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ABSTRACT
In powder bed fusion additive processes the flow properties of the powder influence the quality of the final component and the efficiency of the process. In this investigation an attempt is made to identify flowability indicators which can describe the flow performance of the powder during the powder layering (i.e. recoating) step; common to all powder bed fusion processes. To this end, shear tests were performed by means of a powder rheometer. Bulk density, flow function and degree of cohesion were measured. The results suggest that there is a good correlation between the aforementioned parameters and the flowability of the powder during SLM processing. In addition, it was found that thermal treatments and tumbling enhance flowability. Thermal treatments were performed at 150, 200 and 250°C for a period of 10 min and in air.
Acknowledgement
Trelleborg Sealing Profiles AB is acknowledged for functional testing of the final component.
Disclosure statement
No potential conflict of interest was reported by the authors.
Notes on contributors
Sepehr Hatami completed his MSc degree in Materials Processing at the Royal Institute of Technology in Stockholm, Sweden. He obtained his PhD degree from Chalmers University of Technology (Gothenburg, Sweden) in 2010. His research was in the field of powder metallurgy with focus on the press and sinter technology. After his PhD studies, Sepehr joined SKF as a process specialist and worked several years with joining methods. Since 2015, he is part of the additive manufacturing group at Swerea IVF (a Swedish research institute). Currently, his research is focused on selective laser melting and he is involved in different nationally funded research projects in this area.
Ola Lyckfeldt is a project manager in the field of ceramic and metal powder processing at Swerea IVF; a research institute focused on material processing and manufacturing technologies. He was employed by the former Swedish Ceramic Institute (in 1989); which is now part of Swerea IVF. Ola’s expertise include surface chemistry, dry powder and suspension rheology, filtration processes (slip casting, pressure slip casting), direct casting techniques (Starch Consolidation, Protein Forming, Gel casting), powder granulation and, additive manufacturing. Ola is the author of about 40 publications in refereed scientific journals and conference proceedings as well as 4 patents within the ceramic and powder metallurgy field. Since 2000 he is part-time employed as a research manager in PowderPro AB, a company that develops and provides equipment for freeze granulation.
Lenny Tönnäng is a member of the additive manufacturing group at Swerea IVF (Mölndal, Sweden). He works with both metal and plastic additive manufacturing and his areas of interest are component design and construction. Lenny is a specialist in different AM techniques (SLA, SLM and FDM) as well as different machining operations (e.g. CNC, Wire EDM and Turning). Currently, he has focused on Selective Laser Melting and large scale plastic 3D printing with the aid of robots. Lenny has been working at Swerea IVF since 2006 and has previous industrial experience from Bodycote and Volvo.
Karin Fransson has a MSc degree in analytical chemistry from University of Gothenburg, Gothenburg, Sweden. In 2008 she joined Swerea IVF as a chemist working in Testing, Analysis and Certification group. Since 2015, she has joined the Additive Manufacturing group and currently works with both plastic and metal 3D printing. Her activities are mainly focused on the operational aspects of the Selective Laser Melting process. Karin is an expert operator of SLM Solutions 125HL system. She has completed different advanced courses given by SLM Solutions and Materialise.