Twin Screw Extruder Maintenance Guide: Daily, Weekly, Monthly and Annual Care
Systematic maintenance of twin screw extruders is essential for equipment longevity and production stability. This guide covers all levels of maintenance from daily checks to annual overhauls.
Per-Shift Maintenance (Operator Level)
- Cleaning: After shutdown, use copper spatulas or bamboo scrapers to clean the die head, die orifice, screw tip, and barrel feed port. Never use steel tools for hard scraping.
- Tightening: Check and tighten die head pressure plate bolts, heating ring wiring terminals, and guard screws.
- Lubrication: Apply specified-grade lubricating oil/grease to drive chains and bearing housings. Pay attention to grease fittings on the feeder stirring shaft.
- Cooling system: Observe cooling water flow rate, clean impurities from water filters, and ensure return water is free of bubbles.
- Documentation: Complete the operation log, recording shift output, abnormal sounds, temperature fluctuations, and pressure peaks.
Weekly Maintenance
- Clean dust from motor ventilation covers and heat sinks to prevent motor overheating.
- Check belt tension (for belt-driven machines): press the belt midpoint with finger — deflection should be 10-15 mm.
- Clean oil filter: if gearbox oil pressure drops or metal particles appear on filter surface, remove for cleaning or replacement.
- Check vacuum exhaust port: ensure no blockage and that sealing gaskets show no aging or deformation.
Monthly Maintenance
- Gearbox oil inspection: Sample and observe oil color and viscosity. Replace if blackened, emulsified, or containing metal particles (typically first oil change at 500 hours, then every 2000-3000 hours).
- Clean screw and barrel: Extract the screw, use copper brushes or specialized cleaning agents to remove carbon deposits and scorched material. Measure radial clearance between screw and barrel (single-side clearance within 0.3 mm is normal).
- Calibrate temperature sensors: Compare actual display values against standard thermometers. Correct or replace if deviation exceeds plus or minus 2 degrees Celsius.
- Check coupling concentricity: Use dial indicator to measure offset between motor shaft and screw shaft. Radial runout should be within 0.1 mm. Adjust base plate shims if non-compliant.
Quarterly Maintenance
- Replace gearbox breather cap and dust filter to ensure smooth breathing and prevent oil emulsification.
- Inspect barrel liner wear: measure barrel inner diameter. Consider repair or replacement when wear exceeds 0.5% of original diameter.
- Verify pressure sensors and safety valves to ensure accurate activation at set pressures.
- Clean dust from electrical control cabinets and inspect relay contacts and inverter cooling fans.
Annual Overhaul
- Disassemble screw and barrel for comprehensive wear assessment. Perform alloy overlay welding repair or nitriding treatment on screws as needed.
- Replace all gearbox bearings, seals, and lubricating oil.
- Motor maintenance: measure insulation resistance, replace bearing grease, and correct dynamic balance.
- Comprehensive inspection of cooling water passage scaling. Use acid washing or ultrasonic methods for descaling.
- Recalibrate all instruments and update equipment technical archives.
Common Faults and Prevention
- High main motor current: Excessive feed rate, poor material plasticization, or insufficient barrel heating. Control feed rate and regularly inspect heating rings.
- Large melt pressure fluctuations: Unstable feeder screw speed or blocked exhaust port. Clean feeder and clear vacuum system.
- Die head material leakage: Screen plate not properly tightened or die head bolts loose. Tighten bolts evenly after each assembly/disassembly.
- Screw seizure: Metal foreign objects entered or insufficient preheating. Pass raw materials through magnetic grid and manually crank after heating.
Following this maintenance guide can reduce unplanned downtime by over 30% and extend the service life of core components including screws and barrels.
