Blow molding: It is a method of clamping molten thermoplastic raw materials extruded from an extruder into a mold, and then blowing air into the raw materials. The molten raw materials expand under the action of air pressure, adhere to the wall of the mold cavity, and finally cool and solidify into the desired product shape.
Blow molding can be divided into two types: thin film blow molding and hollow blow molding:
1. Film blow molding
Thin film blow molding is the process of extruding molten plastic into a cylindrical thin tube from the annular gap of the extruder head mold. At the same time, compressed air is blown into the inner cavity of the thin tube from the center hole of the head, and the thin tube is blown and expanded into a larger diameter tubular thin film (commonly known as a bubble tube). After cooling, it is rolled up.
2. Hollow blow molding
Hollow blow molding is a secondary molding technology that uses gas pressure to blow and expand the rubber like blank closed in the mold cavity into hollow products. It is a method for producing hollow plastic products. Hollow blow molding has different manufacturing methods according to the blank, including extrusion blow molding, injection blow molding, and stretch blow molding.
1) Extrusion blow molding: Extrusion blow molding is the process of using an extruder to extrude a tubular billet, clamp it in the mold cavity while it is hot, seal it, and then blow compressed air into the inner cavity of the billet to form it.
2) Injection blow molding: The blank used is obtained by injection molding. The blank is left on the core mold of the mold, closed with a blow molding mold, and compressed air is introduced from the core mold to blow and cool the blank. After demolding, the product is obtained.
Advantages:
The product has uniform wall thickness, small weight tolerance, less post-processing, and small waste corners; Suitable for producing small precision products in large quantities.
3) Stretch blow molding: Place the billet that has been heated to the stretching temperature in the blow molding mold, use a stretching rod for longitudinal stretching, and use compressed air blown in for transverse stretching and blowing to obtain the product.
Application:
1. Film blow molding is mainly used to manufacture plastic films;
2. Hollow blow molding is mainly used to make hollow plastic products (bottles, packaging barrels, spray cans, fuel tanks, cans, toys, etc.).
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