Meaning
Volumetric solids transfer capacity across the entry zone of a processing screw determines maximum throughput relative to screw rotational speed. Positioned directly beneath the hopper assembly, the extruder feed throat introduces polymer pellets and masterbatch into the rotating screw channels. This mechanical passage governs initial solids handling and heat management before plastication begins in the barrel.
The geometry sets the boundary between atmospheric material storage and pressurized barrel melting.
Thermal Control
Water cooling jackets surrounding the entry region prevent thermal conduction from heating zones downstream. Excessive heat inside the extruder feed throat causes polymer pellets to soften prematurely and bridge, blocking gravity feed from the hopper.
Material Flow
Grooved liner inserts inside the entry section enhance mechanical friction between polymer granules and the housing wall. A well-designed extruder feed throat maximizes forward solid conveying while preventing premature melting that causes feed throat bridging. Irregular pellet geometry or high regrind ratios reduce bulk density, decreasing throughput efficiency across the feed zone.
Processing engineers select smooth or grooved feed throats based on resin friction coefficients and feed pressure requirements.
Bridging Defect
Melt bridging halts extrusion production by blocking pellet entry into screw flights. Inadequate cooling at the extruder feed throat allows low-melting-point additives or tacky resins to stick to metal surfaces. Purging clogged feed throats requires stopping the drive motor, opening the hopper drain and clearing agglomerated material manually.
Consistent jacket water temperature prevents feed interruption during high-temperature extrusion of engineering resins.
