The operating principle of PET semi-automatic bottle blowing machine can be divided into three categories: extrusion bottle blowing machine, injection bottle blowing machine, and special structure bottle blowing machine. The processing technology is mainly divided into two types: one-step method and two-step method. The one-step and two-step blow molding processes are mainly used for forming PET and BOPP hollow containers. Both have their own characteristics and are widely used. Compared to other methods, the two-step method is more suitable for centralized production of bottle preforms and dispersed blowing of bottles; And one-step equipment is more suitable for online production of beverage enterprises. The blowing process of a bottle blowing machine mainly consists of six steps: first, place the heated plastic embryo into the mold; Use a locking cylinder to tighten the mold; Use high pressure or mechanical structures to lock the embryo mold; Pre blowing air at medium and high pressure, while stretching the cylinder to expand the mold; High pressure blowing, shaping the preform according to the mold and holding it under pressure for a certain period of time; Release the high pressure from the formed bottle, reset the cylinder - remove the bottle. Pneumatic equipment is widely used in the operation of bottle blowing machines; The series of actions from discharging, locking, stretching, high-pressure blowing, deflation, and bottle retrieval are all assisted by pneumatic equipment. If the high-pressure blowing and deflation circuit is stretched, the air path is divided into two parts, the normal pressure part and the high-pressure part.