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What is the blowing principle and process flow of the bottle blowing machine?

Update:09-09-2021
Summary:

At present, most of the blow molding machines are still […]

At present, most of the blow molding machines are still two-step blow molding machines, that is, plastic raw materials must be made into preforms before blowing. Nowadays, environmentally friendly plastics made of PET are commonly used.

Blowing principle
The blowing process of the bottle blowing machine is divided into two parts
1. Warm up
The preform (embryo) is irradiated by an infrared high-temperature lamp to heat and soften the bad (embryo) body of the preform (embryo). In order to maintain the shape of the bottle mouth, the preform (embryo) does not need to be heated, so it needs to be heated. The cooling device for cooling operation.
2. Blow molding
In this stage, the preheated preform (preform) is placed in the blow mold that has been completed, and the interior is inflated with high pressure. Blow and pull the preform (embryo) into the required bottle.
The automatic bottle blowing machine combines the two operations of bottle blowing through the operation of the manipulator, eliminating the need for manual process of putting the pre-heated preform into the blowing mold. Greatly accelerate the rate of production.


Forming diagram of the bottle blowing machine
Second, the process flow of the bottle blowing machine
The blow molding process of the bottle blowing machine is a two-way stretching process. In this process, the PET chains are extended, oriented and arranged in two directions, thereby increasing the mechanical properties of the bottle wall and improving the tensile, tensile and impact strength. And has very good air tightness. Although stretching helps to increase the strength, it should not be excessively stretched. The stretch-inflation ratio must be controlled: the radial direction should not exceed 3.5 to 4.2, and the axial direction should not exceed 2.8 to 3.1. The wall thickness of the preform should not exceed 4.5mm.

Blowing is carried out between the glass transition temperature and the crystallization temperature, generally controlled between 90 and 120 degrees. In this interval, the PET exhibits a highly elastic state, and becomes a transparent bottle after rapid blow molding and cooling and setting. In the one-step method, this temperature is determined by the length of the cooling time during the injection molding process (such as the Aoki bottle blowing machine), so it is necessary to connect the injection-blowing two stations.

In the blow molding process, there are: stretching-blowing once-blowing twice. The three actions are very short, but they must be well coordinated, especially the first two steps determine the overall distribution of the material and the quality of the blown bottle. Therefore, it is necessary to adjust: stretching start timing, stretching speed, pre-blowing start and end timing, pre-blowing pressure, pre-blowing flow, etc., if possible, it is best to control the overall temperature distribution of the preform, bottle The temperature gradient of the inner and outer walls of the blank.

In the process of rapid blow molding and cooling, induced stress is generated in the bottle wall. For gas-filled beverage bottles, it can resist internal pressure, which is beneficial, but for hot-filled bottles, it is necessary to ensure that it is fully released above the glass transition temperature.

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