Abstract
Powder flowability is key to achieving high process stability and part quality by application of smooth and dense layers in selective laser sintering (SLS). This study sheds light on the rarely investigated effect of tribo-electric charge build-up during powder delivery in the SLS process. This is achieved by a novel approach to quantify electrostatic potentials during doctor blading. The presented model setup is used in combination with charge spectrometry and impedance spectroscopy to investigate the alterations in tribo-electric charging behavior for the most commonly used laser sintering material polyamide 12 in its virgin and aged, c.f. reused, states. We show that the electrostatic charge build-up is significantly enhanced for aged polymer powder material, likely contributing to altered performance in SLS processing.
Highlights
The term Additive Manufacturing (AM) summarizes a variety of techniques that allow the manufacturing of parts from viscous, liquid, powdered or layered materials without the use of any tools or molds
The polymer material used in this study is a commercially available polyamide 12 (PA12)
Two kinds of conditioning were investigated, the virgin and an aged powder state, which has gone through three consecutive building processes in a FORMIGA P110 system (EOS GmbH, Krailling, Germany), each having a building time of 15.5 h, resulting in a cumulated building time of 46.5 h
Summary
The term Additive Manufacturing (AM) summarizes a variety of techniques that allow the manufacturing of parts from viscous, liquid, powdered or layered materials without the use of any tools or molds. AM enables easy individualization of parts and offers high freedom of design unmatched by any conventional manufacturing method, making it ideal and superior to subtractive methods for the manufacture of complex parts at low piece numbers [1]. Among them, fused filament fabrication (FFF), stereolithography (SLA) and binder jetting have become feasible in recent years and allow the production of parts with a wide variety of properties. The mechanical part properties still have to be improved for high loads [2]. One AM technique capable of producing dense parts with superior mechanical performance, favored in industrial environment is the powder-based selective laser sintering
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