Layered manufacturing is an evolution of rapid prototyping (RP) techniques where the part is built in layers. While most of the previous applications focused on building “prototypes”, recent developments in this field enabled some of the prototyping methods to achieve an agile fabrication technology to produce the final product directly. A shift from prototyping to manufacturing of the final product necessitates broadening of the material choice, improvement of the surface quality, dimensional stability, and achieving the necessary mechanical properties to meet the performance criteria. The current study is part of an ongoing project to adapt fused deposition modeling to fabrication of ceramic and multi‐functional components. This paper presents a methodology of the mechanical characterization of products fabricated using fused deposition modeling.

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Layered manufacturing (LM) is an evolution of rapid prototyping (RP) technology whereby a part is built in layers. Fused deposition modeling (FDM) is a particular LM technique in which each section is fabricated through vector style deposition of building blocks, called roads, which are then stacked layer by layer to fabricate the final object. The latest improvements in this technology brought about the possibility of fabricating not only a model but even the finished product. This paper presents the analysis of the liquefier dynamics towards establishing control strategies for flow control during the extrusion phase, which is necessary to achieve the mentioned objective.

Successes in scaffold guided tissue engineering require scaffolds to have speci c macroscopic geometries and internal architectures to provide the needed biological and biophysical functions. Freeform fabrication provides an effective process tool to manufacture many advanced scaffolds with designed properties. This paper reports our recent study on using a novel precision extruding deposition (PED) process technique to directly fabricate cellular poly-ecaprolactone (PCL) scaffolds. Scaffolds with a controlled pore size of 250 m m and designed structural orientations were fabricated.

Fused deposition of ceramics (FDC) is a solid freeform fabrication technique based on extrusion of highly loaded polymer systems. The process utilizes particle loaded thermoplastic binder feedstock in the form of a filament. The filament acts as both the piston driving the extrusion and also the feedstock being deposited. Filaments can fail during FDC via buckling, when the extrusion pressure needed is higher than the critical buckling load that the filament can support. Compressive elastic modulus determines the load carrying ability of the filament and the viscosity determines the resistance to extrusion (or extrusion pressure). A methodology for characterizing the compressive mechanical properties of FDC filament feedstocks has been developed. It was found that feedstock materials with a ratio (E/Z a ) greater than a critical value (3610 5 to 5610 5 s -1 ) do not buckle during FDC while those with a ratio less than this range buckle.

Bone tissue engineering is an emerging field providing viable substitutes for bone regeneration. Recent advances have allowed scientists and engineers to develop scaffolds for guided bone growth. However, success requires scaffolds to have specific macroscopic geometries and internal architectures conducive to biological and biophysical functions. Freeform fabrication provides an effective process tool to manufacture three-dimensional porous scaffolds with complex shapes and designed properties. A novel precision extruding deposition (PED) technique was developed to fabricate polycaprolactone (PCL) scaffolds. It was possible to manufacture scaffolds with a controlled pore size of 350 microm with designed structural orientations using this method. The scaffold morphology, internal micro-architecture and mechanical properties were evaluated using scanning electron microscopy (SEM), micro-computed tomography (micro-CT) and mechanical testing, respectively. An in vitro cell-scaffold interaction study was carried out using primary fetal bovine osteoblasts. Specifically, the cell proliferation and differentiation was evaluated by Alamar Blue assay for cell metabolic activity, alkaline phosphatase activity and osteoblast production of calcium. An in vivo study was performed on nude mice to determine the capability of osteoblast-seeded PCL to induce osteogenesis. Each scaffold was implanted subcutaneously in nude mice and, following sacrifice, was explanted at one of a series of time intervals. The explants were then evaluated histologically for possible areas of osseointegration. Microscopy and radiological examination showed multiple areas of osseous ingrowth suggesting that the osteoblast-seeded PCL scaffolds evoke osteogenesis in vivo. These studies demonstrated the viability of the PED process to fabricate PCL scaffolds having the necessary mechanical properties, structural integrity, and controlled pore size and interconnectivity desired for bone tissue engineering.

A combined effect of protein coating and plasma modification on the quality of the osteoblast-scaffold interaction was investigated. Three-dimensional polycaprolactone (PCL) scaffolds were manufactured by the precision extrusion deposition (PED) system. The structural, physical, chemical and biological cues were introduced to the surface through providing 3D structure, coating with adhesive protein fibronectin and modifying the surface with oxygen-based plasma. The changes in the surface properties of PCL after those modifications were examined by contact angle goniometry, surface energy calculation, surface chemistry analysis (XPS) and surface topography measurements (AFM). The effects of modification techniques on osteoblast short-term and long-term functions were examined by cell adhesion, proliferation assays and differentiation markers, namely alkaline phosphatase activity (ALP) and osteocalcin secretion. The results suggested that the physical and chemical cues introduced by plasma modification might be sufficient for improved cell adhesion, but for accelerated osteoblast differentiation the synergetic effects of structural, physical, chemical and biological cues should be introduced to the PCL surface.

PurposeTo shift from rapid prototyping (RP) to agile fabrication by broadening the material selection, e.g. using ceramics, hence improving the properties (e.g. mechanical properties) of fused deposition modeling (FDM) products.Design/methodology/approachThis paper presents the development of a novel extrusion system, based on the FDM technology. The new set‐up, consisting of a mini‐extruder mounted on a high‐precision positioning system, is fed with bulk material in granulated form, instead that with the more common filament.FindingsPrevious research showed that the applications of new materials with specific characteristics in a commercial FDM system are limited by the use of intermediate precursors, i.e. a filament. The new design described in this paper overcomes the problem thanks to the new feeding system.Research limitations/implicationsThe work presented in this paper is only the starting point for further development. The new system design was tested and encouraging improvements of the final product were achieved. However, several parameters, e.g. size of the feeding granules, still need to be optimized.Practical implicationsThis configuration opens up opportunities for the use of wider range of materials, making the FDM to become a viable alternative manufacturing process for specialty products.Originality/valueThe mini‐extruder deposition system developed in this study exploits the advantages of the RP technologies: ability to shorten the product design and development time; suitability for automation; and ability to build many geometrically complex shapes. Hence, applying the described technology, it will be possible to manufacture customer‐driven product with important cost and time (from design to final product) savings.