Extrusion system includes screw, barrel, hopper, head, and die, plastic through the extrusion system and plasticized into a uniform melt, and in the process of establishing pressure, by the screw continuous extrusion head. (1) screw: is the most important part of the extruder, it is directly related to the scope of application and productivity of the extruder, made of high-strength corrosion-resistant alloy steel. (2) barrel: is a metal cylinder, generally heat-resistant, high compressive strength, strong wear-resistant, corrosion-resistant alloy steel or alloy steel lined with composite steel pipe made. Cylinder and screw with the realization of the plastic crushing, softening, melting, plasticizing, exhaust and compaction, and to the molding system for continuous and uniform delivery of rubber. Generally the length of the barrel is 15-30 times of its diameter, so that the plastic is fully heated and fully plasticized as a principle. (3) hopper: the bottom of the hopper is equipped with a cut-off device, in order to adjust and cut off the flow of material, the side of the hopper is equipped with sight holes and calibration measuring device. (4) head and mold: head by the alloy steel inner sleeve and carbon steel jacket composition, the head is equipped with molding die, the role of the head is to rotate the movement of the plastic melt into a parallel linear movement, uniform and smooth introduction into the mold set, and give the plastic to the necessary molding pressure. Plastic in the barrel plasticization compaction, through the porous filter plate along a certain flow channel through the neck of the head into the head molding mold, mold core mold sleeve appropriate coordination, the formation of the cross-section of the ever-decreasing annular gap, so that the plastic melt in the core line around the formation of a continuous and dense tubular cladding layer. In order to ensure that the head of the plastic flow reasonable, to eliminate the accumulation of plastic dead space, often placed in the diversion sleeve, in order to eliminate pressure fluctuations in plastic extrusion, there are also set up pressure equalization ring. The head is also equipped with mold calibration and adjustment devices, easy to adjust and correct the concentricity of the die core and die set. According to the angle between the material flow direction of the head and the centerline of the screw, the extruder is divided into angled head (angle 120o) and right angle head. The shell of the head is bolted to the body of the machine, the mold in the head has a die core sitting and fixed with a nut in the head inlet port, the front of the die core seat is equipped with a die core, the die core and the center of the die core seat has a hole for passing the core, in the front of the head is equipped with an equalizing ring for equalizing the pressure, the extruded package molding part consists of a die set seat and a die cover, the position of the die cover can be adjusted by the bolts through the support to adjust the relative position of the die cover on the core, which makes it easy to adjust the relative position of the squeeze package molding part. The position of the die sleeve can be adjusted by the bolt through the support to adjust the relative position of the die sleeve to the die core, which is convenient to adjust the uniformity of the thickness of the extruded layer.
2, transmission system
The role of the transmission system is to drive the screw, supplying the screw in the extrusion process of the required torque and speed, usually consists of electric motors, reducers and bearings.
3, heating and cooling devices
Heating and cooling is a necessary condition for the plastic extrusion process. (1) now extrusion machine is usually used for electric heating, divided into resistance heating and induction heating, heating pads installed in the body, the neck, the head of each part. Heating device from the outside to heat the plastic barrel, so that it warms up to achieve the temperature required for the process operation. (2) Cooling device is set up to ensure that the plastic is in the temperature range required by the process. Specifically, it is to exclude the excess heat generated by the shear friction of the rotating screw, so as to avoid the plastic decomposition, scorching or shaping difficulties due to the high temperature. Barrel cooling is divided into water-cooled and air-cooled two kinds, generally small and medium-sized extruder using air-cooled is more appropriate, large-scale water-cooled or a combination of the two forms of cooling; screw cooling is mainly used in the center of the water-cooled, the purpose is to increase the rate of material solids transport, stabilize the amount of rubber, while improving product quality; but the cooling at the hopper, one is to strengthen the role of solid material transport, to prevent the plastic particles due to the temperature of the viscous plastic plugging The second is to ensure that the transmission part of the normal work.