How melt pumps are controlled?

Since more than 35 years gear pumps with associated control system are state-of-the-art. The most common control mode is P1-inlet pressure control in auto-loop.
This means that the pump inlet pressure (P1) is measured by a pressure sensor. The controller evaluates the actual with the set pressure value and regulates the speed of the extruder screw, called extrusion mode (e.g. sheet), or the speed of the extrusion pump, called compounding mode.