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.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.