Extruder and auxiliary equipment
DATE：2022/8/4 8:53:56 / READ： / SOURCE：This station
Extruder and auxiliary equipment
Extruder is the main equipment of plastic extrusion molding production line. The main function of the extruder is to provide plasticized melt for plastic resin extrusion molding plastic products; Ensure that the production raw materials are within the temperature range required by the process, and all components are evenly mixed and plasticized fully; It provides molten materials with uniform flow and stable pressure for the forming mold, so that the plastic extrusion production can be carried out smoothly and smoothly. Auxiliary equipment refers to the equipment that requires the assistance and cooperation of other types of equipment when the extruder produces plastic products. These include the dryer for drying raw materials, the grinder for refining raw materials, the mixer for mixing various raw materials, the extrusion granulator for homogenizing the mixture, the feeding equipment for feeding the extruder, and the production line mainly composed of extruders when producing different plastic products. These auxiliary equipment are combined to form the working sequence of the feeding system in the extruder production line as follows. Raw materials with high wet content are dried, colored slurry and stabilizer are ground and refined, and various raw materials are stored in silos and tanks. Various raw materials are measured according to the dosage of the formulaAccording to the process requirements, the mixer is added in order, and the mixing is uniform. The extruder is used for mixing, and the pre plasticization granulation feeding device Extruder
3.1 extruder
3.1.1 type of extruder
There are many kinds of extruders, and the classification methods are also different. According to the number of screws, extruders include single screw extruder, twin screw extruder and multi screw extruder. According to the functions of extruders, extruders can be divided into general-purpose single screw extruders, exhaust extruders, feed extruders and step extruders. At present, general single screw extruders and twin screw extruders are the most widely used in plastic products factories. Twin screw extruders are generally used to extrude profiles, pipes, plates and extrusion granulation.
3.1.2 production characteristics of plastic products formed by extruder
① Extruder equipment has simple structure, low cost, and less investment in extrusion molding production line. ② The output of extruded products is high. ③ The production operation is relatively simple, the product quality is easy to ensure, and the production cost of products is relatively low. ④ The production line covers a small area and the production environment is relatively clean. ⑤ Extruder has a wide range of applications, which can not only extrude plastic products, but also be used for raw material mixing, pre plasticization, granulation and feeding. ⑥ The length of plastic products produced by the extruder can be extended indefinitely as needed.
3.1.3 types of extruded plastic products
① It can continuously extrude plastic products with different cross-section geometry, such as film, sheet, plate, hard pipe, hose, bellows, profile, wire, cable, packaging belt, rod, net and composite materials. ② It can periodically and repeatedly produce hollow products, such as bottles, barrels, etc.
3.1.4 working principle of extruded plastic products
According to the formula requirements of plastic products, the evenly mixed raw materials are sent into the barrel through the hopper of the extruder. With the rotation of the screw, the raw materials are forced to the front of the barrel. Due to the resistance of the filter screen, perforated plate and forming mold in front of the barrel, and the gradual reduction of the screw thread volume on the screw, the pressure of the raw materials in the barrel is gradually increased. At the same time, the raw materials are also affected by the heat supply outside the barrel. Under the action of extrusion, shear and mixing, plus the friction between the raw materials and the barrel and the threaded working surface, as well as the friction between the raw materials molecules, the temperature of the raw materials in the barrel is gradually increased, Its physical state also gradually changes from glass state to high elastic state, and finally becomes viscous flow state, reaching complete plasticization. As the screw keeps rotating, the uniformly plasticized molten material is extruded from the mouth of the molding die in equal pressure and equal amount to become plastic products. After cooling and shaping, the extrusion of plastic products is completed.
3.1.5 single screw extruder
3.1.5.1 structural features
Single screw extruder is the most widely used general-purpose extruder in the extruder product series. Its structural feature is that the extrusion system of the extruder is composed of a screw and a barrel. The specific structure is shown in Figure 3-2. Single screw extruder is widely used. For the extrusion of different thermoplastics, as long as the structural form of the screw is changed, the production of extruded products with different raw materials can be completed; The equipment structure is relatively simple, the cost is low, the use and operation are easy to master, and the maintenance and overhaul of the equipment are also relatively convenient.
3.1.5.2 specifications, models and basic parameters
Model marking of extruder: it is stipulated in the domestic rubber and plastic machinery standard gb/t12783-91, and the model mark on the label of extruder
The model on the label of the extruder indicates that the extruder is SJ; Plastic exhaust extruder is SJP; The plastic foaming extruder is SJF; The plastic feed extruder is SJW; The extruder for plastic shoes is sje; Step type plastic extruder is SJJ; Twin screw extruder is SJS; Conical twin-screw extruder is sjsf; The multi screw extruder is SJD. The second grid represents auxiliary equipment, code f; If it is an extrusion unit, the code is e. The fifth parameter refers to the length diameter ratio of the screw straight to the screw. The sixth box refers to the design sequence of products, which is arranged in the order of letters A and BC. The first design is not marked with the design number. For example, s]-45x25, this model represents: plastic extruder, research drawing of screw diameter, and the length diameter ratio of screw is 25; 1。 Do not mark when the length diameter ratio of the screw is 20:1. See standard jb/t8061-1906 (table 31) for basic parameters of extruder for extrusion molding of high street polyethylene products, table 3-2 for basic parameters of extruder for extrusion molding of polypropylene products, and standard z195009.1-88 (table 3-3) for basic parameters of extruder for extrusion molding of PVC products= 10= ① screw diameter refers to the outer diameter of the threaded part of the screw, which is generally expressed in D, and the unit is mm. ② The length diameter ratio of screw refers to the ratio of the length of screw thread to the diameter of screw. Expressed in l/d. ③ The speed range of the screw refers to the minimum speed and the maximum speed when the screw works. Expressed in nmin~nmax, the unit is r/min. ④ The power of screw working rotary drive motor is expressed in PM, and the unit is kW. The heating power of the barrel refers to the electric power when the barrel is heated by electricity. It is generally expressed in P, and the unit is kW. ⑥ The number of barrel heating sections means that the barrel heating is controlled by several temperature zones. ⑦ Extruder productivity refers to the production capacity of extruder in unit time. Expressed in Q, in kg/h. ⑧ Nominal specific power refers to the comprehensive index of motor power required by the extruder to produce plastic products per hour. It is expressed in P, that is, p=p/qmx, and the unit is kw/ (kg/h). 9 specific flow refers to the quality of plastic products that can be produced by each rotation of the screw. This value reflects the production efficiency of the extruder, expressed in q=q real class /n real class, and the unit is (kg/h) / (r/min). ⑩ Center height refers to the height between the center line of the screw in the barrel of the extruder and the bottom plane of the base. Expressed in H, in mm.
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