Extrusion is one of the basic molding methods of plastic molding. Most of the thermoplastics can be processed by this method. It has the following characteristics: the production process is continuous, so its products are continuous, high production efficiency, investment Less, the extrusion process is carried out, the plastic heating, friction shear, so that it was viscous flow state, in the case of pressure, so that it has a certain shape of the die made of cross-section and die shape similar Of the continuum, and then by cooling, so that it has a certain geometry and size of the plastic, get the required products.
The product has high strength, high transparency and fine heat resisting quality; sanitation property and physical property is better than organic glass.
| Type | Clear pvc plastic sheet |
Color | Clear, Transparent, White, Black, Colorful..... |
Thickness | Extruded: 0.2mm to 15mm |
Transparency | Transparent, Semi-transparent, Opaque |
Surface | Glossy, Frosted/Matt, Embossed, with masking |
Application | Thermo forming for tool,fishing gear,packing,folding,printing, electronics industry. |
Feature | High gloss, without crystallization point, without flow line, no impact fracture |
Specification | Extrusion line: 0.2mm-3mm width with any size length |
Production process: extrusion → stereotypes cooling → printing → cutting → inspection → packaging → storage
First, the production line composition:
Extruder from the host, head, stereotypes cooling device, printing device, cutting device and other components.
(A) host:
1, screw barrel: screw is the heart of the extruder, all directly or indirectly to the screw as the center, it is the material for transportation, mixing and plastic, a direct impact on product quality, according to the material in the screw changes , Usually the screw is divided into three sections: feeding section, compression section (melting section), measurement section (equalization section).
Feeding section: generally the first area, double screw feeding section of the deep groove, larger volume, is conducive to increase the input and compression of the material, this area temperature is generally not too high, otherwise there will be melt adhesion in the feed Mouth surface, causing the material into the extruder failure or bridge break material.
Compression section: generally two, three two areas, this section is characterized by screw pitch change, tooth breaking teeth and thread width uniform changes in the material subject to a strong squeeze, the material under shear to get a good plastic And mixing, this section has a vacuum vent, the material in the gas discharge.
Metering section: This section of the screw groove in the entire screw in the shallowest, the smallest volume, its screw and thread form is basically the same, molten plasticized material in this section by further compression, and make plasticized evenly refined, As the material in this section of the movement is more uniform, reducing the material out of the volatility, improve the stability of the material into the mold.
Double screw according to the size of the center of the screw can be divided into the type of engagement and non-meshing type: according to the rotation direction can be divided into the same direction of rotation and different rotation; according to the relative position of the screw axis can be divided into parallel twin- Cone for PVC pipe; profile bellows, parallel for large products: such as D400 above pipe.
Our commonly used extruder is an opposite tapered twin screw extruder, its working characteristics:
(1) Forced delivery: In a fully rotating twin screw extruder, the two screws engage each other and the threads of one screw are inserted into the grooves of the other screw, , No backflow or stagnation occurs, regardless of whether the groove is filled, the transmission speed remains essentially unchanged, with a strong transport.
(2) mixing: As the two screw meshing, the material in the extrusion process than the single screw extruder is far more complex movement, continue to be vertical, horizontal shear mixing, resulting in a lot of heat, so that the material The residence time in the barrel is shorter than that of the single screw extruder.
(3) Self-cleaning effect: If the retention time is too long, it will cause the degradation of the material to seriously damage the quality of the product. Therefore, the material should be removed in time, especially for heat-sensitive plastic PVC , The reverse rotation of the twin screw at the engagement, the thread and the groove there is a difference in speed, in the process of mutual rubbing, peeling off the material attached to the screw, the screw to self-cleaning.