‘a Soft Approach’ – Soft Sensor Technology for Extrusion and Opportunities for Monitoring, Control and Fault Diagnostics

This paper highlights a novel technique for monitoring viscosity in polymer extrusion. The device represents a noninvasive technique based on ‘Soft Sensor’ technology; involving sophisticated process modelling and the integration of available on-line data to correct and adjust the model in response to errors and disturbances. The Soft Sensor measurements show excellent performance relative to a rheometric die; accurately tracking fluctuations in the bulk viscosity of the melt at the die due to changing operating conditions and changes in feed material in real-time. The potential to detect changes in feed material properties and to update model parameters accordingly is explored, representing an exciting development for implementation of advanced control schemes to continually optimise the operating conditions to achieve higher quality tolerances, reduce set-up and downtime and consequently reduce energy and material wastage. The technology enables a much more holistic approach to optimisation of settings, disturbance rejection and self-tuning ability than previously attempted in extrusion control.