The machine builds up an appropriate pressure in order to move the melt into the cavity.
Dependent on the extending flow path length until the flow path end the pressure is rising during filling of the part.
The highest injection pressure can be found usually at the machine nozzle at VP-Switch.
Thin wall thickness leads to a higher pressure difference between melt entrance and melt front.
This glossary of plastic industry is provided by PLEXPERT Canada Inc.