Published Article / Rapid tooling (RT) in the context of this research presents the possibility of improving the traditional investment casting process by shortening lead times while still maintaining affordable costs and required quality. Various rapid prototyping processes are available that can be used to create direct metal, polymer or wooden dies for this casting technology. This paper presents results gained in an AMTS project, focusing on RT development for investment casting of light metals. One of the most widely used layer manufacturing processes available in South Africa is selective laser sintering. A machine produced by the German manufacturer EOS (process known as laser sintering) utilising this technology was selected for the study. Two of the materials that are suitable for rapid die making are used, which in tum reflects different mechanical properties and process economics. A standard benchmark part was used as a study base. Two dies were built, one in alumide and one in polyamide. A comprehensive measurement programme was conducted, followed by an appropriate statistical analysis and evaluation regarding accuracy and surface finish. A number of wax patterns were produced. The best wax patterns from each die were selected and evaluated. The subsequently produced castings in AI, Mg and TI were further examined and evaluated. Various issues concerning the reinforcement, wax injection, pattern removal, accuracy and surface finish of the dies are discussed in the paper. The research concludes that rapid tooling techniques can be successfully used for creating accurate dies in order to shorten lead times in the investment casting process chain.

Cellular metals exhibit combinations of mechanical, thermal and acoustic properties that provide opportunities for various implementations and applications; light weight aerospace and automobile structures, impact and noise absorption, heat dissipation, and heat exchange. Engineered cell topologies enable one to control mechanical, thermal, and acoustic properties of the gross cell structures. A possible way to manufacture complex 3D metallic cellular solids for mass production with a relatively low cost, the investment casting (IC) method may be used by combining the rapid prototyping (RP) of wax or injection molding. In spite of its potential to produce mass products of various 3D cellular metals, the method is known to have significant casting porosity as a consequence of the complex cellular topology which makes continuous fluid's access to the solidification interface difficult. The effects of temperature on the viscosity of the fluids were studied. A comparative cost analysis between AM-IC and additive manufacturing methods is carried out. In order to manufacture 3D cellular metals with various topologies for multi-functional applications, the casting porosity should be resolved. In this study, the relations between casting porosity and processing conditions of molten metals while interconnecting with complex cellular geometries are investigated. Temperature, and pressure conditions on the rapid prototyping – investment casting (RP-IC) method are reported, thermal stresses induced are also studied. The manufactured samples are compared with those made by additive manufacturing methods.

This diploma thesis describes the process of production of the cast by the lost-wax casting method. It includes the manufacturing of prototype models by additive technology, creation of ceramic shell molds. The work also includes an experimental part focused on the production of the selected parts by the method of the lost-wax casting and the comparison of this method with other types of production.

Investment casting is a complex manufacturing method with many challenges that must be solved before components of the right quality can be produced. TPC is a company that utilizes investment casting to produce a variety of products, lately the company has higher ambition in wanting to cast higher technical demanding component like heat resistant gas turbine blades. This requires a sprue that can control the filling process, by allowing the fallen stream of molten metal to enter the moulds cavity in a laminar manner. This study has implemented the product development process by (Ulrich, 2012) to develop the requested sprue. The primary support for this study is study material given by the company also known as "PMG running spreadsheet TPC" base on theory and equations from (Jolly, 2002), which is believed to have origin in sand casting manufacturing process. The project began with recreating the textbook model after establishing a number of control parameter such as critical velocity. Then simulation software Nova flow was used to evaluate the velocity and FEM in Solidworks to study if the dimension of the model can be directly use for investment casting process. The results show that it was not possible, therefore in the concept generating phase only theory of casting was used to create new concept. Then 3 existing sprues were chosen for benchmarking to gain deeper understanding about their design intension. One of the concepts was inspired by the CEO Mark Irwin “concentric pipe design” and in total 10 concepts were created of which 6 were tested for both flow and FEM analysis. 2 concepts were chosen for further development which also became 2 final concepts, after 3 iterations of improvement. These concepts show that many improve in terms of laminar filling and higher yield than the existing benchmark sprues. Although further development is required.   The analysis shows that every step in the project has its own flaws, but that is the nature of being an engineer, as long as the problem encountered can be viewed with critical and analytical eyes. A well-considered and balanced solution can be provided, although nothing of this can be certain before a trail of test can provided to confirm any assumptions which is not included in this work.   The discussion section processes the thoughts, experience, and doubts about the project in general and the decision making leading to this report and what could have been done differently. The most significant lesson learn from this is that section is when solving a complex issue there must be very clear delimitations and well-defined goals to every specific solution. Otherwise the workload will be extensive and cause more harm than necessary.   The conclusion of this project shows that two concepts generated with the help from the product development process work better than the case study, which can be found in section 4.3, that was based on “PMG running spreadsheet TPC” calculation model, from the velocity perspective. To achieve this, the sprue uses its own geometry constrain and constricts the flow by collecting the molten metal in a “well” before the calmer stream could be distributed throughout the whole cavity. Indirectly this means that the studied material given from TPC AB could not be directly implemented into the investment production process. The given material should be seen as a complement and guidance when creating new sprues. Concerning the FEM analysis tool, it was helpful in this project in evaluating the sprues geometry expose to the assumed force in the production process to avoid unnecessary failure and therefore waste. Although if the company do not intend further work with the development of other sprues then this method is not necessary and would not have significant value to their current manufacturing process.

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.

Published Article / The design, manufacture and use of diaphragm valves in the minerals industry is becoming increasingly important since this sector is restricted from using excessive amounts of water for their operations. This forces a change in the flow properties of these devices from turbulent to laminar in nature and thus necessitates the characterization of these flows for future designs. Furthermore, diaphragm valves have a short service life due to a variety of reasons that includes the abrasive nature of the flow environment. This paper describes the activities of the Adaptronics Advanced Manufacturing Technology Laboratory (AMTL) at the Cape Peninsula University of Technology in the research and development of diaphragm valves using rapid prototyping technologies. As a first step, an experimental diaphragm valve was reverse engineered and retrofitted with ultrasonic transducers used in Ultrasonic Velocity Profiling (UVP) measurements. The use of this device enables measurements of velocity profiles to gain insight into the flow structure within the valve and the increased pressure losses generated within the valve. It also showed that components fabricated using the Z-Corporation machine could withstand the working environment of diaphragm valves. Research is now conducted on ultrasonic transducer placement in the device to further enhance the velocity profiling through the device. As a second step we produced a thin-walled stainless steel diaphragm valve using rapid prototyping technology and investment casting processes. A study of the durability of this device will be conducted and certain geometric and manufacturing aspects of this valve will be discussed.

Manufacturing processes are getting more and more complex with increasing demands of advanced and light weight engineering components, especially in aerospace industry. The global requirements on lower fuel consumption and emissions are increasing the demands in lowering weight of cast components. Ability to produce components in lower wall thickness will not only help to reduce the cost of production but also help to improve the efficiency of engineering systems resulting in lower fuel consumption and lesser environmental hazardous emissions. In order to produce thin-walled components, understanding of mechanism behind fluidity as it is effected by casting parameters is very important. Similarly, for complex components study of solidification morphology and its effects on castability is important to understand. The aim of this work was to investigate casting of thin-walled test geometries (less than 2mm) in aero-space grades of alloys. The casting trials were performed to investigate the fluidity as a function of casting parameters and filling system in thin-walled sections. Test geometries with different thickness were cast and evaluated in terms of filled area with respect to casting parameters, ı.e. casting temperature and shell preheat temperature. Different feeding systems were investigated to evaluate effects of filling mode on castability. Similarly for complex components where geometries are very organic in shape, solidification morphology effects the quality of castings. Process parameters, that effect the solidification morphology were identified and evaluated. In order to develop a relation between defect formation and process parameters, solidification behaviour was investigated using simulations and casting trials. Similarly the effect of factors that influence grain structure and flow related defects were studied. It was observed that fluidity is affected by the mode of geometry filling in investment casting process. The filling mode also have different effect on defect formation. A top-gated configuration is strongly affected by casting parameters where as a bottom-gated configuration is more stable and thus fluidity is not significantly affected by variation in casting parameters. Less porosity and flow-related defects were observed in the bottom-gated system as compared to top-gated system. In the study about casting defects as affected by process parameters, it was observed that shell thickness is important to avoid interdendritic shrinkage. It was observed that the increased shell thickness induces a steeper thermal gradient which is essential in order to minimize the width of the mushy zone. It was also observed that a slower cooling rate along with a steeper thermal gradient at the metal-mould interface not only helps to avoid shrinkage porosity but also increases fill-ability in thinner sections. The work presented here is focused on the optimization of process parameters, in order, for instance, to improve castability and reduce the casting defects in investment casting process. The work, however, does not focus on externally influencing the casting conditions or modifying the casting/manufacturing process. The future work towards PhD will be focused on externally improving the casting conditions and investigating other possible route of manufacturing for thin, complex components.

O processo de fundição por cera perdida representa, há muitos anos, o principal processo de produção gerador de peças de alta complexidade para atender os mais variados segmentos industriais tais como o automotivo, geração de energia, médico e bélico. A característica principal deste processo é a de obter cascas cerâmicas por meio de banhos de lama cerâmica ancorados por material refratário granulado aplicados sobre a superfície de modelos em cera com o formato da peça final. Estudou-se neste trabalho as propriedades do pó de telhas e também das cascas cerâmicas produzidas com lamas utilizando o próprio pó de telhas como material refratário tanto na lama primária quanto na lama secundária. O pó de telhas apresentou alta dispersão granulométrica #20-#325 mesh e em sua composição foram identificados compostos refratários importantes como a sílica e a alumina. Os ensaios realizados nas cascas cerâmicas confeccionadas com lamas de pó de telhas apresentaram resultados de módulo de ruptura à verde e calcinado (1000 °C) de respectivamente 1,02 MPa e 4,95 MPa e de permeabilidade a quente (1000 °C) 4,2 L/min. Os ensaios nas cascas cerâmicas utilizadas na indústria apresentaram resultados de módulo de ruptura a verde e calcinado respectivamente de 2,48 MPa e 5,7 MPa e permeabilidade de 3,8 L/min. As cascas cerâmicas confeccionadas com pó de telhas apresentaram módulo de ruptura inferior as cascas industriais, porém, com resultado de permeabilidade superior. As cascas cerâmicas com lamas de pó de telhas apresentaram bom comportamento durante o vazamento dos metais líquidos alumínio 356, bronze e ferro fundido cinzento, não foi observado quebras no molde e nem reação com o metal. As peças fundidas com as cascas cerâmicas produzidas com lamas de pó de telhas atenderam as tolerâncias dimensionais exigidas pela norma ABNT NBR 15990. / The lost wax process has for many years been the main production process generating parts of high complexity to meet the most varied industrial segments such as automotive, power generation, medical and military. The main feature of this process is to obtain ceramic shells by means of ceramic slurry baths anchored by granular refractory material applied to the surface of wax models in the shape of the final part. This work evaluated the properties of tile powder and also the ceramic shells produced with slurries using the tile powder itself as a refractory material in both primary and secondary slurries. The powder of tiles presented high particle size dispersion # 20 - # 325 mesh and in its composition important refractory compounds such as silica and alumina were identified. The tests carried out on the ceramic shells made with tile powder slurries showed green and calcined (1000 °C) modulus of 1.02 MPa and 4.95 MPa respectively and a heat permeability of (1000 °C) 4, 2 L / min. The tests in the ceramic shells used in the industry showed green and calcined rupture modulus results of 2.48 MPa and 5.7 MPa and permeability of 3.8 L/min respectively. The ceramic shells made with powder tiles had a lower rupture modulus than the industrial ceramic shell, but with a higher permeability result. The ceramic shells with tile slurries showed good performance during the casting of liquid aluminum 356, bronze and gray cast iron, no mold breaks and no reaction with the metal. The parts cast with the ceramic shells produced with tile powder slurries e met the dimensional tolerances required by ABNT NBR 15990.

Este trabalho tem como foco central a investigação de possibilidades de obtenção de peças metálicas, na forma de esculturas, por fundição, com vazamento por gravidade e que tenham como característica formal uma geometria complexa. Na interface interdisciplinar entre Arte e Engenharia, o estudo aborda a técnica de fundição por cera perdida e suas características, os materiais envolvidos nos processos de construção do modelo e do molde, e a realização prática de peças fundidas. Através do fazer, da aplicação das técnicas de fundição, da construção de um relato de experiências e das reflexões geradas a partir da análise dos resultados, o texto procura estabelecer a viabilidade da aplicação das técnicas de fundição por cera perdida, em atelier de escultura, com propósitos artísticos. / The following work has as its central focus the investigation of possibilities in the attainment of metallic pieces, in the form of sculptures, through foundry with filling by gravity and a complex geometry as their formal characteristic. In the interdisciplinary interface between Art and Engineering, the study approaches the lost wax foundry technique and its characteristics, as well as the materials involved in the processes of construction of the model and the mold and the practical accomplishment of the foundry pieces. The text attempts to establish the viability of the employment of the foundry techniques of lost wax through the execution, the application of the foundry techniques, the elaboration of a report of experiences and the thoughts generated from the analysis of the results in a sculpture studio with artistic purposes.

Este trabalho tem como foco central a investigação de possibilidades de obtenção de peças metálicas, na forma de esculturas, por fundição, com vazamento por gravidade e que tenham como característica formal uma geometria complexa. Na interface interdisciplinar entre Arte e Engenharia, o estudo aborda a técnica de fundição por cera perdida e suas características, os materiais envolvidos nos processos de construção do modelo e do molde, e a realização prática de peças fundidas. Através do fazer, da aplicação das técnicas de fundição, da construção de um relato de experiências e das reflexões geradas a partir da análise dos resultados, o texto procura estabelecer a viabilidade da aplicação das técnicas de fundição por cera perdida, em atelier de escultura, com propósitos artísticos. / The following work has as its central focus the investigation of possibilities in the attainment of metallic pieces, in the form of sculptures, through foundry with filling by gravity and a complex geometry as their formal characteristic. In the interdisciplinary interface between Art and Engineering, the study approaches the lost wax foundry technique and its characteristics, as well as the materials involved in the processes of construction of the model and the mold and the practical accomplishment of the foundry pieces. The text attempts to establish the viability of the employment of the foundry techniques of lost wax through the execution, the application of the foundry techniques, the elaboration of a report of experiences and the thoughts generated from the analysis of the results in a sculpture studio with artistic purposes.