The Three Types of Blow Moulding Methods

The world of plastics and manufacturing is multifaceted and quite complex, featuring a large number of different process that can be used to produce plastic items. One of the methods available today is that of blow moulding.  Blow moulding is a plastic manufacturing process commonly used to create hollow plastic parts, like liquid containers, plastic drums and storage tanks. Blow moulding enables companies to mass-produce plastic items quickly and effectively.

The manufacturing process for blow moulding involves the melting of raw material, which is generally a thermoplastic. Thermoplastics include polyethene, polypropylene and polyvinyl chloride.  The thermoplastic used starts off the form of small granules or pellets, which are melted before being formed.

There are currently three main methods used to create blow moulded products. The different methods each have their individual advantages and disadvantages, and it is up to manufacturers to select the method that best suits their needs.  These methods are:

Extrusion blow moulding:

Extrusion blow moulding is the process best suited to creating complex product shapes. During this process, plastic is melted and then extruded into a hollow tube, also known as a parison. The parison is closed, and the desired shape is achieved by blowing air into the warm plastic. Once the piece is cooled, it is ejected. Extrusion blow moulding can be either continuous or intermittent.

Injection blow moulding:

During this process, plastic or polymer is injected into a core pin, then the pin is rotated by the blow moulding machine until the plastic is inflated into the desired shape. Afterwards, it is cooled and ejected in one simple process. This method is less common than the other two, as it is more time consuming than the other methods.

Injection stretch blow moulding:

Injection stretch blow moulding is a variation on injection blow moulding but uses less material than injection blow moulding. During stretch blow moulding, plastic is moulded into a solid preform. This pre-form gets fed into a stretch blow mould machine and heated. Once heated, the item is blown into a plastic bottle with forced compressed air. This process is commonly used to produce soft drink bottles.

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