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Working principle of bottle blowing machine

Two step bottle blowing is the method used by most bottle blowing machines at present. The so-called two-step method is to first make plastic raw materials into bottle embryos and then blow bottles. Currently, PET environment-friendly plastics are commonly used.
1、 Bottle blowing principle
The bottle blowing process of the bottle blowing machine is divided into two parts
1. Preheating
Irradiate the preform (embryo) through the infrared high temperature lamp, and heat and soften the bad (embryo) part 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 molding
In this stage, the preheated preform (preform) is placed in the prepared blow mold for high-pressure inflation. Blow and pull the preform into the desired bottle.
The automatic bottle blowing machine combines the two operations of bottle blowing through the operation of the manipulator, eliminating the process of manually placing the preheated bottle into the blowing mold. The production rate is greatly accelerated.
2、 Process flow of bottle blowing machine
The blow molding process of the bottle blowing machine is a biaxial stretching process. In this process, the PET chains are biaxially extended, oriented and arranged, which increases the mechanical properties of the bottle wall, improves the tensile, tensile and impact strength, and has good air tightness. Although stretching helps to improve the strength, it is not allowed to stretch too much. The stretching inflation ratio should be controlled well: the radial direction should not exceed 3.5~4.2, and the axial direction should not exceed 2.8~3.1. The wall thickness of the preform shall not exceed
The bottle blowing is carried out between the glass transition temperature and the crystallization temperature, which is generally controlled at 90~120 ℃. In this range, PET shows a high elastic state. After rapid blowing, cooling and shaping, PET becomes a transparent bottle. In the one-step method, this temperature is determined by the length of cooling time in the injection molding process, so the relationship between injection and blowing stations should be well connected.
In the blow molding process, there are: stretching - blowing once and blowing twice. The time of the three actions is very short, but they must be well coordinated. In particular, the first two steps determine the overall distribution of materials and the quality of bottle blowing. Therefore, it is necessary to adjust: stretching starting time, stretching speed, pre blowing starting and ending time, pre blowing pressure, pre blowing flow, etc. If possible, it can control the overall temperature distribution of the preform and the temperature gradient of the inner and outer walls of the preform.
In the process of rapid blow molding and cooling, there is induced stress in the bottle wall. For an inflatable beverage bottle, it can resist internal pressure and is beneficial, but for a hot filled bottle, it should be fully released above the glass transition temperature.