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]
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]
ZIRCONIUM oxide, EUROPIUM compounds, STRUCTURAL rods, RADIATION dosimetry, SOLID state chemistry, and SINTERING
The application of solid state dosimeters in radiation protection has grown significantly as consequence of advances in the development of dosimetric materials using rare earths. The conception of new dosimetric materials concerns synthesis methods, which control the evolution of material structure, including further processing steps as, shaping, drying, and sintering. The present study reports a full bio-prototyping approach to produce europium doped yttria rods with potential application in radiation dosimetry. Ceramic particles synthesized by hydrothermal route were characterized by Photon Correlation Spectroscopy (PCS), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM). The effect of europium on promoting electronic defects in yttria host was evaluated by Electron Paramagnetic Resonance (EPR). Low pressure hydrothermal synthesis led to formation of rounded particles with mean diameter of 410 nm. Aqueous suspensions with 20 vol% of particles prepared at pH 10, and 0.2 wt% binder exhibited apparent viscosity of 213 mPa s, being suitable for bio-prototyping of rods. Sintering of shaped samples at 1600°C for 4 h provided formation of dense ceramic rods. Europium-yttria rods containing 5 at.% Eu exhibited the most intense EPR response. [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]
TOOL-steel, RAPID prototyping, STARCH, and SINTERING
Abstract: In the starch consolidation (SC) process, a water-based slurry containing powder, starch, dispersant and thickener is used to fabricate near net-shape green bodies that are de-binded and further consolidated by sintering. In this study, gas atomized M3/2 as well as high and low carbon V-rich M4 type high speed steel powder (<150μm) are considered. Both material types undergo high volumetric shrinkage during super-solidus liquid phase sintering enabling them to reach near full density. The analyses and the review cover different process aspects like: recipe optimisation, post-gelatinization drying, de-binding and sintering. A SC recipe consisting of 58vol.% powder, 3vol.% starch, 1vol.% dispersant and a thickener solution resulted in a density of >98% than what is theoretically stated after sintering. It is found that the success of the post-gelatinization drying procedure depends on the smoothness of mould material and controlling powder oxidation. The best combination was freeze drying the slurry in a silicon rubber mould. For V-rich alloys a total or partial control of eutectic carbides in the final microstructure could be realized for vacuum and nitrogen sintering atmospheres, respectively. [Copyright &y& Elsevier]
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]
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]
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.
Scherillo, Fabio, Astarita, Antonello, di Martino, Daniela, Contaldi, Vincenzo, di Matteo, Luca, di Petta, Paolo, Casarin, Renzo, Squillace, Antonino, and Langella, Antonio
AIP Conference Proceedings. 2017, Vol. 1896 Issue 1, p1-5. 5p. 3 Black and White Photographs, 1 Diagram, 2 Charts.
THREE-dimensional printing, RAPID prototyping, METAL industry, POWDERS, SINTERING, and HOT working
Additive Manufacturing (AM), applied to metal industry, is a family of processes that allow complex shape components to be realized from raw materials in the form of powders. The compaction of the powders can be achieved by local melting of the powder bed or by solid state sintering. Direct Metal Laser Sintering (DMLS) is an additive manufacturing process in which a focalized laser beam is the heat source that allows the powders to be compacted. By DMLS it is possible to realize complex shape components. One of the limits of DMLS, as for every additive layer manufacturing techniques, is the unfeasibility to realize large dimension parts. Due to this limit the study of joining process of parts made via ALM is of great interest. One of the most promising options is the Friction Stir Welding (FSW), a solid state welding technique that has been proven to be very effective in the welding of metals difficult to weld, above all aluminium alloys. Since FSW is a solid-state technique, the microstructure of the various zone of the weld bead depends not only by the process itself but also by the parent microstructure of the parts to be welded. Furthermore, parts made of aluminium alloy via DMLS have a particular microstructure that is the result of repeated severe thermal cycles. In the present work the authors, starting from the description of the parent microstructure of parts made of AlSi10Mg aluminium alloy, study the microstructure evolution occurred within the joint made by Friction Stir Welding, analysing in details the microstructure of the main well recognized zone of the weld bead. The structure of the parent material is characterized by the presence of melting pools with a very fine microstructure. In the joint the recrystallization, the grain refinement and, above all, the redistribution of intermetallic phases occurs, resulting in an homogenization of the microstructure and in an increase of micro hardness. [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, POROUS materials, SINTERING, COPPER, and MANUFACTURING processes
Purpose – The purpose of this paper is to report the investigation on obtaining a high-porosity Cu-based structure which was sintered successfully using direct laser sintering and to reveal the mechanisms of obtaining high porosity and acceptable strength simultaneously as well as the effect of NaCl content on characteristics of the sintered samples. Design/methodology/approach – Experimental study has been performed. The powder mixture utilized in this experiment includes metal powder (Cu and Cu3P mixture) and porogen [sodium chloride (NaCl)]. Scanning electron microscope, energy-dispersive X-ray analysis and the Archimedes density measurement were used to detect the characteristics of the sintered sample and to reveal the mechanism of forming high porosity and strength structure. Findings – More than 57 per cent porosity can be achieved while the structural strength is acceptable, and the infiltrated experiment verifies the pores in the structure are inter-connected. During laser sintering, NaCl powder melts and brings a larger amount of liquid phase, inducing large rearrange force and fast rearrangement of Cu particles. Therefore, after NaCl is removed, the dense and strong longer-bar shape tracks with larger amount of pores in the microstructure can be obtained. The size of pores as well as the porosity of the sintered sample increase with the NaCl content in the powder mixture. Originality/value – The mechanism of obtaining high porosity and acceptable strength simultaneously was revealed. The effect of NaCl content on characteristics of the sintered samples was also disclosed. [ABSTRACT FROM AUTHOR]