Technical Details of BushingStructural Geometry• The inner bore forms a twin‑screw figure‑eight intermeshing flow channel. The center‑to‑center distance between the two bores is strictly maintained to ensure proper clearance for screw elements. • Closed liner: Fully enclosed figure‑eight inner bore without windows, applied to regular melting and homogenizing barrels. • Open liner: A through window is machined on the upper part to match feeding, venting and side‑feeding windows of the barrel. • C‑type split liner: Constructed of two halves for easy assembly and disassembly. The joint seam carries a slight risk of material accumulation. • Monolithic liner: Integrally formed figure‑eight bore with no joint seams and few material stagnant dead zones, yet with higher machining difficulty and manufacturing cost. • The outer diameter adopts interference fit with the barrel housing. Axial locating shoulders are arranged to prevent axial shifting and circumferential rotation during operation. Material Configuration• 38CrMoAlA nitrided steel: For general compounding applications, cost‑effective with nitriding hardening treatment. • WR5 powder alloy: High wear resistance for glass‑fiber filled and conventional high‑filling compounding. • WR13 powder alloy: Wear‑resistant and corrosion‑resistant for battery slurry and corrosive material systems. • Nickel‑base alloy / Hastelloy: For highly corrosive conditions such as fluoroplastics and reactive extrusion. Manufacturing Process• Forged blank with quenching‑and‑tempering heat treatment. • Precision CNC machining of the figure‑eight inner bore. • Smooth rounded transition for the window edges of open liners. • Inner surface treated by nitriding or powder metallurgy HIP hot isostatic pressing to form hard alloy layer. • Strict control of inner bore dimensions and center‑to‑center distance to secure proper unilateral clearance between screw and liner and guarantee self‑cleaning performance. Process Parameter Characteristics• Maximum operating temperature: 350 °C • Assembly mode: Interference press fit with barrel housing • Unilateral working clearance: 0.2‑0.4 mm (varies with machine size) • C‑type split liner: Simple assembly and disassembly, low cost; slight risk of material accumulation at joint seams • Monolithic liner: No joint seams, good anti‑buildup performance, suitable for frequent color change and heat‑sensitive materials • Thermal conduction: Outer wall fits closely to barrel inner wall; heat transfers to barrel heating and cooling channels | Bushing function•Wear and corrosion protection for barrel housing: Directly bears material friction and chemical corrosion from melt. All wear and consumption concentrates on the liner. Only the liner needs replacement after wear, while the costly barrel housing can be reused for long‑term service, reducing overall spare‑part costs.。 •Form figure‑eight process flow channel: Provides figure‑eight working cavity for screw rotation, ensures intermeshing operation of twin screws, controls clearance between screws and inner wall, and maintains process conditions for material conveying, pressure building, melting and mixing. •Differentiate process windows to adapt to various barrels: Closed liner forms fully enclosed flow channel for closed barrels in melting and homogenizing sections; open liner reserves windows to realize main feeding, side feeding and vacuum devolatilization & venting. •Reduce material stagnation and optimize production stability: Monolithic liner without joint seams plus optimized rounded window edges minimize material adhesion and charring. Suitable for heat‑sensitive materials and frequent color‑change production. C‑type liners fit general compounding scenarios with cost priority. •Heat transfer and exchange: The outer wall of the liner closely contacts the barrel and transfers heat to the barrel heating and cooling channels, achieving precise segmented temperature control of materials. |
