PLASTIC MOLDING PROCESS (2) - BLOW MOLDING

PLASTIC MOLDING PROCESS (2) - BLOW MOLDING

Blow molding: the molten thermoplastic material extruded from the extruder is clamped into the mold, and then the air is blown into the raw material. The molten raw material expands under the action of air pressure, fits to the mold cavity wall, and finally cools to curing into the desired product shape.Blow molding is divided into two types of film blow molding and hollow blow molding:
1.Film blow molding:molten plastic is extruded from a circular thin tube in the annular gap of the die of the extruder head. At the same time, compressed air is blown into the inner cavity of the thin tube from the center hole of the head to blow the thin tube into a diameter larger tubular film (commonly known as bubble tube), take up after cooling. 
2.Hollow blow molding is a secondary molding technology that uses gas pressure to blow the rubber-like parison closed in the mold cavity into a hollow product, and is a method for producing hollow plastic products. Hollow blow molding differs according to the method of manufacturing the parison, including extrusion blow molding, injection blow molding, and stretch blow molding.
1) Extrusion blow molding: Extrusion blow molding is to extrude the tubular parison with an extruder, clamp it in the mold cavity and seal the bottom while hot, and then blow compressed air into the inner cavity of the tube to form the inflation.
2) Injection blow molding: The parison used is obtained by injection molding. The parison is left on the mandrel of the mold. After the mold is closed with the blow mold, compressed air is introduced from the mandrel to blow up the parison and cool it. The product is obtained after demolding.
Advantage:
The products have uniform wall thickness, small weight tolerance, less post-processing, and small waste corners; suitable for the production of large-scale small fine products.
3) Stretch blow molding: place the parison that has been heated to the stretching temperature in the blow mold, longitudinally stretch with the stretch rod, and transversely stretch and blow with the compressed air blown in to obtain the product method.
Application:
1. Film blow molding is mainly used to make plastic thin molds;
2. Hollow blow molding is mainly used for making hollow plastic products (bottles, packaging barrels, watering cans, fuel tanks, cans, toys, etc.).
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