Extruder Screw Barrel The Most Important Parts Of A Plastic Machine
Extruder screw is the most important parts of the plastic machine equipment, it is directly related to the plastic machine plasticizing effect and yield. Extruder screw rotation in the barrel is carried out under high temperature and high pressure, because it will be in the rotation to promote the material forward, at the same time, it also has to withstand the strong friction and plastic decomposition of corrosive gases Erosion, so the extruder screw material must have a high mechanical strength, to withstand the huge torque and high temperature and high pressure conditions without deformation of the performance.
Extruder screw in the rotation process, mainly by the edge of the plastic shear shear plastic, and to promote the plastic forward, so the ribs bear a huge shear stress and friction, due to long-term work in harsh conditions, Wear, screw edge becomes smaller, with the cylinder gap increases, resulting in reduced plastic extrusion, severe plastic will produce a return, and the plastic effect is reduced, there is a serious decline in grain and production capacity of the phenomenon.
The process of melt extrusion is to pre-mix the material from the feed port into the extruder barrel, the first section of the barrel for the feeding section, the material at this stage will not melt, with the extruder screw drive, the material was band Into the second paragraph for the compression section, the section for the heating phase, the material began to melt, the friction between the material increased to form a high viscosity, continue with the extruder screw drive into the high shear of the third paragraph for the homogenization section, so It is very effective separation of pigment aggregates, to achieve the purpose of full dispersion. At present, the extruder used in powder coatings is equipped with a twin extruder screw extruder, a single extruder screw extruder and a star extruder screw extruder, etc. Although the type of extruder, Internal structure is different, but the design is the same purpose, that is, to maximize the material evenly dispersed, so Qingdao Guohao plastic machinery that the extruder directly determines the degree of dispersion of the material.
The main body of the plastic extruder is the extruder, which consists of an extrusion system, a drive system and a heating and cooling system. 1. Extrusion system Extrusion system includes screw, barrel, hopper, head, and mold The main body of the plastic extruder is the extruder, which consists of an extrusion system, a drive system and a heating and cooling system.
1. Extrusion system The extrusion system consists of screws, barrels, hoppers, heads, and molds, which are plasticized into a uniform melt by means of an extrusion system and, under pressure established by this process, Extruder head.
(1) screw: the extruder is the most important components, it is directly related to the scope of application of extruder and productivity, made of high strength corrosion-resistant alloy steel.
(2) barrel: is a metal cylinder, generally with heat, high compressive strength, durable wear, corrosion-resistant alloy steel or alloy steel alloy made of composite steel pipe. Barrel and screw with the realization of the plastic crushing, softening, melting, plasticizing, exhaust and compaction, and to the forming system continuous uniform transport of rubber. The length of the general barrel is 15 to 30 times its diameter, so that the plastic is fully heated and fully plasticized to the principle.
(3) Hopper: The bottom of the hopper is equipped with a truncation device to adjust and cut the material. The side of the hopper is equipped with a viewing hole and a calibration metering device.
(4) nose and die: the nose from the alloy steel sleeve and carbon steel jacket, the machine head with a molding die. The role of the nose is the rotation of the plastic melt into a parallel linear motion, uniform and smooth into the mold sleeve, and give the plastic to the necessary molding pressure. Plastic in the barrel of plastic compaction, the porous filter plate along a certain flow through the nose of the head into the nose forming mold, mold core sleeve with the appropriate cross-section to form a continuous reduction of the annular gap, so that the plastic melt in the A thick, tubular coating is formed around the core. In order to ensure that the plastic channel within the machine is reasonable, to eliminate the accumulation of plastic dead ends, often placed a shunt sleeve, to eliminate the pressure when the plastic extrusion fluctuations, but also set the pressure ring. The head is also equipped with a mold correction and adjustment of the device, easy to adjust and correct the core and die sets of concentricity.
Extruder in accordance with the direction of the head flow and the screw center line angle, the nose is divided into bevel (angle 120o) and right angle head. The head of the nose is fixed with bolts on the fuselage, the mold inside the die has a core sitting, and fixed with a nut in the nose into the line port, the core seat in front of a core, core and core The center of the hole, for the core; in the front of the nose with a pressure ring, used to balance the pressure; squeeze the molding part of the module by the sleeve and mold sleeve, mold sleeve position can be adjusted by the bolt to support , To adjust the relative position of the mold sleeve on the core, easy to adjust the thickness of the extruded layer uniformity. The head is equipped with a heating device and a temperature measuring device.
2. Drive system The role of the drive system is to drive the screw, the supply screw in the extrusion process required torque and speed, usually by the motor, reducer and bearings and other components.
3. Heating and cooling device heating and cooling is the plastic extrusion process can carry out the necessary conditions.
(1) Now the extruder is usually used in electric heating, divided into resistance heating and induction heating, heating film installed in the fuselage, machine neck, nose parts. The heating device is heated by an external heating cylinder to raise the temperature to achieve the desired temperature for the process operation.
(2) The cooling device is designed to ensure that the plastic is at the temperature range required by the process. Specifically, it is necessary to eliminate the excess heat generated by the shear friction of the screw rotation in order to avoid excessive temperature to make the plastic decomposition, scorch or stereotypes difficult. Barrel cooling is divided into two kinds of water cooling and air cooling, general small and medium-sized extruder with air-cooled more appropriate, large-scale use of water or two forms of cooling; , To stabilize the amount of glue, while improving product quality; but in the hopper at the cooling, first in order to strengthen the transport of solid materials to prevent the temperature caused by plastic particles sticky plugging mouth, the second is to ensure that the transmission part of the normal work.