This has two main different methods, namely Single stage and two stage process. Single stage process is again broken down into 3 station and four station machines In the two stage Injection stretch blow molding (ISB) 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 ISB 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. The preform is always stretched with a core rod as part of the process.
Advantages: Very high volumes are produced. Little restriction on bottle design. Preforms can be sold as a completed item for a third party to blow Disadvantages: High capital cost. Floor space required is high. Only suits round bottles