Blow Molding Classification

April 20, 2022

Blow molding can be divided into two categories: extrusion blow molding and injection blow molding. The main difference between the two is the preparation of the parison, and the blow molding process is basically the same. On the basis of these two types of molding methods, there are extrusion-stretch-blow molding and injection-stretch-blow molding and co-extrusion blow molding and co-injection blow molding of multi-layer blow molding.

1.Extrusion blow molding Extrusion blow molding is a blow molding method with the largest output and good economy. Extrusion blow molding can be divided into continuous extrusion method and intermittent extrusion method according to its different discharging methods. The molding process is to take a section of tubular parison extruded from the extruder, put it into the mold while it is still hot, close the split mold and clamp the upper and lower ends of the parison, and then use a blow pipe to inject compressed air to make the mold. The blank is inflated and formed against the surface wall of the cavity. After pressure maintaining, cooling, shaping and exhausting, the mold is finally opened to take out the plastic part.

2. Injection blow molding Injection blow molding is to first form a tube blank on a hollow punch with micro-holes on the peripheral wall of the injection mold, and then move it into the Blow Mold while hot, and press compressed air through the pipe of the mandrel. The parison is inflated and closely adhered to the cavity wall of the mold, after pressure maintaining, cooling, shaping, exhausting, and finally the mold is opened to take out the plastic parts.

3. Injection stretch blow molding Injection stretch blow molding is to first make a parison by extrusion or injection, and then process the parison to an appropriate stretching temperature, through internal (with a stretching mandrel) or external ( The mechanical force of the stretching tool is used to carry out longitudinal stretching, and at the same time or later, it is blown by compressed air for transverse stretching, and finally the product is obtained.

4. Multi-layer blow molding Multi-layer blow molding refers to a parison with more than two layers of blank walls made by a multi-layer extrusion molding process or an injection molding process, which is layered and bonded together, and then blow molding to obtain a multi-layered parison. Forming method of hollow products.

5. Sheet blow molding Sheet blow molding is to reheat the calendered or extruded sheet to soften it, then put it into the mold cavity, and blow compressed air between the sheets after the mold is closed And the processing method of forming hollow plastic parts.

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