Extruder operating points

When making different plastic products, the operating points of the extruder are different, but they also have similarities. The following briefly introduces the same operating steps when extruding various products and the operating points of the extruder that should be paid attention to.
1. Preparations before driving
⑴Plastic used for extrusion molding. The raw materials should meet the required drying requirements and be further dried if necessary. And the raw materials are sieved 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 lines are smooth and leak-free, whether the electrical system is normal, whether the heating system, temperature control, and various instruments work reliably; test run the auxiliary engine at low speed with no power, Observe whether the equipment is operating normally; start the vacuum pump of the setting table and observe whether it is working normally; add oil and lubricate the lubricated parts of various equipment. If any fault is found, eliminate it promptly.
⑶Install the machine head and shaping sleeve. According to the product variety and size, select the machine head specifications. Install the machine head in the following order.
2. drive a car
⑴ After the temperature is constant, the machine can be started. Before starting, 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. The order of tightening the machine head bolts is to tighten diagonally, and the force should be even. When tightening the machine head flange nut, the tightness must be consistent all around, otherwise the material will run away.
⑵ To start the car, first press the "Ready to drive" button, then press the "Start" button, and then slowly rotate the screw speed adjustment knob to start the screw speed slowly. Then gradually increase the speed while adding small amounts of ingredients. When adding materials, pay close attention to the indication changes of the host ammeter 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 directly in front of the die to prevent injury accidents due to bolt breakage or moisture and foaming of the 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 shaping die, and these devices are started. Then according to the indicated value of the control instrument (see Figure 1) and the requirements for the extruded products. Make corresponding adjustments to each part so that the entire extrusion operation reaches normal status. And add enough material as needed, and the twin-screw extruder uses a metering feeder to add material evenly and at a constant speed.
⑶ When the die discharge is uniform and the plasticization is good, the shaping sleeve can be drawn. The degree of plasticization needs to be judged based on experience. Generally, it can be judged based on the appearance of the extruded material, that is, the surface is shiny, free of impurities, foaming, charred material and discoloration. The extruded material should be squeezed by hand to a certain extent without any appearance. 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, various process parameters should be checked regularly according to process requirements to see if they are normal, and the process record sheet should be filled out. Check the quality of profile products according to quality inspection standards, and take timely measures to resolve problems if they are found.
3. Parking
⑴ Stop feeding, extrude all the plastic in the extruder, and when the screw is exposed, turn off the power of the barrel and machine head, and stop heating.
⑵ Turn off the power of the extruder and auxiliary machines to stop the screw and auxiliary machines.
⑶Open the connecting flange of the machine head and disassemble the machine head. Clean the porous plate and various parts of the machine head. In order to prevent damage to the inner surface of the machine head during cleaning, the remaining materials in the machine head should be cleaned with steel bars and steel sheets, and then the plastic adhering to the machine head should be removed with sandpaper, polished, and coated with machine oil or silicone oil to prevent damage. rust.
⑷Cleaning of the screw and barrel. After removing the machine head, restart the main machine, add parking material (or crushing material), and clean the screw and barrel. At this time, the screw should be used at a low speed (about sr/min) to reduce wear. After the stopped material is ground into powder and completely extruded, compressed air can be used 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 Safety items that should be paid attention to when extruding the extruder include: electricity, heat, mechanical rotation, and loading and unloading of bulky parts. The extruder workshop must be equipped with lifting equipment to assemble and disassemble heavy components such as the machine head and screw to ensure safe production.