Plastic extrusion machine extrusion machine is the host, which consists of extrusion system, transmission system and heating and cooling system.
1, the extrusion system
Screw extrusion system includes Pole, barrel, hopper, nose, and mold, plastic extrusion systems and plastics by melt into a uniform, and in the process established under the pressure of being head screw continuous extrusion.
(1) Screw: extruder is the most important parts, it is directly related to the extrusion machine and productivity applications, from high-strength corrosion-resistant alloy steel.
(2) Barrel: a metal cylinder, usually with heat, high compressive strength, extremely resistant, corrosion-resistant alloy steel or steel lined composite steel pipe. Barrel and screw together to achieve the crushing of the plastic to soften, melt, plastics, exhaust, and compaction, continuous and uniform delivery to the molding compound system. Generally the length of its barrel diameter of 15 to 30 times, so that the plastic is fully heated and fully the principle of plastics. (3) Hopper: Hopper bottom with cut off device to adjust and cut off the flow of material, the side with the hole hopper and metering device calibration.
(4) head and die: inside the head by a steel cover and carbon steel jacket structure, the nose that has the mold, the nose is the role of the rotation of the plastic melt into a parallel straight line, uniform steady import mold sets in, and give the necessary plastic molding pressure. Plastics plastic compaction in the machine barrel, the porous plate along a certain flow into the nose through the neck and head mold, punch die sets with the appropriate form of circular cross-section decreasing the gap, so that the plastic melt in the wire around the tube to form a continuous dense coating. To ensure a reasonable flow of plastic within the nose, eliminating the accumulation of plastic corners, often placed a shunt sleeve, plastic extrusion for the elimination of pressure fluctuations, but also set the grading ring. Machine head is also equipped with calibration and adjustment of the mold device, easy to adjust and correct mold core and sleeve concentricity.
Extruder head according to material flow direction and the angle between the centerline of the screw, will head into the nose angle (angle 120o) and right-angle head. Head shell is bolted to the body, head mold core within the mold has to sit, and fixed with a nut into the line port in the head, punch the front seat is equipped with punch, punch and punch seat center hole, used to wire in front of the nose with grading ring for balanced pressure, squeeze bag forming part of the seat from the mold and die sets of sets of components, die sets the position of the bolt through the support to be adjusted to adjust the model sets the relative position of the mold core, easy to adjust the extruded layer thickness uniformity, head outside with heating and temperature measurement devices.
2, transmission system
Transmission is the role of driving the screw, screw in the extrusion process supply the required torque and speed, usually by electric motors, reducers and bearings and other components.
In the same structure under the premise of gear manufacturing costs roughly proportional to its dimensions and weight. Because the shape and weight reducer big, mean consumption of materials, manufacture more than the other bearings are used in relatively large, so that manufacturing costs.
The same screw diameter extruder, high speed and efficiency than conventional extruder extruder consumes more energy, electrical power increased twice, the appropriate gear to increase the frame size is necessary. However, the high screw speed, which means a low reduction ratio. The same size reducer, the low gear ratio, compared with the large reduction ratio of gear modulus increases, the gear's ability to withstand the load increases. Therefore, weight reducer size increases, not with the motor power increases linearly proportional. If out of the amount of the denominator, divided by the weight of gear, high speed and efficient extrusion machine thanks to a small, ordinary extruder thanks to a large.
Per unit of production volume, high efficiency extruder motor power and gear weight is small, fast and efficient means of extruder machine manufacturing costs per unit of production than conventional extruder low.
3, heating and cooling equipment
Heating and cooling of plastic extrusion process to carry out the necessary conditions.
(1) extruder now commonly use the electric heating, resistance heating, and induction into the heating, heating plate mounted on the body, neck machine, all parts of the nose. Heating by an external heating cylinder of plastic, so that warming in order to achieve the required process operation temperature.
(2) cooling of plastic in the process is to ensure that the required temperature range is set up. Specifically, the screw is rotated in order to exclude the excess heat generated by shear friction, in order to avoid overheating the plastic break down, scorch or shape difficult. Barrel cooling into water and air-cooled two most small and medium extruder more appropriate use of air-cooled, large is to use more cooling water, or combination of two forms; mainly center screw cooling water, the purpose is to increase the delivery of solid materials rate, stable volume of the plastic, while improving product quality; but in the hopper at the cooling, one to strengthen the role of the delivery of solid materials, heating the plastic pellets to prevent sticky discharge port plug, the second part is to ensure the transmission to work.
