The application of a powder injection moulding process to the production of fully sintered hardmetal components has been studied. Salient, highly interdependent process variables investigated include; powder and binder characteristics, mixing techniques, feedstock rheological characteristics, mould design features, moulding parameters, debinding and sintering parameters. Fundamental studies were conducted to determine the effect of powder and binder characteristics on the powder loading capacity of feedstocks. Various methods of mixing were investigated. The most favourable methods were identified from the rheological response of their respective feedstocks as determined by capillary rheometry. Thermogravimetric analyses were used to; (a) identify binders and feedstocks essig beneficial debinding kinetics, (b) in the study of suitable debinding atmospheres and (c) to develop thermal debinding profiles for selected feedstocks. A spiral mould was used to assess the mouldability and optimum moulding parameters of selected feedstocks. Feedstock properties and mould design features which promoted moulding defects were identified and solutions developed. It was found that the maximum hardmetal powder loading achievable in a given feedstock was dependent on the powder size, size distribution and level of agglomeration. Low viscosity binders with high dielectric permittivities were found to promote highly loaded feedstocks. Feedstock viscosity increased with powder concentration. This relationship was modelled by a simple exponential power function over a narrow range of shear and powder concentration. Compounding methods utilising high shear melt mixing principles were found most effective in producing low viscosity feedstocks of consistent rheological response. Feedstock compositions of high powder concentrations and based on single, crystalline, wax binder systems were found to exhibit a high thermal dependence of viscosity, high activation energies of viscous flow, a high shear sensitivity and tended to segregate when subjected to shear. Such propensities were found detrimental to moulding behaviour. Spiral mould analysis revealed feedstock compositions were sensitive to changes in thermal parameters. Compositions based on multi-component binder systems were found most preferential in producing defect free mouldings of sound integrity and offered favourable debinding characteristics. Thermal debinding of mouldings was only completely effective by careful control of heating rates and when performed in hydrogen rich atmospheres. The reaction order and activation energy of the binder volatilisation was found to be dependent on the level of binder decomposition. Melt wicking was most effective using a hydrated magnesium aluminium silicate substrate. Sintered engineering components were produced by an injection moulding process with near theoretical densities and acceptable microstructures.

Coagulant dipping constitutes an important part of the rubber glove manufacturing process. Its operation is affected by many variables which dictates the quality of the finished product. Therefore, investigating the controllable factors affecting the quality of the product and process in the presence of noise factors for process improvement is the primary aim of this study. Robust process design for off-line quality control has received much attention in the literature. Application of this design in the rubber examination glove industry as an alternative solution for potential competitive advantage was investigated. The robust design problem is defined in terms of design objectives, controllable factors and noise factors. In this thesis we combined both controllable and noise factors as a single experimental set-up. An L16 orthogonal array was used as it would allow the evaluation of the eight main factors chosen and some of their interactions. The use of fractional factorial reduces the number of runs required. Physical experiments were conducted in the glove manufacturing plant for the case problem. Effects of experimental errors, model assumptions, the experimental design and modelling approaches on the results are discussed. Models capable of predicting the response performance of the process under study are developed and investigated. Experience learnt from the implementation of quality improvement which are human related factors are also addressed in this thesis. From this study we gained a better understanding of the rubber glove manufacturing process. We are therefore in a better position to see what levels of the independent factors will lead to acceptable response values and acceptable variability. This approach allows us to make appropriate compromises between a target value for the response of interest and resulting variance. The additional knowledge were not known before. It could be used as an advantage for the glove manufacturers to better control their processes. The enormous potential benefits that could be reaped from the information gained about the process quantify the efforts for improvements.

The use of computers by naval architects has revolutionised ship design and -construction management. The use of high power laser technology could similarly revolutionise production processes to produce a quantum leap in productivity. Facilitating low heat input materials processing, the laser is suited to various cutting, welding and heat treatment applications in shipbuilding to increase productivity through improved product accuracy. From these processes, the Author has concentrated on the application of high power lasers to the welding of tee section joints - the most common joint configuration in ship structures - by a single sided method (skid welding) to give both the lowest possible heat input and greatest flexibility. -Using a lOkW laser, single pass fully penetrating skid welds may be produced for joints in plate of up to 15mm thick, but using this size of laser, production parameter envelopes to produce visually and structurally sound joints reduce in size as plate thickness increases to greater than 10mm. It is shown that fully penetrating laser skid welds produced in steel conventionally used for surface vessel construction are of superior structural quality to fillet welds as required by classification society rules. The work has shown that achieving process consistency in an automated production based skid welding workstation operating with existing levels of joint tolerance will be dependent not only on well designed laser and beam delivery harware but also on suitable on-line adaptive control systems. It has been demonstrated that by employing laser skid welding for steelwork fabrication, an increase in productivity can be gained, principally through increased processing speed and improved product accuracy.

This study investigates the influence of spray nozzle internal geometry on heat transfer performance and the resultant power requirements. An experimental apparatus was designed and built, which allowed for close control of the heat transfer from air to water and the required energy for droplet production. The apparatus allowed for simultaneous measurements of heat transfer rate from the gas to the spray droplets and the pumping power requirements for the sprayed liquid. A spray chamber was constructed in the form of a Perspex cylinder, 372 mm internal diameter and 372 mm height, mounted on its vertical axis. Thermocouples, humidity sensors, and pressure sensors were used to measure the temperature difference of the air and water, the humidity difference of the air, and the pressure drop across the nozzle. The spray nozzles have been installed at the centre of the upper cover plate directed along the cylinder axis. The heat and mass transfer process was carried out in a counter current flow. Two different nozzle designs were the subject of this investigation. The pressure swirl nozzle works on liquid pressure alone. Droplet formation and size is influenced by changes of the internal geometry and liquid pressure. An effervescent two fluid atomiser with internal mixing was tested. The influence of changes in gas bubble and exit orifice geometry on droplet size and formation was investigated. Analysis of the heat transfer process is based on the energy balance for the whole cylinder. This analysis allows for the determination of the nozzle with the best performance characteristics. From the required energy to produce the droplets and the rate of heat transfer, a new equation for the index of energy performance, was defined. A Laser Doppler Analyser was used to determine the droplet size and velocity for the low pressure nozzles and this data was compared with the existing theory. The droplet distribution of the spray nozzles was determined for various configuration. The measured droplet size was below the calculated droplet size using the derived equations from the literature. Photographs of the spray angle at different liquid pressures were taken for digital analysis. The spray angle showed reasonable agreement with the literature. A three dimensional numerical model was designed to simulate the heat transfer process inside the spray chamber using PHOENICS, a Computational Fluid Dynamics (CFD) software. The software modelled the heat and mass transfer inside the spray chamber. This model then allowed for the testing of different droplet distributions, formations, and their influence on the heat transfer process. In order to validate the results, the necessary variables such as the gas mass flow, liquid mass flow rate, droplet size, spray angle and scatter, hot air inlet temperature, were obtained from the experimental data. The result of the simulation is the air outlet temperature and humidity of the spray chamber. The internal 3D flow field is solved with the Lagrangian and Eulerian equation including the disturbance, solved with the k-epsilon turbulence model, created by the spray droplets. Four different pressure swirl configurations were simulated. Every configuration had five different pressure points. Every pressure point was simulated individually in order to find out if the numerical simulation software was able to predict the correct result for different liquid mass flow rates without altering the boundary setting and parameters. The heat transfer process was found to depend on the droplet size and distribution produced by the spray nozzle. A comparison of the experimental data with the simulation results demonstrated the accuracy of the CFD model. The temperature accuracy was ±5.9% and for the humidity ±12% on average for all simulations. It was found that the heat transfer of the effervescent atomiser depends on the mass ALR and that the highest heat transfer was measured when it was operating with an ALR of 0.1. The tested effervescent atomiser was found to be strongly influenced by the atomising air, an effectiveness of 93% achieved. The change of the internal geometries had no significant influence on the heat transfer rates. The change of the internal geometry, especially the exit orifice diameter, had a strong influence on the pressure swirl nozzle performance, which started at 85% and reached a maximum of 95%. It was found that the pressure requirement for the 4.7 mm exit orifice was only 20% of the pressure requirement of the 2.5 mm exit orifice in order to achieve the same cooling performance. The pressure swirl needed for all flow rates approximately 20 times less energy to achieve the same cooling as the effervescent nozzle.

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