How 2 Cavity Semi-Automatic Pet Bottle Blowing Machines Work

PET bottles are ubiquitous in today’s market, used for products such as mineral water, soft drinks, cosmetics, water sachets, pharmaceuticals, and personal care items. To manufacture these PET bottles, selecting the right blow moulding machine is essential. Let’s take a closer look at a 2 Cavity Semi-Automatic PET Bottle Blowing Machine and how it works.

2 Cavity Semi-Automatic PET Bottle Blowing Machine

The 2 Cavity Semi Automatic PET Bottle Blowing Machine is often the right compromise between cost, output, and flexibility for medium-scale manufacturers of PET blow-moulded products. In order to be able to choose, operate, and maintain such a machine, it is necessary to first know the working principles and the possible areas of use.

What Is a 2 Cavity Semi-Automatic PET Bottle Blowing Machine?

A Semi automatic pet Blowing Machine is a blow moulding machine that automates certain steps of the process while still requiring manual intervention for other steps. “Semi automatic” typically means that a machine requires a manual or semi-manual action to feed the preforms and to remove the finished bottles from the machine, but automates most of the other core process steps, including preform heating, blowing, and mold clamping/opening.

“2 cavity” means that for each operating cycle, the machine has 2 mould cavities. That is, it produces 2 bottles per cycle instead of one. This allows double throughput compared to a single-cavity machine, but with much simpler machine design and less cost than the multi-cavity or fully-automatic machines.

MAIN COMPONENTS & PROCESS FLOW

A Semi automatic blow Moulding Machine with two cavities typically works as shown below, with the key stages and process steps as described:

Preform Loading

The machine uses PET preforms, which are tube-shaped, pre-heated pieces of PET with threaded necks, as input material. A Semi automatic machine needs an operator to manually feed preforms into the heating/preheating chamber or into the preform magazine that pushes them into the heating chamber.

Preform Heating

The preforms are placed in an oven or preheating chamber with infrared heaters that heat them to the desired temperature. Uniform heating along the preform’s length is critical in order to ensure uniform thickness during the blowing process. Some machines even rotate the preforms in the heating zone to ensure heating. Eceng’s YC-2L-2 model, for example, features an infrared rotary oven for uniform heating.

Clamping of Moulds

The heated parts are then transferred to the moulds, which in a 2-cavity machine are two bottle-shaped mould cavities, each mounted on a clamping mechanism. The moulds are then closed using mechanical or pneumatic means. The clamping force has to be large enough to withstand the high pressure exerted during the blowing process.

Stretching & Blowing

After moulds are closed, the stretching rod (if present) may intrude into the preform and physically stretch the PET vertically. Then compressed air (blowing air) is injected to inflate the preform until it expands to press against the mould walls and take up the shape of the mould.

Because there are two cavities, both preforms are inflated simultaneously in parallel. Some machines keep the action vs blowing air circuits separate so that the blowing air system has no moving parts to get in the way.

Cooling

Once the bottle has been blown to shape, it still has to be cooled down (using either cold air blow or cooling water channels inside moulds) in order to solidify the plastic and stabilize the bottle shape and dimensions. The neck of the bottle often has specific cooling to make sure the threads don’t lose shape.

Mould Opening & Bottle Removal

After cooling is complete, the moulds are opened. Since this is a semi-automatic machine, the bottles can either be removed manually (operator needs to remove bottles from moulds) or with the aid of mechanical arms or pushers, depending on the model. Then the process repeats from the beginning.

Repeat Cycle

The two cavities allow for the cycle of heating, clamping, blowing, cooling, removal continuously. The operator generally monitors quality, performs mould changeovers if needed, and manages the preform supply.

Performance & Technical Specifications

Below depicted are some of the numbers and technical features to be found in typical 2 Cavity Semi-Automatic Bottle Blowing Machines:

• Bottle Size Range: Most commonly available in size ranges of about 50 ml up to 2 liters or even more, depending on cavity and mould design.
• Neck Diameter & Bottle Height Flexibility: Neck diameters commonly range from 15-35 mm, body diameters up to 100 to 130 mm, height up to 300 to 400 mm, depending on the mould used.
• Heating Power & Oven Zones: Infrared heating systems with multiple lamp zones, sometimes rotary or with rotating preforms. Adjustable control zones help achieve even heating.
• Blowing Pressure & Air Requirements: Machines need compressed air to do the blowing process; high pressure for blowing, with a separate lower-pressure air for the action of opening/clamping moulds. For example, blow air pressures of 2.0-4.0 MPa and action air of 0.8-1.0 MPa are common.
• Power Consumption: Semi-automatic machines are often more energy efficient than older machines; heaters, ovens, heating lamps, and required air compressors add to the total power.

Advantages of a 2 Cavity Semi-Automatic Pet Blow Moulding Machine

A 2 cavity semi-automatic machine offers a range of advantages, and is especially suitable for:

• Low initial investment compared to multi-cavity, fully automatic machines with complex preform feeding and bottle removal systems.
• Flexibility to trial different bottle designs, types of preforms, and PET materials without having to invest in a big automatic line.
• Easy operation like fewer moving parts or complex automation systems make machine maintenance easier, with minimal or no downtime.

Conclusion

With 2 cavities, these machines have much higher output than single cavity machines, allowing small to medium-scale operations. If your production rate is 800-1000 bottles per hour, you may already be able to serve many local or regional markets.

For getting further information on the 2 cavity semi-automatic PET bottle blowing machine, contact our experts immediately and get instant support.