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| Structural form | ² Specifically designed for manufacturing hollow products without bottom holes or fully enclosed ones.
² It can achieve integrated molding of complex curved surfaces without the need for assembly. |
| Typical application | ² Bottles, barrels, boxes, fuel tanks, toys, containers, complex piping components, etc. |
| Main materials | ² PE (Polyethylene), PP (Polypropylene), PVC (Polyvinyl Chloride), PET (Polyester), etc. thermoplastic plastics |
| Forming principle | ² By analogy with glass blowing, a heated and softened tubular blank is placed in a closed mold.
² Compressed air is introduced to cause it to expand and closely adhere to the mold cavity. ² After cooling and shaping, it is demolded. |
| Wall thickness control | ² The wall thickness is determined by the extrusion/injection parameters and blow-up ratio of the billet.
² Corners are prone to thinning, and uniformity is not as good as injection molding. ² Optimization needs to be achieved through the storage head or program control. |
| Surface marks | ² The products usually have mold lines (flash), which need to be trimmed later in extrusion blow molding;
² Injection blow molding can achieve no edge trimmings and high bottle mouth accuracy. |
| Residual stress | ² Low-pressure molding results in small internal stress, good toughness and strong impact resistance.
² But the dimensional repeatability accuracy and surface finish are generally lower than those of injection molding. |
| Extrusion Blow Molding | ² The most commonly used method, a tubular mold is directly extruded and then blown to form.
² Suitable for large-sized containers (from a few liters to several thousand liters) and handleable products; ² The equipment and molds have low costs production (accounting for approximately 75%-90% of the market). ² The disadvantages are poor uniformity of wall thickness and the flash edges that need to be trimmed. |
| Injection Blow Molding | ² First, a molded blank with a bottom is injection-molded, then it is blown to expand.
² The bottle mouth has high precision, no burrs, uniform wall thickness, good hygiene. ² It is often used in medical packaging and high-precision containers. ² The disadvantages are that the molds are expensive, only suitable for small-sized items (usually < 4L), and without handle. |
| Stretch blow molding | ² Before the blow-up process, two-way stretching enhances strength and transparency.
² Specifically used in packaging PET bottles with high-barrier. ² Requires specialized equipment and high-purity raw materials. |
| Multi-layer Blow Molding | ² A multi-layer material produced by co-extrusion, high barrier and chemical resistance,
² It is used for high-end chemical, food packaging, automotive fuel tanks. |
| Advantages | ² Suitable for lightweight, shock-resistant, and chemically resistant scenarios;
² The mold investment is approximately 1/3 to 1/2 of that for injection molding, ² suitable for medium to large-scale production of hollow containers. |
| Limitations | ² Large dimensional tolerance, not suitable for high-precision mating parts;
² Difficult to control the wall thickness of large components, prone to deformation or uneven sealing; ² Although a wide range of materials are available (PE/PP/PVC/PET, etc.), the application of engineering plastics is limited. |
| Typical applications | ² Daily chemical packaging bottles, industrial barrels and tanks, automotive fuel tanks/ventilation ducts, hollow toys, large storage tanks, etc. |
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