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Most blow moulding machines are still two-step blow moulding machines today.
That is to say, the plastic raw materials must first be formed into preforms before being blown.
PET plastics raw material, which are environmentally friendly, are now widely used. 


The bottle blow moulding machine’s blowing process is divided into two parts.


The preform is irradiated with an infrared high-temperature lamp to heat and soften the preform’s body. The preform neck does not need to be heated to maintain the shape of the bottleneck, so it must be cooled with a unique cooling device.

Blow moulding

The preheated preform is placed in the blowing moulder at this point, and the preform’s inner side is inflated under high pressure. Blow into the required bottle and pull the preform.

The manipulator in the automatic bottle blowing moulder machine combines the two operations of bottle blowing, eliminating the need for a manual process of inserting the preheated preform into the mould. Increase the rate of production dramatically.


The process flow of the bottle blow moulding machine

The blow moulding workflow of the bottle blowing machine is a two-way stretch process.
During this process, the PET chains extend, are oriented and are arranged in both directions.
Thereby, the mechanical properties of the bottle wall are increased, the tensile, tensile and impact strength are improved, and the airtightness is excellent.
Although stretching helps increase strength, it should not be overstretched.
The stretch-inflation ratio must be kept under control: it should not exceed 3.5 to 4.2 times in the radial direction and 2.8 to 3.1 times in the axial direction.
The preform’s wall thickness should not exceed 4.3mm.

Blowing is performed between the glass transition temperature and the crystallization temperature.
Generally controlled between 90 and 110 degrees.
In this interval, PET behaves in a highly elastic state and becomes a transparent bottle after rapid blow moulding and cooling and setting.

In the blow moulding process, there are stretch-blow once-blow twice.
The time for the three actions is concise, but they must be well coordinated.
In particular, the first two steps determine the overall distribution of the material and the quality of the bottle blowing.
Therefore, it is necessary to set the parameters: stretching start timing, stretching speed, pre-blowing start and end time, pre-blowing pressure, pre-blowing flow, etc.
If possible, it is best to control the overall temperature distribution of the preform and the temperature gradient between the inner and outer walls of the preform.

In rapid blow moulding and cooling, induced stress is generated in the bottle wall.
Carbonated beverage bottles 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.

The following is the flow chart of the blow moulder process

iBottling specializes in the production of PET automatic blowing equipment. It is a cutting-edge high-tech company that combines technology development, manufacturing, and independent sales.

For many years, Langxin has been committed to providing complete services for customers’ PET bottle beverage plant planning.
Refined design and manufacturing technology and a strict quality inspection system ensure that the product has excellent performance and a value-for-money price/performance ratio.
If you need to know more information about the blowing process, or if you want to start your own PET bottle production, to further reduce your beverage production costs and beat your competitors, just use the form below to contact us immediately to request a free quote plan.
Get in touch now.

Please check the blow moulder production line we’ve made.

John Lau.

John Lau.

John Lau, a project manager holding an engineering bachelor's degree, became fascinated with optimizing beverage production equipment during his university days. As an overseas project manager, he firmly believes that educating clients on achieving efficient workflows through customized equipment design is one of the most impactful aspects of his job.

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