| dc.description.abstract | The extrusion market of South Africa has a smaller demand for products than
most of the First World countries in which mainly single process twin-screw
extruders are used. This leaves a void for the development for a multi-purpose
twin-screw extruder. This will enable companies to manufacture a greater
diversity of products with one machine, not only in South Africa, but in the rest of
Africa as well.
Africa has one of the biggest rates of poverty and famine in the world . The
famine crisis in Africa is mainly due to the lack of food with a high nutritional
value. The conventional cooking method currently used, that of preparing food
over an open fire, causes the loss of most of the vitamins and essential
nutritional values in the food .
Extrusion is the process whereby high quality food is manufactured by using
simple raw materials. The raw material goes through a process of heating, mixing
and shearing to produce a high quality end product.
The main disadvantage of extruders currently available on the market is their
cost. Extruders are currently manufactured in the First World countries. This
causes that the machines are too expensive and unaffordable for most of the
African markets. This creates the opportunity for an affordable extruder to be
manufactured and maintained in Africa.
This study provides an introduction to extrusion. Chapter 2 contains a literature
study on the various extruders and their respective available sub-components. It
also discusses the differences between different extruders. In Chapter 3 a
generic approach to the design and manufacturing of an extruder unit is
formulated and discussed. Chapter 4 is dedicated to the explanation of basic
screw geometry and designs. Chapter 5 contains case studies on two types of
barrels designed and tested during this study. It also provides the best choices of
designs for various components. In Chapter 6, a case study of a fully operational
twin-screw food extruder is discussed. This extruder was manufactured in Africa,
and maintained in Africa. Recommendations and conclusions of this study are
summarized in Chapter 7. | |
