Published Article / The paper presents a critical review of the techniques that are used to cool plastic injection moulds. It examines research on cooling of injection moulds by conventional cooling, the benefits and the limitations of the method. It compares the deployment mechanisms that have been proposed by various researchers. It also examines how the various mechanisms affect the plastic cooling rate and the overall heat transfer performance of the mould and how the various deployments affect the stress distribution of the mould and mould durability. The paper also presents the possibilities that have been presented by rapid prototyping. It discusses the development of conformal cooling as an alternative to conventional cooling. It presents the state of the art on the method. The paper presents the deficiencies in the current theories on conformal cooling and suggests areas that require further work in order to fully exploit the technique.

Published Article / This article looks at the role that vacuum casting plays in the rapid prototyping and rapid manufacturing process. The accuracy to which components can be reproduced, by looking at the controllable factors in the casting process and the different types of materials that are available, were investigated and the process was also compared to other rapid prototyping and manufacturing processes in terms of cost effectiveness. Castings were made from a typical component under different operating conditions and the characteristics of the cast component, dimensions strength and surface hardness, were measured and plotted to determine the characteristics and accuracy of the process.

Published Article / Over the past few years, methods of layered manufacturing (LM) have advanced substantially to the point where they now provide vital strategic benefits to various organisations. One area of application where LM technologies have begun to reach a critical mass is in the development and production of high-performance tooling in different forming processes. With these tooling capabilities now available, the next challenge becomes the development of optimal process chains to minimise lead times and production costs, while still ensuring high quality of castings. The relevant issues that influence where a break-even point will be between different process chains and thereby also the point of selection between such optimal process chains according to different situations include among others: <ul> <li> the size of production runs, </li> <li> part size and complexity, and</li> <li> the cast materials involved.</li> </ul> <br>This paper reflects some of the experiences gained from an investigation towards developing a set of generic rules (guidelines) for the design of optimal process chains for sand casting prototypes of automotive components using LM methods, and more specifically the 3D Printing process.

Published Article / This paper looks at the development of composite materials in layered manufacturing. It is known that Rapid Prototyping (RP) using a single material compares poorly with other conventional manufacturing processes when making parts from similar materials. For example, injection moulded parts are over 30% stronger than RP fabricated parts of the same material. The incorporation of secondary materials can result in a composite that can improve this situation. This paper will discuss different composites that are commercially available as well as some into which research is being conducted. An advantage of RP is that composites do not have to be manufactured in a homogeneous manner. Functionally graded parts may be fabricated where reinforcing material can be added in appropriate locations and in required orientations.

Published Article / This paper identifies the most significant technological developments made in medical applications of rapid prototyping and manufacturing (RP&M) over the past decade. This assessment is based on a retrospective analysis of the research undertaken by the Medical Applications Group of the National Centre for Product Design and Development Research (PDR), based at the University of Wales lnstitute Cardiff (UWIC). UK. The paper describes the state of technology at the inception of the Group in 1998 and then highlights the significant technological developments that impacted on the activities of the Group over the decade to 2008. The paper will also discuss how these technologies have developed since their initial implementation. The paper will conclude with suggested directions future work should take in order to meet clinical and technical needs.

Published Article / Current fused deposition modelling (FDM) technologies deposit material as flat layers. The result is a "stair-case" effect on non-vertical or horizontal surfaces, and compromised part strength because of weakness between the laminations. This paper describes an FDM method through which layers of build material are deposited as curved layers following the shape of the part, thus removing the stair-case effect and creating parts that have an even strength distribution over their entire surface. Support material is first deposited as conventional flat layers, and build material is then deposited over the support structure following the curves of the part. The paper discusses a proof of concept of the system, the algorithms used to generate the curve paths for the deposition head, and examines the challenges and possibilities of this technology, including the capability of including composite materials.

No description available.

No description available.

Die Erstellung von komplex geformtem Knochenersatz wurde durch den 3D-Pulverdruck unter Verwendung von Calciumphosphatmaterialien beschrieben. Gegenstand der vorliegenden Arbeit war deren Modifikation durch die Verwendung von Methacrylatkunststoffen. Ziel war es, durch die Infiltration von nicht resorbierbaren Kunststoffen, wie sie in kommerziell erhältlichen Knochenzementen verwendet werden, die mechanischen Eigenschaften der nicht gesinterten Keramikstrukturen zu verbessern. Getestet wurden verschiedene Methoden der Infiltration sowie der nachfolgenden Polymerisationsinitiierung durch chemische, thermische oder photochemische Aktivatoren. Daneben erfolgte der Druck von Tricalciumphosphat-Pulvern, die mit Polymethylmethacrylat Partikeln versetzt wurden und durch eine hydraulische Verfestigungsreaktion mit Phosphorsäure aushärten. Die erstellten Materialien wurden auf ihre Porosität, ihre mechanischen Eigenschaften sowie auf die Phasenzusammensetzung ihrer anorganischen Matrix und den Konversionsgrat ihrer organischen Komponente hin untersucht. Es gelang, die freie Porosität der Calciumphosphat-Matrix durch Verwendung von flüssigen, monomeren Kunststoffen zu füllen und diese durch eine thermische Initiierung der radikalischen Polymerisation vollständig zur Aushärtung zu bringen. Bei der Reaktion kommt es neben einer Polymerisationskontraktion im organischen Bestandteil der Kunststoffe zu einer Phasenumwandlung der Bruschitanteile der Calciumphosphat-Matrix. Proben, die mit einem flüssigen Bisphenol-A-Derivat versetzt wurden, zeigten eine Verdreifachung ihrer Festigkeit und erreichten maximale Druckfestigkeiten von 99 MPa, Biegefestigkeiten von 35 MPa und einen E-Modul von 18 GPa. Verglichen mit den biomechanischen Eigenschaften des physiologischen Hartgewebes liegen die Werte damit deutlich über denen von spongiösem und unter denen von kortikalem Knochen. Eine künftige Optimierung erscheint durch die Schaffung einer chemischen Verbundphase zwischen dem anorganischen Calciumphosphat-Gefüge und den Polymerbestandteilen als aussichtsreich. / The production of complex shaped bone graft was described by the 3D powder printing using calcium phosphate materials. The present work dealt with the modification of these materials by adding methylacrylate materials. The objective was to improve the mechanical properties of non-sintered ceramic structures by the infiltration of non-resorbable plastics such as used in commercialized bone cements. Different methods of infiltration as well as chemical, thermal or photochemical polymerization activators have been tested. In addition to that, tricalcium phosphate powders have been enriched by polymethylmethacrylate particles before being printed and cured by an hydraulic hardening reaction with phosphoric acid. The prepared materials have been tested for their porosity, their mechanical properties as well as for the phase composition of their inorganic matrix and the conversion rate of their organic components. It could be achieved to fill the open porosity of printed calcium phosphate matrix by using liquid, monomeric plastics and to cure them completely through a thermal initiation of radical polymerization. Besides the polymerization contraction in the organic component, the thermal treatment led to a phase transformation of the calcium phosphate brushite matrix. Samples, which were infiltrated with a liquid bisphenol-A derivative, showed a threefold increase of their strength and reached a maximum compressive strength of 99 MPa, a flexural strength of 35 MPa and a Young´s modulus of 18 GPa. Compared to biomechanical properties of physiological hard tissues, the levels were significantly higher than those of cancellous and lower than those of cortical bones. To further optimize, it seems promising to create a chemical bond between the inorganic phase of calcium phosphate microstructure and polymer components.

Fused Filament Fabrication (FFF) is a layer manufacturing process which can manufacture highly complex components from CAD files using a polymer extruder. RepRap is an open-source project to produce a rapid prototyping machine which can manufacture its own parts using the FFF process. This thesis focuses on the mechanical design of the ‘RepRap printer’ and documents how it was conceived, developed, tested, and finally used to make a set of its own parts. Self-manufacture was demonstrated by assembling this set of parts into a working copy of the original machine. The child machine went on to demonstrate replication without degeneracy by successfully manufacturing one of its own parts. A part count analysis of the child machine, not including the fasteners it needed in its early development phase, identified a self-manufacturing ratio of 48%. This proportion is relatively low because the design adopts modularity and redundancy principles to encourage development. Should the machine’s design be adapted to fully demonstrate self-manufacture, this ratio could rise to 67% in the near future. To increase the ratio further, the machine needs three new tool heads to print resin, conductive alloy, and flexible polymer. These developments are achievable in the mid-future and could increase the self manufactured parts ratio to 94%. As this machine is the first version of the RepRap printer, these results are encouraging. Parts which the RepRap printer is unlikely to make until the far-future include some of the electronic components, motors, conductive cable, solenoids and a heating element. However, a 94% self-manufacturing ratio will qualify it as an assisted self-replicating machine. As with natural self-reproducing organisms, the printer will benefit from geometric growth and evolution. The author discusses how, by trading power, computing, feedstock and assembly for manufacturing capability with human beings, the RepRap printer may become a household item, offering a radical alternative to the way our society manufactures and consumes.