What are the three types of blow Moulding?

There are three types of production process forms of 

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Blow Molding Machine

: extrusion blow molding process, injection blow molding process, and stretch blow molding process.

blow molding process

, one kind manufacturing methods of thermoplastics. Using fluid pressure to inflate the hot parison closed in the mold into a hollow product. All those with a melt index of 0.04-1.12 are relatively excellent hollow blow molding materials, such as polyethylene, polyvinyl chloride, polypropylene, polystyrene, thermoplastic polyester, polycarbonate, polyamide, cellulose acetate and poly. polyethylene are most commonly used among them.

The processes methods of different production are also quite different.

1. Extrusion Blow molding

The extrusion 

blow molding 

process is to extrude the parison. When the parison reaches a predetermined length, the parison is clamped and positioned, then the head of the parison is formed or sized. Compressed air into the parison to inflate it close to the mold cavity, so that to form a product. After the product is cooled and shaped in the mold, the mold is opened to release the product, and deflashing the product.

2. Injection blow molding

The injection blow molding process is more suitable for the production of some large-batch, but small-volume products. Cosmetics, daily necessities, medicine and food packaging in the daily production are all use injection blow molding. The product has a uniform wall thickness, and there is less waste without joint line.

3.Stretch blow molding

Stretch blow molding is a process in which parison, stretching, and blow molding are completed in one machine line. The parison is semi-finished product in the production process. After cooling, the cold parison is reheated for stretching and blow molding. Oriented stretch blow molding after extrusion molding, maintain a certain stretching speed, orientate before blow molding, after stretching, transparency, impact strength, hardness and rigidity, surface gloss and barrier properties are all improved.The production process of stretch blow molding is to control the temperature of the parison at a temperature lower than the melting point and use the principle of two-generation to increase the strength of the product.

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Blow molding is a manufacturing process that’s designed to create hollow parts. It’s called “blow molding” because it typically involves blowing air or inert gas into the center of a heated object. As the air or inert gas accumulates, it creates an enlarged cavity inside the object. The object is then allowed to cool and harden, after which it will feature a hollow interior. Like with other manufacturing processes, though, there are different types of blow molding, each of which works in a different way. In this post, you’ll learn more about the most common types of blow molding, including extrusion, injection and injection stretch.

Extrusion Blow Molding

Perhaps the most common type of blow molding process is extrusion. With extrusion blow molding, plastic is heated until it turns from a solid state to a liquid state. The liquefied plastic is then forced into an extrusion machine. The extrusion machine also forces air into the melted plastic, essentially inflating it to create a hollow interior. Once finished, the plastic is cooled — typically at room temperature — and the newly created hollow object is ejected and removed from the mold.

Extrusion blow molding can be classified as either continuous or intermittent. The former involves the continuous, nonstop extrusion of the parison, whereas the latter involves interval-based extrusion of the parison.

Injection Blow Molding

Another common type of blow molding process is injection. As the name suggests, injection blow molding involves the “injection” of material, including heated glass and plastic, into a mold. The heated material is typically forced into a core pin, after which the pin rotates around a molding station where the heated material is inflated and then cooled.

Injection blow molding isn’t as popular as extrusion. Nonetheless, it’s a viable molding process for small, hollow objects. Injection blow molding is used to make everything from medical devices to soda bottles.

Injection-Stretch Blow Molding

There’s also injection-stretch blow molding. Injection-stretch blow molding is a variant of standard injection blow molding. It can be performed in either one step or two steps. Both types of injection-stretch blow molding, however, involves stretching the parison. The heated material is literally stretched so that it creates a hollow interior.

To recap, there are three main blow molding processes: extrusion, injection and injection-stretch. Extrusion blow molding involves extruding heated material, injection blow molding involves injecting heated material into a mold, and injection-stretch blow molding involves stretching heated material.

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