The maintenance of plastic injection molding machines is crucial for ensuring stable equipment operation, extending service life, and reducing failure rates. It needs to be systematically carried out from multiple aspects such as daily inspections, regular maintenance, and maintenance of key components. The following are the specific maintenance points:
I. Daily Maintenance (before startup / during operation / after shutdown every day)
Inspection before startup
Appearance and environment: Clean up debris on the surface and around the equipment to ensure the working area is tidy; check whether the connections of power cords, oil pipes, and air pipes are loose or damaged to avoid electric leakage, oil leakage, and air leakage.
Lubrication system: Check the oil quantity at each lubrication point (such as guide pillars, sliders, screw bearings, etc.), add the specified type of lubricating oil (such as hydraulic oil, guide rail oil) according to the instructions to ensure sufficient lubrication.
Hydraulic system: Check the oil level of the hydraulic oil tank. If it is lower than the warning line, replenish the same type of hydraulic oil (do not mix different brands or types); observe the oil temperature gauge to confirm that the oil temperature is within the normal range before startup (usually 25℃~55℃, preheating is required if it is too low).
Heating system: Check whether the barrel heating rings and thermocouples are fastened. After power-on, confirm that the temperature of each section can rise to the set value normally without abnormal alarms.
Safety devices: Test whether the emergency stop button and safety door interlock device are sensitive to ensure that the equipment can stop immediately in case of abnormality.
Monitoring during operation
Parameter stability: Real-time observe whether parameters such as injection pressure, speed, temperature, and clamping force fluctuate. If abnormalities occur (such as a sudden drop in pressure, temperature out of control), stop the machine immediately for inspection.
Abnormal noise and leakage: Monitor the running sound of the equipment. Abnormal sounds such as metal friction may indicate component wear or looseness; check whether hydraulic pipelines, oil cylinders, and valves are leaking oil, and whether air pipes are leaking air. Deal with problems in a timely manner when found.
Mold status: Observe whether the mold opens and closes smoothly without jamming; check whether the ejection mechanism works normally to avoid plastic parts sticking to the mold or deformation during ejection.
Treatment after shutdown
Cleaning work: Turn off the heating system. After the barrel temperature drops below 100℃, clean up the remaining raw materials in the hopper (especially when changing materials or shutting down for more than 8 hours, the remaining materials in the barrel need to be emptied to prevent raw material oxidation and caking); clean the mold surface and spray rust inhibitor (the mold cavity needs to be thoroughly cleaned during long-term shutdown).
Power off and reset: Turn off the main power supply and air source of the equipment, return the screw to its original position, and close the mold to a half-open state to avoid long-term pressure deformation of the mold.
II. Regular Maintenance (performed according to cycles, such as weekly / monthly / quarterly)
Weekly maintenance
Filtration system: Clean the hydraulic oil suction filter and return oil filter. If the filter element is damaged, replace it to prevent impurities from entering the hydraulic system and causing component wear.
Guide rails and guide pillars: After thorough cleaning, reapply grease. Check whether the surface of the guide pillars has scratches or rust, and perform polishing if necessary.
Pneumatic system: Drain water (open the drain valve of the air source processor to discharge condensed water); check whether pneumatic components (such as cylinders, solenoid valves) are leaking air, and clean the air filter element.
Monthly maintenance
Hydraulic system:
Detect the contamination degree of hydraulic oil. If the oil is turbid and has an odor, replace all of it and clean the oil tank;
Check the operation status of the hydraulic pump and hydraulic motor, and measure whether the working pressure is within the normal range. Insufficient pressure may be due to pump wear or valve failure.
Screw and barrel: Dismantle the screw and barrel, check whether the surface has wear, scratches, or coke accumulation. Clean the residual materials with special tools, and repair or replace them if necessary (especially after processing corrosive or glass fiber-added raw materials, more frequent inspections are required).
Electrical system: Check whether the wiring terminals are loose or overheated (for signs of burning), clean the dust in the distribution box (blow it clean with compressed air) to ensure good heat dissipation.
Quarterly / semi-annual maintenance
Clamping mechanism: Check whether the sealing parts of the clamping cylinder are aged and leaking. Adjust the clamping parallelism (if the force on both sides of the mold is uneven, it is easy to cause flash on plastic parts or mold damage); fasten connecting parts such as tie rods and nuts.
Injection system: Check the wear of the injection cylinder, check ring, and sealing ring, and replace aged parts; calibrate the injection volume accuracy to ensure stable metering.
Cooling system: Clean the mold cooling water circuit and equipment cooling tower to remove scale (scale will reduce cooling efficiency and prolong the molding cycle). Professional descaling agents can be used for circulating cleaning.
III. Special Maintenance of Key Components
Screw and barrel
Avoid processing raw materials containing metal impurities (which will scratch the screw and barrel). A magnetic frame should be installed in the hopper to filter impurities.
Before long-term shutdown, clean the barrel with cleaning materials such as PP to prevent residual raw materials from decomposing and corroding.
If the plasticizing capacity decreases (such as uneven melt), it may be due to screw wear, which needs to be replaced in time.
Hydraulic system
Hydraulic oil needs to be replaced regularly (usually every 2000~3000 hours of operation). When changing oil, the oil tank must be thoroughly cleaned to avoid mixing of new and old oil.
Strictly use hydraulic oil with the viscosity specified in the equipment manual (such as No. 46 anti-wear hydraulic oil). In high-temperature summer, oil with slightly higher viscosity can be selected.
Heating and temperature control system
If the heating ring is partially not heating, the heating tube may be burned and needs to be replaced in time to avoid affecting plasticizing quality.
Thermocouples need to be calibrated regularly (compared with standard thermometers) to ensure accurate temperature display (the error should be ≤±3℃).
IV. Maintenance Records and Fault Tracing
Establish equipment maintenance ledgers, recording the time, content, replaced parts, and responsible persons of each maintenance, to facilitate tracking of equipment status.
When a fault occurs (such as weak injection, abnormal clamping), check the cause in combination with maintenance records (for example, failure to change hydraulic oil recently may lead to insufficient pressure) to improve maintenance efficiency.
