Search

Conventionally and digitally manufactured removable complete dentures with different dentition forms were examined for manufacturing accuracy (trueness, precision), fracture forces under torsional loading and subsequent repairability. A total of 90 mandibular prostheses were manufactured. Ten were made using the injection molding technique and finished with prefabricated teeth. 40 bases each, were manufactured subtractively and additively. Digitally the prosthesis' dental arch was divided either into two quadrants or three sextants, or kept as full arch. Afterwards, ten additive and subtractive bases were finished with prefabricated teeth and ten of each with milled quadrants, sextants and full arches. After manufacturing, all specimens were rescanned for accuracy comparisons using the Root Mean Square (RMS). Lastly, all specimens were tested to failure under torsional loading. Conventionally manufactured dentures showed the greatest deviation in accuracy. The type of base manufacturing did not determine the fracture resistance of the prostheses. The dentition form had a significant influence. While prefabricated teeth (86.01 ± 19.76 N) and quadrants (77.89 ± 9.58 N) showed a low fracture resistance, sextants (139.12 ± 21.41 N) and full arches (141.05 ± 17.14 N) achieved the highest fracture forces. Subtractive bases with prefabricated teeth or quadrants were assessed to be repairable, digital dentures with full arch were assessed as not repairable. The presented testing set-up is suitable to determine the fracture behavior of dentures rather than of standards. With the possibility of digital design and individual manufacturing, dentures' mechanical stability can be significantly increased, especially with suitable dentition forms. • In-vitro testing setup for torsional loading of removable complete dentures. • Investigating manufacturing accuracy, fracture forces and repairability of dentures. • Analyzing manufacturing methods alongside various dentition forms. • Base manufacturing affects resistance and repairability less than dentition choice. [ABSTRACT FROM AUTHOR]

• 3D origami-inspired auxetic honeycomb with omni-directional high stiffness is proposed. • Theoretical models for predicting the elastic mechanical properties of the CFRP composite 3D honeycombs are developed. • The 3D honeycomb can be applied where good load-bearing capacity and obvious auxetic effect are simultaneously desired. • The 3D honeycomb suggests a potential for 3D isotropic auxetic design. Traditional 3D auxetic materials face significant limitations, marked by low stiffness and pronounced anisotropy. To address these challenges, here a new kind of 3D origami-inspired auxetic honeycomb with omni-directional high stiffness is proposed by us. Two simplified theoretical models based on different assumptions are developed to predict structural homogenized elastic properties along the principal axes. Combined theoretical and numerical studies are carried out to reveal the auxetic mechanism and dominated deformation characteristics of the 3D honeycomb. In order to gain a understanding of its elastic anisotropy, directional dependence of structural homogenized Young's moduli, Poisson's ratios and shear moduli are also investigated in detail. A detailed examination of the dependence of structural homogenized Young's moduli, Poisson's ratios, and shear moduli on loading direction is conducted to comprehend its elastic anisotropy. This paper introduces a feasible method for the rapid manufacturing of the 3D honeycomb using high-performance continuous carbon fiber reinforced composite (CFRP) based on hot-pressing molding. Subsequently, the compressive elastic behaviors of CFRP 3D honeycombs are characterized and evaluated through experimental tests. A comparison with traditional 3D auxetic materials reveals the 3D honeycomb's superiority in both multi-axial loading and rapid manufacturing. Additionally, the demonstrative example suggests that the 3D honeycomb can offer nearly isotropic Poisson's ratio of about −0.9. These results not only demonstrate that the 3D honeycomb is an excellent candidate for applications where both good load-bearing capacity and notable auxetic effect are simultaneously desired but also highlight its potential for 3D isotropic auxetic design. [ABSTRACT FROM AUTHOR]

Additive manufacturing evolves as a viable manufacturing process for making a multitude of products. The motivation for this paper is to explore the competitiveness of additive manufacturing in making die tools for casting aluminium parts compared to more traditional machining approaches. Thus, the main objective of this study is to analyze additive manufacturing as a competitive advantage for SMEs (Small and Medium Enterprise) within the aluminium casting industry. Today, additive manufacturing is mostly used for producing customized high value products where price sensitivity is low. Literature reports that additive manufacturing mainly has been used where the costs of production is limited to a small number of parts compared to traditional manufacturing. Data is collected from a SME case study, where data on cost, time and quality is assembled to compare the different routes of additive and traditional approaches. Results show that product quality improves and that time to market is significantly reduced by having in-house additive manufacturing capacity and capability. [ABSTRACT FROM AUTHOR]

• Cost estimation of digital light processing in end-use part production during the early product-development process and beyond. • Insights into cost structure and cost drivers, influence of machine sizes and automation concepts. • Application to an automotive end-use part production case study using the CLIP process. Within the last years, digital light processing (DLP) became a viable solution for the manufacturing of end-use parts in various industries among other additive manufacturing (AM) processes. As the number of applications realized in a rapid manufacturing (RM) approach grows, it is necessary to understand the process economics better when moving from laboratory and prototyping applications into the cost-sensitive production scale. This paper presents a production-centered economic assessment of DLP production in the early product development process, based on Continuous Liquid Interphase Printing (CLIP). It is applied to an automotive exterior part case study to reveal expected process economics and estimate part prime cost for different printer sizes and automation concepts. A subsequent sensitivity analysis assesses the influence of relevant cost drivers and identifies opportunities for further cost savings when producing end-use parts with DLP. Results may help machine OEMs and application developers in cost optimization and decision making in RM. [ABSTRACT FROM AUTHOR]

Integration of additive manufacturing (AM) into series production demands for comprehensive methods and tools. An agent-based process chain simulation framework is proposed to embed AM into a cyber-physical production system. A multi-dimensional evaluation supports the planning of AM process chains as well as their day-to-day operation. The detailed evaluation possibilities down to product and single simulation event level are illustrated by a case study, in which an automotive exterior part is produced using the multi-jet fusion technology. Multiple possible process chain configurations are assessed based on their modeled key performance indicators, summarized in a energy value stream map. [ABSTRACT FROM AUTHOR]

With additive manufacturing (AM) becoming a competitive manufacturing process for low to medium production volumes, rapid manufacturing becomes an increasingly relevant manufacturing approach. However, regulations and customers demand more eco-efficient life-cycles of products. This requires engineers and designers to pre-select between productive AM processes like selective laser sintering (SLS) and multi-jet fusion (MJF), based on their expected environmental impact in series production. As SLS already debuted in the mid-1980s, researches broadly explored parts' mechanical properties, energy and resource use. The multi-jet fusion (MJF) technology, introduced in 2017, delivers comparable part properties at considerably higher print speeds. However, its energy and resource use is still scarcely covered. To close this gap, this publication develops a model for evaluation of energy and resource utilization based on a case study with an automotive exterior series part using an EOS P396 SLS and a HP 4200 MJF machine. Data from measurements in energy and material consumption as well as the print job shows a good predictability and builds the basis for an environmental assessment. The derived model and its functional blocks allow estimation and comparison of sustainability for different use cases in rapid manufacturing with MJF and SLS. Despite the process similarities, results concerning greenhouse gas emissions and cumulative energy demand are different. The gained insights enhance pre-selection of manufacturing strategies, a suitable printing technology and the evaluation of AM processes during manufacturing according to sustainability aspects. Printer manufacturers and users may find this research insightful for improvements in sustainability and comparability of future AM processes. [ABSTRACT FROM AUTHOR]

Currently, mass composite manufacturing is dominated by the fiber-reinforced thermosets due to the ease of its processing. However, the addition of multifunctionality to the thermoset composite requires an additional step of manufacturing. This work presents the single-step rapid manufacturing of bespoke designed multifunctional nanocomposite PA6 components. In this method, firstly, the liquid PA6 nanocomposite containing inorganic nano-inclusions was infused into a glass or carbon fibre matrix placed within the mould. Subsequently, the multifunctional composite component was formed via the anionic in-situ synthesis route. The flexibility of this method presented is akin to that of a polymer moulding process, which ensures a reduction in the manufacturing cycle times and increases the production efficiency of the bespoke component. The in-situ reaction is optimised by setting the specific volume of the activator, initiator and including polymer chain terminator, PEG. To prepare the polymer with at least 50% and above crystallinity, the most suitable activator-initiator combination was found to be 0.143 ml and 0.096 ml respectively, with 0.1 g of PEG-6000 for 5 g sample preparation. Such thermoplastic-based components can be easily recycled, present better impact resistance and can be easily formed or fused with heat; eliminating the cost and time associated with the assembly of composite part, unlike thermoset components. [ABSTRACT FROM AUTHOR]

Additive manufacturing is a key technology which applies the ideas of Industry 4.0 in order to enable the production of personalized and highly customized products economically. Especially small and medium sized companies often lack the competence and experience to evaluate objectively and profoundly the potential of additive manufacturing technologies. This paper presents a systematic and user-oriented method for a suitability analysis for the application of additive manufacturing technologies in small and medium sized companies. Furthermore, the method has been validated in a small medical technology company evaluating the additive manufacturing potential of an existing surgery tool. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) is a technology with increasing awareness within industrial production. Whereas rapid manufacturing and rapid prototyping are well known fields of application, AM-based spare part production or AM-based co-creation have a rather visionary character. Nevertheless, companies have started using AM along the product life cycle – from the generation of a product idea, through series production to the supply of spare parts. The findings of the explorative study offer insights into existing and emerging AM-based application fields. Moreover, it gives an overview about the benefits and challenges of implementing those into existing structures in companies in the industrial sector. It is apparent that AM is a complementary manufacturing technology in industrial production. However, the results of this exploration show that uncertencies remain in emerging application fields. [ABSTRACT FROM AUTHOR]

Abstract This paper aims to (1) compare implementation considerations and challenges for metal and polymer rapid manufacturing (i.e. the use of additive manufacturing technologies for final part production) for mass customisation and (2) derive decision trees for firms seeking to implement such an approach. Implementation data from 10 case studies from the dental and hearing aid industries has been captured and used as the basis for the comparison and design of the decision trees. Our objective is to provide evidence on the use of additive manufacturing technologies as enablers for mass customisation and to provide practitioners in industry with guidelines for decision-making on how to install and ramp-up mass customisation production with these technologies. Common considerations and challenges for both metal and polymer applications have been identified. Based on these insights, eight implementation decision trees have been created and represent the main contribution of this paper. [ABSTRACT FROM AUTHOR]

As part of the cosmos of digital fabrication technology, Additive Manufacturing (AM) systems are able to manufacture three-dimensional components and products directly from raw material and 3D design data. The layer-by-layer operating process of these systems does not require the use of tools, moulds or dies. Technology observers speculate that AM will have a profound economic impact on the manufacturing sector and indeed on wider society. By constructing a model of production cost for two different AM systems used commercially for the manufacture of end-use metal parts, Electron Beam Melting (EBM) and Direct Metal Laser Sintering (DMLS), this paper performs an inter-process comparison of cost performance. High specific costs, measured at £2.39 and £6.18 per cm 3 of material deposited respectively, are identified as a central impediment to more widespread technology adoption of such additive systems. The research demonstrates differing levels of system productivity, suggesting that the observed deposition rates are not sufficient for the adoption of EBM and DMLS in high volume manufacturing applications. Despite the absence of amortisable tooling costs, the analysis also reveals that economies of scale are achievable in AM. The results reached are further discussed in the light of the varying strategic requirements posed by the market-pull and technology-push modes of innovation which are both found in the AM industry. [ABSTRACT FROM AUTHOR]

Copyright of Technological Forecasting & Social Change is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Additive Manufacturing technologies Selective Laser Sintering (SLS) and Selective Laser Melting (SLM) are capable to produce thermoplastic or metal parts, which are fit for end-user products. Both technologies create three-dimensional objects directly from a 3D CAD model with little restrictions regarding the shape of the object. This geometrical freedom in design can be utilized to largely improve the functionality of series products by substituting conventional parts with additive manufactured ones. Four criteria are presented here to identify components of a product for a re-design. A successful re-design has to meet the needs of the producer and his customers. The selection criteria and success factors for a re-design are demonstrated in four cases. [ABSTRACT FROM AUTHOR]

Abstract: A significant percentage of materials used in industry start in particulate form. In many modern applications, these systems undergo processing which necessitate a multiphysical analysis. Several manufacturing applications have arisen that involve the multiphysical response of particulate systems in the presence of strongly coupled electromagnetic, optical, and thermal fields. The significant multifield coupling requires methods that can capture the unique and essential physics of these systems. Specifically, in this work, the modeling and simulation of selective laser sintering of particulate materials is discussed. Such processes involve harnessing optical energy to heat and fuse powdered materials together in an additive process. Selective laser sintering allows for the rapid manufacturing or prototyping of parts with complex geometries. In order to simulate such a process in a rapid manner, the approach pursued by the authors is to develop a computational tool by assembling relatively simple, physically meaningful, models at the small scale, for many interacting particles. This allows for much more refined estimates of the resulting overall system temperature and, ultimately, its change of phase from a solid, to a liquid, and possibly even to a gas. Large-scale three-dimensional examples are provided. [Copyright &y& Elsevier]

Abstract: Electroforming is an electrolytic process that enables the manufacture of metallic parts with good mechanical properties and a high level of accuracy and reproducibility. In this process a thin metallic shell is deposited onto a model part and later released from it. However the two main disadvantages of electroforming are the non-uniform thickness distribution and the high time of processing. Procesos de Fabricación research group, of the University of Las Palmas de Gran Canaria (ULPGC), has been working in the electroforming process and its applications focused on rapid manufacturing techniques, for the last twelve years. Elecform3DTM product is an innovative numerical analysis and simulation tool of electroforming process, based on the boundary elements method, which aims to facilitate design and manufacturing tasks for metallic shells production. This product work enables better thickness uniformity as well as lower time manufacturing, achieving High Speed Electroforming therefore enabling new application fields. [Copyright &y& Elsevier]

Abstract: Additive manufacturing (AM) consists in building parts from scratch, usually by stacking layers onto one another. Mostly used for rapid prototyping purposes, several AM processes can use metallic alloys which makes the rapid manufacture of end-use parts possible. Many researches are conducted to improve the manufacturing rate, to assess the environmental impact or to study the mechanical properties of test parts manufactured by such processes. In spite of the large number of studies, there is yet to be a designing methodology to take advantage of these processes. The formalization of the manufacturing capabilities and manufacturing constraints that these processes have has especially hardly been conducted. In this paper we investigate the manufacturing constraints of the Electron Beam Melting process, a metallic additive manufacturing process in order to issue recommendations to the designers. We will review the principle of Electron Beam Melting and look at the manufacturing capabilities designers are offered. Then we will focus on some key manufacturing constraints, the powder removing and the necessity of supporting structures. At last, we will give some recommendations regarding these two topics to take advantage of this process from the designing stage of a part. [Copyright &y& Elsevier]

Abstract: Powder bed fusion is a laser additive manufacturing (LAM) technology which is used to manufacture parts layer-wise from powdered metallic materials. The technology has advanced vastly in the recent years and current systems can be used to manufacture functional parts for e.g. aerospace industry. The performance and accuracy of the systems have improved also, but certain difficulties in the powder fusion process are reducing the final quality of the parts. One of these is commonly known as the balling phenomenon. The aim of this study was to define some of the process characteristics in powder bed fusion by performing comparative studies with two different test setups. This was done by comparing measured temperature profiles and on-line photography of the process. The material used during the research was EOS PH1 stainless steel. Both of the test systems were equipped with 200W single mode fiber lasers. The main result of the research was that some of the process instabilities are resulting from the energy input during the process. [Copyright &y& Elsevier]

Abstract: Laser direct metal deposition (LDMD) is a rapid manufacturing technique, dedicated to new part construction or worn part repairing. The process depends on a various range of parameters and the powder characteristics are one of the main crucial parameters. The powder (size,…) has then a direct impact on an optimized process behavior and the mechanical properties of the manufactured component. This paper focuses on powder investigation, for a better understanding of its influence. The work was performed with different batches of stainless steel AISI316 that have been analyzed and characterized before processing. This paper discusses the results derived from the manufactured samples, highlights the influence of the main powders characteristics and demonstrates the flexibility of the process when the powders meet the specifications. [Copyright &y& Elsevier]

Abstract: Sintered alumina ceramics are used as refractory materials for industrial aluminum furnaces. In this environment the ceramic surface is in permanent contact with molten aluminum resulting in deposition of oxidic material on its surface. Consequently, a lower volume capacity as well as thermal efficiency of the furnaces follows. To reduce oxidic adherence of the ceramic material, two laser-based surface treatment processes were investigated: a powder- based single-step laser cladding and a laser surface remelting. Main objective is to achieve an improved surface quality of the ceramic material considering the industrial requirements as a high process speed. [Copyright &y& Elsevier]

Abstract: Background context: Intervertebral disc implant size, shape, and position during total disc replacement have been shown to affect the risk of implant subsidence or vertebral fracture. Rapid manufacturing has been successfully applied to produce patient-specific implants for craniomaxillofacial, dental, hip, and knee requirements, but very little has been published on its application for spinal implants. Purpose: This research was undertaken to investigate the improved load distribution and stiffness that can be achieved when using implants with matching bone interface geometry as opposed to implants with flat end plate geometries. Study design: The study design comprises a biomechanical investigation and comparison of compressive loads applied to cadaveric vertebrae when using two different end plate designs. Methods: Four spines from male cadavers (ages 45–65 years, average 52 years), which had a total of n=88 vertebrae (C3–L5), were considered during this study. Bone mineral density scans on each spine revealed only one to be eligible for this study. Twenty remaining vertebrae (C3–L3) were potted and subjected to nondestructive compression tests followed by destructive compression tests. Custom-made nonfunctional implants were designed for this experiment. Ten implants were designed with matching end plate-to-bone interface geometry, whereas the other 10 were designed with flat end plates. Testing did not incorporate the use of a keel in either design type. I-Scan pressure sensors (Tekscan, Inc., MA, USA) were used during the nondestructive tests to assess the load distribution and percentage surface contact. Results: Average percent contact area measured during nondestructive tests was 45.27% and 10.49% for conformal and flat implants, respectively—a difference that is statistically significant (p<.001). A higher percent contact area was especially observed for cervical vertebrae because of their pronounced end plate concavity. During destructive compression tests, conformal implants achieved higher failure loads than flat implants. Conformal implants also performed significantly better when stiffness values were compared (p<.0001). Conclusions: One of the main expected benefits from customizing the end plate geometry of disc implants is the reduced risk and potential for subsidence into the vertebral bone end plate. Subsidence depends in part on the stiffness of the implant-bone construct, and with a 137% increase in stiffness, the results of this study show that there are indeed significant potential benefits that can be achieved through the use of customization during the design and manufacture of intervertebral disc implants. [Copyright &y& Elsevier]

Abstract: The Selective Laser Melting (SLM) process fabricates components from powders by adding material and its processing principle is based on track overlapping regime, which has been studied in this paper. The inter-layer stagger scanning strategy was employed to avoid nonuniform distribution of energy input. By theoretical deduction and experimental observation, three types of overlapping regime were revealed: intra-layer overlapping regime, inter-layer overlapping regime and mixed overlapping regime with coexistence of the first two types. The overlapping patterns and the corresponding microstructures were then discussed. Experimental result showed that specimens fabricated by inter-layer overlapping regime had high relative density when track space was not larger than 0.2mm. A cooling insert with relative density of about 93% was also obtained at track space of 0.12mm. [Copyright &y& Elsevier]

Abstract: Additive manufacturing technologies can now be used to manufacture metallic parts. This breakthrough in manufacturing technology makes possible the fabrication of new shapes and geometrical features. Although the manufacturing feasibility of sample parts with these processes has been the subject of several studies, the breakthrough in manufacturing is yet to be followed by a breakthrough in designing process. In this paper, after reviewing the principle of additive manufacturing of metallic parts, the manufacturing capabilities and constraints of these processes will be examined. A designing methodology will then be suggested and illustrated with the redesign of an example part. [Copyright &y& Elsevier]

Abstract: This study has been designed to investigate the effect of inert gas flow within the selective laser melting (SLM) process and the effects induced by this gas flow on the reproducibility of the key attributes (porosity and compression strength) created in the construction of porous titanium components. The work quantifies the characteristics of the manufactured parts and relates results of these characteristics to a predicted gas flow in the build chamber. The results were used to produce design iterations of the gas management system to improve the gas flow distribution in the chamber of a MTT ReaLizer SLM250 machine. Further experiments were then carried out to generate statistical data sets to correlate the flow field quantifying the affect of the redesign on the key measured attributes. Results showed that both the value and the standard deviation of the measured attributes were significantly affected by the improved gas flow, with porosity reducing by 1.7% and the standard deviation of compression strength improving from 12MPa to 5MPa. The design modifications have been incorporated into a new machine design to enable the production of porous components of closer control and greater reproducibility. [Copyright &y& Elsevier]

Abstract: Hybrid Layered Manufacturing is a Rapid Manufacturing process in which the metallic object is built in layers using weld deposition. Each layer built through overlapping beads is face milled to remove the scales and scallops and ensure Z-accuracy. The formations of single beads and overlapping multiple beads are modeled in this paper. While the individual bead’s geometry is influenced by the size of the filler wire and the speeds of the wire and torch, the step over increment between the consecutive beads additionally comes into the picture for the multiple bead deposition. These models were validated experimentally. They are useful not only to predict the bead’s shape but also to optimize the three process parameters. [Copyright &y& Elsevier]

Abstract: Direct Metal Deposition (DMD) is a laser cladding process for producing a protective coating on the surface of a metallic part or manufacturing layer-by-layer parts in a single-step process. The objective of this work is to demonstrate the possibility to create carbide-reinforced metal matrix composite objects. Powders of steel 16NCD13 with different volume contents of titanium carbide are tested. On the base of statistical analysis, a laser cladding processing map is constructed. Relationships between the different content of titanium carbide in a powder mixture and the material microstructure are found. Mechanism of formation of various precipitated titanium carbides is investigated. [Copyright &y& Elsevier]

Abstract: NiTi shape memory alloys are considered to be difficult to machine. Dimensional accuracy can hardly be met especially in micro-machining. Being a non-contact tool and therefore independent from machining forces, the laser is a promising alternative for manufacturing NiTi micro-parts. This paper presents research results on powder bedbased laser sintering of fine NiTi powders. Structures with a minimum width of approximately 50 μm can be generated without losing the special shape memory properties. The structures “remember” the shape which was set in the laser process. We show that phase transformation temperature can be influenced by process parameters. [Copyright &y& Elsevier]

Abstract: In this paper, the results of two different wire based additive-layer-manufacturing systems are compared: in one system Ti-6Al4V is deposited by a Nd:YAG laser beam, in the other by an arc beam (tungsten inert gas process). Mechanical properties of the deposits and of plate material are presented and evaluated with respect to aerospace material specifications. The mechanical tests including static tension and high cycle fatigue were performed in as-built, stress-relieved and annealed conditions. Generally, the mechanical properties of the components are competitive to cast and even wrought material properties and can attain properties suitable for space or aerospace applications. [Copyright &y& Elsevier]

Abstract: An additive manufacturing technique (AM) for ceramics, based on Al2O3–ZrO2 powder by means of Selective Laser Melting (SLM) is presented. Pure ceramic powder is completely melted by a laser beam yielding net-shaped specimens of almost 100% densities without any post-processing. Possible crack formation during the build-up process due to thermal stresses is prevented by a high-temperature preheating of above 1600 ∘C. Specimens with fine-grained nano-sized microstructures and flexural strengths of above 500 MPa are produced. The new technology allows for rapid freeform manufacture of complex net-shaped ceramics, thus, exploiting the outstanding mechanical and thermal properties for high-end medical and engineering disciplines. [Copyright &y& Elsevier]

Abstract: To up-grade SLM process for manufacturing real components, high mechanical properties of final product must be achieved. The properties of a part produced by SLM technology depend strongly on the properties of each single track and each single layer. In this study, effects of the processing parameters such as laser power, scanning speed and powder layer thickness on the single tracks formation are analyzed. It is shown that, by choosing an optimal technological window and appropriate strategy of SLM, it is possible to manufacture highly complex parts with mechanical properties comparable to those of wrought material. [Copyright &y& Elsevier]

Abstract: In laser cladding, the interaction of the substrate material, the laser beam and the powder stream play important roles in determining how the material is deposited. Previous models of the coaxial powder stream have concentrated either on mass flow dynamics or stream heating, neglecting the effect of the substrate. In this work, a comprehensive numerical model that considers the important parameters of the powder stream, the laser beam and the substrate material, is developed. It is clear from the work that the full three-way interaction of these elements, as in real processing situations, is necessary to accurately and reliably predict particle heating and effective fusion into the melt pool. [Copyright &y& Elsevier]

Abstract: Currently many aircraft and aero engine components are machined from billets or oversize forgings. This involves significant cost, material wastage, lead-times and environmental impacts. Methods to add complex features to another component or net-shape surface would offer a substantial cost benefit. Laser Metal Deposition (LMD), currently being applied to the repair of worn or damaged aero engine components, was attempted in this work as an alternative process route, to build features onto a base component, because of its low heat input capability. In this work, low heat input and high-rate deposition was developed to deposit Inconel 718 powder onto thin plates. Using the optimised process parameters, a number of demonstrator components were successfully fabricated. [ABSTRACT FROM AUTHOR]

Abstract: Selective laser melting (SLM) is a powder-based additive manufacturing capable to produce parts layer-by-layer from a 3D CAD model. Currently there is a growing interest in industry for applying this technology for generating objects with high geometrical complexity. To introduce SLM process into industry for manufacturing real components, high mechanical properties of final product must be achieved. Properties of manufactured parts depend strongly on each single laser-melted track and each single layer. In this study, effects of the processing parameters such as scanning speed and laser power on single tracks formation are explored. Experiments are carried out at laser power densities (0.3–1.3)×106 W/cm2 by cw Yb-fiber laser. Optimal ratio between laser power and scanning speed (technological processing map) for 50μm layer thickness is determined for stainless steels (SS) grade 316L (−25μm) and 904L (−16μm), tool steel H13 (−25μm), copper alloy CuNi10 (−25μm) and superalloy Inconel 625 (−16μm) powders. A considerable negative correlation is found between the thermal conductivity of bulk material and the range of optimal scanning speed for the continuous single track sintering. [Copyright &y& Elsevier]

Abstract: Designing load bearing implants with the desired mechanical and biological performance and to fabricate net shape, functional implants with complex anatomical shapes is still a challenge. In addition, patient specific load bearing implants with the possibilities of guided tissue regeneration are gaining significant interest in orthopedics. Novel design approaches and fabrication technologies that can achieve balanced mechanical and functional performance in mono-block implants are necessary to accomplish these objectives. In this article we give an overview of our novel design concepts for load bearing metal implants and demonstrate the manufacturing of unitized implant structures with and/or without porosity using laser engineered net shaping (LENS™) — a solid freeform fabrication technique. We have fabricated porous metal implants with designed porosities up to 70vol.% in various biomedical metals/alloys, such as Ti, Ti6Al4V, NiTi and CoCrMo, and tailored their effective modulus to suit the modulus of human cortical bone, thus eliminating stress-shielding. Unitized structures with functionally graded CoCrMo alloy coating on porous Ti6Al4V alloy have been fabricated using LENS™ to minimize wear induced osteolysis. Finally, this technology can also be used to fabricate porous, net shape implants with functional gradation in structure and/or composition to mimic natural bone. Since the LENS™ fabrication does not change the chemistry of the biocompatible alloys the inherent in vitro and in vivo biocompatibility will remain the same and therefore, we have not provided any biocompatibility results in this article. This article provide an insight into the important aspects of LENS™ fabrication and properties of CoCrMo alloy structures, which can potentially eliminate long standing challenges in load bearing implants such as total hip prosthesis to increase their in vivo life time. [Copyright &y& Elsevier]

Abstract: Selective laser melting (SLM) is emerged as a new manufacturing technique to directly fabricate customised implants using metallic materials. This technique is also capable of processing powder mixtures to generate advanced composites offering desirable properties. In this research, the SLM technique was used to directly fabricate hydroxyapatite (HA) and 316L stainless steel (SS) powders mixture with an objective to develop load-bearing and bioactive implants. SLM processing parameters were identified to fabricate pure SS and SS/HA composite specimens. The visual inspections, density measurements, tensile and hardness tests, and microstructural examinations was conducted to illustrate the effect of SLM parameters and HA particles on the properties of SS/HA composites. It was found that the incorporation of HA particles influenced SLM processing parameters including laser power, scanning speed and scanning procedure. A duplication of scanning procedure was necessary to avoid the balling effects and to form well joined SS/HA composite layer. The highest tensile strength of SS/HA parts produced at optimum processing parameters was close to human bone tensile strength and adequate for load-bearing bone implants. Moreover, the SS/HA part had a finer grain size than that of the SS attributed to the HA particles as nuclei to assist heterogeneous nucleation. These finer grains enhanced the hardness of the SS/HA part. [Copyright &y& Elsevier]

Abstract: Rapid Manufacturing, and specifically Selective Laser Sintering, has the potential to become one of the most useful manufacturing techniques of the future, largely as a result of the extremely high levels of geometric complexity which can be produced. As the use of these technologies becomes more widespread, so the amount, and variety, of materials available for use in these processes also increases. However, the Selective Laser Sintering process can be both expensive and time-consuming when testing new materials. A method of off-line casting has been proposed here, and the tensile properties of parts produced using this method are compared with the properties achieved in Selective Laser Sintered parts produced in the same materials. For the materials tested it has been shown that the casting method provided an acceptable correlation with the properties of the Selective Laser Sintered parts, rendering this a suitable method of assessing the properties of a Selective Laser Sintering material without the requirement to produce a full build. [Copyright &y& Elsevier]

Abstract: Selective laser melting (SLM) allows manufacturing porous 3D parts with customized near-net shape and internal geometry designed at the stage of their computer modeling. The relations between laser operational parameters, computer design of the manufacturing object, composition and microstructure of the obtained fine porous structures are discussed. A series of experiments are carried out on PHENIX PM-100 machine to analyze the influence of the manufacturing strategy on anisotropy and regularity of the internal structure of samples from stainless steel, nickel alloys and metal–polymer powders. The issues of accurate reproduction of the parts geometry, strategy of manufacturing thin-walled 3D filters and filters with customized pattern of the micron-sized channels are addressed. Effect of the porous structure on the material filtering performance is analyzed in order to optimize and diversify design of the porous materials for a given application and to improve their operational behavior. [Copyright &y& Elsevier]

Abstract: Building three dimensional objects in sequential layers is a technique employed by Rapid Manufacturing processes which allow great freedom in the design of the manufactured component. Niche markets for these technologies are continually developing and they challenge conventional methods of design and procurement. In the last few years there have been large scale processes for construction applications developed based on Rapid Manufacturing principles. These processes offer construction automation, the promise of design freedom and the possibility of building in additional functionality into structures. This paper explores the issues surrounding design, data and process in terms of the impact Rapid Manufacturing has had on conventional manufacturing. Large scale processes for construction are described and these issues are then used as the basis for considering the impact these machines may have on the design and production of construction components. [Copyright &y& Elsevier]

Abstract: A range of metallic lattice structures have been manufactured using the selective laser melting (SLM) rapid manufacturing technique. The lattice structures were based on [±45°] and [0°, ±45°], unit-cell topologies. Initially, the structures were loaded in compression to investigate their progressive collapse behaviour and associated failure mechanisms. Tests were then undertaken at crosshead displacement rates up to 3m/s in order to characterise the rate-dependent properties of these architectures. A series of blast tests were then undertaken on a ballistic pendulum in order to investigate the behaviour of lattice structures under these extreme loading conditions. During the compression tests, a buckling mode of failure was observed in the [0°, ±45°] lattice structures, whereas a stable progressive mode of collapse was evident in the [±45°] structures. The yield stress of the lattice structures exhibited moderate rate sensitivity, increasing by up to 20% over the range of conditions considered. The blast resistance of the lattice structures increased with increasing yield stress and has been shown to be related to the structures specific energy-absorbing characteristics. An examination of the lattice samples indicated that the collapse mechanisms were similar following both the compression and blast tests. [Copyright &y& Elsevier]

Abstract: Rapid prototyping process called Optoform shapes functional parts from a photocurable paste. This paste contains metal powder, resin, UV photoinitiator and wetting agent. After processing on the Optoform machine, a post-treatment is applied (debinding+sintering). During the post-treatment, the residual carbon coming from the resin modifies the composition of the metal and its melting point. This modification affects densification mechanisms, which leads to a residual porosity that lowers mechanical characteristics. We will present theoretical consideration leading to the optimization of the formulation. To improve the process, bimodal powder is used and thermal treatment is adapted. [Copyright &y& Elsevier]

Abstract: The free-form net shape laser synthesis of nanostructured ceramics from liquid precursors enables a residual stress-free production of high temperature resistant ceramic units and components for the use in microsystem engineering. Due to the use of molecular compounded liquid, ceramic precursors the resulting ceramic components show outstanding properties, for example high purity and a nanostructured material design. The use of pulsed lasers enables a defined input of energy required to pyrolyse the precursor material into a crystalline ceramic, so the active volume can be reduced significantly compared to other processes, for example pyrolysis by furnace. In this paper several methods for a further minimization of the active volume are presented. The investigations determined different factors affecting the process. Realizing selective experiments allows a determination of their influencing level and the definition of a working area to produce three-dimensional components with high aspect ratio. By several studies, e.g., scanning electron microscopy, transmission electron microscopy as well as X-ray diffraction analysis, the atomic structure and composition of the created components were analyzed and valued, so the different reaction processes can be described extensively. [Copyright &y& Elsevier]

Abstract: Application of selective laser melting for manufacturing three-dimensional objects represents one of the promising directions to solve challenging industrial problems. This approach permits to extend dramatically the freedom of design and manufacture by allowing, for example, to create an object with desired shape and internal structure in a single fabrication step. The design of the part can be tailored to meet specific functions and properties (e.g. physical, mechanical, chemical, biological, etc.) using different materials. Metallic objects were manufactured by Phenix PM 100 machine from Inconel 625 powder. The objective was to analyze the influence of the manufacturing strategy on the internal structure and mechanical properties of the components manufactured by selective laser melting technology. Anisotropy of the internal structure and mechanical properties of the fabricated objects were studied. [Copyright &y& Elsevier]

Abstract: In the present paper, porous refractory ceramics synthesized by selective laser sintering/melting from a mixture of zirconium dioxide, aluminum and/or alumina powders are subjected to optical metallography and X-ray analysis to study their microstructure and phase composition depending on the laser processing parameters. It is shown that high-speed laser sintering in air yields ceramics with dense structure and a uniform distribution of the stabilizing phases. The obtained ceramic–matrix composites may be used as thermal and electrical insulators and wear resistant coating in solid oxide fuel cells, crucibles, heating elements, medical tools. The possibility to reinforce refractory ceramics by laser synthesis is shown on the example of tetragonal dioxide of zirconium with hardened micro-inclusion of Al2O3. By applying finely dispersed Y2O3 powder inclusions, the type of the ceramic structure is significantly changed. [Copyright &y& Elsevier]

Abstract: Due to global competition and product mass customization, the manufacturing industry is now under more pressure than ever to look for and take advantage of processes that can provide flexibility and cost savings to cope with small batches and rapid product changes. Rapid prototyping technology has gained very good acceptance for the quick fabrication of prototypes with low cost irrespective of the complexity of the shape. However, it is cost prohibitive to make more than a handful of models and part materials are also limited. In an attempt to develop a rapid and economical method for making tools with low volume production, some particulate reinforced epoxy composites were investigated in this study. Metal, ceramic or mineral salt powders were used as the particle, respectively and epoxy for the matrix. The mechanical and thermal properties of the above composites in different ratios of fillers were tested to verify the suitability for injection molds and the improvement of material characteristics. By analysis and comparison, a suitable composite, 20% alumina powder filled epoxy composite, was found to work best. A benchmark was designed and built for checking the dimensional accuracy of the tool making process. Also a set of injection mold insert with core and cavity was fabricated using the developed composite material to demonstrate the injecting of thermoplastic parts. [Copyright &y& Elsevier]

Abstract: Selective laser sintering/melting (SLS/SLM) technology is used for manufacturing net-shaped objects from commercial Inox 904L powder with ≤20μm particle size. Experiments were carried out on PHENIX-PM100 machine equipped with a 50W cw fiber laser. Powder is layered by a roller over the surface of a 100mm-diameter build cylinder. Optimal parameters of layer thickness and power input per unit speed for SLM were determined. It was shown that the greater the value of P/V ratio is, the larger is the remelted line (called as “vector”). Influence of the shifting of consecutive single vectors on the process of forming the first layer was studied. Different strategies for forming objects with less than 1mm-sized inner structures were tested, as, for example, forming a 20mm×20mm×5mm box with 140μm-thick inner compartment walls. [Copyright &y& Elsevier]

Abstract: The present work concerns the hardware development of a mid-size humanoid robot, Bonobo, focusing on the use of an integrated application of CAD/CAM/CAE and rapid prototyping (RP) for the rapid development of the robot''s outer body parts. Most parts were three-dimensionally designed with 3D CAD, which enables effective connection with CAE analyses, the basis of which lays in kinematic simulation and structural analysis. To reduce the lead time and investment cost of developing parts, RP and CAM are selectively used to manufacture master parts for the body. These master parts are then replicated by using a vacuum casting process, from which we can repeatedly obtain plastic parts. Through this integrated approach, we successfully developed a prototype of Bonobo with a relatively low time and investment cost. [Copyright &y& Elsevier]

Abstract: Rapid prototyping and manufacturing (RPM) technologies have been widely adopted by the industry because of the potential of these technologies to rapidly fabricate three-dimensional parts with geometrical complexity from a CAD model in a CAD/CAM environment. Machining processes as RPM technologies have shown the fundamental disadvantages of unsatisfactory cutting mechanisms, such as excessive cutting time and leftover material caused by the cutting mechanism. Therefore, a new rapid manufacturing process using the heated tool, rapid heat ablation (RHA) process, has been developed with a new material removal method in order to solve the problems. In this paper, the tool for the RHA process is devised to minimize the heat-affected zone and also investigated for verification. TRIZ well known as creative problem solving method is applied to resolve the contradictive requirements of the tool. The devised tool has tangential grooves on the side of the tool separated into two regions for minimization of the heat-affected zone. For the detailed design of the tool, numerical model is established with several assumptions. Numerical and experimental results show that the devised tool fulfils its requirements. It demonstrates the practicality of the tool that three-dimensional shapes are ablated using the heated tool with tangential grooves. [Copyright &y& Elsevier]

Abstract: Previous reported work on the selective laser melting of a H13 tool steel powder bed surface has shown that there is a scan speed range in which the layer mass increases/fluctuates with increasing speed. This paper expands the investigation towards M2 tool steel and 316L stainless steel powders to identify if they reveal similar behaviours. Wide ranges of scan spacings and scan speeds have been examined, at selected laser powers. Furthermore, the masses of the layers have been compared with those predicted from an existing finite element thermal model. It has been found that at a constant laser power, the variation of mass with scan speed is much less than might be expected from a constant assumed absorptivity into a powder bed. [Copyright &y& Elsevier]

Abstract: Rapid prototyping (RP) and more recently rapid manufacturing (RM) as a part of Engineering Assisted Surgery™ enables manufacturing of customised implants and prostheses prior to surgical procedures. Beginning with CT or MRI scans, implants can be customised—designed for a named patient and optimised for shape and mechanical requirements using digital data only, disregarding all physical models except for the final implant. In this paper, a route to digitise the design of an existing implant is described, consisting of transfer of CT data, design of the prostheses, FE analysis, rapid manufacturing from titanium, and quality control. [Copyright &y& Elsevier]

Abstract: The utilisation of automation technology and processes control found in the automotive and aerospace industries is not paralleled in modern day construction. The industry also struggles to improve health and safety issues and still uses traditional methods of procurement. These problems are compounded by the diminishing skills in the labour force. Methods of production must change if these issues are to be resolved. Rapid Manufacturing is a family of digitally controlled additive processes that have the potential to impact on construction processes. This paper outlines some of the major issues facing construction technology and gives examples of the use of large scale Digital Fabrication in the industry. The term ‘Freeform Construction’ is defined. Potential applications derived from an industrial workshop are presented and results from a series of preliminary studies indicate the viability of mega-scale Rapid Manufacturing for construction. [Copyright &y& Elsevier]