Technical Details of Reverse Kneading ElementsStructural GeometryThreads or kneading discs are staggered with helix direction opposite to forward‑direction elements. - Reverse Conveying Screw Element (L‑thread): Erdmenger fully‑intermeshed left‑hand thread. Twin‑screws realize mutual wiping and self‑cleaning. It inherently pushes material upstream; materials advance only via clearance leakage flow and delivers strong pressure‑building capacity.
- Reverse Kneading Block (Reverse Shear Block): Kneading discs are staggered at reverse helix angle, typical reverse angle 45°. It generates both reverse flow resistance and shear mixing effect. Its pressure‑building capacity is weaker than reverse thread element, while shear intensity is higher.
Model marking examples: SE‑30/30‑L (reverse thread), KB‑45°‑L (reverse kneading block). Inner bore adopts involute spline. Material Configuration- 38CrMoAlA Nitriding Steel: General modification working conditions
- WR5: High‑wear conditions for glass‑fiber and mineral filling
- WR13: Wear‑resistant & corrosion‑resistant, for battery materials and corrosive melts
- Nickel‑base Alloy: Reactive extrusion under severe‑corrosion conditions
Manufacturing ProcessIntegral forging and quenching‑and‑tempering heat treatment; CNC grinding for left‑hand thread / reverse‑staggered kneading discs; intermeshing clearance strictly controlled; large root fillet reduces risk of material hanging‑up. Process Parameter Characteristics- Shear level: Medium‑high shear; reverse kneading block ＞ reverse conveying thread element
- Conveying capacity: No forward conveying tendency, intrinsic reverse pushing effect; materials pass through only by leakage flow
- Shear heat: High, causing obvious melt temperature rise
- Mixing type: Strong dispersive mixing + strong distributive mixing
- Self‑cleaning performance: Excellent (fully‑intermeshed structure)
- Filling degree: Nearly 100 % melt filling within element zone
- Residence time: Significantly prolonged
- Pressure: High‑pressure zone formed at upstream, low‑pressure zone at downstream
| Functions of Reverse Kneading Elements•Build melt back‑pressure and increase screw channel filling degree It creates flow resistance and builds high‑pressure zone at upstream. The screw channel is fully filled with melt to increase shear input and promote sufficient resin melting. Widely used in melting sections for crystalline plastics and high‑melting‑point resins. •Prolong melt residence time and enhance dispersive & distributive mixing Back‑flow and leakage‑flow extend residence time, improve de‑agglomeration of fillers and color‑pigment clusters, and optimize melt homogeneity. Suitable for masterbatch and polymer alloy blending systems. •Pressure sealing upstream of vent port (vacuum pressure‑locking) Installed upstream of vacuum devolatilization section to form high‑pressure sealing barrier. It prevents melt overflow toward vent port and material blow‑out, and guarantees vacuum devolatilization efficiency. It serves as standard configuration for vacuum port layout. •Seal upstream of downstream feeding port Reverse elements fitted upstream of side‑feeding port form pressure barrier, preventing melt back‑flow into side‑feeding barrel and ensuring smooth downward feeding of powders and fibers. |
