Meaning
The injection speed profile is a programmed velocity curve that controls screw advancement during the filling phase of thermoplastic moulding. This operational parameter regulates shear heating and molecular orientation within polymer melts before the material enters the mould cavity. Melt viscosity drops when ram velocity rises because pseudoplastic resins experience structural breakdown under high rates of shear deformation.
Ram Kinematics
The injection speed profile is configured on the machine control unit prior to production runs. Rapid initial displacement prevents premature freezing during thin wall filling sequences. Deceleration phases near the end of the stroke prevent flash formation along parting lines.
Screw velocity commands translate directly into volumetric flow rates across distinct barrel zones.
Defect Mitigation
The injection speed profile prevents surface blemishes and structural failures in finished parts. Low velocity settings during initial gate transit avoid jetting marks on aesthetic components. High acceleration rates overcome flow hesitation in complex geometries with thin wall sections.
Pressure spikes occur when the ram encounters sudden geometrical restrictions inside the tooling.
Economic Variance
The injection speed profile maintains acceptable part quality when switching between virgin polymer and post consumer regrind materials. Virgin pellets exhibit predictable melt flow indices under standard thermal histories. Recycled polymers display variable viscosity that demands customized velocity curves to offset batch discrepancies.
Machine feedback loops adjust hydraulic pressures constantly to ensure the programmed speed profile remains stable despite feedstock variations.
