Papers by Keyword: Solid Freeform Fabrication

Paper TitlePage

Authors: Yu Li, Lei Zhang, Chang Yong Liu, Yu Zhao, Wei Sun
Abstract: Solid freeform fabrication (SFF) technology has been widely used to fabricate three-dimensional (3D) cell constructs. As multi-cell construct is a heterogeneous object (He-Object), it is a trend of biomanufacturing to use SFF technology to fabricate multi-cell constructs. In this paper, a novel multi-nozzle deposition system, called as 3D direct controlled cell assembling (CA) system, was developed to fabricate 3D multi-cell constructs. The developed system design was demand-oriented and applied functional modular design method. As the key part of this system, the multi-nozzle system was designed and described in details. Experimental study was conducted and results showed that the system could meet the requirements of the process and be used to fabricate complex 3D cell constructs. By comparison, the developed system could precisely deposite biomaterials with high viscocity and form constructs with big size in continuous deposition mode.
Authors: J. Russias, Eduardo Saiz, Sylvain Deville, Antoni P. Tomsia
Abstract: The development of novel biodegradable scaffolds for the treatment of bone and cartilage defects is the subject of intense research. A successful scaffold will guide cell-attachment, proliferation and tissue regeneration. The objective of this study is to use freeform fabrication (robocasting) for the preparation of porous hybrid organic/inorganic materials with a well controlled architecture and porosity. Polymer/hydroxyapatite (HA) pastes with ceramic contents ranging between 0 to 70 wt. % are prepared by mixing ceramic powders with a solution of the polymer in methylene chloride. Two different polymers are studied: polylactide (PLA) and polycaprolactone (PCL). During the compression tests, the scaffolds show an elasto-plastic behavior with large plastic yielding and do not fail in a brittle manner. The mechanical response is anisotropic and depends significantly on the ceramic content and the type of polymer.
Authors: Zhi Yong Yu, Yan Huang, D.J. Zhang, R.J. Zhang, Xue Min Cui, Shi Xi Ouyang
Authors: Hong Jun Liu, Dong Jian Li, Ya Min Li
Abstract: The precision of ceramic component gotten by some Solid Freeform Fabirication processes based on paste extrusion is dependent to a considerable degree on paste extrudate. To get clearer understanding about paste extrudate, the experimental works were carried out to investigate some important extrudate features for ram extrusion process in this paper. The velocity, diameter, liquid content and mass of extrudate of alunima paste by ram extrusion were studied. The liquid content of extrudate tests show that the occurance liquid phase migration depends on the ram velocity. Without liquid phase migration, the extrudate velocities have a corresponding relations to extrusion force. The dilation of extrudate occurs in commonly used ram velocities. So extrudate velocities should not be calculated by nozzle diameter but by the average diameter of dilated extrudate. The mass of extrudate in the very end of extrusion is greatly reduced and should not be used.
Authors: Thomas Seefeld, C. Theiler, E. Schubert, G. Sepold
Authors: Leenaporn Jongpaiboonkit, C.Y. Lin, P.H. Krebsbach, S.J. Hollister, J.W. Halloran
Abstract: Calcium phosphate cement is a bioceramic with potential applications for bone-tissue engineering. In this work, controlled porous calcium phosphate scaffolds with interconnected pores were computationally designed by an image-based approach and fabricated by indirect solid freeform fabrication (ISFF) or ‘lost mold’ technique. Voxel finite-element analysis (FEA) showed that mechanical properties of design and fabricated scaffold can be predicted computationally. Scaffolds were then implanted subcutaneously to demonstrate tissue in-growth. Previously, we showed the ability of porous calcium phosphate cement scaffolds to have sufficiently strong mechanical properties for bone tissue engineering applications. This work shows the image-based FEAs from micro-CT scans in vivo (four- and eight weeks). Extensive new bone apposition was noted with micro-CT technique after four- and eight weeks. FEA models of the original design and scaffolds with newly bone formed were compared.
Authors: Quan Wu, Xiang Lin Zhang, Meng Jun Li
Abstract: This paper investigated solid freeform fabrication(SFF) and microwave sintering processes of high strength HA porous scaffold. A newly developed SFF method called motor assisted micro-syringe freeform fabrication system was introduced to construct HA scaffolds. Sintering conditions that influenced the phases, microstructure and mechanical strength of scaffolds were discussed. Study of microstructure images and strength test results showed that densification and grain size were found to play an important role in determining the mechanical properties of sintered porous scaffolds, and microwave sintering process could get a sintered scaffold with small grain size and uniform structure more rapidly at lower sintering temperature than that of the conventional sintering. The fabricated HA scaffolds with controlled architecture (interconnected macro pore of 200-400μm, micro pore of 1-10μm within the rods) and improved mechanical properties (45.2MPa, 56.2% porosity ) may find potential applications in bone tissue engineering.
Authors: M.E. Thomas, P.W. Richter, J. Crooks, U. Ripamonti
Authors: David W. Heard, Julien Boselli, Raynald Gauvin, Mathieu Brochu
Abstract: Aluminum-lithium (Al-Li) alloys are of interest to the aerospace and aeronautical industries as rising fuel costs and increasing environmental restrictions are promoting reductions in vehicle weight. However, Al-Li alloys suffer from several issues during fusion welding processes including solute segregation and depletion. Solid freeform fabrication (SFF) of materials is a repair or rapid prototyping process, in which the deposited feedstock is built-up via a layering process to the required geometry. Recent developments have led to the investigation of SFF processes via Gas Metal Arc Welding (GMAW) capable of producing functional metallic components. A SFF process via GMAW would be instrumental in reducing costs associated with the production and repair of Al-Li components. Furthermore the newly developed Controlled-Short-Circuit-MIG (CSC-MIG) process provides the ability to control the weld parameters with a high degree of accuracy, thus enabling the optimization of the solidification parameters required to avoid solute depletion and segregation within an Al-Li alloy. The objective of this study is to develop the welding parameters required to avoid lithium depletion and segregation. In the present study weldments were produced via CSC-MIG process, using Al-Li 2199 sheet samples as the filler material. The residual lithium concentration within the weldments was then determined via Atomic Absorption (AA) and X-ray Photoelectron Spectroscopy (XPS). The microstructure was analyzed using High Resolution Scanning Electron Microscopy (HR-SEM). Finally the mechanical properties of welded samples were determined through the application of hardness and tensile testing.
Authors: Efrain Carreño-Morelli, Sebastien Martinerie, J. Eric Bidaux
Abstract: A novel variant of the three-dimensional printing technique has been developed and used to manufacture NiTi parts. Instead of metal powder the process uses granules, which consist of a mixture of metal powder and organic binder. These granules are spread on a working table. Then a solvent is dispensed with a printer head to consolidate a selected area of the granule bed and the table is moved down. The "solvent on granule" printing process is repeated until a threedimensional green body is obtained. The green part is finally debinded and sintered to obtain a dense and fully metallic part. NiTi parts have been successfully produced by this technique with densities of about 95% of the theoretical density. Detailed information on the microstructure has been obtained by X ray diffraction. Sintered parts exhibit shape memory effect, which has been measured during thermal cycling under tensile stress.
Showing 1 to 10 of 11 Paper Titles