Recycle of PA12 Scrap: Mechanical and Structural Performance of FDM Printed Parts from SLS Waste

Additive manufacturing is rapidly expanding across industries but generates substantial polymer waste, particularly in Selective Laser Sintering (SLS), of which considerable quantities of unfused powder and faulty prints are typically discarded. The development of sustainable recycling pathways is therefore essential to minimize losses in material and adopt circular economy strategies in polymer processing.

In the present research, a recycling process is proposed for polyamide 12 (PA12) waste retrieved from SLS 3–Dimensional (3D) printer. Faulty parts and scrap material were collected, mechanically pulverized to an average particle size of ~2 mm for ease of handling, and subsequently reprocessed with a filament extrusion system. Homogeneous continuous filament with a diameter of 1.75 ± 0.05 mm was successfully produced and used as Fused Deposition Modeling (FDM) input material. Standardized tensile (ASTM D638) and compressive (ASTM D695) test samples were printed using FDM for determination of the mechanical properties of the recycled material.

Since the PA12 would undergo three (3) consecutive thermal cycles—initial sintering in SLS, re-melting in filament extrusion, and FDM printing—this study addresses the measurement of the effects of these thermal cycles on the structural integrity and mechanical behavior of the resultant FDM prints. In addition, Differential Scanning Calorimetry (DSC) and X-ray Diffraction (XRD) analyses were performed to investigate the semi-crystalline nature of PA12 and to evaluate possible changes in crystallinity after recycling. The outcomes of mechanical testing provide information on the retention of properties and compatibility of recycled PA12 as an input for FDM. The outcomes reveal the possibility of converting SLS scrap into FDM filament and demonstrate a feasible recycling process that not only minimizes polymer waste but also enhances material usage on multiple platforms of additive manufacturing.