Principle of bottle blowing
Jul 16, 2024
The blowing process of the bottle blowing machine is divided into two parts
1. Preheating
The preform (embryo) is illuminated by an infrared high-temperature lamp, which heats and softens the damaged body of the preform (embryo). In order to maintain the shape of the bottle mouth, the preform (embryo) mouth does not need to be heated, so a certain cooling device is required to cool it.
2. Bottle blowing machine blow molding
During this period, the preheated preform (embryo) is placed into the pre made blow mold and high-pressure inflated inside. Blow and pull the preform into the desired bottle.
The fully automatic bottle blowing machine combines the two bottle blowing operations through the operation of a robotic arm, eliminating the need for manual placement of preheated bottle preforms into the blowing mold at the center. Greatly accelerated the production rate.
Bottle blowing machine
3, Process flow of bottle blowing machine
The blow molding process of the bottle blowing machine is a bi-directional stretching process, in which the PET chains are stretched, oriented, and placed in both directions, thereby increasing the mechanical properties of the bottle wall, improving the tensile, tensile, and impact strength, and having excellent airtightness. Although stretching can help improve strength, it should not be excessively stretched. It is important to control the stretching inflation ratio: do not exceed 3.5-4.2 in the radial direction and 2.8-3.1 in the axial direction. The wall thickness of the preform should not exceed 4.5mm.
Blow molding is carried out between the glass transition temperature and the crystallization temperature, usually controlled between 90 and 120 degrees. In this range, PET exhibits a high elasticity state, and after rapid blow molding and cooling shaping, it becomes a transparent bottle. In the one-step process, this temperature is determined by the length of cooling time during the injection molding process (such as the Aoki blow molding machine), so it is necessary to connect the injection and blowing stations well.
In the blow molding process, there are three actions: stretching, first blowing, and second blowing. The duration of these three actions is short, but they must be well coordinated, especially the first two steps determine the overall dispersion of the material and the quality of the blown bottle. Therefore, it is necessary to regulate the starting and ending opportunities of stretching, stretching speed, pre blowing start and end opportunities, pre blowing pressure, pre blowing flow rate, etc. It is best to control the overall temperature distribution of the preform and the temperature gradient of the inner and outer walls of the preform.
