single-screw machine and twin-screw machine

Weifang Jin Shida Plastic Machinery Factory to provide you with explanations: The basic principle of plastic extruder Spiral feed, the principle of the material Extruder out of the machine function is the use of heating, pressure and shear, etc., the solid plastic into a uniform Consistent melt, and the melt to the next process. Melt production involves blending masterbatches and other additives, blending resins, and then pulverizing. The finished melt must be uniform in concentration and temperature. Pressurization must be large enough to extrude the tacky polymer. Extruder through a barrel with a screw and spiral to complete all of the above process. Plastic pellets enter the barrel through the hopper at one end of the barrel and are then routed to the other end of the barrel by a screw. In order to have sufficient pressure, the thread depth on the screw drops as the distance to the hopper increases. External heating and internal heat generated by friction between the plastic and the screw cause the plastic to soften and melt. Is a simplified extruder. Different polymers and different applications, the design requirements of the extruder are often different. Many options relate to the discharge port, the multiple feed openings, the special mixing device along the screw, the cooling and heating of the melt, or the absence of an external heat source (adiabatic extruder), a relative change in the gap between the screw and the barrel , And the number of screws and so on. For example, twin-screw extruders provide more thorough melt mixing than single-screw extruders.
1. Squeeze the system
The extrusion system consists of a screw, a barrel, a hopper, a head, and a die. The plastic is plasticized into a uniform melt by the extrusion system and is continuously extruded from the head by the screw under the established pressure in the process.
(1) Screw: The most important part of the extruder, which is directly related to the application of the extruder and the productivity, made of high strength and corrosion resistant alloy steel.
(2) barrel: a metal cylinder, generally with heat, high compressive strength, strong wear-resistant, corrosion-resistant alloy steel or composite steel lined steel pipe made. Barrel and screw with the realization of the smashing of plastics, softening, melting, plasticizing, exhaust and compaction, and to the molding system for the continuous delivery of rubber. The length of the barrel is generally 15 to 30 times its diameter, so that the plastic is fully heated and plasticized as a principle.
(3) hopper: the bottom of the hopper equipped with truncation device, in order to adjust and cut off the stream, the side of the hopper equipped with visual hole and calibration metering device.
(4) nose and mold: nose from the alloy steel sleeve and carbon steel jacket composition, the nose is equipped with forming mold.
The role of the nose is the rotational movement of the plastic melt into parallel linear motion, uniform and smooth into the die set, and give the plastic with the necessary molding pressure. Plastic plastic compaction in the barrel, the porous filter plate along a certain flow through the neck neck into the nose molding machine, die core die sets appropriate fit to form a reduced cross-sectional annular gap so that the plastic melt in the Around the core wire to form a continuous dense tubular coating. In order to ensure that the plastic flow path in the nose is reasonable and eliminate the dead space of accumulated plastic, a shunt sleeve is usually arranged. In order to eliminate the pressure fluctuation when the plastic is extruded, a pressure equalizing ring is also provided. The nose is also equipped with mold correction and adjustment of the device, easy to adjust and correct mold core and die sets of concentricity.
According to the extrusion machine extrusion direction of the head and the screw center line angle, the head is divided into bevel head (angle 120o) and right-angle head. The head of the shell is bolted to the fuselage, the nose of the mold with a mold core to sit and nut fixed to the nose into the port, the front of the mold core with a mold core, mold core and core seat The center of the hole, for through the core line; in front of the nose are equipped with pressure ring, for equalization pressure; extrusion molding part by the die sets and die sets, the die sleeve position by the bolt through the support to adjust , In order to adjust the relative position of the mold sleeve to the mold core to facilitate the adjustment of the uniformity of the thickness of the extrusion coating. The nose is equipped with heating device and temperature measuring device.
Transmission system
The function of the drive system is to drive the screw, which supplies the required torque and speed of the screw in the extrusion process, usually composed of a motor, a reducer and a bearing.
3. Heating and cooling device
Heating and cooling are necessary conditions for the plastic extrusion process.
(1) The extruder is usually used for electric heating, divided into resistance heating and induction heating, heating film installed in the fuselage, neck, head of the various parts. Heating device by the external heating tube plastic, so that the temperature, in order to achieve the required temperature of the process operation.
(2) The cooling device is set to ensure that the plastic is in the temperature range required by the process. Specifically, in order to exclude excess heat generated by the shear friction of screw rotation, to avoid the temperature is too high to break down the plastic, scorching or setting difficult. Cylinder cooling is divided into two kinds of water-cooled and air-cooled, the general small and medium-sized extruder with air-cooled more appropriate, large are more water-cooled or combined with the two forms of cooling; screw cooling is mainly used in the center of water-cooled, the purpose is to increase the solid material delivery rate , And stabilize the amount of plastic, while improving product quality; but in the hopper cooling, one is to strengthen the role of solid material transport to prevent the plastic particles due to temperature rise blockage mouth, and second, to ensure that the transmission part of the normal work.