Influence of the Origin of Polyamide 12 Powder on the Laser Sintering Process and Laser Sintered Parts

Abstract

Different features of polymer powders influence the process of laser sintering (LS) and the properties of LS-parts to a great extent. This study investigates important aspects of the "powder/process/part"-property relationships by comparing two polyamide 12 (PA12) powders commercially available for LS, with pronounced powder characteristic differences (Duraform ® PA and Orgasol ® Invent Smooth). Due to the fact that the primary influence factor on polymer behaviour, the chemical structure of the polymer chain, is identical in this case, the impacts resulting from powder distribution, particle shape, thermal behaviour, and crystalline and molecular structure, can be studied in detail. It was shown that although both systems are PA12, completely different processing conditions must be applied to accomplish high-resolution parts. The reason for this was discovered by the different thermal behaviour based on the powder production and the resulting crystalline structure. Moreover, the parts built from Orgasol ® Invent Smooth unveil mechanical properties with pronounced anisotropy, caused from the high melt viscosity and termination of polymer chains. Further differences are seen in relation to the powder characteristics and other significant correlations could be revealed. For example, the study demonstrated how the particle morphology and shape impact the surface roughness of the parts.

Production and Processing of a Spherical Polybutylene Terephthalate Powder for Laser Sintering

“…These results show that the melt emulsification process is exceptionally suited to produce particles with sizes and shapes that resemble and even surpass commercially used laser sintering materials. As demonstrated in [15][16][17][18][19], the particle shape to a large extent determines the flowability and packing density of the powder, and in this way the density and mechanical properties of produced parts. The favorable shape of the current PBT powder permits the production of dense, mechanically stable parts.…”

“…It was found that in general, a smooth and spherical particle shape contributes to the laser sintering material performance. In a comparison of two laser-sinterable PA12 powders, Schmid et al [19] found increased tensile strength and elongation at break for the powder with the higher sphericity. This was attributed at least partially to the improved packing density achieved with spherical particles.…”

“…The influence of blend ratio PBT/PEG on the particle size was investigated as well. An ideal and aimed for size range for typical laser sintering powders lies between 10-100 µm [19]. After optimization of extruder settings and blend ratio, the powder was extracted from the extrudate through a series of washing, drying, and classification steps.…”

“…Sci. 2019, 9, x FOR PEER REVIEW 4 of 17 lies between 10-100 µm [19]. After optimization of extruder settings and blend ratio, the powder was extracted from the extrudate through a series of washing, drying, and classification steps.…”

Acoustic absorption of passive destructive interference cavities

“…The laser sintering of PA12 is a manufacturing process where a solid body is created out of an unstructured and formless powder bed using focused laser power. This means that besides the shape, the properties of the part will also be created to a certain extent during the manufacturing process [53]. Accordingly, the properties of the processed material are as listed in Table 2.…”