PET Bottle Manufacturing: Preforms, Blow Moulders and ABB

Most soft drinks and bottled water now come in clear plastic bottles that start life as small, thick tubes called preforms. PET bottle manufacturing turns those preforms into finished bottles in seconds, using heat, a steel rod and compressed air. This post looks at how drinks were bottled before PET, how a DuPont engineer's 1973 invention changed the industry, and what a bottling line looks like today, using a new in-house blow moulding line in Alabama as the example. It also covers where ABB robots work around injection presses, case packers and palletizers, and what recycling means for the next generation of plants.

A Krones Contiform S24 stretch blow moulder linked to a Modulfill filler in one block. Photo: Krones / Wikimedia Commons (CC BY-SA 3.0)

From glass bottling halls to Wyeth's plastic bottle

For most of the 20th century, soft drinks and beer went into glass. Big breweries ran huge bottling halls. A postcard from around 1910 shows the bottling department of Anheuser-Busch in St. Louis, rated at 800,000 bottles a day, with long rows of workers at tables and machines. Glass bottles were heavy, broke easily and were usually returned, washed and refilled. Our post on glass bottle manufacturing covers how those bottles were blown, first by hand and later by machine.

The Anheuser-Busch bottling department in St. Louis, rated at 800,000 bottles a day, on a postcard from around 1910. Photo: unknown author via Wikimedia Commons (public domain)

The plastic came first. John Rex Whinfield and James Tennant Dickson of the Calico Printers' Association in Manchester patented polyethylene terephthalate, or PET, in 1941, and DuPont began making PET fibre under the name Dacron in 1950. Turning it into a bottle that could hold carbonated drinks under pressure was harder. DuPont engineer Nathaniel Wyeth solved that problem, and DuPont patented his PET bottle in 1973. The key was stretching the plastic in two directions while blowing it, which aligns the molecules and makes a thin wall strong enough for fizzy drinks.

A PET preform with its moulded screw thread, next to a polyethylene cap. Photo: Frank Murmann / Wikimedia Commons (CC BY 3.0)

That idea became the standard process. First a preform, shaped like a test tube with the screw thread already formed, is injection moulded. Then the preform is heated, stretched with a rod and blown with compressed air into a mould, a step called stretch blow moulding. It can run on one machine or on two, with preforms made in one place and blown somewhere else. Lighter, unbreakable PET bottles soon spread across soft drinks and water, and the large two litre bottle became a fixture on supermarket shelves.

Pallets of two litre soda bottles seen from the mezzanine at Coca-Cola Bottling Company of Cape Cod, 2011. Photo: Ktr101 / Wikimedia Commons (CC BY-SA 4.0)

Blow moulding lines and robots in 2026

On 7 October 2026 Buffalo Rock, a Pepsi bottler, opened an in-house blow moulding operation at its Oxmoor Campus in Homewood, Alabama, ABC 33/40 reported. The company used to buy bottles already formed and labelled. Now it receives preforms, heats them in an oven and blows them into 20 ounce bottles at about 800 per minute, then labels, fills, packs and palletizes them on site. The roughly 22,000 square foot operation supports 18 jobs, 12 of them new hires, which the company describes as more technical and better paid.

A Krones Contiform S14 stretch blow moulding machine, which heats preforms and blows them into bottles. Photo: Krones / Wikimedia Commons (CC BY-SA 3.0)

Not every plastic bottle is PET. ALPLA announced in early October that its new plant in North Las Vegas will open in spring 2027 and make bottles by extrusion blow moulding, a different process used for many household and personal care containers. In PET lines the blow moulder is a rotary machine with its own transfer wheels, and robots tend to work at the stations before and after it. Injection presses that make preforms often have a robot to unload them, and one example on the site is an ABB IRB 4400 taking parts from an ENGEL injection moulding machine in Spain. Our post on injection molding covers that side in detail.

An ABB IRB 4400 unloads parts from an ENGEL injection moulding machine in a Spanish plant. Photo: ABB

At the end of the line, ABB robots handle the filled bottles. IRB 360 FlexPicker delta robots can pick bottles or packs from a moving conveyor at high speed, and PickMaster software sets up vision guided picking. The four axis IRB 460 and IRB 660 palletizers stack packs and shrink wrapped bundles into pallet layers, often with layer grippers. We found no published ABB project at Buffalo Rock or ALPLA, so treat these as the usual jobs for such robots on bottling lines. Lines like these are often laid out and tested first in ABB's RobotStudio simulation software.

ABB IRB 360 FlexPicker robots packing small items into cartons at high speed. Photo: ABB

Recycled PET and the next bottle plants

The biggest change ahead is recycled PET. Bottles carry resin code 1 and are widely collected, and recycled PET, or rPET, can be made into new bottles as well as fibre and strapping. Switzerland reported an 82 percent PET recycling rate for 2020. More recycled content means more variation in the material, so blow moulders and inspection systems need to adjust to it. Robots may take on more of the handling in recycling plants too, sorting bales and feeding lines.

Bales of crushed PET drink bottles at a recycling site in Frauenfeld, Switzerland, 2021. Photo: JoachimKohler-HB / Wikimedia Commons (CC BY-SA 4.0)

Bottling plants are also moving bottle making in house, as Buffalo Rock did, to cut the cost of shipping and storing empty bottles. That favours compact, flexible lines that change quickly between bottle sizes and flavours. Robots can help with mould and format changes, preform handling and the frequent switch of pallet patterns. For homes, the visible change is lighter bottles and more recycled content, plus deposit machines that take bottles back, a topic we cover in our post on reverse vending machines.

An ABB four axis palletizing robot with a layer gripper in a packaging line cell. Photo: ABB

Blow moulding and filling equipment is expensive, and a bottler has to be sure of steady volume before it buys its own line. Hot moulds, high pressure air and heavy pallets also make these lines hazardous, which is why palletizing cells sit behind fences or use safety scanners. Then there are people to run it all. Buffalo Rock said equipment suppliers trained its staff to run and maintain the new system, and every new plant will need technicians who can keep blow moulders, robots and vision systems running.

A heap of clear PET preforms before they are blown into bottles. Photo: dierk schaefer / Wikimedia Commons (CC BY 2.0)

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