Sequential blow molding

Two basic methods are used in this process to deliver material to the processing units. These are extrusion and injection. In the next step, the preformed material is expanded to form parison. There are many commercial variations on this basic technique some of which include continuous-extrusion-blow-molding, coextrusion-and-sequential-blow-molding, and injection-stretch-blow-molding. Both extrusion and injection molding are the subjects of later discussions below, we will concentrate here on the parison formation, its processing, and the related effects. 

Sequential blow molding is used for producing bent three-dimensional shapes, for example, a convoluted heat exchange tubular panel and filler pipes in automobiles. The parison is deformed and then manipulated with programmable 3-D manipulators or six-axis robots before being placed directly into a mold cavity. 

Injection stretch-blow molding may be performed on a single one-stage machine in sequence or on two independent sequential two-stage machines. PET carbonated beverage botties are usually produced by injection stretch blow molding. 

Figure 6.1 2 Examples of different shaped sequential extrusion blow molding products...

Thielen, M., Blow Molding, Sequential Coextrusion Advanced Technology Opens Door into a New World of Tailored Parts, Modem Plastics Encyclopaedia, 1999. 

Air ducts are produced by sequential extrusion or blow molding alternating rigid PBT sections and soft elastomeric polyester accordion sections, which reduces weight, cost, number of components, and NVH. 

Sequential extrusion blow molding is a special multi-material technique (Fig. 10.41) used for the production of technical articles. The different materials are chosen typically to contribute complementary mechanical properties and are present in distinct sequential zones in the finished part. Normally two materials... 

To enhance water-vapor- or gas-barrier properties, layers of different plastics may be injected together or sequentially. Multilayer injection-molded pieces may be prepared as packaging or for blowing into bottle or jar shapes. 

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