Common faults in laboratory twin-screw extruders include mechanical failures, electrical failures, process failures, etc. The following is a specific analysis:
Mechanical failure
Screw stuck
Cause: It may be that the material accumulates excessively in the screw, or foreign objects such as metal enter the screw, causing the screw to fail to rotate normally. It may also be a fault in the lubrication system, causing excessive friction between the screw and the barrel.
Performance: The motor cannot drive the screw to rotate, the equipment makes abnormal noise, and may even cause the motor to be overloaded.
Bearings damaged
Cause: After long-term use, the bearing is prone to damage due to wear, poor lubrication, overload or improper installation.
Performance: Vibration and noise increase during the equipment operation, and the screw rotates unstablely. In severe cases, it may cause the screw to eccentrize and affect the extrusion effect.
Gearbox failure
Cause: The gears in the gear box may malfunction due to long-term meshing wear, insufficient lubrication, oil contamination or excessive load.
Performance: Gear meshing noise, excessive oil temperature, and reduced transmission efficiency will occur. In severe cases, the gear may break and prevent the equipment from operating normally.
Electrical failure
Motor failure
Cause: The motor may fail due to long-term overheating operation, short-circuit or circuit breaker of windings, overload, unstable power supply voltage, etc.
Performance: The motor cannot start, abnormal speed, severe heat or abnormal noise, etc.
Temperature control fault
Cause: Failure of temperature sensor, damage to heating components, failure of temperature control instruments or failure of control lines may all lead to temperature control problems.
Performance: The temperature cannot be stable at the set value, and there are phenomena such as excessive temperature fluctuations, slow temperature rise or no temperature rise, and abnormal cooling, which affects the plasticization and extrusion effect of the material.
Control system failure
Cause: The circuit board of the control system may fail due to component aging, short circuit, moisture, etc., or the program may be incorrect.
Performance: The device’s operating interface is unresponsive, parameter settings cannot be saved or display abnormalities, device operation logic is chaotic, etc.
Process failure
Poor plasticization of materials
Cause: It may be that the screw speed is too low, the temperature setting is unreasonable, the material formulation problem, or the screw structure is not suitable for the material, etc.
Performance: The extruded material has rough surface, bubbles, uneven color, and the mechanical properties and appearance quality of the product are degraded.
Uneven discharge
Cause: Unstable feeding system, uneven material conveying caused by screw wear, unstable head pressure or unreasonable mold design may cause uneven material discharge.
Performance: The cross-sectional dimensions and shape of the extrudate are irregular, and the thickness or diameter fluctuates, affecting the dimensional accuracy and mass stability of the product.
Material blocking the head or mold
Cause: Impurities may be mixed in the material, or the material may stay in the machine head or mold for too long, causing scorching, clumping, etc., resulting in blockage.
Performance: The extrusion pressure suddenly increases, the discharge of the material is not smooth, and even no discharge of the material is completely out. In severe cases, the head and mold may be damaged.
In order to effectively prevent the failure of the laboratory twin-screw extruder, measures can be taken from the preliminary selection, installation and commissioning of the equipment, to daily operating specifications, maintenance, and personnel training. The specifics are as follows:
Equipment selection and installation
Reasonable selection: Select a twin-screw extruder with appropriate specifications and performance parameters according to experimental needs and material characteristics. Consider factors such as screw diameter, aspect ratio, speed range, motor power, etc. to ensure that the equipment can meet the experimental requirements and avoid overloading of the equipment or failure to achieve the expected results due to improper selection.
Correct installation: Strictly follow the equipment installation instructions to ensure the equipment installation level, the components are connected firmly, and the electrical circuit connection is correct. During the installation process, pay attention to checking the sealing of the equipment to prevent material leakage and dust from entering.
Operation specifications
Material handling
Raw material inspection: Strict inspection of the materials before use to ensure that the materials are pure and free of impurities, moisture exceeding the standard, etc. For materials that are prone to moisture absorption, drying should be carried out to prevent moisture from affecting the plasticization effect and equipment performance.
Uniform feeding: Use a suitable feeding device to control the speed and amount of materials to maintain uniform and stable feeding, and avoid material accumulation or breakage.
Parameter settings
Temperature setting: According to the characteristics of the material and experimental requirements, the temperature of each heating section is reasonably set to ensure the uniform temperature distribution. Before the equipment is operated, preheat it to make the equipment reach a stable working temperature.
Speed control: Select the appropriate screw speed according to the nature of the material and extrusion requirements to avoid excessive or low speed. When the equipment starts and shuts down, adjust the speed slowly to prevent shock.
Operation monitoring: During the operation of the equipment, pay close attention to various parameters, such as temperature, pressure, speed, torque, etc., and adjust it in time or shut down to check if abnormalities are found. At the same time, observe the extrusion status of the material, such as whether the discharge is uniform and whether the material surface is smooth, etc. If there are any problems, deal with it in time.
Maintenance
Daily maintenance
Cleaning equipment: After each use, clean the dust, oil and residual materials on the surface of the equipment in a timely manner. Regularly use special cleaning agent to clean parts such as screws, barrels and molds to prevent material accumulation and coking.
Check parts: Check all parts of the equipment every day, including screws, screw barrels, heads, molds, etc., to see if there is any wear, cracks, deformation, etc. Check the belt, chain, gear and other components of the transmission system to ensure stable transmission.
Regular maintenance
Lubrication maintenance: Lubricate the moving parts of the equipment regularly and replace the lubricant or grease according to the recommendations of the equipment manufacturer.
Electrical system inspection: Check the electrical system regularly, including motors, wires, plugs, sockets, etc., to ensure good electrical connection and no safety hazards such as leakage or short circuits. Check the accuracy of temperature sensors, pressure sensors and other instruments, and calibrate them in time if there are any deviations.
Personnel training
Operation training: Provide professional training to equipment operators to make them familiar with the structure, working principle, operating method and safety precautions of the equipment. The training content should include equipment startup, shutdown, parameter settings, troubleshooting, etc., to ensure that the operator can operate the equipment correctly.
Safety training: Strengthen safety awareness training for operators to understand the possible safety risks of equipment, such as high-temperature scalds, mechanical injuries, electrical safety, etc. Training safety operating procedures and emergency response methods, such as the use of emergency shutdown buttons, fire extinguishing, etc.
