International Journal of Production Research. 3/1/2006, Vol. 44 Issue 5, p919-938. 20p. 4 Color Photographs, 8 Diagrams, 6 Charts, 2 Graphs.
RAPID prototyping, PRODUCTION engineering, MANUFACTURING processes, INDUSTRIAL engineering, POWDER injection molding, MARAGING steel, SINTERING, INJECTION molding of metals, MATERIALS, 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]
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]
RAPID prototyping, PROTOTYPES, MANUFACTURING processes, MATERIALS handling, LITHOGRAPHY, and SINTERING
Selection of the most suitable rapid prototyping and manufacturing (RPM) process for a specific part creation is a difficult task due to the proliferation of RPM processes and materials. The paper studies the four dominant RPM processes currently in the market-stereolithography, selective laser sintering, fused deposition modeling and laminated object manufacturing through a benchmark part. Generic models for surface roughness, building time and building cost are also presented. Multiple considerations such as good dimensional accuracy, fine surface finish and short building time are all desirable objectives.
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.
ALGORITHMS, INDUSTRIAL efficiency, PROBLEM solving, PRODUCTION (Economic theory), SURFACE roughness, and SINTERING
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]
Machine Design. 4/8/2010, Vol. 82 Issue 6, p52-55. 4p. 3 Color Photographs, 1 Black and White Photograph.
RAPID prototyping, PRINTING, ENGINEERING equipment, MACHINE design, 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.
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]
RAPID prototyping, LITHOGRAPHY, MODELING (Sculpture), SINTERING, and MOLDING (Founding)
The article presents several rapid-prototyping techniques for micromolded parts which include stereolithography (STL), fusion-deposition modeling (FDM) and selective laser sintering (SLS). It says that the first technique utilizes liquid ultraviolet (UV) curable photopolymer resin touched on a UV laser beam. The second technique extrudes a modeling material through a nozzle while the last one uses a high-temperature laser to melt metal into a three-dimensional (3D) part.
RAPID prototyping, MACHINERY, MANUFACTURING processes, LATHES, DRILL presses, and SINTERING
The article focuses on several types of prototyping machines. Prototyping machines can be classified in terms of applications, such as for material removal or addition, and in terms of mechanism, either driven by electricity or controlled by human hands or automatic means. For material removal, there are hands-on and automatic lathes and drill presses. For material additive processes, there are computer-controlled stereolithography and selective laser sintering. There is also cold casting of plastic in silicon rubber molds.
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]
In the process of rapid prototyping by the method of selective laser sintering, transient temperature has a direct effect upon the sintering performance. In the present work, a model is developed to predict the three-dimensional transient temperature field. It uses the finite element method to model the variation of thermal properties and solid-liquid two-phase interface in sintering the mixture of Al2O3-coated ceramic powder and polystyrene powder. A high-speed charge-coupled device image temperature measurement system is used to obtain real data from laser sintering experiments for comparison. The test results validate the simulation data and imply that the modelling method is useful in predicting the transient sintering temperature when correct thermal properties and key factors of two-phase interface are main concerns. The performance characteristics of the sintering process are predicted by the modelling method. [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]