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. 2024 Nov 25;16(23):3278.
doi: 10.3390/polym16233278.

Support-Free Low-Temperature Laser-Based Powder Bed Fusion of Polymers Using a Semi-Sintering Process

Ryuichi Kobayashi  1 , Takashi Kigure  1 , Yuki Yamauchi  1
Affiliations

Support-Free Low-Temperature Laser-Based Powder Bed Fusion of Polymers Using a Semi-Sintering Process

Ryuichi Kobayashi et al. Polymers (Basel). .

Abstract

In conventional laser-based powder bed fusion of polymers (PBF-LB/P), aging of the powder due to preheating of the powder bed is a significant issue. This paper proposes a method for low-temperature PBF-LB/P using a semi-sintering process that minimizes powder aging caused by preheating. By partially semi-sintering the low-temperature powder bed, it was possible to execute the PBF-LB/P while avoiding the aging of most of the powder. Furthermore, the suppression of curling by the semi-sintered body eliminated the need to connect the base plate to the parts, which was necessary in previously reported low-temperature PBF-LB/P. Using the semi-sintering process, we successfully built cuboid and tensile test specimens in a polyamide 11 powder bed maintained below the crystallization temperature, where the powder hardly aged. The apparent densities of the built specimens were comparable to those produced using high-temperature PBF-LB/P. However, the elongation in the building direction of the built parts by the semi-sintering process should be improved. This study represents the first step toward the practical application of low-temperature PBF-LB/P using semi-sintering.

Keywords: laser sintering; low-temperature powder bed fusion; semi-sintering.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Schematic of low-temperature PBF-LB/P using a semi-sintering process. In this process, (a) Preheating, (b) First laser irradiation, and (c) Second laser irradiation are sequentially performed within the same layer.
Figure 2
Figure 2
Three-dimensional model for building the cuboid specimen: (a) cuboid with anchors, (b) cuboid without anchors.
Figure 3
Figure 3
Three-dimensional model showing the basic shapes of the tensile test specimen and semi-sintered body: (a) isometric view, (b) front view.
Figure 4
Figure 4
Three-dimensional model with warpage correction.
Figure 5
Figure 5
Slices calculated from body EE: (a) stack, (b) widest slice.
Figure 6
Figure 6
Three-dimensional model of a tensile test specimen with its build direction and longitudinal direction aligned: (a) isometric view, (b) front view.
Figure 7
Figure 7
Relationship between the powder preheating temperature and changes in powder properties.
Figure 8
Figure 8
DSC curve of virgin PA11 powder.
Figure 9
Figure 9
Image of the powder bed after laser irradiation.
Figure 10
Figure 10
Cuboid specimen with a semi-sintered body: (a) as built, (b) during the removal of semi-sintered body.
Figure 11
Figure 11
SEM image of the semi-sintered body; the arrow indicates the necking formation between the powder particles.
Figure 12
Figure 12
Images of cuboid specimens built under various laser parameters.
Figure 13
Figure 13
Apparent density of cuboid specimens with and without anchors.
Figure 14
Figure 14
Representative images of the 3D scan data of the tensile specimen. A–A shows the location where the effectiveness of warp correction was evaluated.
Figure 15
Figure 15
Cross-sectional view of the 3D scan data of tensile test specimens.
Figure 16
Figure 16
Tensile test results: (a) stress–strain curves of specimens built using 3D model EE (note that m-7_z2 shows the results of the 3D model GG for comparison), (b) stress–strain curves of specimens built using the 3D model GG.
Figure 17
Figure 17
X-ray CT scanning images of specimens: (a) m-5, (b) m-7, (c) m-9. White arrows point to the regions where interlayer bonding was insufficient.
Figure 18
Figure 18
DSC curves of the tensile test specimen, semi-sintered body, and powder aged at 150 °C.
See this image and copyright information in PMC

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