Blowing typologies: extrusion blowing and injection blowing

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Blow moulding technology for transformation of plastic material can be classified in two types: by extrusion and by injection.

extrusion blow moulding | injection blowing

The processes of blowing by extrusion and injection

The processes of blowing by extrusion and injection, in spite of being part of the same production technology, are arranged in different phases according to the type.

  • In blow moulding by extrusion, plastic is melted and extruded (“pushed”) in a hollow tube. The extrusion process occurs throughout the compression of the material in a matrix, which pushes the plastic material towards the extrusion head. Thanks to the walls of the extruder and to the electrical resistances, the plastic material is melted and then funnelled in a metal mould. Air is blown thereinto, inflating the plastic and obtaining the final product shape.
  • In the blow moulding by injection, the plastic material is printed on a central pin, which is rotated in a blowing station, and then it is inflated and cooled. The blowing machine melts the plastic, which is pushed into a manifold and injected into a heated cavity. The mould becomes the outer shape and is coupled around a rod, which is the internal shape of the object. At this point, the die is released, and the central rod is rotated and locked in the cavity; this way the compressed air is allowed inside, and by inflating, shapes the finished product.

extrusion blow moulding | injection blowing

The strategic qualities of the processes of blowing by extrusion and by injection include low cost, high production rates, the possibility of shaping complex parts, adaptability to produce large volumes and few restrictions on the design. Fisem has gained thirty years of experience in the production of blown articles, using the technology of the plastic blowing by extrusion, supporting its customers with many types of technical items bearing different levels of complexity and offering the customer the possibility of co-moulding different components and other specific technical requests nonetheless achieving and keeping a high degree of standardization of the workpiece and constant quality throughout the whole production process.

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