The twin-screw extruder is the core equipment for food puffing, feed processing, and modified material production. Its operational stability directly determines product texture, appearance, qualification rate, and overall production line capacity. Frequent machine clogging, abnormal temperature rise, rapid screw wear, abnormal noise, and oil leakage in most factories are rarely caused by equipment quality defects, but inadequate daily maintenance and non-standard maintenance procedures.
This article provides a practical and easy-to-implement full maintenance solution for twin-screw extruders. With hierarchical maintenance plans for shift, weekly, monthly, and annual cycles, covering cleaning, lubrication, component inspection, fault prevention, and prohibited operations, it can be directly applied by both new and senior operators to effectively extend equipment service life and reduce downtime and maintenance costs.
I. Daily Shift Maintenance (Pre-operation / Operation / Post-shutdown)
Daily maintenance is the key to avoiding the accumulation of minor faults. Spending 5-10 minutes on maintenance per shift can eliminate 80% of common equipment failures, making it the most cost-effective maintenance method.
1. Pre-start Inspection
No complicated operations are required before startup; focus on checking basic operating conditions to prevent faulty startup: Keep the equipment surface and control panel clean without dust or debris, and ensure buttons and displays are sensitive and normal; check that air and water pipelines are firmly connected without air leakage, water leakage or blockage; confirm all fasteners are tightened and no foreign matter accumulates at the feeding and discharging ports; verify that the lubricating oil and coolant levels are within the standard scale range and replenish them in a timely manner if insufficient.
2. In-operation Patrol Inspection
Monitor equipment status in real time during operation to detect abnormal signals promptly: Continuously observe operating noise and vibration; stop the machine immediately for troubleshooting if abnormal noise or severe vibration occurs; check temperature and pressure gauge readings to ensure stable parameters within the process standard range and avoid over-temperature and over-pressure operation; ensure uniform feeding and smooth discharging without material clogging, backflow or intermittent feeding; monitor the operating status of motors and reducers to prevent overheating, peculiar smells and oil leakage.
3. Immediate Cleaning After Shutdown
The cooling stage after shutdown is the optimal cleaning period, which effectively prevents material carbonization and adhesion: After the equipment temperature drops below 100°C and the power is completely cut off, clean residual materials from the hopper, feeder and die head to avoid drying and carbonization of residual materials; wipe dust and oil stains off the equipment body and operating platform to keep the equipment clean; simply clean the cooling fan and heat dissipation holes to prevent heat dissipation failure caused by dust accumulation; complete shift operation records and mark all minor hidden troubles such as abnormal noise, temperature rise and pressure fluctuation.
II. Weekly In-depth Maintenance (Precision Cleaning / Calibration / Tightening)
Perform weekly in-depth maintenance during shutdown, focusing on blind spots of daily cleaning and vulnerable parts to ensure equipment operation accuracy and stabilize production quality.
1. Thorough Cleaning of Core Components: Disassemble the feeding system, die head and flow guide parts to remove stubborn accumulated materials and carbon layers; clean screws and barrels gently with nylon or copper brushes. Soak stubborn residues with food-grade solvent before gentle scraping. Strictly prohibit open flame baking, steel wire brushing and hard scraping with iron tools to avoid damaging the nitride and coating layers on the screw and barrel surfaces, which will cause permanent wear.
2. Transmission System Maintenance: Fully check the tension of chains, gears and transmission belts, adjust improper tension in a timely manner, and supplement grease for chains and gears to ensure smooth transmission without jamming; tighten all bolts on the machine body, flanges and couplings to prevent screw loosening and equipment offset caused by long-term vibration.
3. Parameter Calibration and Detection: Calibrate temperature sensors and pressure gauges to avoid uneven material puffing and increased defective rates caused by parameter deviation; inspect emergency stop switches and safety interlock devices to ensure normal safety protection functions and eliminate potential production safety hazards.
4. Cooling System Cleaning: Clean dust from the electric control box cooling fan and machine heat dissipation air ducts to prevent equipment overheating and aging of electronic control components.
III. Monthly Special Maintenance (Wear Detection / Oil Circuit / System Maintenance)
Monthly maintenance focuses on checking vulnerable part wear, oil circuit conditions and cold & hot circulation systems to predict component replacement cycles in advance and avoid sudden shutdown failures.
1. Screw and Barrel Wear Detection: Extract the screws and comprehensively inspect the screws, screw sleeves and barrel inner walls for wear, corrosion and scratches, record the wear degree, and repair or replace parts when wear exceeds the standard; calibrate the coaxiality of twin screws to ensure stable operation without friction and scraping.
2. Lubrication System Inspection: Check the quality of lubricating oil in gearboxes and distribution boxes, observe whether the oil is turbid, black, impure or emulsified; clean oil circuit filter elements and breathable caps to ensure unobstructed oil circulation; replenish oil as required and strictly control the oil level between the upper and lower scales to prevent dry wear due to oil shortage and oil leakage.
3. Cold and Hot System Maintenance: Thoroughly remove scale and dust from heating rings and cooling water channels, check uniform heating and efficient cooling performance to avoid abnormal local temperature affecting production processes.
4. Electrical System Inspection: Tighten loose wiring terminals in the electric control box, clean internal dust, and eliminate hidden dangers such as aging circuits and virtual connections to prevent unstable voltage, sparking and tripping faults.
IV. Annual Overhaul Maintenance (Complete Machine Inspection / Oil Replacement / Accuracy Calibration)
Annual overhaul is critical for long-term stable equipment operation, realizing comprehensive inspection of the whole machine, wear repair and factory accuracy recovery.
1. Complete Lubricating Oil Replacement: Drain old oil from gearboxes and distribution boxes when the machine is hot (hot oil drainage is more thorough and can take away internal impurities and iron filings), clean the box interior, and replace with new lubricating oil suitable for working conditions; under normal working conditions, replace reducer oil every six months, clean and replace distribution box oil every two months in the initial stage, and every six months in the later stage.
2. Comprehensive Inspection of Core Parts: Disassemble and inspect thrust bearings, rolling bearings and seals, replace aging, worn and failed parts; check wear conditions of couplings and transmission shafts, and calibrate equipment transmission accuracy.
3. Whole Machine Accuracy Calibration: Re-calibrate equipment levelness, screw coaxiality and die head concentricity to solve equipment offset and excessive vibration caused by long-term operation.
4. In-depth Electrical Safety Detection: Conduct full detection of the electric control system, check circuit aging and component wear, detect circuit hot spots via infrared temperature measurement to avoid short circuit and fire risks; fully test all safety protection devices to ensure production safety.
V. Exclusive Maintenance Skills for Three Core Components (Key to Extending Service Life)
1. Screw & Barrel (Most Valuable Core Parts)
The core maintenance priorities for screws and barrels are wear resistance and carbonization prevention: Prohibit metal foreign matters from entering the barrel to avoid scratching the inner wall and screws; thoroughly clean the machine when switching materials to prevent residual material carbonization and adhesion wear; prohibit over-temperature and over-load forced operation to reduce screw fatigue loss; clean, dry and apply protective oil for long-term shutdown to achieve rust and dust prevention.
2. Transmission & Lubrication System (Power Core of Equipment)
Insufficient lubrication is the main cause of equipment abnormal noise, jamming, oil leakage and gear damage: Strictly distinguish oil models for gearboxes, distribution boxes and bearings, and prohibit mixed use of inferior lubricating oil; replace standard lubricating oil suitable for local working conditions in a timely manner after new equipment commissioning; regularly check oil seals and gaskets, and replace them immediately in case of oil seepage or leakage to prevent equipment wear caused by oil shortage.
3. Temperature Control & Cooling System (Core of Process Stability)
Abnormal temperature and cooling directly lead to poor material puffing performance and high defective rates: Regularly clean accumulated materials and scale on heating rings to ensure uniform heating; dredge cooling water pipelines to avoid delayed cooling caused by scale blockage; calibrate temperature probes regularly to prevent temperature display deviation and actual over-temperature.
VI. Common Maintenance Misoperations (Pitfalls for Most Factories)
1. Incomplete post-shutdown cleaning: Residual materials carbonize at high temperature, causing long-term screw wear, die head blockage and frequent clogging failures.
2. Violent cleaning: Hard scraping with steel wires and iron tools damages the equipment wear-resistant coating, resulting in accelerated later wear, material leakage and uneven discharging.
3. Over-temperature & over-load operation: Forcing speed, temperature and pressure increase to boost output greatly shortens the service life of bearings, gears and screws.
4. Delayed oil replacement: Continuous use of turbid and black lubricating oil causes accelerated wear of gears and bearings, leading to abnormal noise, jamming and shaft locking.
5. Disassembly under high temperature & pressure: Disassembling equipment without cooling, power cutoff and pressure relief easily causes equipment damage and safety accidents.
VII. Summary: Standardized Maintenance Equals Cost Reduction and Efficiency Improvement
Twin-screw extruders rely on proactive maintenance rather than remedial repair. Implementing standardized maintenance by shift, weekly, monthly and annual cycles, and adhering to the five core principles of cleaning, lubrication, calibration, tightening and anti-wear, can significantly reduce downtime and maintenance costs, stabilize product quality, improve production efficiency, and extend equipment service life by 3-5 years.
For puffing food, feed and modified material production lines, standardized equipment maintenance is the lowest-cost and highest-return production management method.