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What Is Blow Moulding And How Do I Find Blow Moulders?

Blow moulding uses a split tool that is similar to that used in injection moulding but has no core, just a cavity. Tooling costs are, therefore, lower.

Hot extruded plastic forms a tube that has one end open, which is called a parison. The mould closes over the parison, and compressed air then forces the material outward to conform to the inside shape of the mould. Once cooled, the mould is opened and the hollow component is removed.

Examples of blow moulded products are bottles, fuel tanks, watering cans and containers.

Visit here to contact the leading UK companies that can provide you with advice and quotes for your blow moulding project.

Watch this video of an extrusion blow moulding machine in action - Video courtesy of GDK represented in the UK by 3PA.

What are the Main Blow Moulding Processes?

Extrusion blow moulding
Extrusion blow moulding is the most common and simplest production method and is detailed above. It can produce a wide range of products for a minimum set up cost and in high volume. It is, however, difficult to control wall thickness, scrap rates are relatively high, and products tend to have high levels of flashing around the split line (excess plastic that escapes between the two halves of the tool) that has to be removed.

Injection blow moulding
Injection blow moulding is a hybrid of injection moulding and blow moulding. It involves dispensing a more precise amount of material onto a core pin, that then rotates into a blow moulding station. The process is therefore limited to smaller items, but more complex forms can be created, with minimal variation and no requirement for trimming off excess material.

Injection stretch blow moulding
Injection stretch blow moulding is often used to make PET bottles and adds a material stretching process. It is a two-stage process that involves pre-forms to be injection moulded in advance. The pre-forms are then transferred to the stretch blow station where they are initially reheated. The production rate can be much higher than with the other two forms of blow moulding, but it is much more expensive to set up.

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