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Hugo, Philip. "Suitability of layer manufacturing technologies for rapid tooling development in investment casting." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/847.
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Trevor, Simon. "Dimensional accuracy of investment casting shells /." [St. Lucia, Qld.], 2000. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16943.pdf.
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Torres, Jesus Cirre. "Thermo physical properties of investment casting waxes." Thesis, University of Birmingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410856.
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Kumar, Naresh. "The modelling of precision investment casting processes." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47521.
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Rutto, Hilary Kiplimo. "Urea-based moulding compounds for investment casting." Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-05132009-155138/.
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Harun, Zawati. "Simulation of drying for multilayer investment casting shells." Thesis, Swansea University, 2007. https://cronfa.swan.ac.uk/Record/cronfa42815.
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The number of interacting variables influencing the drying of ceramic shells is large and to explore by experimental means is prohibitive. Therefore, the main advantage of the proposed theoretical model in this work, is that the effect of the drying conditions on their other important parameters (such as saturation, temperature, gas pressure) and transport properties (permeabilities, diffusivity) that control final properties of a multilayer ceramic shell can be investigated without extensive experimentation. This is very important in avoiding shell failure due to incomplete drying. Due to the fact that a porous ceramic body is a three phase system (solid, liquid and gas), modelling its transport and thermodynamic behaviour involves a complex solution due to the highly nonlinear physics that capture their evolution. A twodimensional numerical model based on the fundamental equations of heat, mass and gas transport was developed to establish the drying and thermodynamic response of the ceramic shell system. This complete coupled set is based on Whitaker's model that includes the mass, momentum and energy equation which also embodies the constitutive diffusion and capillary flow theory and its evaporation-condensation term in the flow phases; conduction, convection and latent heat of evaporation in the energy equation; along with the gas transport equation. The most widely implemented numerical solution (the fully implicit backward time stepping scheme) in the area of multiphase flow and drying in porous media was chosen for the temporal solution. The finite element method was employed for the spatial solution, due to its flexibility in dealing with complex geometries, and also it shows an ideal approach to employ in the solution of this class of problem. Both of the temporal and spatial numerical solutions for the theoretical solution were implemented into a computational code by using the Fortran programming language. This simulation scheme has been benchmarked against thermal test cases (to confirm the correct functioning of the thermal analysis) and for the first time the brick drying benchmark by Stanish in which it is demonstrated to provide the best solution. The scheme was then extended to address the drying of a single ceramic layer and compared with the published work, again showing good agreement. For the first time a simulation approach for the drying of a multilayer system that includes the impact of wet layer addition is proposed. The principles of an ab initio scheme are demonstrated that again show good agreement with experimental trends. Further work is required to obtain a better match with experimental data, but to do so will require improvements in deriving a compatible material data set that is appropriate for this simulation approach. The scheme set out in this thesis may be used to guide the test selection tofacilitate derivation of these material properties.
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FORNO, ILARIA. "Investment Casting of Precious Metals: Materials and Methods." Doctoral thesis, Politecnico di Torino, 2012. http://hdl.handle.net/11583/2502741.
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Aim of this work is the analysis of the materials and parameters related to the investment casting process,mainly focusing on peculiarities and criticisms of the casting of precious metals in jewelry production.Precious metals casting is traditionally and historically targeted to overcoming limitations in terms of geometries and final quality of the cast part. Moreover, an increasing interest rises concerning the use of new technologies and the industrializations of typical handcraft skills. New materials are therefore introduced into the process, in order to be able to get thin and intricate shapes, hollow parts and innovative design features. This is leading to a substantial rearranging of the process, with a constant innovation regarding technologies and medication of traditional materials. Considering the whole process, nvestment casting is dealing with a wide range of materials, from metallic, polymeric and ceramic classes. All these materials cannot be considered as single identities, but their synergetic behavior has to be studied, not just meaning that all of them contribute to the final quality of the cast part, but taking into account possible mutual interdependencies.
The research work has been divided in a preliminary analysis of the process, in order to deepen the knowledge about material features, and in a extended study on the application of competences deriving from other sectors to the specific one. In fact it’s almost impossible to find sector boundaries between jewelry and fashion accessories both in terms of process and in terms of market. Therefore the analysis of the state of the
art has been widened to other processes and applications, in particular focusing on fashion accessories and eyewear component production. Market analysis clearly show a high interest of jewelry towards innovative processes/materials, often deriving from completely different fields of application. For this reason, an analysis of the investment casting
process applied in the automotive and biomedical sectors can give valuable hints for the jewelry production optimization.
Particular attention has also been paid to fluid dynamic analysis of the casting system, considering metal flow into the flask and following cooling and solidification. For this purpose, computational fluid dynamic has been applied to the process. Material analysis, needed for both the simulation and for a complete understanding of the process, has been carried out. Physical and thermal properties of metals and investment materials have been analyzed in order to get a proper database for casting simulation. Waxes and resins have been tested both in terms of thermal, mechanical and chemical characteristic, in order to understand their respective roles into the process and try to optimize them. Following the analysis, process implementation has been performed in order to apply information deriving
from experimental tests to the process. Many parameters can be taken into account when optimizing precious metal casting; in order to focus the research activity, some limitation in terms of process have been applied.
Casting trails were conducted using a static vacuum casting machine on sterling silver and 18 kt. Gold alloys, referring to traditional investment casting process.
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Ho, Kwok-hung Eric. "Dimensional calibration of castings in phosphate bonded investment." Click to view the E-thesis via HKUTO, 1994. http://sunzi.lib.hku.hk/HKUTO/record/B3862798X.
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Ho, Kwok-hung Eric, and 何國雄. "Dimensional calibration of castings in phosphate bonded investment." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1994. http://hub.hku.hk/bib/B3862798X.
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Deez, Brent Steven. "An investigation on the suitability of layer manufacturing methods for rapid tooling development in investment casting of light metal alloys." Thesis, Cape Peninsula University of Technology, 2010. http://hdl.handle.net/20.500.11838/2228.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2010.The research presented in this report focuses on Investment Casting capabilities for light metal alloys in South Africa and forms part of the Advanced Manufacturing Technology Strategy's (AMTS): Light Weight Metals flagship programme. The research is centred on the suitability of rapid prototyping (RP)/Iayer manufacturing (LM) methods to produce patterns for the investment casting of aluminium (AI), magnesium (Mg) and titanium (Ti) alloys, together known as Rapid Investment Casting. Three core RP technologies are investigated namely: Three Dimensional Printing - Drop-on-Bed from Z-corporation, Three Dimensional Printing - Drop-on- Drop from ThermoJet - 3D Systems and Selective Laser Sintering from EOS. Various RP/LM processes are discussed in detail and highlight the technologies selected in this study. A standard benchmark part, adapted from the European project framework FP6, designed and utilised in similar studies is used as the basis for the research. The Investment Casting process is discussed fully and compared to the Rapid Investment Casting, listing both the advantages and disadvantages of the above mentioned methods. In addition a special study has been conducted on investment casting of large components using layer manufactured patterns. This study not only helped to establish and validate the shrinkage value calculated for the aluminium castings but also showed substantial capability lacks in SA foundries to handle this type of components, which are by definition most often of high added value.
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Swain, Luke James. "Modelling ceramic mould deformation in the investment casting process." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/8015/.
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Core and shell deformation during the firing stage of the investment casting process was investigated. Relevant thermo-mechanical and thermal properties were characterised for a commercial core and shell system. A finite-element model was created using the experimentally obtained data. Four major mechanisms were shown to contribute to ceramic mould deformation; general thermal expansion, sintering, phase transformations and creep. The shell system experienced little deformation form phase transformation, the core system exhibited minor deformation from sintering. The sintering behaviour of shell material was observed to be highly dependent on the temperature-time profile of the firing cycle, with lower heating rates resulting in more sintering. The crystallisation of amorphous silica to β-cristobalite in core materials was also seen to follow this trend. A rule of mixtures approach showed that inter-layer interaction in shell materials was minimal. An Avrami-based kinetic modelling approach was applied to pressed silica pellets, showing very good prediction of similar heating rates, but an interaction effect between crystallisation and sintering behaviour needs to be established to predict a wider range of heating cycles. A master sintering curve approach was adapted to incorporate crystallisation to predict the displacement of pellets mimicking core materials. Due to silica crystallisation inhibiting sintering, lower heating rates produced less displacement. In order to validate the finite-element model, an experimental test was developed capturing the deformation of a shell test bar in a three-point bend rig at high temperature using photography. Images were then analysed in ImageJ® to measure the bending of the shell material, this was validated using a transducer attached to a three-point bend knife. Comparison of the finite-element model with the validation test showing good agreement. The creep exponents which were the main proponent of shell bending were optimized to be used in future models.
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Dooley, Gavin. "Shell improvements for the investment casting of orthopaedic implants." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7273/.
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This project focuses on understanding and improving the technology used in the ceramic processing of the investment casting of orthopaedic implants. The shell making process is a time consuming and costly stage of the Investment casting process. This work reviews the use of a super absorbent polymer as a means to decrease lead time within the shell room and improve capacity. The technology allowed a typical shell which had 2 hours dry time to be reduced by 75% to 30 minutes between coats. Following initial analysis, a greater understanding on the flaws of the Rapid Shell system was sought. Work was also conducted to improve and understand the parameters which affect a generic shell system. Changes to the raw material were reviewed by changing the particle size of stucco and flour materials to improve strength. Different processing methods were also analysed to gain a better understanding into the fundamentals of ceramic processing. The use of rainfall and fluid bed stucco applications were analysed within a DOE experiment to better understand the effect of changes in microstructure affecting the overall performance of the shell. The results showed the microstructure varied greatly between processing method which in turn affected the thickness and strength of the respective shell systems. Rainfall sanded shells exhibited a thinner stucco layer while the flexural strength was 20% higher than fluid bed shells.
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Taylor, Benjamin Luke. "Reaction systems and phase development for investment casting ceramics." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5932/.
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Aero engine turbine blades are commonly produced via investment casting methods utilising sacrificial ceramic cores during casting to provide internal features such as cooling channels. During the firing process the conversion of the main ingredient (amorphous silica) to β-cristobalite plays a significant role, as it directly affects the dimensional stability, shrinkage, and leachability of the core after casting. Dilatometry, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were utilised to evaluate common additives such as zirconium silicate and aluminosilicate. Zircon was found to act as a nucleation site with high temperature stability while aluminosilicate acts as a flux enhancing cristobalite formation rates. This understanding was utilised to mimic the performance of the formulation using both a novel engineered material and alternative naturally sourced silica. An innovative method was also developed utilising confocal Raman spectroscopy (CRM) and polarised light microscopy (PLM) for analysis of ceramic systems studied with a hot stage up to 1500 °C. Polarised light microscopy was shown to be favourable for analysis of crystal growth mechanisms and low temperature (≈250 °C) α-β cristobalite phase transitions. Developments in Raman spectroscopic technique enabled the location and crystallinity of devitrified amorphous silica (cristobalite) to be observed via a quasi-real time method, providing insight to the source, direction and corresponding crystal growth rates. The combination of analytical techniques has provided sufficient understanding to explain the role of key components in ceramic core formulations, which can be used to improve control and the predictability of the system during development and manufacture.
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Charmeux, Jean-Francois. "Capabilities of the Investment Casting process for producing meso/micro metal castings using Rapid Prototyping manufacturing routes." Thesis, Cardiff University, 2007. http://orca.cf.ac.uk/54701/.
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This thesis examines the capabilities of different Rapid Prototyping (RP) manufacturing processes for producing sound metallic parts incorporating features in the micrometre range using the Investment Casting (IC) process. RP has been growing in the past twenty years and is nowadays widely employed in the area of precision investment casting since the technology offers the possibility of manufacturing wax patterns which can be directly implemented into investment casting. Owing to the steady improvements of the technology, some of the recently developed RP building machines offer the possibility of manufacturing small parts incorporating micro-features. In this work, a detailed description of the accuracy and capabilities of the IC process regarding its potential for producing sound meso/micro components is given using two types of conventional RP machines. The results of this analysis are then compared through a benchmarking study with a recently developed RP process suitable for the direct manufacture of ceramic moulds. The different technological chains are compared regarding their overall accuracy, surface finish, the amount of structural defects present in the castings and their relative production costs and lead-time. Finally, the potential of the investment casting process for manufacturing sound micro-castings with high aspect ratio is approached from a structural point of view. Through a metallographic analysis study, the research investigates the size-scale effect of cast micro-components upon their microstructure and the subsequent changes in their mechanical properties.
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Tarrant, Luke. "Formulation and development of ceramic mould materials for investment casting." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3399/.
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The relationship between the formulation of ceramic mould materials for investment casting and their mechanical properties was investigated. A number of different ceramic materials were employed throughout the investigation including alumina, zirconia, mullite and colloidal silica. Ceramic shell specimens were investigated by measuring mechanical strength using flexural and compressive testing with the former being conducted at both room and elevated temperatures. Samples were further investigated by thermal expansion measurement and Archimedes porosity measurement. It was determined that the incorporation of unstabilised zirconia as both a stucco and filler material was effective in terms of reducing the fired strength of investment casting ceramics. Structural observations of samples under SEM revealed that the weakened samples featured significant cracking in the fired condition due to the occurrence of the zirconia phase transition. Thermal expansion measurements confirmed both the presence of the phase transition and the extent of the disruption caused. It was observed for slurries containing silica and alumina, that variation of the proportions of either had a significant effect on the properties of the final shell material. It was also shown that the size of the ceramic particles within the slurry had a significant effect on the final properties of the ceramic body.
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Jones, Samantha. "Improved sol based ceramic moulds for use in investment casting." Thesis, University of Birmingham, 1993. http://etheses.bham.ac.uk//id/eprint/788/.
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An investigation has been carried out into the mechanisms of failure of silica bonded investment casting moulds, with the aim of reducing failure rates for larger components. The analysis begins with a detailed microstructural examination of a current commercial mould system using scanning electron microscopy and other allied analysis techniques. The mould structure is shown to be nonuniform and unpredictable, with poor packing of the ceramic constituents leading to a non-uniform porosity network. The structure and distribution of the binder is also established and this indicates that the major load bearing points within the mould consist of thin areas of silica. As such, the overall performance of the mould is directly related to that of the silica itself. This binder is shown to contain impurity elements leached from the ceramic filler at various stages during mould manufacture. These elements alter the phase composition and thermal properties of the binder. Mould temperature profiles for a range of casting sizes have been measured and used to illustrate the relationship between metal weight and maximum temperature attained within the mould section. The profiles are also used to investigate the creep response of silica based binders. It is found that a combination of high temperatures and creep within the silica phase is responsible for the casting defects found with larger components. From these observations, a prediction is made regarding failure mechanisms and suggested remedial action. The thermal properties of several commercial water based binders are evaluated and the suitability of each as an alternative binder is discussed.
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Lee, Kevin. "Understanding shell cracking during de-wax process in investment casting." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6783/.
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In investment casting, the removal of wax from the shell is a critical step which may cause shell failure. It would be advantageous to predict the stress development during de-waxing process with computer simulation. The process was simulated with the consideration of two aspects: (i) The thermo-physical data required to model the shell and wax behaviour in the autoclave environment and (ii) A simulation capable of capturing the interaction between shell, wax and the autoclave environment. Data on mechanical properties, thermal properties, permeability, rheology, thermal expansion and density was gathered for wax and shell as appropriate. Flow-3D was used to simulate the de-wax process such that the shell and wax can be simultaneously modelled. It was shown that the Von misses stress exceeded the expected critical failure stress at certain nodes after steam was introduced to the system. Waxes with higher viscosity were predicted to reach the critical stress sooner. The simulation showed that for the selected drainage orifice sizes that was no or little difference in the time taken to reach the critical stress. Wax compressibility which was considered to represent shell permeability was predicted to have a large effect on shell cracking prediction. In general, the statistics of failure in validation test limited the conclusions that could be drawn. Waxes predicted to show differences in cracking and drainage with increasing orifice size did so in the experiment. The simulated drainage times were greater than determined experimentally by around 380s and this requires further investigation.
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Roach, Peter J. "Electrophoretic deposition of primary coat onto investment casting wax patterns." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/3859/.
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The objective of the work reported in this thesis was to tailor a colloidal processing technique called electrophoretic deposition (EPD) for use within the investment casting shell formation process, where the EPD coating procedure would be used to form the primary ceramic coating on the melt-out substrate. EPD takes place due to the presence of an electric field within the suspension medium, which attracts charged particles in the suspension towards an electrode of opposite charge, onto which they are deposited. For the complex structures created using investment casting, the die cast patterns used as the substrate for the ceramic have to be easily removed, and so substrates materials that can either be melted or dissolved out the material to leave the hollow ceramic shell used. To implement EPD into the investment casting process, this substrate needed to be conducting, and so conducting particle-filled investment casting waxes were created and analysed. Carbon black and graphite filler were incorporated into waxes, and the conductivity and rheology of the resultant composites were studied, to gauge their suitability as an investment casting pattern material. On the basis of both cost and for environmental reasons, the use of aqueous suspension media for EPD was preferred over the more commonly used organic systems. EPD was carried out using zircon in aqueous suspension, and the low particle concentration suspensions were stabilised through pH modification and anionic dispersant addition. The effect of suspension parameters and EPD set-up parameters on the coatings formed on compressed graphite electrodes and conductive wax electrodes were studied, through yield measurements and cross sectional analysis using scanning electron microscopy.
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Su, Xiuling. "Computer Aided Optimization of an Investment Bi-Metal Casting Process." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin998405696.
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Ibrahim, Ahmad Rashdi Yan. "Methodology for Fine Art formulation applied to investment casting moulds." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/1842/10436.
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This research concerns the development of a methodology for formulation in Fine Art, Design and Craft practice. The methodology is applied to the choosing of formulations for bronze and glass investments casting moulds in which a significant ingredient is cuttlefish bone powder, but it is claimed to have an applicability beyond this particular example. The methodology involves four steps; identifying key attributes (effects) which the required formulation must display, identifying the roles, shapes and sizes of the components of the formulation, finding a model which combines the component characteristics into a visualisation of the formulation, referred to as a "microstructure drawing", and using the microstructure drawing to describe the behaviour of the formulation. The research approach taken is to search for a suitable set of formulations using a traditional trial-and-error process. The key attributes required of the formulation are defined in terms of the handling characteristics, and the mechanical integrity of the hardened mould. The components are then characterised using micrographic images and a set of symbols developed to represent their size, shape and function. Then a visualisation of the formulation is developed by mixing symbols in proportion to the amount used in the formulation. These microstructure drawings are then used to describe the behaviour of the formulation. Conclusions are drawn as to the value of the microstructure drawing as an additional "sense" which the practitioner can use when searching for a suitable formulation. Comments are made on the generic aspects of the work, the feasibility of using cuttlefish bone powder for investment casting moulds, and on the communicability of the methodology.
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Prathan, Kanthee. "Optimization of sprue design for advanced investment casting through FEA analysis." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-50027.
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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.
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Bednárik, Marko. "Návrh změny výroby tvářené součásti na technologii lití do keramických skořepin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-445164.
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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.
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Malan, A. G. "Investigation into the continuum thermodynamic modelling of investment casting shell-mould drying." Thesis, Swansea University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637987.
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The work presented in this thesis constitutes the first phase in the development of aerospace-investment casting shell-mould drying continuum-modelling capabilities. The modelling of the heat and mass transfer processes prevalent in the porous shell, as well as the surrounding fluid flow, have been considered separately. Aspects researched are the mathematical description, discretization as well as the computer code implementations. It is believed that current technology has been advanced in each of these areas. A set of volume averaged equations have been constructed for the drying shell based on a balanced mathematical-continuum thermodynamics approach. With regards to the spatial discretization, a refined edge-based vertex-centred finite volume scheme is proposed. The artificial compressibility (AC) technique is employed for the modelling of the external fluid flow and a new locally generalised preconditioner has been developed. The numerical schemes have been transcribed into a functional computer code using object-oriented C++ which have enhanced the computational efficiency and performance. The fluid flow and porous material drying modelling capabilities have been validated successfully through the simulation of problems for which benchmark solutions or experimental data exist. Enhancements in a number of other aspects have also occurred because of the new developments. These include improved spatial accuracy, stability and convergence characteristics.
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Wilson, Paul James. "Investigating the formulation of silica-based ceramic core materials for investment casting." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/2829/.
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An investigation has been performed into the formulation of silica-based ceramic core materials for investment casting. The formulation of 3 materials that are currently used by Ross Ceramics was investigated in detail and the data from this used to determine the elements of the formulation that should be investigated in more detail. The techniques used included a variety of mechanical tests at both room and high temperatures, dilatometry, phase analysis by XRD and chemical analysis by XRF, pore analysis by simple Archimedes tests and mercury porosimetry and both scanning electron and transmitted light microscopy. A large number of materials were created with different formulations and the various characterisation techniques employed were used to determine the function of the different constituent. It was determined that the function of zircon was to prevent grain boundary movement at elevated temperatures via the Zener effect, by acting as a non-reactive secondary phase. The zircon also had an additional consequence from the inherent contamination, with alumina, from the ball-mill procedure performed by the supplier. This had the effect of significantly affecting several high temperature properties. The effect of several dopant materials: TiO2, Al2O3, MgO, cristobalite seed and Molochite addition was also investigated. The latter two were determined to function mainly by their inherent contamination. The other additives affected the materials in different ways depending on the amount used and the presence of any phase eutectics that had detrimental effects on the high temperature material properties. The particle size distribution of the materials was also investigated. It was determined from the experiments that the D20 was an important factor for deterring final material properties and that most materials obeyed a modified Griffith’s crack theory relation, with the exception of materials with a larger zircon particle size than that of the main silica constituent. From this work new materials could be created using the knowledge gained and material properties could be optimised to meet specific requirements by changing zircon quantity, dopant levels and particle size.
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Williams, Kendra Ann 1966. "Feasibility study of investment casting pattern design by means of three dimensional printing." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/13050.
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Cendrowicz, Aleksander. "The characterisation of wax injection moulding and de-wax processes in investment casting." Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416512.
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The wax injection moulding and de-wax processes in investment casting were investigated; by measuring the relevant material properties of two commercially available pattern waxes; performing experimentation on industrial equipment; and using analytical and numerical techniques to solve some of the fluid mechanics, heat transfer and solid mechanics equations associated with each process. The rheological behaviour of the molten pattern waxes was found to be Newtonian at higher temperatures and shear-thinning at lower temperatures. The viscosity was also found to depend on shear and thermal history. Samples pre-sheared by both "screw" and "tank" type injection moulding machines were found to give lower vi~cosities than freshly melted pellets. The extensional viscosity was higher at lower temperatures and lower shear rates than that expected for a Newtonian liquid. The pressureflowrate- time relationship for the flow through a tube of a power-law fluid with exponential dependency with temperature was obtained by solving the coupled dimensionless heattransfer and fluid mechanics equations. The method was used to correct capillary viscometry results for viscous heating. Predictions of the pressure-drop through cold cylindrical running systems during injection moulding were found to agree qualitatively with experimentally measured values, although quantitative agreement was limited by the constitutive model that was used. The formation of surface defects during the injection of patterns was investigated by using flow-visualisation and computational fluid dynamics. It was found that substantial flow-lines occur when the flow-front velocity is below 10 mm.s-l, and significant air entrapment occurs at flow-front velocities above 1 m.s-1 A model was developed to predict the freezing time of running systems during the holding stage of the injection moulding cycle and the subsequent shrinkage behaviour of the pattern, which were found to be influenced most by the wax temperature, hold pressure, hold time, and runner diameter for thick unrestrained pattern geometries. The gas-assisted injection moulding process was adapted for wax pattern production, and was observed to reduce shrinkage by a factor of two. A onedimensional dynamic model was developed to calculate the stress in a cylindrical investment shell during de-waxing. The relevant physical properties of un-sintered ceramic shells were measured, including the pore size distribution, wax permeability, thermal expansion and hot & wet stress-strain behaviour. It was shown how the geometry, material properties and operating conditions can affect the frequency of shell cracking during the de-wax process.
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Rzyankina, Ekaterina. "Numerical and experimental investigation of directional solidification in vacuum investment casting of superalloys." Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/1243.
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Thesis submitted in fulfilment of the requirements for the degree
Master of Technology: Mechanical Engineering
in the Faculty of Engineering
at the Cape Peninsula University of Technology
2013High temperatures encountered in combustion chambers of jet engines has demanded the creation of new technologies and new materials for the construction of one of the most critical elements of these systems - the stator and rotor turbine blades. They have to withstand extreme temperatures for extended periods without the loss of mechanical strength, conditions under which many steels and alloys fail. Such failure is ascribed to the combination of high temperatures and high centrifugal forces, resulting in creep. The high temperature creep mechanism of grain boundary sliding has limited the operation capability of fine-grained equiaxed castings. Higher operating temperatures were achieved with higher alloy contents and coarse-grained equiaxed castings. This is especially prevalent in multi-crystalline structures in which grain boundaries present weaknesses in the structure. However, notwithstanding these improvements, high temperature resistant alloys formed as single crystal structures offer the necessary material properties for safe performance under these extreme conditions. Damage to turbine blade surfaces is often caused by oxidation and hot corrosion. For this reason, turbine blades are coated with a thermal barrier coating (TBC), which consists of ceramic materials that reduce the heat flux through the airfoil. In this research work, modelling and simulation techniques were initially used to study the directional solidification (DS) of crystal structures during vacuum investment casting. The modelling of the solidification process was implemented using a Finite Element casting simulation software, ProCAST, to predict thermal and flow profiles. These models allowed the study of the dendritic growth rate, the formation of new grains ahead of the solid/liquid interface and the morphology of the dendritic microstructure. These studies indicated the opportunity to optimise the velocity of the solidification front (solidification rate) for single crystal structures. The aim of this research was therefore to investigate the effect of the solidification rate (or withdrawal velocity) on the quality of SC castings. The investigations were carried out for nickel-based superalloy CMSX-4 turbine blade casts and rods using the Bridgman process for vacuum investment casting. The SC castings were heat treated to improve the grain structure for enhanced creep resistance. The heat treated SC castings were inspected by X-ray diffraction to analyse crystallographic orientation and chemical composition; and by SEM, OP (optical microscopy) and microprobe analysis to analyse the microstructure; in addition to macrostructural investigations. In the experimental analysis, the formation of new grains ahead of the solidi/liquid interface and the effect of dendrite packing patterns on the primary dendrite spacing were investigated. Creep tests were conducted to compare the creep properties of the SC castings for different withdrawal rates, and to draw conclusions regarding the effect of withdrawal rate on the microstructure (and hence the creep properties) of SC castings.
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ZHOU, XINYU. "COMPUTER SIMULATION AND LOW-COST OPTIMIZATION OF AN INVESTMENT BI-METAL CASTING PROCESS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1123793441.
Full text
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Lim, Chu-Sing. "The production and evaluation of fibre preform-infiltrated metal matrix composite castings produced by a developed pressure-assisted investment casting process." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/28175.
Full textAbstract:
The squeeze casting process is well known for its ability to produce castings with good integrity due to the high direct pressure application on the liquid metal during solidification. This concept has been used to squeeze infiltrate fibre preforms with liquid metal for metal-matrix composite (MMC) production. Squeeze casting employs fast cycle times to produce high integrity castings. The squeeze casting process is, however, limited in terms of shape complexity and flexibility (e.g. thin sections). One-offs or small production runs become very expensive to produce because of the complex nature and high cost of the die steel tooling.
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Ferreira, Anelise Rodolfo. "Estudo da dilatometria do titânio e das expansões de presa e térmica de revestimentos fosfatados /." Araraquara : [s.n.], 2004. http://hdl.handle.net/11449/97297.
Full textAbstract:
Orientador: Gelson Luis AdaboBanca: Renata Garcia Fonseca
Banca: Ricardo Faria Ribeiro
Resumo: O estudo avaliou a expansão térmica dos materiais metálicos titânio c.p. (RMI Company, Ohio, EUA), Co-Cr-Mo-W (Dentaurum, Pforzhem, Alemanha) e Ni-Cr (Dentaurum, Pforzhem, Alemanha) para estimar a contração de fundição do titânio e determinou a expansão de presa e térmica dos revestimentos fosfatados Rematitan Plus (Dentaurum, Pforzhem, Alemanha), específico para titânio e Rema Exakt (Dentaurum, Pforzhiem, Alemanha) e Castorit Super C (Dentaurum, Pforzhem, Alemanha). Cada concentração de líquido especial foi variada na proporção de (100%, 75% e 50%) de água destilada, com o objetivo de determinar em que concentração de líquido e em que temperatura a somatória da expansão de presa e térmica seriam suficientes para compensar a contração estimada. Para a dilatometria dos metais padrões de cera com 14 mm de altura e 7 mm de diâmetro foram obtidos a partir de um padrão metálico, em seguida, montados em base formadora de cadinho com o conduto de alimentação e incluídos com cada revestimento na concentração de 100%. Os padrões foram incluídos e aquecidos no forno EDG (EDG - Equipamentos, São Carlos, SP). O Ti c.p. foi fundido na máquina Discovery - Plasma (EDG - Equipamentos, São Carlos, SP), e as outras ligas a fundição ocorreu em máquina de fundição centrífuga convencional. Após o polimento, os corpos de prova foram analisados e a expansão térmica foi registrada no Dilatômetro DIL 409 (Netzch) em atmosfera de ar, numa taxa de aquecimento de 10ºC/min. O Ti c.p. foi aquecido até 1550ºC, o Co-Cr-Mo-W até 1160ºC e o Ni-Cr até 1090ºC. Para a medida da expansão de presa, os revestimentos foram misturados com líquido especial e vertidos no molde de silicone (Siqmol) com cavidade de 50 mm X 10 mm X 10 mm. Uma lâmina de vidro e o apalpador (Tesa)...(Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This study evaluated the thermal expansion of the metallic materials titanium c.p. (RMI Company, Ohio, USA), Co-Cr-Mo-W (Dentaurum, Pforzhem, Germany) and Ni-Cr-Mo (Dentaurum, Pforzhem, Germany) to estimate the casting shrinkage of titanium and determine the setting and thermal expansion of phosphate-bonded investment materials. This investment used were Rematitan Plus (Dentaurum, Pforzhem, Germany), specific for titanium, Rema Exakt (Dentaurum, Pforzhem, Germany) and Castorit Super C (Dentaurum, Pforzhem, Germany). Each concentration of special liquid/distilled/water was varied in which ratio by 100%, 75% and 50%. This aim of this study was to determine what liquid concentration and temperature the overall expansion could be enough to compensate the casting shrinkage. For the dilatometry of the metals, wax patterns (14 mm X 7 mm) were made, attached to sprue, mounted in and mounted on crucible formers and included in 100% of special liquid. The invested patterns were heated in a burnout EDG (EDE - São Carlos - Brazil). Ti c.p. was casting in the machine Discovery - Plasma (EDG - Equipments, São Carlos, SP), and the other alloys were casting in a conventional centrifugal casting machine. After polishing, the samples were analyzed and the thermal expansion was recorded in the equipment Dilatômetro DIL 409 (Netzch) in air's atmosphere, in a rate of heating of 10ºC/min. The Ti c.p. was heated up to 1550ºC, the Co-Cr-Mo-W up to 1160ºC and Ni-Cr-Mo up to 1090ºC. For measurement of the vertical setting expansion, those investments were mixed with special liquid and invested into silicone moulds of the metal pattern (50 mm x 10 mm x 10 mm). A glass plate and dial gauge were seated on the sample, and after two hours the setting expansion was measured (Se). The distance between the ends (De)...(Complete abstract, click electronic access below)
Mestre
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Nogueira, Fabiane. "Efeito de um revestimento com processamento rápido para fundição de titânio na camada de reação, porosidade interna, fluidez, rugosidade superficial e adaptação marginal de Copings /." Araraquara : [s.n.], 2009. http://hdl.handle.net/11449/98027.
Full textAbstract:
Orientador: Gelson Luis AdaboBanca: Renata Garcia Fonseca
Banca: Ricardo Faria Ribeiro
Resumo: A aplicação do titânio e ligas de titânio para implantes dentários e próteses têm crescido nos últimos anos devido às suas excelentes propriedades físicas e mecânicas. No entanto, o titânio tem alto ponto de fusão (1668ºC) e sob elevadas temperaturas, reage com elementos do ar atmosférico (oxigênio, nitrogênio, hidrogênio) e com componentes de diversos revestimentos. As reações entre o metal fundido e alguns elementos de revestimentos, principalmente fosfatados ou à base de sílica, resultam na formação de uma zona de contaminação superficial denominada "α-case". Para minimizar este problema, revestimentos contendo óxidos menos reativos, tais como Al2O3, MgO, ZrO2 e CaO, têm sido desenvolvidos. Os revestimentos especiais para fundição de titânio à base de sílica, de MgO, alumina e espinélio apresentam um tempo de processamento bastante longo (8 a 10 horas). Recentemente, foi desenvolvido um revestimento à base espinélio com processamento acelerado (Trinell - Dentaurum, Ispringen, Germany) que permite a utilização de uma técnica de secagem em forno de microondas e temperatura de aquecimento inicial do forno de 400 ºC, diminuindo o tempo de processamento para cerca de 5 horas. No entanto, não existem estudos que comprovem a eficiência deste novo revestimento. O propósito deste estudo foi avaliar o efeito do novo material Trinell (TR) na camada de reação, porosidade interna, fluidez, rugosidade superficial e adaptação marginal de estruturas fundidas em titânio, quando comparado a dois revestimentos convencionais para fundição de titânio: um revestimento fosfatado, Rematitan Plus (RP) - controle negativo e outro à base de espinélio Rematitan Ultra (RU) - controle positivo. A camada de reação foi avaliada por meio de ensaio dureza Vickers; a medida da porosidade interna foi determinada por exame radiográfico; a rugosidade superficial... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The use of titanium and titanium alloys in dental implant and prosthesis has increased in the past few years because of their excellent physical and mechanical properties. However, titanium has a high melting point (1668 ºC) and inherent reactivity with elements of atmospheric air (oxygen, nitrogen, hydrogen) and with components of several investment materials under high temperatures. The reactions between molten metal and some of the elements of phosphate-bonded and other silica-based investment materials result in the development of a surface contamination zone called "α-case". To minimize this problem, new investment materials containing less reactive oxides, such as Al2O3, MgO, ZrO2 and CaO have been developed. The commercial silica-, MgO-, Al2O3 - and spinel-based investments especially formulated to titanium casting demand a processing time in a range of 8 to 10 hours. Recently, a new short-cycle spinel-based investment (Trinell - Dentaurum, Ispringen, Germany) was developed. It has a reduced processing time - 5 hours in the furnace- because of an investment drying technique into microwaves oven followed by an initial heating in furnace at 400 °C. However, there are not studies which verify the efficiency of this new investment. The aim of this study was to evaluate the reaction layer, the internal porosity, the surface roughness, the castability and the marginal misfit of titanium castings performed with the new material, Trinell (TR), in comparison to two conventional investments for titanium castings: phosphate-bonded Rematitan Plus (RP) - negative control, and the spinel-based Rematitan Ultra (RU) - positive control. The reaction layer was evaluated by Vickers hardness; the measure of the internal porosity was determined by radiographic test; the surface roughness was measured with a surface-test analyzer, the castability was determined by the percentage of completely... (Complete abstract click electronic access below)
Mestre
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Hague, R. J. M. "The use of stereolithography models as thermally expendable patterns in the investment casting process." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339642.
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Raza, Mohsin. "Process development for investment casting of thin-walled components : Manufacturing of light weight components." Licentiate thesis, Mälardalens högskola, Innovation och produktrealisering, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-27807.
Full textAbstract:
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.
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Dimitrov, D., P. A. Hugo, and B. Deez. "Suitability of layer manufacturing technologies for rapid tooling development in investment casting of light metals." Journal for New Generation Sciences, Vol 8, Issue 2: Central University of Technology, Free State, Bloemfontein, 2010. http://hdl.handle.net/11462/558.
Full textAbstract:
Published ArticleRapid 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.
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Kodira, Ganapathy D. "Investigation of an Investment Casting Method Combined with Additive Manufacturing Methods for Manufacturing Lattice Structures." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc283786/.
Full textAbstract:
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.
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Solanki, Riten. "Formulation of zircon-free slurries and the development of ceramic shell moulds for investment casting." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8078/.
Full textAbstract:
Ceramic slurries for investment casting with the potential to replace the use of zirconium silicate have been investigated. Alumina, aluminoslicates, mullite, zirconia-mullite and zircon refractory materials were characterised and paired with colloidal silica to evaluate their slurry properties. It was found that the particle size distribution of the filler affected the viscosity of the slurries under a shear rate of drainage. A larger proportion of fines in the filler were shown to form slurries with a longer draining time. This was found to impact the shell thermo-mechanical properties by influencing the type of siloxane network formed and the rate of sintering. A combination of synthetic fused mullite and alumina fillers with different ratios was evaluated. It was shown that the shell mechanical properties at cast temperatures could be altered by adjusting the proportion of alumina present, which influenced the extent of reaction sintering occurring. The compatibility of colloidal silica types with mullite and alumina fillers were assessed to determine the stability of slurries. An optimised slurry formulation that substitutes zirconium silicate with synthetic refractories was developed; with long slurry stability and the ability to tailor the shell strength at cast temperatures, through changing the filler ratio. Casting of turbine blades was performed with the optimised shell system and found to give satisfactory casting performance for the number of trials undertaken.
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Bang, Won B. "Improving the strength of 3DP parts and development of controlled strength cellular structure investment casting shell." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38200.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996.Includes bibliographical references (p. 79).
Three Dimensional Printing (3DP) is a rapid prototyping process that creates a three dimensional part directly from computer models by printing a sequence of two dimensional layers. In this research, the strength of 3DP parts were improved by using different "print styles" (the way binder is deposited on the powder bed in creating a 3DP part) for use in investment casting process. The print styles that were created optimized line to line interaction between the printed lines, binder overlap, and the amount of unprinted powder surrounding the printed features. The strength of the parts are measured in three different axes (X-fast, Y-slow, Z). The strength improved by factors of 2, 8, and 7 for the three different axes. A controlled strength cellular structure investment casting shell that enables the creation of a metal part without any stress related defects has been created. The ceramic shell has an open cell frame structure with thin inner shell where the metal casting is poured. The flexibility of the 3DP technology applied to controlled strength cellular structure investment casting shell will incorporate all the advantages of 3DP to investment casting (Sach 1992, ASME) as well as reduction in material consumption, controlled heat transfer, permeability, and of course controlled strength to eliminate stress related defects. The cellular structure ceramic mold is designed to withstand the pouring pressures of the molten metal and survive the handling during processing yet fail when the stresses from the contracting metal becomes excessive. The 3DP molds are usually 60% porous and cellular structure investment casting shells consist of only 35% of the 3DP material per volume. A controlled strength cellular structure investment casting shell is designed to fail when excessive stress is applied to the shell structure. The stress on the casting shell is caused by the shrinkage of the metal part. The controlled strength investment casting shell has an open cellular structure frame with a thin inner shell where the metal casting will form.
by Won B. Bang.
S.M.
38
Ferreira, Anelise Rodolfo [UNESP]. "Estudo da dilatometria do titânio e das expansões de presa e térmica de revestimentos fosfatados." Universidade Estadual Paulista (UNESP), 2004. http://hdl.handle.net/11449/97297.
Full textAbstract:
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O estudo avaliou a expansão térmica dos materiais metálicos titânio c.p. (RMI Company, Ohio, EUA), Co-Cr-Mo-W (Dentaurum, Pforzhem, Alemanha) e Ni-Cr (Dentaurum, Pforzhem, Alemanha) para estimar a contração de fundição do titânio e determinou a expansão de presa e térmica dos revestimentos fosfatados Rematitan Plus (Dentaurum, Pforzhem, Alemanha), específico para titânio e Rema Exakt (Dentaurum, Pforzhiem, Alemanha) e Castorit Super C (Dentaurum, Pforzhem, Alemanha). Cada concentração de líquido especial foi variada na proporção de (100%, 75% e 50%) de água destilada, com o objetivo de determinar em que concentração de líquido e em que temperatura a somatória da expansão de presa e térmica seriam suficientes para compensar a contração estimada. Para a dilatometria dos metais padrões de cera com 14 mm de altura e 7 mm de diâmetro foram obtidos a partir de um padrão metálico, em seguida, montados em base formadora de cadinho com o conduto de alimentação e incluídos com cada revestimento na concentração de 100%. Os padrões foram incluídos e aquecidos no forno EDG (EDG - Equipamentos, São Carlos, SP). O Ti c.p. foi fundido na máquina Discovery - Plasma (EDG - Equipamentos, São Carlos, SP), e as outras ligas a fundição ocorreu em máquina de fundição centrífuga convencional. Após o polimento, os corpos de prova foram analisados e a expansão térmica foi registrada no Dilatômetro DIL 409 (Netzch) em atmosfera de ar, numa taxa de aquecimento de 10ºC/min. O Ti c.p. foi aquecido até 1550ºC, o Co-Cr-Mo-W até 1160ºC e o Ni-Cr até 1090ºC. Para a medida da expansão de presa, os revestimentos foram misturados com líquido especial e vertidos no molde de silicone (Siqmol) com cavidade de 50 mm X 10 mm X 10 mm. Uma lâmina de vidro e o apalpador (Tesa)...
This study evaluated the thermal expansion of the metallic materials titanium c.p. (RMI Company, Ohio, USA), Co-Cr-Mo-W (Dentaurum, Pforzhem, Germany) and Ni-Cr-Mo (Dentaurum, Pforzhem, Germany) to estimate the casting shrinkage of titanium and determine the setting and thermal expansion of phosphate-bonded investment materials. This investment used were Rematitan Plus (Dentaurum, Pforzhem, Germany), specific for titanium, Rema Exakt (Dentaurum, Pforzhem, Germany) and Castorit Super C (Dentaurum, Pforzhem, Germany). Each concentration of special liquid/distilled/water was varied in which ratio by 100%, 75% and 50%. This aim of this study was to determine what liquid concentration and temperature the overall expansion could be enough to compensate the casting shrinkage. For the dilatometry of the metals, wax patterns (14 mm X 7 mm) were made, attached to sprue, mounted in and mounted on crucible formers and included in 100% of special liquid. The invested patterns were heated in a burnout EDG (EDE - São Carlos - Brazil). Ti c.p. was casting in the machine Discovery - Plasma (EDG - Equipments, São Carlos, SP), and the other alloys were casting in a conventional centrifugal casting machine. After polishing, the samples were analyzed and the thermal expansion was recorded in the equipment Dilatômetro DIL 409 (Netzch) in air's atmosphere, in a rate of heating of 10ºC/min. The Ti c.p. was heated up to 1550ºC, the Co-Cr-Mo-W up to 1160ºC and Ni-Cr-Mo up to 1090ºC. For measurement of the vertical setting expansion, those investments were mixed with special liquid and invested into silicone moulds of the metal pattern (50 mm x 10 mm x 10 mm). A glass plate and dial gauge were seated on the sample, and after two hours the setting expansion was measured (Se). The distance between the ends (De)...(Complete abstract, click electronic access below)
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Kučera, Tomáš. "Rozměrová přesnost odlitků ze slitin Al vyráběných metodou vytavitelného modelu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228154.
Full textAbstract:
The aim of my diploma thesis was to find the possibilities of reaching the dimensional tolerance in the individual phases of casting by the investment casting process. The accuracy of the selected wax patterns and castings were measured by a caliper. At first the selected dimensions of the wax models were measured right after taking them out of the mold and then they were measured during seven days. The castings were measured after pouring. The obtained figures were statistically evaluated. The results show that the large-scale and thick-wall wax model should be coated after seven days of stabilization because the dimensions of the wax model are not stable.
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Curodeau, Alain. "Three dimensional printing of ceramic molds with accurate surface macro-textures for investment casting of orthopaedic implants." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11256.
Full text
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Nogueira, Fabiane [UNESP]. "Efeito de um revestimento com processamento rápido para fundição de titânio na camada de reação, porosidade interna, fluidez, rugosidade superficial e adaptação marginal de Copings." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/98027.
Full textAbstract:
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A aplicação do titânio e ligas de titânio para implantes dentários e próteses têm crescido nos últimos anos devido às suas excelentes propriedades físicas e mecânicas. No entanto, o titânio tem alto ponto de fusão (1668ºC) e sob elevadas temperaturas, reage com elementos do ar atmosférico (oxigênio, nitrogênio, hidrogênio) e com componentes de diversos revestimentos. As reações entre o metal fundido e alguns elementos de revestimentos, principalmente fosfatados ou à base de sílica, resultam na formação de uma zona de contaminação superficial denominada “α-case”. Para minimizar este problema, revestimentos contendo óxidos menos reativos, tais como Al2O3, MgO, ZrO2 e CaO, têm sido desenvolvidos. Os revestimentos especiais para fundição de titânio à base de sílica, de MgO, alumina e espinélio apresentam um tempo de processamento bastante longo (8 a 10 horas). Recentemente, foi desenvolvido um revestimento à base espinélio com processamento acelerado (Trinell - Dentaurum, Ispringen, Germany) que permite a utilização de uma técnica de secagem em forno de microondas e temperatura de aquecimento inicial do forno de 400 ºC, diminuindo o tempo de processamento para cerca de 5 horas. No entanto, não existem estudos que comprovem a eficiência deste novo revestimento. O propósito deste estudo foi avaliar o efeito do novo material Trinell (TR) na camada de reação, porosidade interna, fluidez, rugosidade superficial e adaptação marginal de estruturas fundidas em titânio, quando comparado a dois revestimentos convencionais para fundição de titânio: um revestimento fosfatado, Rematitan Plus (RP) - controle negativo e outro à base de espinélio Rematitan Ultra (RU) - controle positivo. A camada de reação foi avaliada por meio de ensaio dureza Vickers; a medida da porosidade interna foi determinada por exame radiográfico; a rugosidade superficial...
The use of titanium and titanium alloys in dental implant and prosthesis has increased in the past few years because of their excellent physical and mechanical properties. However, titanium has a high melting point (1668 ºC) and inherent reactivity with elements of atmospheric air (oxygen, nitrogen, hydrogen) and with components of several investment materials under high temperatures. The reactions between molten metal and some of the elements of phosphate-bonded and other silica-based investment materials result in the development of a surface contamination zone called “α-case”. To minimize this problem, new investment materials containing less reactive oxides, such as Al2O3, MgO, ZrO2 and CaO have been developed. The commercial silica-, MgO-, Al2O3 - and spinel-based investments especially formulated to titanium casting demand a processing time in a range of 8 to 10 hours. Recently, a new short-cycle spinel-based investment (Trinell - Dentaurum, Ispringen, Germany) was developed. It has a reduced processing time - 5 hours in the furnace- because of an investment drying technique into microwaves oven followed by an initial heating in furnace at 400 °C. However, there are not studies which verify the efficiency of this new investment. The aim of this study was to evaluate the reaction layer, the internal porosity, the surface roughness, the castability and the marginal misfit of titanium castings performed with the new material, Trinell (TR), in comparison to two conventional investments for titanium castings: phosphate-bonded Rematitan Plus (RP) - negative control, and the spinel-based Rematitan Ultra (RU) - positive control. The reaction layer was evaluated by Vickers hardness; the measure of the internal porosity was determined by radiographic test; the surface roughness was measured with a surface-test analyzer, the castability was determined by the percentage of completely... (Complete abstract click electronic access below)
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Jinnapat, Apichart. "The manufacture and characterisation of aluminium foams made by investment casting using dissolvable spherical sodium chloride bead preforms." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.588085.
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This project sought to design, implement and evaluate a process for the manufacture of porous, spherical salt beads, in order to enhance the reproducibility in mechanical properties of open cell aluminium foams made by a replication-based manufacturing technique. Porous beads were favoured in order to increase the dissolution rate of the salt from the preform, thereby making the manufacture of large foam parts practical. Salt beads were made by a novel method using fine NaCI powder, flour and water to make a paste that was subsequently disintegrated into large beads by mechanical stirring in oil. The NaCI paste viscosity was found to be important to the production of spherical beads and by varying the intensity of mechanical disintegration of the paste, control of the bead size was possible. The salt beads with sizes from 0.5 to 3 mm diameter were compacted into preforms and made into moulds for infiltration with molten pure aluminium by pressure- assisted investment casting. The heat treatment used to "cure" the plaster mould containing the preform was sufficient to remove the flour from the beads, sinter the preform and increase its strength. The effect of preform compaction conditions on the size, shape and volume fraction of porosity was quantified using a number of techniques, including mercury porosimetry, which was used to model the infiltration process. At the highest infiltration pressure 0.25 MPa (2.5 bar) the resulting foam densities were higher, but led to extensive penetration of molten aluminium into the porous beads, slowing down salt removal. In general, the compression strength increased with increasing foam density, and was highly reproducible, but where metal infiltration into the beads was extensive, the foam density increased but with little improvement in the compressive strength.
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Dai, Huijuan. "A study of solidification structure evolution during investment casting of Ni-based superalloy for aero-engine turbine blades." Thesis, University of Leicester, 2009. http://hdl.handle.net/2381/4551.
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The need to achieve increased efficiency and performance in aerospace gas turbines requires advanced single crystal Ni-based superalloys to exhibit increased temperature capabilities. High temperature creep resistance of the turbine blades is one of the major limitations to meet increased performance goals of gas turbines. The ultimate creep resistance of the Ni-based superalloys is dependent on solidification structures formed during casting. In this study, multi-scale modelling method was used to study the solidification structure evolution occurring at various scales during investment casting. Modelling of solidification on the macroscopic scale of the process was implemented using a macroscopic Finite Element casting model, ProCAST, to predict thermal and flow profiles. The predicted thermal and flow data were then used as input in a meso-scale model Cellular Automaton Finite Element (CAFE) to predict grain structure and grain orientations during solidification. At the micro-level, detailed dendritic morphology and solutal interaction were investigated using a μMatIC model. Using the multi-scale approach, grain selection in spiral grain selector, formation of new grains ahead of solidification interface and the effect of dendrite packing patterns on primary dendrite spacing were investigated. The effect of spiral shape on grain selection in single crystal grain selector has been systematically studied. It was found that the efficiency of the spiral selector significantly depends on its geometry and dimensions. The spiral becomes more efficient with a smaller wax wire diameter, larger spiral diameter and smaller take-off angle. Formation of new grains ahead of solid/liquid growth front was simulated. Stray grain formation in the platform region of turbine blades was investigated, indicating that the alloy with greater susceptibility to the formation of stray grains has lower critical nucleation undercooling. The columnar-to-equiaxed transition (CET) during solidification was predicted and the effect of material properties on the CET was analyzed. The analysis results revealed that the CET can be promoted by: (1) decreasing the critical nucleation undercooling; (2) increasing the nuclei density of the melt; and (3) extending the solidification range. Dendrites with different packing patterns were used to simulate dendrite spacing adjustment during solidification. It was found that the branching of secondary and tertiary arms in the hexahedral packing is easier than that in the cuboidal packing, leading to a smaller average spacing.
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Viens, Nicolas. "Étude des transferts thermiques lors de la coulée dans le procédé de fonderie à cire perdue." Thesis, Reims, 2016. http://www.theses.fr/2016REIMS039.
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Les méthodologies de conception des grappes de fonderie reposent fondamentalement sur l’analyse de l’énergie dégagée par le métal au cours de sa solidification. En effet, l’interprétation de ces transferts thermiques permet de calculer localement le temps de solidification et donc d’identifier les points chauds d’une pièce de fonderie. Dans le cas du moulage en sable, ces échanges thermiques sont bien connus et depuis longtemps modélisés (Chvorinov). Leur modélisation correspond à un moule thermiquement infini, c’est à dire que toute l’énergie dégagée par le métal lors de sa solidification est absorbée par le moule. En revanche, dans le cas d’une carapace ou d’une coquille, une partie de cette énergie est transmise à l’environnement via le moule ; ainsi la modélisation la plus adaptée sera donc celle considérant le moule comme un milieu thermiquement fini. Des manipulations de référence ont permis d’acquérir une bonne compréhension des mécanismes thermiques intervenant dans ce procédé de fonderie et mettent en évidence toute la complexité des échanges, à la fois internes et externes au moule (qui se produisent en simultané pendant la phase de solidification du métal). Ces manipulations ont permis par ailleurs, à l’aide de modèles statistiques, d’estimer les paramètres physiques qui sont difficilement accessibles du fait de leurs dépendances et des conditions de travail expérimentales (les échanges avec le milieu ambiant, le coefficient d’échange et le flux entre le métal et le moule). Ces valeurs issues d'expérimentations réalisées en condition réelles serviront à alimenter les bases de données matériaux utilisées en fonderie et dans les simulations numériques. La démarche et les modèles développés dans le cadre de ce travail de thèse permettent un calcul plus fiable qui servira au dimensionnement des masselottes dans le cas du procédé à cire perdue. A plus long terme, cette démarche pourrait être étendue à d’autres procédés de fonderie puisque la méthodologie développée sur du moulage à cire perdue sera transposable aux cas des moules à noyau, des moules métalliques ou autres procédés similairesDesign casting methodologies are based on the analysis of the energy released by the metal during its solidification. Indeed, the knowledge of this heat transfer permits to faithfully predict local solidification time and to identify last solidified zones. In the case of sand casting, heat exchanges are well known and have been modeled for a long time (Chvorinov). The last, modelize "thermally infinite mold" so in this case whole metal energy threw solidification phase is absorbed by the mold. In contrary, for a shell, a portion of metal energy is transmitted to environment threw the shell, so in this case, the most appropriate model is "a thermally finished mold". Reference experimentations gives a good understanding of energy / thermal mechanisms involved in the casting process and highlight both internal and external shell thermal exchanges complexity (which occur simultaneously during solidification metal). These manipulations allow to use inverse method to estimate hardly measured parameters (such as external heat transfer coefficient or metal-mold interfacial heat transfer), and therefore to build reliable thermal parameters databases used in numerical simulations. Methodology and models developed in this study allow a reliable sizing feed calculation for investment casting. On the long-range, this knowledge could be applied to other foundry processes since the methodology developed on investment casting will be transposed to core molds, die-casting or other molds
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Lomax, Lawrence Talbot. "The development of a self-disintegrating core-body for use in an art bronze-casting foundry which employs the ceramic-shell investment technique." Thesis, Nelson Mandela Metropolitan University, 2004. http://hdl.handle.net/10948/219.
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The development of a disintegrating core-body for use in an art bronze foundry, which employs the ceramic shell investment process, begins with an investigation of four principal materials that will constitute the core formula. The specifications for the disintegration of the designed core-body formula fall within the parameters that are normally set and used in the ceramic shell art bronze casting process. The raison d’ être for the disintegrating formula is based on the premise that cement breaks down (spalling) after being subjected to heat above a certain temperature. It was shown that pure cement in the form of naked test bars 100 mm x 20 mm x 20 mm does indeed break down into separate pieces when fired to and above 9000C; where 9000C is the lowest recommended temperature required for sintering the ceramic shell investment mould. The addition of calcium carbonate to pure cement in the form of naked test bars, produced a more unified formula that did not break into separate pieces when fired to 9450C. However this combination of cement and calcium carbonate had a slow setting time of 12 hours and a shrinkage value of 2,3%, which were both above the parameters being sought for a quick-setting formula with a shrinkage value of below 1%. The combination of cement, plaster of paris and silica produced formulae that set within six hours and had shrinkage values of less than 1% but did not disintegrate within 72 hours. It was only after the addition of calcium carbonate to the these mixes that formulae resulted that set within six hours, had relatively low shrinkage values and showed signs of breaking up after 60 hours. It was further shown that by altering the ratios of cement, plaster of paris, calcium carbonate and silica, that the parameters for quick-setting formulae with shrinkage values of 1% and below, that also disintegrated within 55 hours, could be achieved. xvi It was also proved by subjecting these formulae to higher relative humidity conditions that the disintegrating times could be reduced and brought to below 48 hours. Selected formulae were then subjected to temperatures of between 9000C and 10000C. It was found that as the temperatures were increased so the disintegration times were reduced and were even further reduced under higher relative humidity conditions. It was found from the above experiments that the selected formula determined to be suitable in all respects as a disintegrating core-body was too difficult to remove from the hollow bronze cast when subjected to an actual bronze pour. Further experimentation using increased proportions of silica in the formula resulted in a final core-body that could be quickly and easily removed from its bronze cast as soon as the core-body had cooled to room temperature. The selected core-body formula (F21D) that was used in the final set of bronze casting procedures was found to function optimally when fired to a temperature of 9000C and could be quickly and easily removed from the bronze casts leaving a clean inner bronze surface, free from any remnants of the fired core. The document concludes by recording the delimitations and advantages of the final core-body formula F21D, as well as making recommendations based on these parameters for further study relating to disintegrating core-body formulations.
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Umshaus, Josef. "Přesné lití odlitků ze slitin TiAl." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228183.
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Intermetallic alloys gama TiAl are prospective materials of future thanks its excellent machanical qualities and low density. However this alloy clash with for wider expansion to the practice on burdensomeness production and processing. Among disavantages belongs to also her bad fluidity. The diploma work is angaged in possibilities imporing fluidity alloys TiAl by the help of centrifuge casting. Casting healthy casts was achieved in experimental part.
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Šmíd, Dušan. "Optimalizace technologie vybraných náročných odlitků ze slitin Al." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228725.
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The main target of this thesis is to choose the suitable hard filled wax for the invest-ment casting foundry Fimes a.s. There are several suppliers of these waxes in the World and in this work waxes of the most reputable suppliers from Europe have been investigated. During these tests there were mainly technological properties of the waxes and also dimensions of both wax patterns and also the final castings measu-red. Suitability of the tested waxes, their technological characteristics, analysis of di-mensions and finally basic economical calculations have been then used in this the-sis as a tool for the recommendation for the most suitable wax for the Fimes foundry.
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Lederer, Vojtěch. "Vliv procesních parametrů zařízení Cyclone na kvalitu keramických skořepin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-416631.
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Diploma thesis contains introduction into shell drying, its monitoring and influence on shell properties. The thesis works with the Cyclone machine described further. The shell drying process in the machine and experiments are carried out broadening understanding of functions and parameters of rapid drying process. Experiments comparing courses of drying under respective settings of Cyclone and under common drying in air-conditioned room are carried out. Also mechanical properties of commonly dried shells and shells made by the Cyclone machines are compared. The positive effect of the machine on the ultimate strenght of dried shells and positive effect on the drying speed has been confirmed.
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Matoušek, Roman. "Optimalizace lití a tuhnutí axiálních turbínových kol pro dosažení jemnozrnné struktury v odlitku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-241942.
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The aim of this thesis is to investigate the influence of the structure of castings from the nickel superalloy Inconel 713 LC using rotation and cycling by casting table. The aim is to achieve a fine-grained structure and the best mechanical properties through varying the oscillation parameters during casting crystallization. Six castings of axial turbine wheel were initially casted for the purpose of this thesis. After evaluating their macrostructure, microstructure and mechanical properties, four additional axial turbine wheels were casted in order to validate the results.
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Humphreys, P., E. Erfort, V. Fester, M. Chhiba, R. Kotze, O. Philander, and M. Sam. "Development of an experimental diaphragm valve used for velocity profiling of such devices." Journal for New Generation Sciences, Vol 8, Issue 2: Central University of Technology, Free State, Bloemfontein, 2010. http://hdl.handle.net/11462/559.
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Published ArticleThe 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.