Meaning
Dynamic interactions between a material and the boundary wall cause the output to alternate rapidly between adhering to the surface and surging forward. Stick-slip flow creates jerky movements in high viscosity liquids that lead to uneven thickness and periodic waves in a finished product. It signals an instability where the internal pressure of the system builds up and then discharges suddenly.
Mechanism Detection
Monitoring the pressure gauge at the pump head reveals the cyclic spikes that identify this unstable condition. During stick-slip flow, the melt effectively bounces through the pipe rather than sliding. This phenomenon ruins the accuracy of sensors and can lead to damage in the sensitive parts of the die over time.
Product Uniformity
Surface defects from this pulsing motion appear as repetitive bands or bars across the material. While the chemical yield remains unchanged, the visual and mechanical yield drops significantly because the parts do not meet dimension tolerances. The removal of this effect often requires changing the finish of the internal metal pipes or adding friction reducers.
Frequency Analysis
Adjusting the drive speed of the motor helps engineers find the quiet window where the material moves steadily. A stable process run avoids stick-slip flow by keeping the throughput within a range where the polymer molecules can consistently relax against the metal. It determines the boundary between a usable line speed and an unpredictable failure.
