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How to distinguish whether plastic products are injection molding or blow molding?

2022-05-02 Hits: 41 views

Today, let’s talk about how to distinguish whether plastic products are injection molding or blow molding.

Plastic molding is an engineering technology that involves various processes that transform plastics into plastic products. Commonly used processing methods are injection molding and blow molding.

Let’s talk about injection molding first.

Injection molding is a method in which plastic raw materials are uniformly plasticized in a heating barrel, and then pushed into the cavity of a closed mold by a plunger or a moving screw. Injection molding is suitable for almost all thermoplastics. In recent years, injection molding has also been frequently used to mold some thermoset plastics. Because the molding cycle of injection molding is short, from a few seconds to a few minutes, the mass of the molded product can range from several grams to tens of kilograms, and it can form a molded product with a complex shape, precise dimensions, and metal or non-metal inserts at one time. Therefore, the method has strong adaptability and high production efficiency.

Let’s talk about blow molding.

Blow molding is a method in which the hot parison closed in the mold is blown into a hollow product by gas pressure, or a tube parison is blown into a tube film without a mold. This method is mainly used in the manufacture of various packaging containers and tubular films. Generally, those with a melt index of 0.04 – 1.12 are relatively good hollow blow molding materials, such as polyethylene, polyvinyl chloride, polypropylene, polystyrene, thermoplastic polyester, polycarbonate, polyamide, cellulose acetate and polyamide. Acetal resins, etc., among which polyethylene is used more. Extrusion blow molding is commonly used; that is, the plastic is first made into a bottomed parison by extrusion, and then the parison is moved to a blow mold to blow it into a hollow product.

In addition to injection machines and extruders, injection molding equipment and blow molding equipment are mainly blow molding molds. The blow mold is usually composed of two parts, which are provided with coolant channels, and the small holes on the parting surface can be inserted into the air blowing pipe.

So, how do we distinguish whether a plastic product is injection molded or blow molded?
Generally speaking, there is a very simple and important difference point that injection molding parts have a glue inlet, while blow molding parts do not have a glue inlet. Injection molding products generally have a smooth surface, while blow molding products are mostly matte. Blow molding can be used for hollow products, but injection molding is not. Blow molding is generally based on HDPE, while injection molding is suitable for various plastics. Injection molding is relatively widely used for complex structures. Blow molding is generally used for hollow products, especially those with large bottle body and small mouth, and injection molding cannot remove the core.

Blow molded products are all hollow; injection molding has an injection port, so the molded product will have a small part similar to the tail, which will be cut off in the next process, but it can be found if you observe carefully.

The above is how to distinguish whether a plastic product is injection molded or blow molded.