Technical Details of Involute SplineStructural Geometry• External spline (core shaft): Multi-tooth involute external teeth are milled or ground on the outer circle of the core shaft. • Internal spline (screw element): Involute internal teeth are machined on the inner bore of conveying, kneading and mixing elements. • Torque is transmitted via meshing tooth flanks with flank centering. Axial positioning and locking of elements are realized by lock nuts and retaining rings. Material Configuration• Core shaft: 40CrNiMoA high-strength alloy steel, quenched & tempered + tooth surface hardening. • Screw element body: 38CrMoAlA, WR5, WR13, nickel-base alloy. • Precision grinding on spline tooth flanks to improve hardness and wear resistance. Manufacturing Process• Forging and quenching & tempering of core shaft; hobbing/milling followed by tooth grinding. • Bore machining of screw element blanks, broaching or grinding for involute internal teeth. • Tooth profile modification to reduce stress concentration. • Strict control of tooth alignment and accumulated pitch error to guarantee interchangeability. Process Parameter Characteristics• Torque capacity: High specific torque. Suitable for high-torque and high-speed main extruders. Load capacity is much higher than single key under the same shaft diameter. • Centering accuracy: High. Stable phase after repeated assembly and disassembly with minimal circumferential clearance. • Interchangeability: Excellent. Elements of the same specification are universal across different machines. • Assembly & disassembly: Elements can slide axially for mounting and removal; lubrication on spline tooth flanks is required. • Failure modes: Tooth flank wear and pitting; tooth breakage rarely occurs. Wear is generally caused by long-term lack of grease lubrication. | Functions of Involute Spline•High torque transmission. Multiple teeth mesh simultaneously to transfer torque output from gearbox through core shaft to all screw elements. It withstands alternating impact torque during compounding and adapts to high filling and high-viscosity working conditions. •High-precision centering to maintain screw phase. Flank centering ensures stable circumferential phase of screw elements, maintains twin-screw meshing clearance, reduces abnormal wear and stabilizes compounding process. •Modular screw configuration assembly. Screw elements can slide freely along the core shaft in axial direction. Elements can be rearranged, added or removed arbitrarily for flexible adjustment of screw process configuration. | 
