Aging behavior of thermoplastic elastomers in the laser sintering process
- PDF / 870,570 Bytes
- 11 Pages / 584.957 x 782.986 pts Page_size
- 91 Downloads / 284 Views
Frank Wöllecke Rapid Technologies Center, BMW Group, Munich, Bavaria 80788, Germany
Christopher J. Tuck, Ruth D. Goodridge, and Richard J.M. Hague Additive Manufacturing and 3D Printing Research Group, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, United Kingdom (Received 25 February 2014; accepted 16 June 2014)
It is known that polymers used in laser sintering (LS) change their intrinsic properties due to processing conditions that are close to the crystalline melting temperature. This paper evaluates the aging behavior of a thermoplastic polyurethane powder, comparing with to a commercially available LS elastomeric material (DuraformÒFlex, 3D Systems). To represent a realistic production environment, the materials were aged during 14 processing cycles in the LS process without refreshing with virgin material. Following each aging cycle, both the powder and the sintered parts were examined for chemical and physical aging effects. The results showed that the materials observed could be used without refreshing throughout the 14 aging stages, however, changes in the processing behavior as well as in the parts’ mechanical properties were evident. These changes were due to the differing aging states of the LS-powder showing an increase in the particle size affecting the bulk materials packing density. Modifications in the rheological properties can be seen in a decrease of molecular weight likely to reduce the mechanical strength of tensile specimens.
I. INTRODUCTION
Powder bed fusion (PBF) is a category of additive manufacturing (AM) that includes the specific technology known as laser sintering (LS).1 LS is one of the main additive processes which can be used to produce functional parts by fusing together successive layers of polymer powder.2 LS is of interest to industry as it does not require tooling and therefore enables manufacturers to offer parts with a high degree of design freedom. This opens new opportunities toward an increased level of personalization or individualization and reduces the often high investments for tooling within luxury or one-off products. Furthermore, it is possible to combine many individual parts of an assembly into a single component helping to eliminate part numbers, inventory, assembly steps, labor, and inspection.3 Since there are many different requirements for polymer consumer products, it is clear that the current repertoire of available polymers in LS is no longer sufficient. The most common polymers used in LS are semicrystalline polymers typically polyamides (PA12 or PA11), polyamide-based compounds as well as some filled varieties and a small number of a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.172 J. Mater. Res., Vol. 29, No. 17, Sep 14, 2014
http://journals.cambridge.org
Downloaded: 09 Dec 2014
thermoplastic elastomers.4,5 During LS of polymers, the laser is used to only introduce the amount of energy needed to push the material into the melting phase, requiring that the majority of the e
Data Loading...
