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Thesis (M.Eng.). / Written for the Dept. of Mechanical Engineering. Title from title page of PDF (viewed 2008/01/14). Includes bibliographical references.

Thesis (MEng (Industrial Engineering))--University of Stellenbosch, 2006. / This thesis represents the results of a study for the use of conformal cooling in blow mould design. As a part of this, design case studies and comparative experiments were conducted to determine the difference in performance of blow moulds incorporating conventional cooling and those with conformal cooling. The cooling configurations are compared using simulation to identify the shortcomings of conventional cooling. In addition modern manufacturing methods able to manufacture complex conformal cooling designs, are evaluated. The relevant cooling principles are explained using mould designing handbooks as well as heat flow handbooks. The tie between them is made and the differences explained. The moulding cycles of injection as well as blow moulding process are explained and the applicable simulation software used in these fields is described.

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This dissertation presents work involving the manufacture and analytic modeling of microcantilever parts (length-width-thickness of roughly 500-100-10 microns). The manufacturing goals were to devise a means for and demonstrate repeatable production of microcantilevers from techniques not used in the integrated-circuit field, which are the exclusive means of current microcantilever production. The production of microcantilevers was achieved via a solvent casting approach and with injection molding, which produced parts from various thermoplastic polymeric materials (amorphous, semi-crystalline, fiber- and nanoclay-filled) in a repeatable fashion. Limits of the injection molding process in terms of the thinnest cantilevers possible were examined with 2 microns being the lower bound. Subsets of the injection-molded parts were used in a variety of sensing applications, some results were successful (e.g., vapor-phase, resonance- and deflection-based sensing), while others showed poor results, likely due to experimental shortcomings (e.g., fluid-phase, deflection-based sensing). Additionally, microcantilever parts with integrated tips were injection-molded and showed to function at the same level as commercial, tipped, silicon-nitride parts when imaging an optical grating; this experimental work was the first demonstration of injection-molded parts for chemical sensing and force spectroscopy. The scientific results were (i) the derivation of a length scale dependent bending stiffness and experimental evidence showing that such an effect was observed, (ii) the development of a new microcantilever experimental mode (surface stress monitoring via microcantilever bending resonant frequencies) and experimental validation of the technique, and (iii) a new method for determining microcantilever geometry based upon measurement of a bending, lateral, and torsional mode and experimental validation of the procedure.

published_or_final_version / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

The extrusion blow molding process is an important polymer processing operation which involves a complex thermo-mechanical history. / Specimens were obtained from two commercial, blow molding grade, high density polyethylene resins, employing an instrumented Impco reciprocating screw blow molding machine. High speed cinematography was employed in conjunction with a parison pinch-off mold and a transparent blow mold to characterize the dimensional changes of the parison during the parison formation and the clamping and inflation stages. The contact temperature and the heat removal rate were measured during the cooling stage. Numerical methods were employed to investigate the thermal history during various stages. After molding at various operating conditions, the molded specimens were extensively characterized in relation to the distribution of thickness, crystallinity, orientation and impact behavior. / The distributions were analyzed in relation to the data obtained regarding the thermo-mechanical history during the molding process and some theoretical considerations of the relevant flow and heat transfer phenomena.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2009. / The objective of this project was to measure the performance of high-strength aluminium alloys as injection mould material compared against conventionally used tool steel.

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