Abstract
High Speed Sintering is a novel powder-bed fusion Additive Manufacturing technique that uses an infrared lamp to provide intensive thermal energy to sinter polymer powders. The amount of thermal energy is critical to particle coalescence related defects such as porosity. This study investigates the effect of energy input on porosity and the resulting mechanical properties of polyamide-12 parts. Samples were produced at different lamp speeds, generating varying amount of energy input from a low to a high level. They were then scanned using X-ray Computed Tomography technique, following which they were subject to tensile testing. A strong correlation between energy input, porosity and mechanical properties was found, whereby pore formation was fundamentally caused by insufficient energy input. A greater amount of energy input resulted in a reduced porosity level, which in turn led to improved mechanical properties. The porosity, ultimate tensile strength and elongation achieved were 0.58%, 42.4 MPa and 10.0%, respectively, by using the standard parameters. Further increasing the energy input resulted in the lowest porosity of 0.14% and the highest ultimate tensile strength and elongation of 44.4 MPa and 13.5%, respectively. Pore morphology, volume, number density and spatial distribution were investigated, which were found to be closely linked with energy input and mechanical properties.
Highlights
With continued technology evolution, Additive Manufacturing (AM) is gaining increasing interests due to its capability of producing geometrically complex end-use parts in low to medium volume production [1,2]
High Speed Sintering is a novel powder bed fusion (PBF) polymer AM technique, which is different to other polymer AM processes (e.g. Laser Sintering) in terms of thermal behaviour
There is a lack of understanding of porosity of parts produced via High Speed Sintering (HSS)
Summary
Additive Manufacturing (AM) is gaining increasing interests due to its capability of producing geometrically complex end-use parts in low to medium volume production [1,2]. High Speed Sintering (HSS) is an advanced powder bed fusion polymer AM technique aimed at medium to high volume production [6]. Dewulf et al [11] investigated the influence of laser power, hatch spacing and scan speed on the size and distribution of pores in Laser Sintering (LS). O'Connor et al [19] examined the porosities of PA12 and glass bead filled PA12 parts produced by HP's Multi Jet Fusion (MJF) technique. Both parts were found to be lower than 1% porosity, but the PA12 part exhibited a significantly higher Ultimate Tensile Strength (UTS) and Elongation at Break (EAB). Craft et al [20] compared the porosity of PA12 samples produced by LS, MJF and large area projection sintering processes, and a general trend observed was that samples with a lower porosity exhibited a higher EAB
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