The Actual Operating Principle Of The Pressure Control System in A PPR Pipe Extruder

This system installs high-precision melt pressure sensors at the extruder die or mold inlet to collect real-time pressure data and transmit it to a programmable logic controller (PLC) or a dedicated temperature controller. The controller compares the measured values with the process-set target pressure, performs PID calculations, and outputs analog or digital signals to drive the variable frequency drive (VFD) of the extruder's main motor, thereby adjusting the screw speed-when the measured pressure is too high, the speed is automatically reduced to decrease feed rate; conversely, the speed is increased to boost extrusion output. Simultaneously, the system can also coordinate adjustments to the haul-off speed, achieving finer pressure balance through two-stage interlocking. This closed-loop control mechanism keeps melt pressure fluctuations within an extremely narrow tolerance range (typically ±0.1–0.5 MPa), thereby effectively preventing pipe wall thickness deviations, internal stress concentration, or surface defects caused by unstable pressure, and ensuring dimensional accuracy and product consistency during high-speed continuous extrusion.