Blow molding machine: from the preform to the bottle
A blow molding machine creates plastic bottles starting from a preform generally made of PET. The preform is nothing more than a bottle that has not yet been formed or printed. It has the shape of a small test tube where only the threaded mouth for the cap is not changed. The rest of the body, on the other hand, is first heated inside the blow molding oven and then molded by blowing.
The reason why we don’t start directly from the finished bottle is due to the space required for storage and transport. The space for transporting the preforms is significantly less than the bottle. This obviously affects the costs associated with the entire bottling production cycle.
Types of blow molding machines
Like with other types of machinery, there are various types of blowing machines, both linear and rotary.
A linear blowing machine usually work for medium hourly production speeds, up to 20,000 bph. Furthermore, a linear blow molding machine is preferable in the event that the space inside the bottling plant is limited, as these machines require less space than rotary blow moulders.
When workloads require high production speeds, a rotary blow molding machine is usually used. The rotary blow molding machines can produce up to and above 50 / 60.000 bph.
That’s why large companies which use plastic containers prefer rotary blowers. Even if this involves having a machine that occupies much more space than a linear blow molding machine.
How a blow molder works
An automatic tilter unloads the preforms and conveys them into a tank ready to be loaded through a toothed hopper.
This hopper then sends the preforms to a preform orientator which positions them in an orderly row and directs them into the blow molding machine. At this point they pass through gripping and transfer pliers and are positioned on a gear that places them into the heating furnace of the blowing machine.
Inside the oven there are various lamps that heat all the parts of the preforms at different temperatures. The machine automatically directs them into the mold which forms them (blowing) at 40 Bar by means of compressed air that arrives from the HP compressor. These lamps located in the furnace of the machine can be of different quantity and intensity and their action is regulated by the PLC of the blower. The blowing machine is a fully automatic machine which can have different automation systems and different control PLCs.
Manufacturers such as Krones, Sidel, Sipa, Khs, Sacmi, to name a few, produce high-performance blowing machines for the global market, each with its own specifications.