Extrusion blow molding in plastics processing

Extrusion blow molding: a tried-and-tested process for the production of hollow bodies

Whether canisters, drums, ventilation ducts, or ampoules – when used to produce hollow bodies, extrusion blow molding makes it possible to realize extreme shapes and designs efficiently. A distinction is made between continuous and intermittent extrusion. The former is regarded as the basic process and is used to produce a wide range of packaging. Here, the plastic melt is forced out of the nozzle continuously and slowly. In the latter process, the melt is first collected in an accumulator head, and is only pushed quickly out of the nozzle head by a piston once the filling volume has been reached. This technique is therefore particularly suitable for long and heavy extruded plastic hoses. In technical extrusion blow molding, the entire process – from extrusion blow molding itself through final processing – is closely matched to the specific product. Robots, machines, and tools are likewise adapted on a project-by-project basis and are therefore only used for the predefined products

The downstream equipment – as used for cutting, drilling, stacking, or extraction operations, for example – is also customized. To realize customer preferences as effectively as possible, Greiner Assistec also specializes in intermittent extrusion. This method is mainly used to produce technical parts, such as condensate traps for washing machines and dryers or feed pipes for dishwashers.

At Greiner Assistec, we can respond precisely to our customers’ individual needs. We know which equipment particular products require and are therefore able to coordinate products, technologies, processes, and quality standards to achieve optimal results.

The advantages of extrusion blow molding:

  • Ability to produce extreme geometries
  • Low tooling costs
  • Multilayer components for tanks, etc.

Three extrusion blow molding categories

This technology is primarily used to manufacture packaging and technical parts. Greiner Assistec uses both continuous and intermittent extrusion techniques.

The majority of plastic packaging used in the bottle and container industry consists of a single layer and is therefore produced using single-layer material. The single-layer continuous extrusion process is the basic method used in extrusion blow molding to make blow-molded items from an extruded tube. For this technique, Greiner Assistec uses extrusion heads that have been technically designed to guarantee uniform material distribution even under different throughput requirements and with extremely short material and color changeover times.

This technology is primarily used to manufacture consumer goods and industrial packaging. Greiner Assistec uses both continuous and intermittent extrusion techniques in this area, too.

The term “multilayer” or “coextrusion” refers to the simultaneous processing of multiple materials that are added to the extrusion head. This results in what is known as an extruded multilayer tube. For particularly demanding applications, the equipment used to produce the multilayer extrusion head can comprise up to seven layers.

The inclusion of a barrier layer in the production process is easily achieved by Greiner Assistec. Examples of use include protecting food products from environmental influences or oxidation, and preventing chemicals from being released into the environment through permeable packaging. By applying pigments only to the thin, outer decorative layer, material costs can be minimized and tactile effects, such as rough finishes or rubber coatings, can be produced at the same time. Further savings in material costs can be achieved by integrating recycled materials or a material mix – involving bioplastics, for example – into a separate layer.

This technology is based on the use of robots and is particularly suited to the production of technical parts such as pipes. It involves a robot placing a long and thin extruded pipe produced by the machine into a mold.

3D blow molding technology was developed to meet the requirements of the automotive industry for the manufacture of pipes and tubes in various designs. In addition to the automotive market, the technology is also used for other segments, such as the production of assemblies for household appliances, which are often fitted with long tubes in complex shapes. At Greiner Assistec, we are able to support our customers with innovative ideas to suit these applications, too.

The process of 3D extrusion blow molding begins with the production of a semimolten plastic tube, which is then processed in various ways. The tube can be sucked through a closed mold and then blown out of the mold after the inner walls have been formed. This process is also known as 3D suction blow molding, which is particularly well-suited to products with circular cross sections. In sequential 3D extrusion blow molding, various material compositions are used consecutively, which means that flexible bellows sections or ducting with complex geometries can be produced with optimal results. This production technology solution does not generate large amounts of waste either.

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Extrusion blow molding references

Extrusion blow molding can be used to produce large and small containers individually and efficiently. You can read more about some of the projects we have successfully implemented using this technology in our online magazine.