A process optimisation based on a desired objective function
(Ye et al., 1997; Wang and Smith, 1997) (in this case,
minimum variation of final part thickness from the desired
thickness) was implemented. An initial parison thickness (die
gap opening) was taken from the results of trial 3 (Fig. 3a).
The thickness distribution of the parison was then manipulated
using a profiled gradient-based approach based on the
difference between the target thickness and the predicted thickness from a given iteration. Process constraints were
taken into account; namely, minimum and maximum die gap
opening.