Injection stretch blow molding.
With the commercial introduction of containers, stretch blow molding became a common term in the blow molding industry. Stretch blow molding is the method of producing a plastic container from a preform or parison that is stretched in both the hoop direction and the axial direction when the preform is blown into its desired container shape. Stretch blow molding is possible for various thermoplastic materials such as acrylnitrile(AN), polystyrene (PS), Polyvinyl chloride (PVC), nylon, polycarbonate (PC), Polysulfone, acetal, polyarlyate, polypropylene (PP), surlyn, and polyethylene terephthalate (PET). Amphorous materials such as PET. Etc.
In the stretch blow molding (SBM) process, the plastic is first molded into a "preform" using the injection molding process. These preforms are produced with the necks of the bottles, including threads (the "finish") on one end. These preforms are packaged, and fed later (after cooling) into a reheat stretch blow molding machine. In the SBM process, the preforms are heated (typically using infrared heaters) above their glass transition temperature, then blown using high pressure air into bottles using metal blow molds. Usually the preform is stretched with a core rod as part of the process. In the single-stage process both preform manufacture and bottle blowing are performed in the same machine. The stretching of some polymers, such as PET (polyethylene terephthalate) results in strain hardening of the resin, allowing the bottles to resist deforming under the pressures formed by carbonated beverages, which typically approach 60 psi.The main applications are bottles, jars and other containers.
Advantages of blow molding include: low tool and die cost; fast production rates; ability to mold complex part; produces recyclable parts. Increase the material’s tensile strength, barrier properties, clarity. Reduce weight stretch blow molding produces a container from less raw material and with improved economics and bottle properties.
Disadvantages of blow molding include: limited to hollow parts, wall thickness is hard to control.