Precautions During The Operation Of PVC Pipe Extruder Machine

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Correct and reasonable use of PVC pipe extruder machine can give full play to the machine’s efficiency, maintain good working conditions, and extend the machine’s service life.

The use of PVC pipe extruder machine includes a series of links such as machine installation, adjustment, test run, operation, maintenance and repair. Its use has the typical characteristics of general machines, mainly in drive motor and speed reducer.

However, the working system of the PVC pipe extruder machine is the extrusion system, but it has unique characteristics, so special attention should be paid when using the screw extruder.

vertical type dwc pipe machine
vertical type dwc pipe machine

The installation, adjustment, and test run of the machine are generally clearly stipulated in the operating instructions of the extruder. Here is a brief description of the operation method, maintenance and maintenance of the extruder as follows:

The operation method of PVC pipe extruder machine

Operators must be familiar with the extruder’s structural characteristics, especially to correctly grasp the structural characteristics of the screw, heating and cooling control instrument characteristics, head characteristics and assembly conditions, etc., to correctly grasp the extrusion process conditions. 

vertical type double wall corrugated pipe machine
vertical type double wall corrugated pipe machine

The operating methods of extruding different plastic products are different, but there are also similarities. The following briefly introduces the same operation steps and matters that should be paid attention to when extruding various products.

1. Preparation Before Driving

  1. Plastics used for extrusion moulding. The raw materials should meet the required drying requirements. If necessary, further drying is required, and the raw materials should sieve to remove agglomerates and mechanical impurities.
  2. Check whether the water, electricity, and gas systems in the equipment are normal to ensure that the water and gas paths are unblocked and leak-free, whether the electrical system is standard, whether the heating system, temperature control, and various instruments are working reliably; low-speed test of the auxiliary machine empty car Operate and observe whether the equipment is operating normally; start the vacuum pump of the sizing table to observe whether it usually works; add oil to lubricate the lubricated parts of various equipment. If any fault is found, remove it in time.
  3. Install the machine head and sizing sleeve. According to the variety and size of the product, select the specifications of the machine head. Install the machine head in the following order.
    • The machine head should be assembled and installed on the extruder as a whole.
    • Before assembling the machine head, wipe off the grease applied during storage, carefully check the surface of the cavity for bruises, scratches, and rust spots, perform necessary polishing, and then apply a layer of silicone oil on the surface of the runner.
    • Assemble the plates of the machine head in order, apply high-temperature grease to the threads of the bolts, and then tighten the bolts and flanges.
    • Place the perforated plate between the flanges of the machine head to ensure that the perforated plate is pressed tightly without overflow.
    • Adjust the horizontal position of the die before tightening the fastening bolts of the connecting flange between the die head and the extruder. The square die head can adjust horizontally, and the round die head should be based on the bottom surface of the finalized model. The bottom surface of the mould is leveled.
    • Tighten the connecting flange bolts, tighten the machine head fastening bolts, install the heating ring and thermocouple, pay attention to the heating ring to be close to the outer surface of the machine head.
    • Install the sizing sleeve and adjust it in place, check whether the centerline of the main engine, the sizing sleeve and the tractor are aligned. After adjustment, tighten the fixing bolts. Connect the water pipes and vacuum tubes of the sizing sleeve.
    • Turn on the heating power supply to evenly heat the machine head and cylinder. At the same time, open the cooling water at the bottom of the hopper and the gearbox and the water inlet valve of the exhaust vacuum pump. When heating, the temperature of each section is first adjusted to 140°C, and when the temperature rises to 140°C, the temperature is kept for 30-40min. Then the temperature is raised to the temperature during average production. When the temperature rises to the temperature required for regular production, please keep it for about 10 minutes to stabilize each part of the machine before it can start production. The length of the heat preservation time varies according to different extruders and types of plastic raw materials. Keep the temperature for some time to keep the temperature inside and outside the machine consistent to prevent the meter from indicating that the temperature has reached the required temperature, but the actual temperature is too low. At this time, if the material is put into the extruder, the actual temperature is too low, and the melt viscosity of the material is too high. Causes axial force overload and damages the machine.
    • Feed the raw materials used for driving into the hopper for use.

2. Drive

  1. You can start driving after the constant temperature. Before driving, tighten the head and the flange bolts of the extruder again to eliminate the difference in thermal expansion between the bolts and the head. The order of tightening the head bolts is to tighten diagonally. Evenly. When tightening the flange nuts of the machine head, the tightness of all sides must be consistent. Otherwise, the material will run out.
  2. When driving, select and press the “Ready to Start” button, then connect the “Start” button, then slowly rotate the screw speed adjustment knob. The screw speed starts slowly. Then gradually speed up while adding a small amount of material. Pay close attention to the indication changes of the host ammeter and various indicator heads when feeding. The screw torque cannot exceed the red mark (generally 65%-75% of the torque meter). Before the plastic profile is extruded, no one can stand directly in front of the die to prevent injury accidents caused by bolts breaking or due to damp and foaming raw materials. After the plastic is extruded from the die of the machine head, the extrudate needs to be slowly cooled and led to the traction device and the shaping die, and these devices are activated. Then according to the indicated value of the control instrument and the requirements for extruded products. Adjust each part accordingly to make the entire extrusion operation reach a normal state. And add enough material as needed. The twin-screw extruder uses a metering feeder to feed evenly and at a constant rate.
  3. When the die is evenly discharged, and the plastic is suitable, it can pull into the shaping sleeve. Judgment of the degree of plasticization requires experience. Generally, it can judge according to the appearance of the extruded material. That is, the surface is glossy, free of impurities, no foaming, burnt material, and discoloration, and the extruded material is squeezed by hand to a certain extent and does not appear. Burrs and cracks have a certain degree of elasticity, which means that the material is plasticized well. If the plasticization lacks, the screw speed, barrel, and head temperature can adjust appropriately until the requirements are met.
  4. During the production process of the PVC pipe extruder machine, check whether the various process parameters are expected according to the process requirements and fill in the process record sheet. According to the quality inspection standards, check the quality of the profile products and take timely solutions when problems are found.

3. Parking

  1. Stop feeding and squeeze out the plastic in the PVC pipe extruder machine. When the screw is exposed, turn off the power of the barrel and head, and stop heating.
  2. Turn off the extruder and auxiliary machines’ power supply and stop the screw and auxiliary machines.
  3. Open the connecting flange of the machine head and disassemble the machine head. Clean the perforated plate and various parts of the machine head. To prevent damage to the inner surface of the machine head during cleaning, the residual material in the machine head should be cleaned with steel laws and steel sheets. Then the plastic adhering to the machine head should be removed with sandpaper, polished, and coated with engine oil or silicone oil. 
  4. Cleaning the screw and barrel. After removing the head, restart the main engine, add parking material (or crushed material), and clean the screw and barrel. At this time, the screw should be at a low speed (about sr/min) to reduce wear. After the stopped material is crushed into powder and wholly extruded, compressed air can be used to repeatedly blow out the remaining pellets and powder from the feeding port and the exhaust port until there is no residual material in the barrel, then reduce the screw speed to zero and stop the extrusion Turn off the main power supply and the main cold water valve.
  5. The safety items that should be paid attention to when extruding are electricity, heat, mechanical rotation, and the loading and unloading of heavy parts. The extruder workshop must be equipped with lifting equipment, assembling and disassembling the head, screw and other heavy parts to ensure safe production.

Maintenance And Maintenance Of PVC Pipe Extruder Machine

double wall corrugated pipe extrusion machine
double wall corrugated pipe extrusion machine

The screw extrusion system is maintained in two ways: daily maintenance and regular maintenance.

  1. Daily maintenance is routine work, which does not take up equipment operating hours, and is usually completed during start-up. The focus is to clean the machine, lubricate the moving parts, tighten the threaded parts that are easy to loosen, check and adjust the motors, control instruments, various working parts, and pipelines in time.
  2. Regular maintenance is usually carried out after the extruder has been continuously operated for 2500-5000h, and the machine is shut down. The machine needs to be disassembled for inspection, measurement, and identification of the wear of the main parts, replacement of parts that have reached the specified wear limit, and repair of damaged parts.
  3. It is not allowed to run empty to avoid the screw and the machine from rolling.
  4. If abnormal noise occurs during the operation of the extruder, it should stop immediately for inspection or repair.
  5. Strictly prevent metals or other debris from falling into the hopper to avoid damage to the screw and barrel. To prevent iron debris from entering the barrel, a magnetic absorption component or a magnetic frame can install at the material inlet of the barrel to prevent debris from falling into the barrel. The material must screen in advance.
  6. Pay attention to a clean production environment, and do not mix garbage and impurities into the material to block the filter plate, affecting the output and quality of the product and increasing the machine head’s resistance.
  7. When the extruder needs to be stopped for a long time, it should be coated with anti-rust, lubricating grease on the working surface of the screw, machine shaft, and head. The small screw should be hung in the air or placed in a special wooden box and be leveled with wooden blocks to prevent the screw from deforming or bumping.
  8. Regularly calibrate the temperature control instrument to check the correctness of its adjustment and the sensitivity of control.
  9. The maintenance of the reducer of the extruder is the same as that of the general standard reducer. Mainly check the wear and failure of gears and bearings. The gearbox should use the lubricating oil specified in the machine manual and add the oil according to the specified oil level. If the oil is too little, the lubrication will not reverse, and the service life of the parts will reduce; too much oil, high heat generation, high energy consumption, easy oil Deterioration also makes lubrication ineffective and causes damage to the parts. The sealing gasket (ring) should replace the oil leakage part of the reduction box to ensure the amount of lubricating oil.
  10. The inner wall of the cooling water pipe attached to the extruder is prone to scale formation, and the outside is prone to corrosion and rust. Careful inspection should be done during maintenance. The excessive scale will block the pipeline and fail to achieve the cooling effect. If the rust is severe, water leakage will occur. Therefore, measures of descaling and anti-corrosion cooling must take during maintenance.
  11. For the DC motor that drives the screw to rotate, it is essential to check the wear and contact of the brush. Whether the insulation resistance value of the motor is above the specified value should also be measured frequently. In addition, check whether the connecting wires and other parts are rusty and take protective measures.
  12. Designate a person responsible for equipment maintenance and include detailed records of each maintenance and repair situation in the factory equipment management file.
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