PET blow molding features of technology and equipment selection

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Raw materials and their properties

Polyethylene terephthalate in granular form is used as a raw material for the production of PET containers, including bottles. If the technology of melting and subsequent cooling after the formation of the container is not violated, bottles made of such material are durable, sufficiently rigid (to perform their functions). They do not lose color, which, in addition to decorativeness, also plays a protective role, preventing the negative effect of light on the contents of the container.

Blowing PET containers – technology, equipment and materials used … This is a two-stage process, at the first stage of which PET preforms are made – miniature blanks of future bottles . At the second stage, the final blowing of the PET container is performed .

Pet Blowing

PET blow molding process

The main part of the technology is implemented on an injection molding machine, where preforms heated to a certain temperature are installed (visually at this moment they look like plastic test tubes). Blowing PET in general terms resembles the creation of soap bubbles – under high pressure compressed air “straightens” the pliable material after heating, and the walls of the mold ensure compliance with the given configuration.
The most important point is the correct supply of compressed air, in which the pressure will be the same at each point. If this condition is fulfilled, the resulting container will be of the correct shape, and the wall thickness will meet the requirements.
Finished bottles are cooled by blowing with compressed air or using liquid carbon dioxide.

Necessary equipment for production lines

PET blowing  can be performed on various equipment. Moreover, the main unit is selected depending on the required number of containers and other conditions, and the auxiliary unit is selected in accordance with the type of the main machine and the characteristics of the technological process.

  • For large-scale production, it is recommended to choose a two-phase technology, in which the heating of the molds is carried out separately, they come for blowing already prepared.
  • For a small volume, you can limit yourself to a single-phase process, in which heating and blowing are performed on the same machine.
Pet Blowing

Basic technique

In addition to the above differences, thermoplastic machines are divided into two main categories, depending on how automated the production process is.

  • Semi-automatic machines require loading and unloading, this requires the direct participation of the operating personnel.
  • On full automatic machines, all technology is carried out and monitored automatically. In particular, heated molds are fed through a special conveyor channel with a high temperature, which prevents the blanks from cooling.

In addition, automatic and semi-automatic machines differ in productivity – about 12,000 and 700 bottles per hour, respectively.

Auxiliary equipment

If a two-phase production is planned, in addition to the thermoplastic machine, a special oven will be required to heat the preforms. Workpieces in such a furnace move evenly on a conveyor, while turning. This method provides a high-quality uniform temperature rise.
When installing a line in an enterprise that produces drinks or other products that are packaged in PET bottles, you will also need:

  • equipment for filling liquids and subsequent packaging of containers,
  • equipment for labeling bottles,
  • automated lines for packaging and transportation of finished products.

Practice shows that investments in the purchase of equipment for blowing PET containers, subject to the correct choice of configuration, quickly pay off, and modern production equipment increases labor productivity and ensures that products comply with sanitary standards.