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Thesis (MScEng (Industrial Engineering))--University of Stellenbosch, 2008. / This thesis forms part of the AMTS Project on Investment Casting Capabilities for Light Metal Alloys in South Africa, the focus area being Rapid Tooling Development. Various issues of the investment casting process are being discussed from an industrial engineering point of view. These issues are related to the possibilities of improving the investment casting process’ lead times by shortening it while still maintaining affordable costs and required quality. Hereby the possibilities given by the newly developed “rapid technologies” are investigated. The focus is on Rapid Pattern Making as one of the most essential components for accelerated development of new products. Three of the most widely used layer manufacturing processes available in South Africa are selected for the study, namely Three Dimensional Printing – Drop-on-Bed (ZCorporation), Selective Laser Sintering (EOS) and Three Dimensional Printing – Drop-on-Drop (ThermoJet - 3D Systems). These three methods represent different materials; therefore different mechanical properties, different process economics as well as different technological characteristics. A standard benchmark part is used as a study base. Four patterns are produced by these three methods. A comprehensive measurement programme is conducted, followed by an appropriate statistical analysis and evaluation regarding accuracy and surface finish. Rapid Die Making is analysed with the possibilities of using additive methods for rapid tooling. Two dies are built with the same technology – Selective Laser Sintering (EOS), but in different materials. The same evaluation methodology is used for the statistical analysis and comparison. The two dies are injected with wax in order to produce the original benchmark part. The best wax patterns from each die are selected and evaluated, using the same methodology for analysis and comparison. The current state of Direct Shell Production is shortly discussed. The research concludes that RP&T techniques can successfully be used for creating accurate patterns and dies in order to shorten lead times in the investment casting process chain. Each RP&T process has its own set of advantages and disadvantages. All users should evaluate their requirements and the capabilities of the variety of techniques before deciding on a process to apply.

<p>Doktorska disertacija razmatra primenu savremenih aditivnih proizvodnih tehnologija u postupku preciznog livenja ortopedskih implantata i njihov uticaj na skraćenje vremena i smanjenje tro&scaron;kova izrade topljivih modela. Konvencionalni postupak preciznog livenja ortopedskih implantata zahteva značajno vreme i tro&scaron;kove za izradu kalupa za topljive modele. U disertaciji je razvijena metoda za &bdquo;brzo precizno livenje&ldquo; kojom se elimini&scaron;e potreba za izradom kalupa za topljive modele ortopedskih implantata. Potrebno je utvrditi da li se pomoću predložene metode &bdquo;brzog preciznog livenja&ldquo; koja predstavlja integraciju aditivnih proizvodnih tehnologija i reverznog inženjerstva sa konvencionalnim preciznim livenjem, može dati značajniji doprinos daljem razvoju u oblasti izrade prilagođenih ortopedskih implantata.</p> / <p>The doctoral thesis discusses the application of modern additive manufacturing technologies in investment casting of orthopaedic implants and their impact on time and cost savings in meltable wax models development. The conventional procedure of investment casting of orthopaedic implants demands considerable time and costs when developing moulds for meltable wax models. The thesis shows a method of &ldquo;rapid investment casting&rdquo; developed to avoid the making the moulds for meltable wax models of orthopaedic implants. It is necessary to establish whether the proposed method of &ldquo;rapid investment casting&rdquo;, which integrates additive manufacturing technologies and reverse engineering with conventional investment casting, may give a significant contribution to further development of manufacturing of customized orthopaedic implants</p>