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In the light of the requirement for a controllable and reliable extrusion plant for preforming various types of inorganic pigment into spaghetti shape onto a convective band dryer to facilitate drying, a study of the preforming method currently in use by the sponsors has revealed that the screw extruder being used cannot perform this function satisfactorily. The main reason being the thixotropic nature of the pigments. They do not readily tolerate mixing or working, which is inherent in the screw extruder. This necessitated a study of other preforming methods. The thesis reviews the available methods of preforming, existing theories on extrusion of material, and various extruder concepts generated during the initial stages of the project. The concept chosen is discussed. A mathematical model based on test results carried out on a Laboratory model of the chosen extruder concept and tile complete design of the full scale extrusion machine, together with its charging units and the plants' control system is presented. An analysis of the performance tests carried out on the new plant is discussed. The thesis concludes with a comparison between the new plant and the screw extruder in current use regarding their performances and product qualities. Proposals for further work and test are also made.

The butt fusion process is extensively used in the joining of polyethylene (PE) pipes by the water and gas industries. This welding process although deceptively simple, is rather poorly understood, with much of the initial developments being of a rather empirical nature. The Water Research centre (WRc) have funded the present research in an attempt to optimise the welding of high pressure pipeline (PE100) systems. The main aims of this research were to investigate the effect of different welding conditions on the physical and mechanical properties of the joints produced and to investigate these effects on the micro- and macro-structures of the joints produced. A series of welds were made using Eltex Tub 124 and Rigidex 002-50 pipes of 180mm diameter. The fusion pressure and heatsoak times were varied. A milling machine witha twin cutter arrangement was used to obtain the test specimens from around the circumference of the pipes. Differential scanning calorimetry was used to study the effect of sample preparation methodology on the thermo-oxidative stability. Polarised light microscopy and image analysis were used to study the macro- and micro-structural developments in the weld joint. Joint strength was evaluated via standard and non-standard tensile test methods. Milling the samples to produce the test specimens was found to decrease significantly the thermo-oxidative resistance of the polymer. Reasons for this behaviour have been proposed. In order to achieve high quality thin films from microtomy, custom-made blades were used. This programme also developed the optimum polishing method for the microtomed blades. The macro-structure of the bead: its shape and dimensions were found to be a function of temperature and pressure. Correlation was found between the bead geometry and the position around the circumference of the pipe. The macrostructures within the weld zone also showed this dependence on the position along the circumference of the pipe. An examination of the microstructures of each weld had shown the presence of five different zones. The feasibility of using microtomed thin sections in a tensile test was demonstrated. The test method provides a means to study failure initiation and propagation in the tensile test specimen. Initial deformation was found to occur in the centre of the melt-affected zone (MAZ) and the final failure occurs at the junction of the weld bead and the bulk polymer. Tests on films without the weld bead showed that maximum deformation occurred at the centre of the sample within the MAZ. The presence of the bead and the asymmetry in the test specimens caused by the welding process were found to have a significant influence on the failure mode and the failure strain. The strain rate was also found to play a significant role in both beaded and debeaded samples. The failure was initiated from the pseudo notches in the beaded samples. In the debeaded sample the failure was within the MAZ.

The economic aspects of the design of fabricated components have been analysed and clarified. The parameters affecting fabrication economy have been discussed based on the information available to a designer. The approach to the most effective design parameters has been studied and specified.

The present research has arisen from a continuation of the WRAPS (Welding Robotic Adaptive Programming and Simulation) project at Loughborough University, and its development as the supervisory controller of a flexible welding system. A knowledge based expert system (PIKBES) has been developed for on-line expert modification of pre-programmed welding procedures during fabrication of batches in a flexible adaptive robotic welding environment.

The thesis reports an investigation concerned with the optimisation of materials and methods in the production of precision cast H13 die steel tooling. The investigation was conducted in four stages: (i) mould material evaluation; (ii) metallurgical processing; (iii) test casting production and evaluation; (iv) finishing procedures.

The objective of the current work was to establish a viable manufacturing technology for 1-3 piezoelectric ceramic/polymer composites, capable of meeting the high volume production requirements. To this end, an extensive development and fabrication programme has been successfully completed, which demonstrates the feasibility of the injection moulding process as a potential fabrication route. The technology will make available to the MOD a new generation of low-cost transducers tailored to perform in the frequency range suitable for underwater applications. The piezoelectric ceramic used throughout this study was PZT-5H. During the course of the investigation two types of feedstock formulation were evaluated. The first employed a binder system developed in-house based on polypropylene, microcrystalline wax and stearic acid. The second formulation employed a commercial binder system designed specifically for ceramic/metal injection moulding. In the case of the 'in-house' binder, two formulations were prepared with approximately 62% by volume PZT-5H but with differing ratios of polypropylene to microcrystalline wax. Three formulations were prepared with the 'commercial' binder system containing approximately 55%, 58% and 60% by volume PZT-5H respectively. Compounding by twin screw extrusion produced a feedstock consisting of discrete particles of PZT-5H, approximately 0.5 ?m in diameter, homogeneously distributed within the organic binder. All formulations displayed shear thinning behaviour when evaluated by capillary rheometry and had shear viscosities below 1000 Pa s at a shear rate of 100 s-1 Further, all formulations displayed tension thinning behaviour-and were characterised as viscoelastic. Attempts to produce an acceptable 1-3 preform moulding from feedstock based on the in-house binder system were unsuccessful. It was necessary to reduce the ceramic loading to 30% by volume before a complete 1-3 preform could be moulded. The failure to mould preforms from the in-house formulation was attributed to its high elongational viscosity. It was therefore concluded that an elongational viscosity of 30 kPa s at a tensile strain rate of 58 S-1 is undesirable for moulding this particular component. Satisfactory conditions were established for the production of 1-3 preform mouldings from the commercial feedstock formulation containing 58% by volume PZT-5H. Optimisation of the injection rate and hold pressure was possible by investigating the variation in pillar-density across the 1-3 preform mouldings. Satisfactory heating schedules for both the binder removal and sintering stages were established. Microstructural characterisation of sintered pillars revealed grain sizes ranging from 2 to 7 ?.m in diameter. Orientation effects in the sintered microstructure were not apparent in samples moulded at different injection rates. The addition of cover plates to poled composites containing epoxy resin was found to increase the hydrophone figure of merit (HFOM) by an order of magnitude. HFOM values measured during the present work for injection moulded 1-3 composites are comparable with similar composites fabricated by the dice-and-fill technique.

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