Bottle Blowing Machine: Everything You Need To Know

Did you know that a modern bottle-blowing machine can produce up to 1000 bottles every minute? A manual blow molding machine could only output 1000 bottles in an hour. The difference is staggering. The reason is the semi-automatic type,  automatic linear type and rotary type blow molding machine. Whether you are aiming to purchase a blow molding machine for bottle making or want to learn about the technology, this article is the ideal guide for you.

Blow molding machines are the standard for bottle production worldwide. In the simplest of explanation they blow air into a melted PET preform. The PET preform is placed into a container that is shaped like a bottle. The mold is then opened, and a fully made bottle is extracted. As simple as the process may seem, the technology has evolved from the basic hand-operated glass-blowing techniques to automatic machine control through advanced servo control systems. Let's understand how a 32+ cavity mold bottle blowing machine produces 70,400 BPH.

The Evolution of Bottle Blowing Technology

The roots of the technology go back to the 1st century B.C. Syrian where glass blowing was first used to shape molten material. The transition to plastic came much later in 1938, when Enoch Ferngren and William Kopitke submitted the first commercial patent for the blow-molding machine.

Large-scale production using bottle blowing machine began in the 1950s. The machine became completely transformed in the year 1975. The creation of strong plastic that stretched in two directions, called biaxially oriented PET, changed blow molding completely. It allowed the machine to inject plastic into the mold, strencha nd blow it into a bottle in a single continuous step.

How Bottle Blowing Machines Work

▶The Core Process Steps

To understand the key steps in which the automatic bottle blow molding machine works, we can divide them into three phases. Each phase represents the major working mechanism of the blow molding machine.

• Phase 1: It is the first part of the bottle production where thick plastic preforms are heated in an infrared oven. These plastics reach a soft, rubbery and stretchable condition called the thermoelastic state. The most popular PET material reaches this point at 100 °C.
• Phase 2: Once the plastic is heated to the exact point, it is moved into the mold. In particular, stretch and blow systems, a mechanical rod pushes the tub to stretch it axially. After the stretch, it immediately becomes a highly pressurized gas. Aseptic air is blown into the plastic through a nozzle. It causes the preform to inflate like a balloon. The plastic expands until it hits the internal walls of the mold and tightly hugs the surface curves and details.
• Phase 3: As the plastic hits the cold metal mold walls, it hardens into its final shape. The metal mold is kept at 8 to 16 °C using cold water. Once the bottle is solidified, it is pushed out of the mold, and any scraps of plastic around the seams, called flashes, are trimmed. 

▶Critical Process Parameters

There are some parameters that the operators need to monitor closely. They need to perfectly match the process to ensure that the bottle product is clear and has the right physical properties.

• Pre-Blowing Delay: Before the air is blown into the preform, there is a slight delay of around 0.18 to 0.2 seconds. The reason is to allow the preform to stretch properly, avoiding the necking defects.
• Friction Coefficient: At the very bottom of the bottle, the preform undergoes intense stretching and physical deformation. It can lead to tearing if not overseen. Engineers set the slip of the stretch rod and the heated, unshaped plastic tube called a preform. It helps prevent the tearing.
• Heat Transfer Coefficient: When the plastic finally cools down, it happens very quickly. Engineers calculate the rate at which the heat is extracted from the bottle material once it touches the mold. The interaction happening between 100 to 260 W/m2K is considered ideal.

Major Types of Blowing Machines

◆Injection Stretch Blow Molding (ISBM) / Stretch Blow Molding Machine(SBM)

The most common method to produce plastic bottles is the injection molding of a preform. The process in which the preform is stretched and blown inside a single stage. Or sometimes split into two stages, where the starting products are cooled and saved for later use.

It is the top choice of carbonated soft drink /beverage/ food containers/ edible oil bottle production facilities. They need the strength that comes with the strength of preform. The process of stretch makes the material's specific density due to strain-induced crystallization. It improves the bottle's overall physical properties.

◆Extrusion Blow Molding (EBM)

Another method that is majorly utilized requires continuous pushing of a hot, melted tube of plastic. The process is called extruding parison. A mold is clamped around the parison, and the machine clips the parison outside the mold. Then another probe blows air inside the tube bounded by the mold to shape the bottle. The whole process is collectively called extrusion blow molding.

It is the ideal process for making large, bottle-like 20L water tanks or industrial drums. It allows manufacturers good control over the wall thickness. It also works well with thicker plastics like HDPE, PP and PVC.

◆Hot-Fill Technology

The process is used for advance PET bottles that can withstand very hot liquids, typically around 95 °C, without deformation. The process is used for the production of juices, energy drinks and teas that must be brought to high temperatures, killing bacteria.

The hot-fill process uses electronic temperature monitoring sensors and uses a high-end controller with specialized mold designs. To ensure that the bottles made using technology remain physical strong, the bottle neck is kept cool while the mold is kept heated. The process increases the crystallinity of the bottle walls, making them heat-resistant. It ensures that the opening stays stiff so that the capping can be performed.

Material Selection and Properties 

✔Common Thermoplastics

• PET: Owing to the gas barrier properties of PET, it is the most popular choice for carbonated drink bottles. They keep the gas inside and act as a barrier.
• HDPE: In case of chemical exposure, HDPE is the go-to material. It is an extremely safe plastic that is the go-to choice for mil juds and household cleaners.
• Polypropylene (PP):  In case the bottle needs to ensure extreme heat and sterile medical wrapping, PP is the ideal choice. Its low-density plastic is known for its toughness.
• Polycarbonate (PC): For reusable water bottles and medical syringes, PP takes the lead. It is known for its glass-like clarity and offers high impact resistance.

✔Material Maximization and Waste Reduction

In comparison to the older methods, modern machines are highly efficient when it comes to material utilization. There is a reduction of plastic waste up to 20% using the stretch blow molding. There are  build-in tools that automatically slice off excess plastic crusts. These are known as auto deflasher devices and trimming systems. The machine instantly regrinds the scrap and melts it for reuse.

Conclusion

Choosing the right bottle blowing machine manufacturer is a major business decision. The machinery's capabilities decide the factory output, energy efficiency, and product quality. For a factory that needs straight-line machines driven with linder servo-controlled PER machines, and rugged setups that can extrude thick plastics, experience matters. It is recommended to partner with a manufacturer like Vfine Machine. We utilize extensive 20+ years of experience to help factoreis setup an efficient system. our bottle blow molding machine can handle PET, PP and HDPE material for the production of bottles.

FAQs

1. What is the difference between a one-stage and a two-stage blowing machine?

In a one-stage bottle blowing machine, the injection molding and blowing happen in a single continuous step. It is great for small batches. The two-stage blowing machines are faster. They use pre-made preforms. It results in higher production speed and flexibility.

2. How much energy can be saved with air recycling systems?

By using the air recycling system on a standard bottle molding machine, businesses can save upto 25% of high-pressure air. When it comes to hot-fill and thick-bottle machines, the savings can go up to 60%.

3. Why is cooling water temperature so important for cycle times?

The temperature of the mold determines how fast the bottle solidifies. Solidification starts when hot plastic touches the cold mold. Lower temperature around 10 °C means faster cooling and higher bottle production rates.