On the reuse of SLS Polyamide 12 powder

• Published in: Materials Vol. 15; no. 16; pp. 1 - 16
• Main Authors: Gomes, Pedro C., Piñeiro, Oscar G., Alves, Alexandra C., Carneiro, O. S.
• Format: Journal Article
• Language: English
• Published: Switzerland Multidisciplinary Digital Publishing Institute (MDPI) 10.08.2022; MDPI AG; MDPI
• Subjects: Additive manufacturing; Aging; Computed tomography; Cooling; Crystallization; Cycle time; High temperature; Laser sintering; Lasers; Mechanical properties; Melt temperature; Milling and filtering; Moisture absorption; Molecular weight; Morphology; Polyamide 12; Polyamide resins; Polyamides; Polymers; Powder reuse; Powders; Printing; Process controls; Rapid prototyping; Residual stress; Science & Technology; Selective Laser Sintering; Sintering (powder metallurgy); Tensile tests; Polyamide 12; milling and filtering; powder reuse; morphology; Selective Laser Sintering; mechanical properties
• DOI: 10.3390/ma15165486
• ISSN: 1996-1944

In the Selective Laser Sintering (SLS) technique, the great majority of the powder involved is not included in the final printed parts, being just used as a support material. However, the quality of this powder is negatively affected during the process since it is subjected to high temperatures (close to its melting temperature) during a long time, i.e., the printing cycle time, especially in the neighborhood of the printed part contour. This type of powder is relatively expensive and large amounts of used powder result after each printing cycle. The present paper focuses on the reuse of Polyamide 12 (PA 12) powder. For this sake, the same PA 12 powder was used in consecutive printing cycles. After each cycle, the remaining non-used powder was milled and filtered before subsequent use. Properties of the powder and corresponding prints were characterized in each cycle, using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), computed tomography (CT), and tensile tests. It was concluded that subjecting the same powder to multiple SLS printing cycles affects the properties of the printed parts essentially regarding their morphology (voids content), mechanical properties reproducibility, and aesthetical aspect. However, post-processing treatment of the powder enabled to maintain the mechanical performance of the prints during the first six printing cycles without the need to add virgin powder. O.S.C. acknowledges funding by National Funds through the FCT—Portuguese Foundation for Science and Technology, References UIDB/05256/2020 and UIDP/05256/2020. A.C.A. acknowledges the partial support of the Portuguese Foundation for Science and Technology (FCT), Portugal, under the UIDB/04436/2020 project.