Blow molding started in the glass blowing industry where a liquid glass pulp is enclosed in a two-piece mold and then expanded by blowing into to the pulp.
This causes the glass retains the contour of the mold and form a hollow area on the inside.
With the invention of polymeric thermoplastics, this technology started to rev up in the plastic bottle industry.
Starting in 1977, the number of plastic containers rose from zero to 10 billion plastic bottles in 1999 due to the soft drink companies in the USA.
The outcome isn’t exactly good for the environment, but if you use biodegradable materials or recycle thermoplastic bottles made from PET, things look a bit better.
Blow Molding versus Injection Molding
So, what’s the difference between parts made by injection molding and parts made by a blow molding machine? Injection molding creates solid parts, while blow molding creates hollow parts.
If you are looking for something that needs only one rigid wall, injection molding is the right process. Think of bottle caps, cases, combs, and housings for computers and televisions.
If you need a flexible, structural piece that even can hold fluid, you’re best off with blow molding. No wonder that billions of water bottles stand for the blow molding technology.
How Plastic Bottles are Made?
Producing plastic bottles does not greatly differ from the glass blowing process. The technology used by the bottle forming process is called Injection Blow Molding (IBM). This requires a so-called preform which is much smaller than the actual bottle.
The preform can be transported easily and if variants do not differ in weight it can be used uniformly. Like in the glass manufacturing process, the preform is heated up, put into the mold and inflated.
Due to the preform, the material expands equally, resulting in a better flow control, surface quality and transparency.
After the blow molding process, the bottle heads have to be threaded and the excess material cut off.
What are the Advantages of Blow Molding?
Blow molding scores especially at mass producing at a low price. Depending on the quality of the mold, it can produce more than over 1 million pieces before it has to be replaced.
The production is also very fast compared to other molding processes, ejecting a finished product every few seconds. Thin walls and water-cooled molds also reduce cycle time.
In addition, once the machine parameters are calibrated, the outputs quality is constant. This is achieved because factoring parameters are stable and controllable.
The process of blow molding is also perfect for automation, reducing the need for workers working in a monotone environment.
What are the Limitations of Blow Molding?
Purchasing a molding machine may seem like the biggest investment of a company to start producing. However, before you start producing, you will need a mold.
The biggest disadvantage of blow molding lies with the problem of all molding processes.
For each type of product you want to produce, you need a new type of mold and this comes with a very steep price.
The molds have to be machine milled and produced with a very high surface quality. The molds also have cannulas running through the walls to transport cooling fluids.
In addition, the mold often has to be hardened to increase its lifespan. This high cost of molds often reduces a company’s incentive of producing prototypes, especially for low piece numbers.
Technical Specifications of Auto PET Blow Moulding Machine:
EFPL manufactures excellent quality Automatic PET Blow Moulding Machines for PET bottle production.
Our Automatic PET Blow Moulding Machines have wider wide-mouth capability, faster production rates, and shorter changeover times.
Also have features such as preferential heating or heat-setting capability. Our Two stage Plastic PET machines can make bottles from round to flat bottle styles.
Attributes of Automatic PET Blow Molding Machine: