Blow molding also known as blow forming is a manufacturing process by which hollow plastic parts are formed. In general, there are three main types of blow molding: extrusion blow molding, injection blow molding, and stretch blow molding. The blow molding process begins with melting down the plastic and forming it into a parison or preform. The parison is a tube-like piece of plastic with a hole in one end in which compressed air can pass through. The parison is then clamped into a mold and air is pumped into it. The air pressure then pushes the plastic out to match the mold. Once the plastic has cooled and hardened the mold opens up and the part is ejected.
Most blow molding is done in the packaging industry for common products such as bottles, barrels and bulk containers for the chemical industry, as well as technical parts such as tables or automotive parts.
Mostly recycling in these industries is done in-house. For small bottles the GSL slow speed granulators are very well suited. bigger bottles and canisters can be processed in the compact soundproofed GSC series, they can be used to recycle PET preforms as well. Larger parts such as barrels, car tanks, tables and so on can be processed with the GSH heavy duty granulator series, which are able to handle the solid top and tail flush as well.
For extremely big volume parts such as IBCs a shredder/granulator combination is commonly used, here the ZIS shredders with their large volume hoppers offer an optimal solution.