PET Plastic Bottle Blowing Process Introduction

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PET blow molding bottles can be divided into two types, one is a pressure bottle, such as a bottle filled with carbonated drinks; the other is a non-pressure bottle, such as a bottle filled with water, tea, edible oil, etc.


1. Equipment

At present, manufacturers of PET automatic blow molding machines are mainly imported from France's SIDEL company, Germany's KRONES company, and domestically produced by FILLEX. Although the manufacturers are different, the principles of their equipment are similar, and they generally include five parts: blank supply system, heating system, bottle blowing system, control system and auxiliary machinery.


2. PET bottle blow molding process

The important factors affecting the PET bottle blow molding process are preform, heating, pre-blow, mold and production environment.

2.1 Preforms

When preparing blow-molded bottles, PET chips are first injection-molded into preforms. According to the National Food Safety Law, secondary recycled materials must not be used for food and pharmaceutical packaging. Injection molded preforms need to be stored for more than 24 hours before they can be used. The preforms that have not been used up after heating must be stored for more than 48 hours before being reheated. Preforms cannot be stored for more than six months.

PET Bottle Blow Molding

2.2 Heating

The preform is heated by a heating oven and its temperature is manually set and automatically adjusted. In the oven, far-infrared light emitted by the far-infrared lamp tube heats the preform radiation, and the fan at the bottom of the oven performs thermal cycling to make the temperature in the oven uniform. The preform rotates while moving forward in the oven, so that the preform wall is evenly heated. The heat of the oven is controlled by the number of lamps turned on, the overall temperature setting, the power of the oven and the heating ratio of each section.


2.3 Pre-blowing

Pre-blowing in a blow molding machine for PET bottle is a very important step in the two-step bottle blowing method. It means that the pre-blowing is started while the stretching rod is lowered during the blow molding process, so that the preform takes shape. The pre-blowing position, pre-blowing pressure and blowing flow rate in this process are three important process factors. The shape of the pre-blow bottle determines the difficulty of the blow molding process and the quality of the bottle.


2.4 Auxiliaries and molds

Auxiliary equipment mainly refers to equipment to maintain the constant temperature of the mold. Mold constant temperature plays an important role in maintaining product stability. Generally, the temperature of the bottle body is high, and the temperature of the bottom of the bottle is low.


 2.5 Environment

The quality of the production environment also has a greater impact on process adjustments. Constant temperature conditions can maintain process stability and product stability. PET bottle blow molding is generally better at room temperature and low humidity.



The PET bottle blow molding process is adjusted for the corresponding material. If the material is not good, the process requirements are very harsh, and it is even difficult to blow out a qualified bottle. It’s quite important to choose a reliable bottle blow molding machine factory. FILLEX is professional in manufacturing bottle blow molding machine and we will fill your ideas by our efforts.


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