Operation Points Of Plastic Extruder

When making different plastic products, the operating points of the extruder are different, but there are also similarities. The following is a brief introduction to the same operation steps when extruding various products and the operating points of the extruder that should be paid attention to.
1. Preparation Before Driving
⑴ Plastics for extrusion molding. Raw materials should meet the required drying requirements, and further drying is required if necessary. And the raw material is screened to remove agglomerates and mechanical impurities.
⑵ Check whether the water, electricity and gas systems in the equipment are normal, ensure that the water and gas channels are smooth and leak-free, whether the electrical system is normal, whether the heating system, temperature control, and various instruments work reliably; Observe whether the equipment is operating normally; start the vacuum pump of the setting table to observe whether it is working normally; lubricate the lubricating parts of various equipment. If a fault is found, eliminate it in time.
⑶ Install the machine head and the setting 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.
2. Drive
⑴ After the temperature is constant, the machine can be started. Before starting the machine, the machine head and extruder flange bolts should be tightened again to eliminate the difference in thermal expansion between the bolts and the machine head. When tightening the flange nut of the machine head, it is required that the four sides are tight and tight, otherwise the material will run out.
⑵ To drive, first press the "Ready to drive" button, then connect the "Drive" button, then slowly rotate the screw speed adjustment knob, and the screw speed starts slowly. Then gradually speed up, while adding a small amount of feed. When feeding, pay close attention to the indication changes of the ammeter of the main engine and various indicator heads. The screw torque cannot exceed the red mark (generally 65%~75% of the torque table). Before the plastic profile is extruded, no one is allowed to stand in front of the die, so as to prevent injury accidents caused by bolts being broken or raw materials being wet and foamed. After the plastic is extruded from the die of the machine head, the extrudate needs to be cooled slowly and led to the traction device and the calibrating die, and these devices are started. Then according to the indication value of the control instrument (see Figure 1) and the requirements for extruded products. Adjust each part accordingly so that the entire extrusion operation can reach a normal state. And add enough material according to the need, and the twin-screw extruder uses a metering feeder to feed the material evenly and at a constant speed.
⑶ When the output of the die is uniform and the plasticization is good, it can be drawn into the setting sleeve. The judgment of the degree of plasticization needs to be based on experience. Generally, it can be judged according to the appearance of the extruded material, that is, the surface is shiny, free of impurities, foaming, scorched and discolored. Squeeze the extruded material by hand to a certain extent without appearing Burrs, cracks, and a certain degree of elasticity indicate 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.
⑷ 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 to problems found.
3. Parking
⑴ Stop feeding, squeeze out the plastic in the extruder, and when the screw is exposed, turn off the power of the barrel and head, and stop heating.
⑵ Turn off the power supply of the extruder and auxiliary machines to stop the screw and auxiliary machines from running.
⑶ Open the connecting flange of the machine head and disassemble the machine head. Clean the perforated plate and various parts of the machine head. 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 laws and steel sheets, and then the plastic adhered to the machine head should be removed with sandpaper, polished, and coated with machine oil or silicone oil to prevent rust.
⑷ Cleaning of the screw and barrel, after removing the machine head, restart the main machine, add parking material (or crushed material), and clean the screw and barrel. At this time, the screw is selected at a low speed (about sr/min) to reduce wear. After the parking material is ground into powder and completely extruded, use compressed air to repeatedly blow out the residual pellets and powder from the feeding port and exhaust port until there is no residual material in the barrel, then reduce the screw speed to zero and stop extrusion machine, turn off the main power supply and the main cold water valve.
⑸ The safety items that the extruder should pay attention to during extrusion include: electricity, heat, mechanical rotation and loading and unloading of heavy parts. The extruder workshop must be equipped with lifting equipment to assemble and disassemble bulky parts such as machine heads and screws to ensure safe production.