The laboratory twin-screw extruder may encounter various common faults during use. The following is a detailed summary of these faults and their possible causes:
Motor related faults
Screw driven motor cannot start
Reason: The fuse in the circuit is broken, the interlocking effect of the lubricating oil pump motor is not released, and there is an error in the driving sequence.
Solution: Check the fuse, release the interlock, and drive in the correct order.
The current of the screw driven motor is unstable after driving
Reason: The feeding screw rotates unstably, the feeding amount is uneven, the temperature error of each section of the machine barrel or head fluctuates greatly, and the lubricating oil of the transmission system is sometimes not in place.
Solution: Check the feeder, stabilize the heating temperature, and ensure that the lubricating oil in the transmission system is in place.
The current of the screw driven motor is too high
Reason: Insufficient constant temperature time after heating, low temperature of material plasticization process, and non working section of heating system.
Solution: Extend the heating time, increase the plasticizing temperature of the material, and inspect and repair the heating system.
Abnormal working sound of electric motor
Reason: Severe wear of carbon brush, damaged bearings, and malfunction of thyristor components.
Solution: Replace the carbon brush, replace the bearing, check the thyristor rectifier circuit, and replace the faulty component.
The temperature of the motor bearing position is too high
Reason: Insufficient lubricating oil, severe bearing wear, and rotor shaft bending and deformation.
Solution: Add lubricating oil, replace bearings, calibrate or replace rotor shaft.
Screw and head mold related faults
The screw rotates unstably during operation
Reason: The screw drive motor rotates unstably, there is a large fluctuation error in heating temperature, there is blockage in the inner cavity of the machine head mold, and the material plasticization is uneven.
Solution: Check and repair the screw drive motor, stabilize the heating temperature, clean the inner cavity of the machine head mold, and adjust the material plasticization process.
The safety pin is broken
Reason: Insufficient constant temperature time in the heating process results in insufficient plasticization of the material, or metal foreign objects are mixed into the material and stuck in the screw during normal production, or low process temperature leads to poor plasticization of the material.
Solution: Ensure that the constant temperature time of the heating process is sufficient, check for foreign objects in the material and clean the screw, and increase the process temperature appropriately.
Head mold blockage
Reason: Impurities in the material, insufficient heating temperature leading to insufficient plasticization of the material, etc.
Solution: Clean the clogged foreign objects in the machine head mold, ensure the purity of the material, and adjust the heating temperature.
Heating and temperature control related faults
The heater is not working
Reason: Damage to heater, malfunction of temperature control system, etc.
Solution: Check the heater and replace damaged parts, check the temperature control system and repair the fault.
Inaccurate temperature control
Reason: Temperature control instrument malfunction, uneven distribution of heaters.
Solution: Regularly calibrate the temperature control instrument, check the distribution of heaters and adjust them to be uniform.
Lubrication system related faults
Insufficient oil supply in the lubrication system
Reason: Severe wear of the oil pump, blockage of foreign objects in the suction pipeline, etc.
Solution: Replace the oil pump and clean the foreign objects in the suction pipeline.
Mechanical malfunction
Screw and barrel wear
Reason: After long-term operation, there may be wear between the screw and the barrel, resulting in an increase in gap and affecting the extrusion effect.
Solution: Regularly check the wear of the screw and barrel, and repair or replace them if necessary.
Transmission system malfunction
Reason: Severe wear of transmission gears, bearings, and other components, or loose transmission chains, leading to unstable transmission.
Solution: Check the wear of each component in the transmission system, replace severely worn parts in a timely manner, and adjust the tightness of the transmission chain.
Electrical malfunction
Main motor malfunction
Reason: Main motor circuit failure, bearing damage, thyristor rectifier circuit failure, etc.
Solution: Check the main motor circuit, replace damaged bearings and thyristor components to ensure the normal operation of the main motor.
Inverter fault
Reason: Damage to internal components of the frequency converter, incomplete discharge of induced electricity, etc.
Solution: Turn off the main power and wait for a period of time before restarting. If the problem still cannot be solved, check the internal components of the frequency converter and replace the damaged parts.
Control system malfunction
Temperature control system malfunction
Reason: Temperature control instrument malfunction, heater damage, temperature sensor malfunction, etc.
Solution: Check the operating status of temperature control instruments, heaters, and temperature sensors, replace faulty components in a timely manner, and ensure the accuracy and reliability of the temperature control system.
Program control system malfunction
Reason: Program error, controller malfunction, etc.
Solution: Check and correct program errors, replace faulty controllers, and ensure the normal operation of the program control system.
Other faults
Supply system malfunction
Reason: Low speed of the feeding screw, small feeding amount, or insufficient feeding due to “bridging” phenomenon in the hopper.
Solution: Increase the speed of the feeding screw, solve the “bridging” problem in the hopper, and ensure the stability and reliability of the feeding system.
The extruder has a loud noise
Reason: Loose components, poor lubrication, friction between screws and barrels, etc.
Solution: Check and tighten all components, add or replace lubricating oil, and adjust the gap between the screw and the barrel.
Decreased production
Reason: There is a “bridging” phenomenon in the hopper, which leads to insufficient feeding and blockage of foreign objects in the machine head mold.
Solution: Solve the “bridging” problem in the hopper and clean up the blocked foreign objects in the machine head mold.
Program error
Solution: Check and correct the driving procedure.
To prevent these malfunctions, it is recommended to regularly maintain the laboratory twin-screw extruder, including cleaning the machine, lubricating various moving parts, checking for loose fasteners, and replacing severely worn components. At the same time, attention should be paid to observing the operating status and abnormal phenomena of the equipment during use, and timely measures should be taken to eliminate and repair them. In addition, targeted maintenance plans can be developed based on the specific situation of the equipment to extend its service life and improve production efficiency.
