1、 Key operating points of extruder

When making different plastic products, the operating points of the extruder are different, but there are also similarities. Below is a detailed introduction for everyone.

1. Preparation before driving

(1) Plastic used for extrusion molding. The raw materials should meet the required drying requirements, and further drying may be necessary if necessary. And sieve the raw materials to remove clumps and mechanical impurities.

(2) Check whether the water, electricity, and gas systems in the equipment are normal, ensure that the water and gas paths are unobstructed and leak free, whether the electrical system is normal, and whether the heating system, temperature control, and various instruments are working reliably; Run the auxiliary machine at low speed without load and observe whether the equipment is operating normally; Start the shaping table vacuum pump and observe whether it works normally; Add oil and lubrication to various lubrication parts of the equipment. If any faults are found, they should be promptly resolved.

(3) Install the machine head and shaping sleeve. Choose the appropriate machine head specifications based on the variety and size of the product. Install the machine head in the following order.

2. Drive

(1) After the constant temperature is maintained, the machine can be driven. Before driving, the flange bolts of the machine head and extruder should be tightened again to eliminate the difference in thermal expansion between the bolts and the machine head. The sequence of tightening the machine head bolts is diagonal tightening, and the force should be uniform. When tightening the flange nut of the machine head, it is required that the tightness around is consistent, otherwise the material will run off.

(2) To drive, first press the "Ready to Drive" button, then connect the "Drive" button, and slowly rotate the screw speed adjustment knob to start the screw speed slowly. Then gradually increase the speed while adding a small amount of material. Pay close attention to the changes in the readings of the host ammeter and various indicator heads when adding materials. The torque of the screw should not exceed the red mark (usually 65%~75% of the torque gauge). Before the plastic profile is extruded, no one is allowed to stand directly in front of the die to prevent injury accidents caused by bolt breakage or soaking due to wet raw materials. After the plastic is extruded from the die of the machine head, the extruded material needs to be slowly cooled and led onto the traction device and shaping die, and these devices need to be activated. Then, based on the indication values of the control instrument and the requirements for the extruded product. Adjust each part accordingly to ensure that the entire extrusion operation reaches a normal state. And according to the needs, sufficient material is added, and the twin-screw extruder adopts a metering feeder to uniformly and uniformly feed at a constant speed.

(3) When the discharge from the mouth mold is uniform and well plasticized, it can be pulled into the shaping sleeve. The degree of plasticization needs to be judged based on experience, usually based on the appearance of the extruded material, that is, the surface has luster, no impurities, no foaming, coking, and discoloration. If the extruded material is squeezed to a certain degree by hand without burrs or cracks, and has a certain degree of elasticity, it indicates that the material is well plasticized. If the plasticization is poor, the screw speed, barrel, and head temperature can be adjusted appropriately until the requirements are met.

(4) During the extrusion production process, it is necessary to regularly check whether various process parameters are normal according to the process requirements and fill out the process record form. Inspect the quality of profile products according to quality inspection standards, and take timely measures to solve any problems found.

3. Parking

(1) Stop feeding, squeeze the plastic out of the extruder, and when the screw is exposed, turn off the power supply to the barrel and head, and stop heating.

(2) Turn off the power supply of the extruder and auxiliary equipment to stop the operation of the screw and auxiliary equipment.

(3) Open the connecting flange of the machine head and disassemble the machine head. Clean the various components of the porous plate and machine head. To prevent damage to the inner surface of the machine head during cleaning, residual materials inside the machine head should be cleaned with steel plates and steel sheets. Then, the plastic adhered to the machine head should be sanded off and polished, and coated with engine oil or silicone oil for rust prevention.

(4) Cleaning of screws and barrels: After removing the machine head, restart the main engine, add parking material (or crushed material), clean the screws and barrels, and choose low speed (around SR/min) for the screws to reduce wear. After the parking material is completely crushed into powder and extruded, compressed air can be used to repeatedly blow out residual granules and powders from the feeding port and exhaust port until there is no residual material in the barrel. Then, reduce the screw speed to zero, stop the extruder, and turn off the main power and cold water main valve.

(5) The safety items that should be paid attention to during extrusion of the extruder include: electrical, thermal, mechanical rotation, and loading and unloading of bulky components. The extrusion locomotive room must be equipped with lifting equipment to install and remove bulky components such as machine heads and screws to ensure safe production.

2、 Maintenance and upkeep

(1) Daily maintenance is a regular routine work that does not take up equipment operating hours and is usually completed during driving. The key is to clean the machine, lubricate all moving parts, tighten loose threaded parts, timely inspect and adjust the motor, control instruments, various working components and pipelines, etc.

(2) Regular maintenance is generally carried out after the extruder has been running continuously for 2500-5000 hours and then stopped. The machine needs to be disassembled, inspected, measured, and evaluated for the wear of its main components, replaced with parts that have reached the specified wear limit, and repaired for damaged parts.

(3) Empty operation is not allowed to prevent the screw and barrel from rolling.

(4) If there is any abnormal noise during the operation of the extruder, it should be stopped immediately for inspection or repair.

(5) Strictly prevent metal or other debris from falling into the hopper to avoid damaging the screw and barrel. To prevent iron impurities from entering the barrel, magnetic suction components or magnetic frames can be installed at the feeding port of the barrel to prevent impurities from falling in. The materials must be sieved in advance.

(6) Pay attention to the cleanliness of the production environment, and do not allow garbage and impurities to mix into the material and block the filter plate, which will affect the product output, quality, and increase the resistance of the machine head.

(7) When the extruder needs to be stopped for a long time, anti rust lubricating grease should be applied to the working surfaces of the screw, barrel, and head. Small screws should be suspended in the air or placed in specialized wooden boxes, and leveled with wooden blocks to prevent deformation or damage to the screws.

(8) Regularly calibrate temperature control instruments, check their correctness of adjustment and sensitivity of control.

(9) The maintenance of the gearbox of the extruder is the same as that of a general standard gearbox. Mainly inspect the wear and failure of gears, bearings, etc. The gearbox should use the lubricating oil specified in the machine manual, and add oil according to the specified oil level height. Insufficient oil and lubrication can reduce the service life of the parts; Excessive oil, high heat generation, high energy consumption, and easy deterioration of oil can also cause lubrication failure and damage to parts. The sealing gasket should be replaced in a timely manner at the oil leakage location of the gearbox to ensure the amount of lubricating oil.

(10) The inner wall of the cooling water pipe attached to the extruder is prone to scaling and the outside is prone to corrosion and rust. Careful inspection should be carried out during maintenance. Excessive scale can block the pipeline and fail to achieve cooling effect. Severe corrosion can lead to water leakage. Therefore, descaling and anti-corrosion cooling measures must be taken during maintenance.

(11) Special attention should be paid to checking the wear and contact of the electric brush of the DC motor that drives the screw to rotate. The insulation resistance value of the motor should also be measured regularly to ensure that it is above the specified value. In addition, check whether the connecting wires and other components are rusted and take protective measures.

(12) Designate a dedicated person to be responsible for equipment maintenance and upkeep. And include detailed records of each maintenance and repair in the factory equipment management file.