Effects of polyamide-11 powder refresh ratios in multi-jet fusion: A comparison of new and used powder

Pandelidi, Chrysoula; Lee, Kok Peng Marcian; Kajtaz, Mladenko

doi:10.1016/j.addma.2021.101933

Cited by 18 publications

(29 citation statements)

References 23 publications

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“…Industrial sectors such as medical, aerospace and architecture have benefitted immensely from the use of additive manufacturing and more specifically the PBF technology. This is a result of the advantages the technology offers including customization, light-weighting, and the ability to create complex geometries [6][7][8][9]. The most common PBF technique is laser sintering (LS) [3], but more recently, HP introduced the multi-jet fusion (MJF) process [7].…”

Section: Introductionmentioning

confidence: 99%

“…This is a result of the advantages the technology offers including customization, light-weighting, and the ability to create complex geometries [6][7][8][9]. The most common PBF technique is laser sintering (LS) [3], but more recently, HP introduced the multi-jet fusion (MJF) process [7]. Both processes involve storing thermoplastic powder at an elevated temperature, close to the melting point, before the localised application of heat to consolidate the material into a 3D part [3].…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Physical Aging and Degradation on the Re-Use of Polyamide 12 in Powder Bed Fusion

et al. 2022

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Powder bed fusion (PBF) is an additive manufacturing (AM) technique which offers efficient part-production, light-weighting, and the ability to create complex geometries. However, during a build cycle, multiple aging and degradation processes occur which may affect the reusability of the Polyamide 12 (PA-12) powder. Limited understanding of these phenomena can result in discarding re-usable powder unnecessarily, or the production of parts with insufficient properties, both of which lead to significant amounts of waste. This paper examines the thermal, chemical, and mechanical characteristics of PA-12 via an oven storage experiment that simulates multi jet fusion (MJF) conditions. Changes in the properties of PA-12 powder during oven storage showed two separate, time-dependent trends. Initially, differential scanning calorimetry showed a 4.2 °C increase in melting temperature (Tm) and a rise in crystallinity (Xc). This suggests that secondary crystallisation is occurring instead of, or in addition to, the more commonly reported further polycondensation process. However, with extended storage time, there were substantial reductions in Tm and Xc, whilst an 11.6 °C decrease in crystallisation temperature was observed. Fourier transform infrared spectroscopy, a technique rarely used in PBF literature, shows an increased presence of imide bonds—a key marker of thermo-oxidative degradation. Discolouration of samples, an 81% reduction in strength and severe material embrittlement provided further evidence that thermo-oxidative degradation becomes the dominant process following extended storage times beyond 100 h. An additional pre-drying experiment showed how moisture present within PA-12 can also accelerate degradation via hydrolysis.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Effect of Physical Aging and Degradation on the Re-Use of Polyamide 12 in Powder Bed Fusion

et al. 2022

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“…Polyamide 11, being a bioplastic that belongs to the nylon family, is unique among other polyamides in that it is non-petroleum sourced [22] and is derived from castor plants [23]. It is also less common than, e.g., PA12 in the field of 3D printing.…”

Section: Introductionmentioning

confidence: 99%

The Influence of the Material Type and the Placement in the Print Chamber on the Roughness of MJF-Printed 3D Objects

Dzienniak

2022

Machines

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This paper describes a surface-roughness study performed on samples manufactured additively using the Multi Jet Fusion (MJF) technology. The samples were divided into three groups based on the material used in the process: polypropylene (PP), thermoplastic polyurethane (TPU), and polyamide 11 (PA11). Subsequently, they were tested by means of a roughness-measuring system, which made it possible to determine the typical surface roughness parameters (Ra, Rq, Rz). The tests were designed to examine whether the placement and orientation of 3D objects while printing, in connection with the material used, can significantly influence the surface quality of MJF-printed objects. The results show that the TPU samples have a surface roughness much higher than the PP and PA11 ones, which exhibit roughness levels very similar to each other. It can also be concluded that surfaces printed vertically (along the Z-axis) tend to be less smooth—similarly to the surfaces of objects made of TPU located in the central zones of the print chamber during printing. This information may be of value in cases where low surface roughness is preferred (e.g., manufacturing patient-specific orthoses), although this particular study does not focus on one specific application.

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“…One of the advantages of this processing technique is the ability to produce parts with high geometric complexity. Pandelidi et al [ 50 ] characterized PA11 powders processed by the multi-jet fusing technique (MJF, another category of PBF techniques) and investigated the effects of PA11 refresh ratios on its mechanical performance. These two polyamides are favorable in these techniques due to the broad temperature range between their melting and crystallization temperature during heating and cooling, respectively.…”

Section: Introductionmentioning

confidence: 99%

Comparative Characterization of Hot-Pressed Polyamide 11 and 12: Mechanical, Thermal and Durability Properties

2021

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Chemically speaking, polyamide 11 (PA11) and polyamide 12 (PA12) have a similar backbone, differing only in one carbon. From an origin point of view, PA11 is considered a bioplastic polyamide composed from renewable resources, compared to oil-based PA12. Each of them has a number of advantages over the other, which makes their selection a challenging issue. Depending on the target application, diverse assessments and comparisons are needed to fulfill this mission. The current study addresses this research gap to characterize and compare PA11 and PA12 manufactured by the hot press technique in terms of their mechanical, thermal and durability properties for the first time, demonstrating their potential for future works as matrices in composite materials. In this regard, different characterization techniques are applied to the hot-pressed polymer sheets, including X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The mechanical performance of the PA11 and PA12 sheets is compared based on tensile tests and shore hardness measurement. The durability behavior of these two polyamides is evaluated in water and relative humidity conditions at different aging times. The experimental results show the ductile behavior of PA12 with respect to the quasi-brittle PA11. Both have a relatively small water and moisture gain: 1.5 wt% and 0.8 wt%, respectively. The higher crystallinity of PA12 (2.1 times more than PA11) with γ-phase is one of the leading parameters to achieve better mechanical and durability properties. The FTIR spectra displayed slight acid hydrolysis. Accordingly, absorbed water or moisture does not cause plasticization; thus, neither hardness nor dimension changes.

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Effects of polyamide-11 powder refresh ratios in multi-jet fusion: A comparison of new and used powder

Cited by 18 publications

References 23 publications

The Effect of Physical Aging and Degradation on the Re-Use of Polyamide 12 in Powder Bed Fusion

The Effect of Physical Aging and Degradation on the Re-Use of Polyamide 12 in Powder Bed Fusion

The Influence of the Material Type and the Placement in the Print Chamber on the Roughness of MJF-Printed 3D Objects

Comparative Characterization of Hot-Pressed Polyamide 11 and 12: Mechanical, Thermal and Durability Properties

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