Cable insulation and high-performance crosslinked polyolefins are trending toward high-filler, high-reactivity systems. In twin-screw extrusion, XLPE and silane/peroxide cross-linking systems exhibit coupled high-viscosity flow and reaction behavior, while in high-filler ATH/MDH systems (>50%), system resistance rises dramatically, keeping the equipment in a prolonged high-torque load condition. Under these conditions, the twin-screw transforms from a standard mixing machine to a high-resistance reactive energy-input system, with the torque-carrying capacity and fatigue reliability of the core drive components serving as crucial control factors.
Cold-Formed High-Torque Screw Shafts Project
Twin-Screw Extruder Shaft
Fatigue reliability for 800 kW high-torque crosslinked polyolefin processing
Customer Challenges
At 800 kW-class high-torque operation, the shaft carries cyclic torque loads over time. The spline region eventually develops fretting wear and accumulated fatigue, which manifests as increased torque fluctuation and reduced transmission efficiency. Conventionally machined shafts, whose grain flow is disrupted by cutting, are prone to root stress concentration during high torque fluctuations, which can cause fatigue cracks and pose a major risk to overall equipment stability.
Why the Customer Changed Suppliers
The existing machined-and-milled shafts had reached their performance limits in a high-torque crosslinked-material system; their fatigue life and wear resistance could no longer meet continuous-production requirements. As equipment power increased to 800 kW, high torque density made structural reliability the limiting factor. To increase system reliability, the customer prioritised shaft fatigue performance and stability in the selection process and chose a cold-formed shaft solution.
Our Solution
Lesun employed cold-forming to shape the spline structure through plastic deformation, ensuring that the grain flow continues along the tooth form. This significantly diminishes the structural severing effect and enhances the resistance to torsional fatigue in comparison to machining. The process also generates a work-hardened surface layer that enhances the resistance to abrasive wear on the tooth flanks and introduces a stable residual compressive stress in the tooth-flank region to prevent the initiation and propagation of cracks. This achieves a balance between strength and toughness when combined with a high-toughness alloy material system and quench-and-temper heat-treatment control. Additionally, microstructural uniformity control and deformation management ensure spline-meshing accuracy and dimensional stability.
The Value Delivered
The stability of equipment operating under high-torque crosslinked-material conditions was enhanced by the implementation of cold-formed shafts. This resulted in a decrease in the rate of spline wear, a convergence of torque fluctuation, and a decrease in the frequency of abnormal alarms. The melt energy input was more uniform, which helped reduce the risk of localized overheating and premature cross-linking, improved the stability of the XLPE process, and extended the maintenance intervals. This was achieved through a more stable torque transmission.
Project Summary
Twin-screw systems are being pushed toward high-torque platforms by the high-resistance processing of crosslinked materials, which has resulted in a shift in the core bottleneck from drive capacity to transmission-structure reliability. Lesun's cold-formed shafts significantly enhance fatigue and wear resistance under high-torque crosslinked-material conditions by reconstructing grain flow, strengthening the surface, and controlling residual compressive stress, in conjunction with coordinated material and heat-treatment optimization. This meets the requirement for stable, continuous 800 kW-class operation.