Introduction and application of single screw extruder

Introduction and application of single screw extruder

(1) Introduction of single screw extruder

As the name implies, a single screw extruder means that there is a screw in the barrel. Generally divided into three sections in effective length. Determine the effective length of the three sections according to the screw diameter, pitch and screw depth. Generally divided by 1/3 each.

The first section: starting from the last thread of the material port, it is called the conveying section. The material here is not required to be plasticized, but it must be preheated and compacted. In the past, the old extrusion theory believed that the material here was loose, and later proved that the material here is actually a solid plug. That is to say, the material here is a solid like a plug after being squeezed. Therefore, as long as the delivery task is completed, it is its function.

The second section: compression section. The volume of the screw groove in this section gradually becomes smaller, and the temperature must reach the degree of plasticization of the material. Compression occurs here (From the volume 3 of the conveying section, it can be compressed to volume 1 here,

This is called the compression ratio of the screw-3:1, some machines are also different). The plasticized material enters the third stage.

The third section: the measurement section. The material here maintains the plasticizing temperature. It’s just as accurate and quantitative delivery of the melt material as a metering pump to supply the machine head. At this time, the temperature cannot be lower than the plasticizing temperature, generally slightly higher.

(2) Application of single screw extruder

The single-screw extruder is mainly used for the extrusion of pipes, sheets, plates and profiles, and granulation of some modified materials.

(3) Maintenance of single screw extruder

① Since the electrical control system has high requirements for ambient temperature and dust prevention, the electrical system should be isolated from the production site, and ventilation or ventilation fans should be installed. It is recommended to put the electric control cabinet in a simple room, keep the room clean and ventilated, so that the indoor temperature is not higher than 40℃.

② The single-screw extruder is not allowed to run empty to prevent the screw and barrel from rolling. When the main extruder starts idling, it is not allowed to exceed 100r/min; Start the main extruder at a low speed first, check for abnormal noise after starting the main extruder, and then slowly increase the main extruder speed to within the technological allowable range (adjustable to the best state is better). When the new machine is running in, the current load should be 60%-70%, and the current during normal use should preferably not exceed 90%. Note: If abnormal noise occurs when the extruder is running, it should be stopped immediately for inspection or repair.

③ Turn on the oil pump first when starting up, and turn off the oil pump after shutting down; The water pump keeps working in the whole production process, and the operation of the water pump cannot be stopped, so as to avoid the temperature rise of the barrel and the decomposition and carbonization of the material in the barrel; The asbestos air hood of the main motor fan needs to be cleaned frequently to avoid excessive dust adhesion and blocking the air hood, resulting in insufficient heat dissipation of the motor and tripping due to overheating.

④ Clean up the dirt, tools and sundries on the surface of the extruder machine set in time.

⑤ Strictly prevent metals or other debris from falling into the hopper to avoid damage to the screw and barrel. In order to prevent iron debris from entering the barrel, a magnetic absorption component or a magnetic frame can be installed at the material inlet of the barrel to prevent debris from falling into the barrel. The material must be screened in advance.

⑥ Pay attention to the clean production environment. Do not mix garbage and impurities into the material to block the filter plate, which will affect the output of the product and increase the resistance of the machine head.

⑦ The gearbox should use the lubricating oil specified in the machine manual, and add oil according to the specified oil level, if the oil is too little, the lubrication is not enough, and the service life of the parts is reduced; Excessive oil, heat generation, energy consumption, and oil is easy to deteriorate, which also makes lubrication ineffective and causes damage to parts. The sealing gasket (ring) should be replaced in time for the oil leakage part of the reduction box to ensure the amount of lubricating oil.

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