1、 Daily cleaning and pre-treatment

1. Cleaning of feed inlet and crushing chamber
   • Residual material removalAfter each shutdown, use specialized tools (such as soft brushes, compressed air spray guns) to clean the residual materials in the feed inlet and crushing chamber to avoid material agglomeration or corrosion of the chamber.
   • Low temperature environment maintenanceIf the equipment uses liquid nitrogen or refrigeration unit for cooling, it is necessary to check whether the surface of the cold trap or condenser has excessive frost (defrosting is required when the thickness is greater than 5mm) to prevent affecting the refrigeration efficiency.
   • Moisture proof treatmentIn a humid environment, after shutdown, use dry nitrogen to blow the inside of the equipment to prevent water vapor condensation from causing electrical short circuits or metal parts rusting.
2. Screen and discharge port maintenance
   • Screen cleaningRemove the sieve every week and use an ultrasonic cleaning machine or soft bristled brush to remove clogged fine powder (especially when dealing with high viscosity materials) to ensure uniform particle size of the discharged material.
   • Inspection of discharge pipelineCheck if there is material accumulation at the bend of the discharge pipeline every month, and install a vibrator to assist in discharging if necessary to avoid pipeline blockage.

2、 Key component maintenance

1. Cutting tools (grinding discs/hammers)

• Wear detectionMeasure the dimensions of key parts of the cutting tool (such as blade thickness and tooth height) with a vernier caliper every month, compare them with the initial values, and replace them when the wear exceeds 30% of the design value.
• Dynamic balance calibrationEvery quarter, conduct dynamic balance testing on the rotating tool assembly (balance accuracy level G1.0) to prevent excessive vibration during high-speed operation (vibration value ≤ 0.2mm).
• Material SelectionSelect tool materials based on material hardness (such as D2 tool steel for crushing plastics and hard alloy for crushing metals), and regularly perform surface carburizing treatment (hardness ≥ HRC58).

2. Refrigeration system

• Liquid nitrogen tank inspectionIf liquid nitrogen refrigeration is used, check the liquid level daily (if the liquid level is below 20%, it needs to be replenished), and confirm that the tank pressure is within the range of 0.8-1.2MPa to prevent the safety valve from tripping due to excessive pressure.
• Maintenance of refrigeration unitClean the dust on the condenser fins monthly (using compressed air for reverse blowing), replace the compressor lubricating oil (such as POE oil) every six months, and check for refrigerant leaks (using a halogen leak detector).
• Temperature control calibrationCalibrate the temperature sensor of the equipment with a high-precision thermometer (accuracy ± 0.1 ℃) every quarter to ensure that the deviation between the actual temperature and the displayed value is ≤ ± 1 ℃.

3. Transmission system

• Belt tension adjustmentCheck the tightness of the belt every week (measured with a tension meter, the tension value meets the requirements of the equipment manual). If it is too loose, it will cause slipping, and if it is too tight, it will accelerate bearing wear.
• Coupling alignmentCheck the coaxiality of the motor and spindle coupling every six months (radial deviation ≤ 0.05mm, axial deviation ≤ 0.1mm) to avoid vibration transmission to the bearings.
• Lubrication of gearboxChange the gear oil (such as ISO VG220 industrial gear oil) every 500 hours of operation and check if the oil level is at the centerline of the oil window.

3、 Lubrication management

1. Bearing lubrication
   • lubrication intervalAdd lubricating grease (such as lithium molybdenum disulfide grease) to the main shaft bearing every 200 hours of operation, with a filling amount not exceeding 1/2 of the bearing chamber, to prevent excessive temperature rise.
   • lubrication methodWhen using an automatic centralized lubrication system, check the oil pipes for blockages every month, and use an oil gun to evenly lubricate manually.
2. Lubrication of seals
   • Dynamic seal maintenanceApply silicon-based grease to shaft seals (such as mechanical seals or labyrinth seals) every month to reduce friction and prevent low-temperature brittleness.
   • Static seal inspectionCheck the sealing gasket (such as fluororubber O-ring) at the flange connection of the equipment every quarter, and replace it promptly if aging or deformation is found.

4、 Electrical system inspection

1. Motor maintenance
   • insulation testMeasure the insulation resistance of the motor winding with a megohmmeter every six months (when the rated voltage is below 500V, the resistance value should be greater than 1M Ω). If it is lower than the standard value, the motor should be dried or replaced.
   • Heat dissipation cleaningClean the dust on the motor cooling fan and fins every month to ensure smooth air ducts and prevent motor overheating (temperature rise ≤ 75K).
2. Control system calibration
   • Sensor calibrationCalibrate temperature sensors, pressure sensors, and speed sensors quarterly (if using a standard signal source input, the error should be ≤± 0.5% FS).
   • PLC program backupBackup the PLC program once a year and update the anti-interference filter parameters (such as adding common mode inductance) to prevent electromagnetic interference from causing program confusion.
3. Cable and terminal block
   • Visual inspectionCheck the cable sheath for damage and whether the wiring terminals are loose or oxidized (such as copper green phenomenon) every week.
   • Tightening treatmentWhen loose terminals are found, use a torque wrench to tighten them again according to the equipment manual requirements (such as M8 bolt torque of 15-20N · m).

5、 Operating standards and training

1. Start and stop process
   • Cold start restrictionAfter the equipment has been shut down in a low-temperature environment for more than 4 hours, the main shaft bearings need to be preheated (such as by using an electric heating belt to raise the temperature to -10 ℃ or above) before starting to avoid cold brittle fracture.
   • no-load operationAfter each start-up, run the machine without load for 5 minutes, check if the vibration and noise are normal, and then gradually load it to the rated load.
   • Gradual shutdownBefore shutting down, reduce the feed rate to zero and let the equipment idle for 3-5 minutes to discharge any remaining materials, then turn off the refrigeration system and main motor.
2. Material control
   • Pre cooling treatmentPre cool high toughness materials (such as nylon) in a -20 ℃ environment for 2 hours in advance to reduce crushing difficulty and tool wear.
   • Feed particle size controlEnsure that the material size does not exceed 80% of the feed inlet diameter to prevent large pieces of material from jamming the tool.
3. Operator training
   • regular assessmentOrganize an operational skills assessment every six months, with a focus on checking safety regulations (such as emergency response to liquid nitrogen leaks) and equipment parameter settings (such as temperature and speed).
   • Fault simulation drillConduct a fault simulation training once a year (such as simulating tool jamming or refrigeration failure) to enhance the emergency response capabilities of operators.

6、 Preventive Maintenance Plan

7、 Common faults and quick handling

1. Fault phenomenonUneven discharge particle size
   • reasonScreen blockage or tool wear.
   • processStop the machine to clean the sieve, check the tool size, and replace worn parts.
2. Fault phenomenonExcessive vibration of the equipment
   • reasonTool imbalance or spindle bending.
   • processRe calibrate the tool dynamic balance and check the spindle straightness (runout ≤ 0.05mm).
3. Fault phenomenonCooling efficiency decreases
   • reasonInsufficient pressure in the liquid nitrogen tank or dust accumulation in the condenser.
   • processAdd liquid nitrogen to the specified pressure and clean the dust on the condenser fins.

Through systematic maintenance, the low-temperature grinding machine can achieve the following effects:

• Extend service lifeKey components such as cutting tools and bearings have a 30% -50% increase in lifespan;
• 降低故障率Reduce sudden failures by over 60% and downtime by 80%;
• Ensure product qualityThe stability of the discharge particle size has been improved, and the decomposition rate of thermosensitive materials has been reduced to below 0.5%.