Mechanical behavior of calcium sulfate scaffold prototypes built by solid free-form fabrication Mitra Asadi-Eydivand Biomedical Engineering, Amirkabir University of Technology, Tehran, Islamic Republic of Iran and Biomedical Engineering, University of Malaya, Kuala Lumpur, Malaysia Mehran Solati-Hashjin Biomedical Engineering, Amirkabir University of Technology, Tehran, Islamic Republic of Iran, and Noor Azuan Abu Osman Department of Biomedical Engineering, Center for Applied Biomechanics, University Malaya, Kuala Lumpur, Malaysia and University of Malaysia Terengganu, Terenggganu, Malaysia Abstract Purpose – This paper aims to investigate the mechanical behavior of three-dimensional (3D) calcium sulfate porous structures created by a powder- based 3D printer. The effects of the binder-jetting and powder-spreading orientations on the microstructure of the specimens are studied. A micromechanical finite element model is also examined to predict the properties of the porous structures under the load. Design/methodology/approach – The authors printed cylindrical porous and solid samples based on a predefined designed model to study the mechanical behavior of the prototypes. They investigated the effect of three main build bed orientations (x, y and z) on the mechanical behavior of solid and porous specimens fabricated in each direction then evaluated the micromechanical finite-element model for each direction. The strut fractures were analyzed by scanning electron microscopy, micro-computed tomography and the von Mises stress distribution. Findings – Results showed that the orientation of powder spreading and binder jetting substantially influenced the mechanical behavior of the 3D- printed prototypes. The samples that were fabricated parallel to the applied load had higher compressive strength compared with those printed perpendicular to the load. The results of the finite element analysis agreed with the results of the experimental mechanical testing. Research limitations/implications – The mechanical behavior was studied for the material and the 3D-printing machine used in this research. If one were to use another material formulation or machine, the printing parameters would have to be set accordingly. Practical implications – This work aimed to re-tune the control factors of an existing rapid prototyping process for the given machine. The authors achieved these goals without major changes in the already developed hardware and software architecture. Originality/value – The results can be used as guidelines to set the printing parameters and a model to predict the mechanical properties of 3D- printed objects for the development of patient- and site-specific scaffolds. Keywords Prototyping, Mechanical properties, Rapid prototyping, Scaffolds Paper type Research paper Introduction The fabrication of complex porous structures, or scaffolds, has attracted the attention of bone tissue engineers to additive manufacturing (AM) techniques. Compared with conventional manufacturing methods, AM allows the most control over predefined structures (Lohfeld et al., 2005; Lantada and Morgado, 2012; Krishnan et al., 2012; Syamsuzzaman et al., 2014). Among the various AM methods, the powder-based three-dimensional (3D) printing technology is considered to be one of the most suitable solid free form methods for fabrication of scaffolds for hard tissue engineering applications (Peltola et al., 2008; Bose et al., 2013; Castilho et al., 2014; Klammert et al., 2010; Suwanprateeb et al., 2010). In 3D printing, a thin layer of powder is spread by a roller and selectively jetted by a binder liquid; the build bed is subsequently lowered and prepared for the next powder layer. The repetition of this procedure produces a 3D structure with high fidelity to its design (Billiet et al., 2012). During the printing and drying stage, unloose powder supports the structure. Powder-clearing or depowdering is the final step, wherein the unbound powder is removed by air pressure. Depowdering is particularly difficult when the object has micropores (Utela et al., 2008; Butscher et al., 2011; Bahn, 1966). Mechanical properties are critically important in rapid manufacturing, where the stiffness and strength of the structures should be adequate for the depowdering step and service loading; the application requirements must also be met The current issue and full text archive of this journal is available on Emerald Insight at: www.emeraldinsight.com/1355-2546.htm Rapid Prototyping Journal 24/8 (2018) 1392–1400 © Emerald Publishing Limited [ISSN 1355-2546] [DOI 10.1108/RPJ-06-2015-0077] Received 29 June 2015 Revised 22 August 2016 26 July 2017 6 February 2018 19 March 2018 Accepted 22 April 2018 1392