PHOSPHATES, RAPID prototyping, STEREOLITHOGRAPHY, SINTERING, and BONE regeneration
The aim of this study was to present a direct fabrication technique of β-tricalcium phosphate(β-TCP) scaffolds by a bottom-up mask projection stereolithography(MPSL) technology, which provided an excellent control of the internal pore architecture. The debinding and sintering schemes of β-TCP were determined by TG-DSC analysis, the scaffolds with designed pore architecture were obtained. The physical properties of β-TCP scaffolds were investigated including pore morphology, size and pore distribution, the crystal phase and chemical composition of sintered β-TCP were measured. Results indicated that the β-TCP scaffolds fabricated with a pore size of 0.4-0.7mm, a porosity of 58.50% and an average compressive strength of 20.92MPa met the requirements of bone scaffold. The effectiveness of degradation and cell proliferation of β-TCP scaffold were also evaluated, the results showed that β-TCP scaffolds had some certain degradability and bioactivity, which may stimulates bone tissue repair and regeneration. [ABSTRACT FROM AUTHOR]
International Journal of Production Research; 3/1/2006, Vol. 44 Issue 5, p919-938, 20p, 4 Color Photographs, 8 Diagrams, 6 Charts, 2 Graphs
POWDER injection molding, RAPID prototyping, MARAGING steel, SINTERING, INJECTION molding of metals, PRODUCTION engineering, MANUFACTURING processes, MATERIALS, INDUSTRIAL engineering, RESEARCH methodology, and METALLURGICAL research
In this research work, attempts have been made to design, develop and evaluate the performance of mould inserts for injection moulding by using a powder-sintering process. Maraging steel powder, sintering aid and binder are materials used in this proposed development process. Attempts have been made to perform in-depth studies and to apply the powder-sintering process, to eventually produce the final sintered components. In addition, an analysis of the dimensional accuracy of the respective stereolithography master models and an analysis of the sintered specimens during various stages of powder-sintering process have been carried out. The intelligent manufacturing systems (IMS) test part with minor modifications has been used in the evaluation of dimensional accuracy, tolerances, distortion and volumetric variations. The main reason for using this unique geometry is the suitability of its design for injection-moulding processes and tooling. [ABSTRACT FROM AUTHOR]
Purpose – This paper aims to introduce selective vacuum manufacturing (SVM), a powder-based rapid prototyping (RP) technique, and the ongoing development to improve its capability to apply in temporary scaffold fabrication. Design/methodology/approach – SVM employs a combination of sand casting and powder sintering process to construct a prototype layer by layer. A dense layer of support material is prepared and selectively removed to create a cavity where part material is filled and sintered to form a solid layer. In order for SVM to be considered for scaffold fabrication, besides preparing poly-lactic acid (PLA) for part material, support material preparation and process parameters identification have been studied. Redesigning of SVM machine to be more suitable for the real usage has also been presented. Findings – Particle size of salt has been controlled, and its suitable composition with flour and water has been determined. Process parameters have been identified to scale down the size of scaffolds to meso-scale and to achieve mechanical requirement. Properties of fabricated scaffolds have been enhanced and can be used for soft tissue applications. A prototype of the medical SVM machine has been constructed and tested. An examination of scaffolds fabricated on this new machine also showed their qualification for soft tissue application. Research limitations/implications – Further study will be on conducting a direct cytotoxicity test to provide the evidence for tissue growth before the clinical usage, on continuing to scaling down the scaffold size, and on improving SVM to meet the requirement of hard tissue. Originality/value – This simple, inexpensive RP technique demonstrates its viability for scaffold fabrication. [ABSTRACT FROM AUTHOR]
Singhal, S.K., Jain, Prashant K., Pandey, Pulak M., and Nagpal, A.K.
International Journal of Production Research; Nov2009, Vol. 47 Issue 22, p6375-6396, 22p, 1 Color Photograph, 4 Diagrams, 2 Charts, 6 Graphs
SURFACE roughness, SINTERING, ALGORITHMS, INDUSTRIAL efficiency, PROBLEM solving, and PRODUCTION (Economic theory)
In the present work an attempt has been made to achieve minimum average part surface roughness (best overall surface quality), minimum build time and support structure for stereolithography (SL) and selective laser sintering (SLS) processed parts by determining optimum part deposition orientation. A conventional optimisation algorithm based on a trust region method (available with MATLAB-7 optimisation tool box) has been used to solve the multi-objective optimisation problem. It is observed that the problem is highly multi-modal in nature and a suitable initial guess, which is used as an input to execute the optimisation module, is important to achieve a global optimum. A simple methodology has been proposed to find out the initial guess so that global minimum is obtained. Finally the surface roughness simulation is carried out with optimum part deposition orientation to have an idea of surface roughness variation over the entire part's surface before depositing the part. Case studies are presented to demonstrate the capabilities of the developed system. The major achievements of this work are consideration of multiple objectives for the two rapid prototyping processes, successful use of conventional optimisation algorithm available with MATLAB to handle multiple objectives and development of graphical user interface-based system. [ABSTRACT FROM AUTHOR]
POLYMERIC composites, RAPID prototyping, RAPID tooling, SINTERING, LASERS, and HUAZHONG University of Science & Technology (Beijing, China)
Rapid prototyping (RP) and tooling (RT) are the technologies for quickly fabricating functional components and tooling inserts directly from CAD data by selectively adding material layer by layer. In this paper, multiphase polymeric materials for RP and RT technologies and their applications, which are developed by the Rapid Manufacturing (RM) Center of Huazhong University of Science and Technology (HUST) in China, were introduced. Selective laser sintering (SLS) is a powder-based RP process. Multi-types of multiphase polymer materials for SLS process were successfully developed in the RM center, and the SLS components were formed from these materials by using the commercial SLS machines HRPS series for various applications. High impact polystyrene (HIPS)/wax blend SLS parts were used as lost patterns for the investment casting process to make complex metal parts rapidly; nylon-12/organically modified rectorite and nylon-12/nanosilica composite powders were used to fabricate functional parts, which showed higher thermal and mechanical properties than neat nylon-12 SLS parts. As a RT application, Fe/epoxy composite tooling inserts were rapidly fabricated by SLS and post-processing. Stereolithography (SLA) uses photocurable resins to rapidly manufacture components with high accuracy and mechanical properties. A freeradical and cationic mixed-type radiation curable composite resin was also successfully developed, and SLA parts without obvious distortion were built on the SLA machines HRPL series from this hybrid resin, successfully and efficiently. [ABSTRACT FROM AUTHOR]
Xu, Anping, Hou, Hongye, Qu, Yunxia, and Gao, Yanping
Journal of Integrated Design & Process Science; Sep2005, Vol. 9 Issue 3, p15-27, 13p, 2 Color Photographs, 4 Diagrams
RAPID prototyping, INTERNET, COMPUTER systems, PROTOTYPES, and SINTERING
The part quality and cost are greatly affected by process parameters during rapid prototyping (RP). This paper proposes a Virtual Rapid Prototyping System (VRPS) and describes its functions, characteristics and realization method. Moreover, aimed at the Selective Laser Sintering (SLS) technology, an Internet-based virtual rapid prototyping system named VRPS-I is implemented using Java and Virtual Reality Modeling Language (VRML). The system resembles the physical fabrication system of SLS. With the aid of this system, not only can the visual rapid prototyping process be dynamically previewed, but the forming process and some part-quality-related parameters can also be predicted and evaluated. Therefore, the reasonable rapid prototyping parameters can be predetermined according to the simulated results without any physical RP machine. Hence, it can help optimize the prototyping process, improve part quality, enhance fabrication efficiency, and lower the model making cost significantly. [ABSTRACT FROM AUTHOR]
Dong Guo, Long-tu Li, Kenji, Kai Cai, Kenji, Zhi-lun Gui, Kenji, and Ce-wen Nan, Kenji
Journal of the American Ceramic Society; Jan2004, Vol. 87 Issue 1, p17-22, 6p
PIEZOELECTRIC ceramics, LASERS, SINTERING, PIEZOELECTRICITY, CERAMICS, and RAPID prototyping
This article presents a new lost mold rapid prototyping method which combines selective laser sintering (SLS) and gelcasting techniques for fabricating piezoelectric ceramics. SLS was used to fabricate sacrificial molds of the desired structure of the ceramic part. Then aqueous PZT (lead zirconate titanate) suspension was cast in the mold and solidified in situ through formation of a three-dimensional network gel. Because the polymer mold can be easily removed at the initial stage of sintering and the gelcast PZT body has a high green strength, the desired geometry of the PZT part can be completely retained after sintering of the ceramics. Complex-shaped PZT parts were successfully fabricated after using concentrated PZT suspension with low viscosity. Densities and electrical properties, such as the d[sub 33], the relative permittivity ε, the dielectric loss tgδ and the electromechanical coupling factor K[sub p] of the gelcast PZT parts were also compared with those of the die-pressed PZT samples. The results indicated that the gelforming process did not deteriorate the electrical properties of the samples, if proper dispersant was selected in developing concentrated ceramic slurry. [ABSTRACT FROM AUTHOR]
3-D printers, RAPID prototyping, THREE-dimensional printing, and SINTERING
The article discusses how three-dimensional (3D) printers benefit ZARE SrL, a provider of rapid prototyping services and a variety of additive manufacturing technologies. It explains how the company started creating only large monolithic prototypes using metal sintering but eventually expanded its capabilities by having Fortus 3D production system made by Startasys Ltd.
Gbureck, Uwe, Hölzel, Tanja, Biermann, Isabell, Barralet, Jake E., and Grover, Liam M.
Journal of Materials Science: Materials in Medicine; Apr2008, Vol. 19 Issue 4, p1559-1563, 5p, 1 Color Photograph, 1 Diagram, 2 Charts, 3 Graphs
CALCIUM phosphate, ORTHOPEDIC implants, ARTIFICIAL implants, BONE substitutes, PHOSPHORIC acid, RAPID prototyping, and SINTERING
Custom made tricalcium phosphate/calcium pyrophosphate bone substitutes with a well-defined architecture were fabricated in this study using 3D powder printing with tricalcium phosphate (TCP) powder and a liquid phase of phosphoric acid. The primary formed matrix of dicalcium phosphate dihydrate (DCPD, brushite) was converted in a second step to calcium pyrophosphate (CPP) by heat treatment in the temperature range 1,100–1,300°C. The structures exhibited compressive strengths between 0.8 MPa and 4 MPa after sintering at 1,100–1,250°C, higher strengths were obtained by increasing the amount of pyrophosphate formed in the matrix due to a post-hardening regime prior sintering as well as by the formation of a glass phase from TCP and calcium pyrophosphate above 1,280°C, which resulted in a strong densification of the samples and compressive strength of >40 MPa. [ABSTRACT FROM AUTHOR]
This study presents a novel rapid prototyping process to fabricate silicate/hydroxyapatite (HA) bone scaffolds for tissue engineering applications. The HA particles are embedded in the gelled silica matrix to form a green part of bioceramic bone scaffold after processing by selective laser sintering. The composition of the bioceramic scaffold is in the series of SiO·PO·CaO. Results indicate that the proposed process could fabricate a multilayer hollow shell structure with brittle property but sufficient integrity for handling prior to post-processing. The fabricated bone scaffold models had a surface finish of 25 μm, a dimensional shrinkage of 16 %, a maximum bending strength of 4.7 MPa, and an apparent porosity of 28 % under the laser energy density of 1.5 J/mm. In vitro bioactivity evaluation by optical density value using a microculture tetrazolium test assay revealed that the bioceramic bone scaffolds were suitable for cell culture, demonstrating their application in tissue engineering. [ABSTRACT FROM AUTHOR]
RAPID prototyping, PROTOTYPES, MANUFACTURING processes, TIME to market (New products), NEW product development, SINTERING, and LASERS
Traditional methods of creating new products are being challenged by the rise of 'rapid' techniques and technologies. A company wanting to engage in 'rapid manufacturing' now has a wide choice of machines, processes and technologies for getting its product ideas quickly into production. What many of these processes are essentially about is 'growing' parts out of minuscule pieces, as opposed to traditional manufacturing methods of machining, shaping or injection-moulding materials. Commonly, rapid manufacturing (also known as rapid prototyping) involves using laser technology to solidify or shape liquids or materials very precisely. [ABSTRACT FROM AUTHOR]
Machine Design; 4/8/2010, Vol. 82 Issue 6, p52-55, 4p, 3 Color Photographs, 1 Black and White Photograph
RAPID prototyping, ENGINEERING equipment, MACHINE design, PRINTING, and SINTERING
The article presents survey findings on the capability of rapid-prototyping (RP) technique for micromolded components in a machine design in the U.S. The gathered data primarily focuses on the dimensions, features and performance of various RP technologies, considering the technology requirement in the medical, optical and microelectronics industries. Among the assessed RP tools include stereolitography, 3D printing or inkjet printing, and selective laser sintering.