Direct Pin Sensor Placement and Dynamic Viscosity Control in Micro-Moulds
Direct pin pressure sensing in micro-moulds compensates for melt viscosity drift by dynamically adjusting injection speed to hold precise shear rates.
Slit Die Viscometer
Meaning
An inline or laboratory testing instrument measures the viscosity of polymer melts under actual process pressures and shear rates by monitoring pressure drops along a rectangular channel. Chemical producers and compounders use the slit die viscometer to obtain accurate flow data that reflects how a polymer will behave inside an industrial extruder. This direct measurement avoids the flow disruptions caused by traditional capillary instruments.
Operating Mechanism
The melt is pumped through the rectangular slit at a controlled flow rate. Pressure transducers located along the length of the channel measure the pressure drop as the fluid moves. By analyzing this drop, the slit die viscometer calculates the shear stress and the shear rate of the polymer melt simultaneously.
Industrial Utility
The output data guides the calibration of flow simulation software before cutting steel for new tools. Accurate viscosity profiles prevent errors in gate sizing and runner design. Testing the material with this instrument ensures that recycled resin lots meet the processing requirements before they are loaded into production silos.
Limit Condition
The accuracy of the measurement depends on maintaining a stable temperature along the die walls. Thermal variations distort the pressure readings, rendering the calculated viscosity invalid.