◽  
New Approach ◽  
Metallic Substrates ◽  
Polyamide 12 ◽  
Melting Temperatures ◽  
Hybrid Approaches

We introduced a new approach in selective laser sintering for hybrid multicomponent systems by fabricating the sintered polyamide 12 (PA12) part directly onto a similar (PA12) or dissimilar (polyamide 6 (PA6) and tool steel 1.2709) joining partner. Thus, the need for adhesive substances or joining pressure was completely circumvented, leading to the possibility of pure hybrid lightweight bi-polymer or metal–polymer systems. By taking advantage of the heating capabilities of the sinter laser regarding the substrate surface, different exposure strategies circumvented the lack of overlapping melting temperatures of dissimilar polymers. Therefore, even sintering on non-PA12 polymers was made possible. Finally, the transfer on metallic substrates—made up by selective laser melting (SLM)—was successfully performed, closing the gap between two powder-based additive processes, selective laser sintering (SLS) and SLM.

Surface roughness of polyamide 12 parts manufactured using selective laser sintering

2019 ◽  
Vol 80 ◽  
pp. 106094 ◽  
Author(s):  
Sean Petzold ◽  
James Klett ◽  
Andrew Schauer ◽  
Tim A. Osswald
Keyword(s):  
Surface Roughness ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Polyamide 12

Characterization and Quantification of Ultrafine Particles and Carbonaceous Components from Occupational Exposures to Diesel Particulate Matter in Selected Workplaces

2020 ◽  
Vol 64 (5) ◽  
pp. 490-502 ◽  
Author(s):  
Alan da Silveira Fleck ◽  
Cyril Catto ◽  
Gilles L’Espérance ◽  
Jean-Philippe Masse ◽  
Brigitte Roberge ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Size Distribution ◽  
Ultrafine Particles ◽  
Occupational Exposures ◽  
Total Carbon ◽  
Geometric Standard Deviation ◽  
Diesel Particulate Matter ◽  
Subway Tunnel ◽  
Diesel Particulate ◽  
Exposure Levels

Abstract Questions still exist regarding which indicator better estimates worker’s exposure to diesel particulate matter (DPM) and, especially for ultrafine particles (UFP), how exposure levels and the characteristics of the particles vary in workplaces with different exposure conditions. This study aimed to quantify and characterize DPM exposures in three workplaces with different exposure levels: an underground mine, a subway tunnel, and a truck repair workshop. The same sampling strategy was used and included measurements of the particle number concentration (PNC), mass concentration, size distribution, transmission electron microscopy (TEM), and the characterization of carbonaceous fractions. The highest geometric means (GMs) of PNC and elemental carbon (EC) were measured in the mine [134 000 (geometric standard deviation, GSD = 1.5) particles cm−3 and 125 (GSD = 2.1) µg m−3], followed by the tunnel [32 800 (GSD = 1.7) particles cm−3 and 24.7 (GSD = 2.4) µg m−3], and the truck workshop [22 700 (GSD = 1.3) particles cm−3 and 2.7 (GSD = 2.4) µg m−3]. This gradient of exposure was also observed for total carbon (TC) and particulate matter. The TC/EC ratio was 1.4 in the mine, 2.5 in the tunnel and 8.7 in the workshop, indicating important organic carbon interference in the non-mining workplaces. EC and PNC were strongly correlated in the tunnel (r = 0.85; P < 0.01) and the workshop (r = 0.91; P < 0.001), but a moderate correlation was observed in the mine (r = 0.57; P < 0.05). Results from TEM showed individual carbon spheres between 10 and 56.5 nm organized in agglomerates, while results from the size distribution profiles showed bimodal distributions with a larger accumulation mode in the mine (93 nm) compared with the tunnel (39 nm) and the truck workshop (34 nm). In conclusion, the composition of the carbonaceous fraction varies according to the workplace, and can interfere with DPM estimation when TC is used as indicator. Also, the dominance of particles <100 nm in all workplaces, the high levels of PNC measured and the good correlation with EC suggest that UFP exposures should receive more attention on occupational routine measurements and regulations.

Sign in / Sign up

Export Citation Format

Share Document