Residence time

Visualisation of the dwell time progression

REX: PSI:

Blue curve: The blue curve represents the minimum dwell time of the material along the screw. It describes the shortest time that a material particle spends in the extruder.
Red curve: The red curve shows the average residence time of the material. It describes the average time that a particle spends in the extruder before it leaves the extrusion process.

Minimum dwell time (blue curve): This minimum residence time is important to ensure that even the fastest material flows are sufficiently thermally processed and exit the extruder homogeneously.
Average residence time (red curve): The mean residence time provides a general overview of the processing time and is an important indicator of the thermal load on the material.
Curves match up to the point of melt vortex formation: Up to the point of melt vortex formation, where the material begins the melting process, the blue and red curves overlap. This is based on the assumption that pure solids conveying is a block flow, so that no differences in the residence times can occur.
PSI only: Vertical jumps due to downtimes and injection times: Vertical jumps can occur in the graphical representation, which are caused by downtimes and injection times. In these phases, the material stops for a certain period of time and is not transported any further, which leads to sudden increases in dwell times.