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Using the extruder correctly and reasonably can give full play to the efficiency of the machine, maintain a good working condition, and extend the service life of the machine.
The use of screw extruder includes a series of links such as machine installation, adjustment, test run, operation, maintenance and repair. Its use has the common characteristics of general machines, mainly in the drive motor and speed reduction device. However, the working system of the screw extruder is the extrusion system, but it has unique characteristics. Pay special attention to its characteristics when using the screw extruder. The installation, adjustment, and test run of the machine are generally clearly specified in the extruder's instruction manual. Here is a brief description of the operation method, maintenance and maintenance of the extruder as follows: 1. The operation method of the extruder: the operator must be familiar with The structural characteristics of the extruder you operate, especially the structural characteristics of the screw, heating and cooling control instrument characteristics, head characteristics and assembly conditions, etc., in order to correctly grasp the extrusion process conditions and operate the machine correctly. The operation methods of extruding different plastic products are different, but there are also similarities.
1. Preparation before driving
(1) Plastics used for extrusion molding. The raw materials should meet the required drying requirements, and further drying should be done 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, to ensure that the water and gas paths are unblocked and leak-free, whether the electrical system is normal, whether the heating system, temperature control, and various instruments are working reliably; low-speed test of the auxiliary engine empty car Operate and observe whether the equipment is operating normally; start the vacuum pump of the sizing table to observe whether it works normally; add oil to lubricate the lubricating 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.
①The machine head should be assembled together and installed on the extruder as a whole.
②Before 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.
③Assemble the plates of the machine head in order, apply high-temperature grease to the threads of the bolts, and then screw on the bolts and flanges.
④Place the perforated plate between the flanges of the machine head to ensure that the perforated plate is pressed tightly without overflow.
⑤The horizontal position of the die should be adjusted before the fastening bolts of the connecting flange between the die head and the extruder are not tightened. The square die head can be adjusted horizontally, and the round die head should be based on the bottom surface of the finalized model. The bottom surface of the mold is leveled.
⑥Tighten 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.
⑦Install the sizing sleeve and adjust it in place, check whether the center line 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.
⑧Turn on the heating power supply to evenly heat up the machine head and cylinder. Open the cooling water at the bottom of the hopper and the gear box and the water inlet valve of the exhaust vacuum pump at the time. When heating, the temperature of each section is first adjusted to 140℃, and when the temperature rises to 140℃, the temperature is kept for 30-40min, and then the temperature is raised to the temperature during normal production. When the temperature rises to the temperature required for normal production, keep it for about 10 minutes to stabilize the temperature of each part of the machine before it can start production. The length of the heat preservation time varies according to different types of extruders and types of plastic raw materials. Keep the temperature for a period of time to keep the temperature inside and outside the machine consistent, so as to prevent the meter 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, because the actual temperature is too low, the melt viscosity of the material will Causes axial force overload and damages the machine.
⑨ Feed the raw materials used for driving into the hopper for use.
You can start driving after the constant temperature. Before driving, tighten the head and extruder flange bolts again to eliminate the difference in thermal expansion between the bolts and the head. The order of tightening the head bolts is to tighten them diagonally, and the force should be even. 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, and 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 is allowed to stand directly in front of the die, to prevent injury accidents caused by bolts breaking or damp 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.
In the plastic extrusion molding equipment, the plastic extruder is usually called the main machine, and the subsequent equipment that is matched with the plastic extrusion molding machine is called the auxiliary machine. After more than 100 years of development, the plastic extruder has been derived from the original single-screw, multi-screw, and even non-screw and other models. The plastic extruder (host) can be used with various plastic molding auxiliary machines such as pipe, film, holding material, monofilament, flat wire, strapping, extruding net, board (sheet) material, profiled material, pelletizing, cable coating, etc. Matching to form various plastic extrusion molding production lines to produce various plastic products. Therefore, plastic extrusion molding machinery is one of the widely used models in the plastics processing industry no matter now or in the future. Classification of extruders With the wide application and continuous development of plastic extrusion molding technology, the types of extruders are being updated day by day. There are mainly the following five types of classification methods.
(1) According to the installation position, it can be divided into vertical extruder and horizontal extruder;
(2) According to the purpose, it can be divided into extruder for molding, extruder for mixing and drawing and feeding extruder for feeding;
(3) According to the number of screws, it can be divided into screwless extruder, single screw extruder, twin screw extruder and multi-screw extruder
(4) According to whether it is vented, it can be divided into vented extruder and non-vented extruder
(5) According to the screw speed, it can be divided into ordinary extruder, high speed extruder and super high speed extruder.