Volume energy density and laser power: key determinants in SLS-processed PA12 mechanical properties

Abstract

Additive manufacturing (AM) represents a significant breakthrough in the field of engineering, revolutionizing the way products and components are designed and manufactured. Among the various methods used to employ polymer materials in AM, powder bed fusion (PBF) processes, specifically selective laser sintering (SLS), stand out as one of the most widely utilized approaches. This method offers substantial advantages over other AM techniques for treating polymers. However, SLS is inherently based on complex underlying physical mechanisms and phenomena and it involves a significant number of process parameters, making a comprehensive and extensive study of the process necessary. In the present article, we conduct an experimental study to examine the impact of two pivotal process parameters in SLS: volumetric energy density (VED) and nominal laser power (LP), on the mechanical properties of Polyamide 12 (PA12). The assessment of the material’s mechanical behavior was conducted by measuring its tensile, compressive, and flexural properties, adhering to the respective ASTM standards. Additionally, we employed appropriate statistical tests, including the Coefficient of Variation (CV) to estimate the process’s repeatability and consistency, and Fisher’s least significant difference (LSD) method to determine significant differences between mean property values for different process parameters. The results revealed the impact of volumetric energy density (VED) and nominal laser power (LP) on each mechanical property and mechanical index. Furthermore, the study identifies general rules and trends related to the efficiency and feasible thresholds of the process. Finally, we provide an interpretation of the results based on the fundamental physical mechanisms, also supported by the respective XRD and microscopy images.

Optimization of Mechanical Properties and Evaluation of Fatigue Behavior of Selective Laser Sintered Polyamide-12 Components

“…At higher applied energy densities, an elevated crystallinity was observed, and material discontinuity was reduced [2,18]. Better coherence and lower porosities within the material structure lead to improved fatigue behavior, as defects cause crack initiation and propagation [22]. For lower applied energy densities, porosities evolve due to a lack of fusion between two successive layers [23].…”

Impact of Part Positioning along Chamber Z-Axis and Processing Parameters in Selective Laser Sintering on Polyamide Properties

“…Energy density depends on the power and speed of the laser and on the hatch distance or on the laser beam diameter [1,[4][5][6][7][8][9].…”

“…Fit statistics for the thickness at the lower level of the working chamber. = 4.99 − 4.86 × HD − 0.016 × α + 0.073 × HD × α + 6.52 × HD 2 + 0.000026 × α 2 − 0.10009 × HD 2 × α(9) …”