Meaning
Hydraulic or electric adjustments within an injection moulding machine maintain consistent cavity filling by modifying the ram speed or injection pressure in response to real-time sensor data from the nozzle or mould. Melt pressure compensation stabilizes the volumetric flow rate when resin viscosity changes occur due to batch variations or thermal fluctuations in the barrel. This function stops applying when the system reaches the mechanical limit of the hydraulic pump or the maximum torque of the electric drive motor.
Calibration Procedure
Engineers adjust the control loop gains to align sensor input with the physical movement of the screw. Melt pressure compensation relies on the PID controller to calculate the offset required to balance the actual output against the target setpoint. Precise tuning prevents overshooting the peak cavity pressure during the initial stages of filling.
Consistent results depend on the sensitivity of the transducer placed at the nozzle entry.
Production Outcome
Deviations in material grade lead to inconsistencies in part weight and dimension without active correction. Melt pressure compensation mitigates the impact of regrind additions by sensing the change in resistance during the filling phase. Parts produced with this system demonstrate lower variance in shrinkage across large manufacturing lots.
Higher scrap rates result when the machine lacks the dynamic capacity to correct for these sudden viscosity shifts.
Thermal Stability
Barrel temperature fluctuations cause significant shifts in the flow behavior of polymers. Melt pressure compensation accounts for these heat induced changes by adjusting the injection force during every cycle. Proper operation requires a stable sensor signal that remains free of electronic noise or mechanical vibration.
Stable internal pressure ensures the structural integrity of the final moulded component.
