Detailed Process and Precautions for Operating Twin-screw Extruder

Ⅰ. Preparations before the twin screw extruder starts up (works)

1. Plastics for extrusion molding. The raw materials should meet the required drying requirements. Further drying is required if necessary. The raw materials are sieved to remove agglomerates 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. Check whether the electrical system is normal, and whether the heating system, temperature control and various instruments work reliably. Try to run the auxiliary machine at low speed with empty car and observe whether the equipment is running normally. Start the vacuum pump of the setting table and observe whether it works normally. Oil and lubricate the lubricating parts of various equipment. If a fault is found, remove it in time.

3. Install the machine head and the setting sleeve. According to the variety and size of the product, select the head specification. Install the handpiece in the following order.

Ⅱ. The twin screw extruder starts up

1. You can start up when the temperature is constant. The head and extruder flange bolts should be tightened again before starting to eliminate the difference in thermal expansion between the bolts and the head. The order of tightening the head bolts is to tighten diagonally and the force should be even. When tightening the flange nut of the machine head, it is required to be tight around the same, otherwise the material will run out.

2. To start up twin screw extruder, select and press the "ready to start" button, and then press the "start" button. Slowly rotate the screw speed adjustment knob and the screw speed starts slowly. Then gradually increase the speed, adding small amounts at the same time. When feeding, pay close attention to the indication changes of the host ammeter and various indicating heads. The screw torque cannot exceed the red mark (usually 65%-75% of the torque table).

Before the plastic profile is extruded, no one should stand in front of the die to prevent injury accidents caused by bolts breaking or due to wet foaming of raw materials. When the plastic is extruded from the die of the die, the extrudate needs to be cooled slowly and led to the pulling device and the setting die. Activate these devices. Then, according to the indication value of the control instrument and the requirements for the extruded products, each part is adjusted accordingly, so that the entire extrusion operation can reach a normal state. And add enough material according to the need, the twin screw extruder uses a metering feeder to feed the material evenly and at the same speed.

3. When the die discharge is uniform and the plastic is good, it can be used for pulling the setting sleeve. The judgment of the degree of plasticization is based on experience, which can generally be judged according to the appearance of the extruded material. The surface is shiny, free of impurities, no foaming, coke and discoloration. Squeeze the extruded material by hand until there are no burrs and cracks, and it is still elastic. At this moment, it means 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 in the process record sheet. Check the quality of profile products according to the quality inspection standards, and take timely solutions if problems are found.

Ⅲ. Stop the twin screw extruder

1. Stop feeding and squeeze out the plastic in the extruder. When the screw is exposed, turn off the power of the barrel and the head, and stop heating.

2. Turn off the power supply of the extruder and auxiliary machine to stop the operation of the screw and auxiliary machine.

3. Open the connection flange of the machine head and disassemble the machine head. Clean the perforated plate and various parts of the handpiece. In order 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 wire and steel sheet. Use sandpaper to remove and polish any plastic stuck to the inside of the handpiece. Apply engine oil or silicone oil to prevent rust.

4. The cleaning of screw and barrel. After removing the machine head, restart the main engine, add the stopped material (or crushed material), and clean the screw and barrel. At this time, the screw adopts low speed (about sr/min) to reduce wear. When the stopped material is completely extruded in powder form, the residual pellets and powder can be repeatedly blown out from the feeding port and the exhaust port with compressed air until there is no residual material in the barrel. Reduce the screw speed to zero, stop the extruder, and close the main power supply and the cold water main valve.

5. The safety items that should be paid attention to when the twin screw extruder is working include: electricity, heat, mechanical rotation and the loading and unloading of heavy parts. The extruder workshop must be equipped with lifting equipment, assembly and disassembly of bulky parts such as screw heads to ensure safe production.