Meaning
Precision volumetric feeders belong to the mechanical dosing class designed for controlled metering of masterbatch pellets, liquid colorants or additive powders into primary extrusion streams. Within polymer processing machinery, a micro dosing screw features narrow flight depths and small flight pitches to convey minor additive quantities at low rotational speeds. The component operates directly below a feed hopper to discharge exact mass increments into the main throat of an injection moulding machine or extruder.
Precise flight geometry minimizes output pulsing during continuous feeding.
Volumetric Delivery
Rotational speed controls material volumetric displacement through small screw flights. A micro dosing screw relies on consistent bulk density and uniform particle geometry to maintain steady dosing rates. Variable speed stepping motors drive the auger shaft to adjust output by fractional revolutions per minute.
Bridging or compaction inside the feed hopper alters flight filling and interrupts volumetric output.
Additive Metering
Color consistency and property modification depend on accurate additive delivery ratios during polymer melt compounding. Fluctuations in micro dosing screw performance produce color streakiness or localized thermal degradation from unmixed additive concentrations. Using highly concentrated masterbatch pellets reduces total dosing volume but demands higher metering precision.
Inconsistent feeding of expensive additives increases scrap rates and raw material expenditure.
Mechanical Boundary
Volumetric dosing screws assume constant material bulk density and do not measure gravimetric loss in weight directly. A micro dosing screw cannot compensate automatically for changes in pellet size distribution or bulk density shifts without external scale feedback.
