Enhancing the introduction of shell mould casting technique in Ghanaian practice

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2011-06-19
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Abstract
The increase in demand of cast goods in Ghana including some machine and engine parts, calls urgently for the development of additional and better methods other than sand casting (especially where sand casting which is about the most widely practiced in Ghana and for casting only few simple items such as corn milling plates, cannot meet the casting standards (close tolerance and good surface finish) required). As a contribution to this development the shell mould method which gives better surface finish and close tolerances than the sand casting process was developed in this project for use in Ghana. Phenol formaldehyde (PF) resole resin and calcium stearate synthesized locally from beef tallow and calcium oxide were used instead of phenol formaldehyde (PF) novolac type. This was successful for the production of the core but collapsed during the production of the main mould. The collapsed resole precoated sand was, however, utilized by reinforcing it with sodium silicate and the hot box route slightly altered to produce the main mould. A hand operated muller and a shell mould ejector mechanism were fabricated and were utilized to produce the shell core and mould which were used to cast a machine part. Among the findings, collapsed precoated sand is not a waste. It can be used again by making a shell “pattern imitator” to go with the pattern, at a maximum allowance of 10 mm from pattern surface on an “opened–top metallic table” and then ramming onto the metal pattern before drying in furnace and then stripping from the pattern surface. This can be duplicated for mass production. Binders can be developed from local sources such as cashew nut shell oil, corn, cassava, protein/peptide materials and also from gum Arabic. All these are readily available in Ghana.
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A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of the Degree of Master of Science in Mechanical Engineering.
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