Meaning
In injection molding, automatic compensation of the plasticizing stroke corrects for volumetric fluctuations in melt density. This active correction, known as dynamic screw stroke adjustment, modifies the recovery position of the screw in real time to ensure a constant weight of resin is delivered to the mold cavity. The action applies to high-precision technical parts where ambient temperature or regrind variation alters melt volume, but ceases to function when screw check-valve leakage exceeds the capability of the displacement sensor.
Mechanical Control
Hydraulic or electric drive systems measure the melt pressure during plasticizing to calculate the necessary stroke shift. Dynamic screw stroke adjustment automatically moves the screw back position to maintain a uniform shot size. The controller executes this calculation before the injection phase begins.
Resin Processing
Fluctuations in polymer viscosity alter the pressure profile during the recovery phase. When raw material density increases, the screw must recover to a shorter stroke to avoid overpacking. This control loop helps molding shops maintain a consistent melt temperature.
Shot Repeatability
Weight variation in molded parts decreases when the molding machine adjusts its stroke to match the raw material changes. Flash and short shots are eliminated because the correct polymer volume enters the runner system every cycle. This stabilization reduces scrap rates during long production runs.
