International Journal of Production Research; 3/1/2006, Vol. 44 Issue 5, p919-938, 20p, 4 Color Photographs, 8 Diagrams, 6 Charts, 2 Graphs
Subjects
POWDER injection molding, RAPID prototyping, MARAGING steel, SINTERING, INJECTION molding of metals, PRODUCTION engineering, MANUFACTURING processes, MATERIALS, INDUSTRIAL engineering, RESEARCH methodology, and METALLURGICAL research
Abstract
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]
POLYMERIC composites, RAPID prototyping, RAPID tooling, SINTERING, LASERS, and HUAZHONG University of Science & Technology (Beijing, China)
Abstract
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
Subjects
RAPID prototyping, INTERNET, COMPUTER systems, PROTOTYPES, and SINTERING
Abstract
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]
LASERS, SINTERING, RAPID prototyping, STEREOLITHOGRAPHY, and POLYMERS
Abstract
Purpose – The purpose of this paper is to report experimental investigations performed to analyze the effect of process parameters on the shape accuracy of selective laser sintered (SLS) parts. Design/methodology/approach – The effect of process parameters, namely build orientation, laser power, scan speed, cylinder diameter and build chamber temperature has been studied on shape accuracy by using geometric tolerances such as cylindricity and flatness. Central composite design (CCD) is used to plan the experiments and a second order regression model has been developed to predict flatness and cylindricity. The significance of process variables on flatness and cylindricity has been evaluated using analysis of variance technique. Findings – It is observed that interaction effects are more dominant than individual effects. In case of cylindricity, it is found that the interaction between the scan speed and orientation is the dominant factor next to the orientation and quadratic effect of the geometry. In case of flatness, the interaction between build chamber temperature and scan speed is the dominant factor. Research limitations/implications – The empirical models presented in this paper work within the range of values used for the experiments and most of these models need to be redeveloped for use with other materials. Practical implications – The empirical models developed in this work would be useful in deciding the process parameters for parts with improved geometrical tolerances. The optimum parameters identified from the empirical model are found to yield accurate parts with minimum shape error. Originality/value – The paper establishes the interactions between this build orientation, geometry and process parameters on the shape accuracy of SLS process. [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
Subjects
PIEZOELECTRIC ceramics, LASERS, SINTERING, PIEZOELECTRICITY, CERAMICS, and RAPID prototyping
Abstract
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
Abstract
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
Subjects
CALCIUM phosphate, ORTHOPEDIC implants, ARTIFICIAL implants, BONE substitutes, PHOSPHORIC acid, RAPID prototyping, and SINTERING
Abstract
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]
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
Subjects
SURFACE roughness, SINTERING, ALGORITHMS, INDUSTRIAL efficiency, PROBLEM solving, and PRODUCTION (Economic theory)
Abstract
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]
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
Subjects
THREE-dimensional printing, RAPID prototyping, METAL industry, POWDERS, SINTERING, and HOT working
Abstract
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]
Ning, Y., Fuh, J. Y. H., Wong, Y. S., and Loh, H. T.
International Journal of Production Research; 1/1/2004, Vol. 42 Issue 1, p183-199, 17p, 2 Black and White Photographs, 5 Diagrams, 3 Charts, 1 Graph
Subjects
SINTERING, METAL powders, RAPID prototyping, MANUFACTURING processes, ARTIFICIAL neural networks, and BACK propagation
Abstract
As one of the promising Rapid Prototyping (RP) processes, the Direct Metal Laser Sintering (DMLS) technique is capable of building prototype parts by depositing and melting metal powders layer by layer. Metal powder can be melted directly to build functional prototype tools. During fabrication, four important resulting properties of interest to the users are: the processing time, mechanical properties, geometric accuracy and surface roughness. By adjusting an identified set of process parameters, these properties can be properly controlled. The process parameters involve: the laser scan speed, laser power, hatch density, layer thickness and scan path. But the relationships between these parameters and their resulting properties are quite complicated. In many cases, the effects of different parameters on the resulting properties contradict one another. In this paper, an intelligent system to assist the RP user to choose the optimal parameter settings based on different user requirements is presented. For the accurate prediction of the resulting properties of the laser-sintered metal parts, a method based on the feed-forward neural network (NN) with backpropagation (BP) learning algorithm is described. Through experiments, some input-output data pairs have been identified. After continuous training by using the data pairs, this NN constructs a good mapping relationship between the process parameters and their resulting properties. The system developed can determine the most suitable parameter settings containing the process parameters and predict resulting properties from the database built based on different process requirements automatically. It is very useful to RP users for saving material cost and reducing processing time. [ABSTRACT FROM AUTHOR]
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