Meaning
Continuous measurement of fluid flow properties during the actual production run provides real-time data for process control. The practice of in-line rheology involves installing sensors directly in the melt stream of an extruder or moulding machine to monitor viscosity changes as they happen. This method replaces manual sampling and laboratory testing, offering immediate feedback on the condition of the polymer melt.
It allows operators to detect deviations in material quality before defective products are formed.
Process Feedback
Sensor outputs can be used to automatically adjust process parameters during operation. With in-line rheology, the control system monitors shear stress and shear rate directly in the feed channel. If the viscosity drifts beyond the specified limits, the machine can adjust the temperature or screw speed to maintain product consistency.
Quality Assurance
Recycled resins often present challenges due to batch-to-batch variations in molecular weight. Implementing in-line rheology helps processors manage the quality of regrind by detecting changes in melt behavior instantly. This capability ensures that the final product maintains its physical specifications despite raw material variability.
Sensor Placement
Accurate measurements depend on locating the detection equipment at a point where the flow is stable. Typically, in-line rheology uses slit dies or capillary sensors integrated into the nozzle or adapter plate. This positioning ensures that the measured viscosity represents the actual state of the polymer as it enters the moulding cavity.
