Blow molding machines are mainly divided into three categories: extrusion blow molding machines, injection blow molding machines, and special structure blow molding machines. The processing technology is mainly divided into one-step and two-step methods. One-step and two-step blow molding processes are mainly used for molding PET and BOPP hollow containers. Both have their own characteristics and are widely used. Comparatively, the two-step method is more suitable for centralized production of preforms and decentralized bottle blowing; while one-step equipment is more suitable for online production in beverage companies.
The blow molding process of a blow molding machine mainly consists of six steps:
1) First, the heated preform is placed into the mold;
2) The mold is locked using a locking cylinder;
3) The preform is then locked using high pressure or mechanical structures;
4) Medium- and high-pressure pre-blowing is performed, while the stretching cylinder expands the preform;
5) High-pressure blowing is performed, the preform is shaped according to the mold, and pressure is maintained for a certain time;
6) The high pressure in the formed bottle is released, the cylinder resets-the bottle is removed.
