Digitalisation has become omnipresent in nearly every aspect of manufacturing and continues to evolve year after year. Plastic packaging is no exception. From measuring airflow and temperatures on the production line to driving greater efficiencies, digital technology is delivering enhanced process improvements through the creation of “intelligent factories” that advance blow moulding technologies.
History of Blow Moulding
Plastic blow moulding was popularized in the 1950s with the emergence of high-density polyethylene (HDPE), which led to mass production of blow moulded packaging. Throughout the 1950s and 1960s, plastic was extruded with machines that pushed or pulled the parison downward.
In 1970, Graham Packaging developed equipment that extruded plastic in a new way by using an upward extrusion with the parison plastic. Even though this process works against gravity, it allows for greater control of the bottle’s thickness.
It wasn’t until the 1990s that polyethylene terephthalate (PET) was introduced into the blow moulding process to create consumer packaging for food and beverage, personal care and other household products. Since then, blow moulding has evolved to include PET multilayer barriers, hot-fill PET and extruded PET.
Although the concept of extrusion blow moulding hasn't changed, the ability to do things faster, lighter, at a lower cost and with more sustainable materials has improved with the onset of new and emerging technologies.
Extrusion Versus Injection
Extrusion blow moulding is the process of pushing or pulling a hot tube of plastic out of a die head, blowing air into it and then closing the mould. This process is used for most HDPE containers, such as laundry detergent and motor oils.
There are two different types of injection stretch blow moulding — single stage and two stage. Single stage involves making the preform and the bottle in the same machine. With two stage, the preform is made separately. It is then cooled, stored and shipped where it is reheated and formed by another machine. This process can take place over the course of a day or months and is ideal for high-performance PET applications such as juices, sports drinks, condiments and peanut butters.
Single-Stage Versus Two-Stage Blow Moulding
There are benefits to both single-stage and two-stage blow moulding. Two stage is more appropriate for higher volume production and ideal for hot-fill applications. Manufacturers can get significant output from the machinery, and the process places little to no restriction on the design and shape, making this the preferred approach for most beverage containers.
Single-stage blow moulding is better suited for lower volume production or designs that have a specific neck orientation that may enable a special pour or dosing feature. This process is used in PET bottles for cold-fill liquids or spirits. While it can restrict bottle design, single stage is also a more energy-efficient manufacturing method since there is no need to cool down the preform and then reheat it for the blow process.
The single-stage process requires a smaller footprint and can be a more cost-effective solution for low volume requirements. A benefit with this process is that there isn’t any double handling of the preform which can lead to scuffing and helps ensure the surface of the container remains blemish-free.
Recycled PET in Blow Moulding
Increased access to post-consumer recycled (PCR) content allows packaging companies to acquire resin pellets ground from PCR to use in the blow moulding process. With more and more brands committed to increasing the levels of recycled content in their containers, some resin suppliers are now offering a single-pellet solution, which incorporates recycled PET into the virgin pellet itself. This makes it easier for packaging producers to interchangeably use PCR and standard virgin resin in packaging designs.
However, as manufacturers use higher percentages of PCR, a colour shift may occur in the container. This can be offset by adding coloured resin toners. Some PET recyclers even add toner into their moulding process and then deliver pellets of recycled content that create more of a neutral colour instead of yellow.
Use of Barrier Technologies
Barrier technologies extend the shelf life of a product by protecting it from oxygen, moisture, light, etc., which could adversely impact flavour or freshness. In the past, non-food grade recycled PET couldn’t be present on the inner layers of food grade containers due to contamination concerns. This led to the use of multilayer technologies, which allowed non-food grade recycled PET to be “sandwiched” between layers of virgin PET.
Today, the majority of available recycled PET is food-contact certified and can be moulded into a monolayer structure. This translates into simpler technologies and significant cost-savings for both manufacturers and their customers.
While no longer the norm, multilayer products can be beneficial in helping to preserve the freshness and flavour of beverages such as iced tea and orange juice. Applying a barrier material to an inner layer of a juice, beer or food container can prevent alterations to its natural taste.
Simulation and Modelling
Designing a container that is more sustainable and higher performing often involves computer simulation with structural analysis to predict bottle function before it reaches the production line. This ensures there's no loss in performance along with other attributes when PCR is incorporated to reduce the weight of a container.
Simulation and modelling have led to significant advancements in blow moulding technology, including vertically applied processing. The process, dubbed AccuStrength by Graham Packaging, allows for additional plastic to be placed along a vertical orientation of the parison. This allows the manufacturer to concentrate the container’s thickness in the corners only while removing excess material from areas where it isn’t required — all without compromising structural integrity.
Two key advantages of plastic packaging versus glass are the substantial savings in freight costs and the reduced amount of product loss due to breakage in the supply chain. Ongoing efforts to further advance lightweight plastic packaging technology are helping to drive material savings and reduce the environmental carbon footprint.
Digitalisation and Shelf Appeal
While sustainability is a critical factor in plastic packaging, brands continue to seek out designs that help move product and boost sales. With so many stakeholders involved in the design process, the most efficient and productive way to achieve an optimal packaging outcome is to ensure everyone has a seat at the table. “Live Design” is a process that brings together experts from design, engineering, marketing, procurement and operations — either in person or virtually — to engage in real-time packaging design.
Using a variety of technologies throughout the design process, Graham’s design team develops unique, sustainable solutions while maintaining a brand’s identity and social mission. This is done by integrating art, communication, engineering, technology and manufacturing to optimise the development of customized, sustainable packaging solutions.
Enhancing Design Flexibility
Another innovative design technique known as “active base technology” is ideal for beverage containers such as sports drinks, juices and teas. This process allows the active base to flex during the fill process and respond to changes in the pressure of the container while cooling.
Active base technology not only supports the bottle during the fill process, it also allows for additional design freedom. By using less PET, bottles can be lightweight and offer added sustainability benefits, in addition to being able to be designed into inviting shapes.
Creating an Intelligent Factory
Plastic packaging manufacturers are increasing their commitment to establish processes that create smarter, more sustainable products. Developing “intelligent factories” involves embedding measurements and analytics into plants to help monitor and optimise quality and energy consumption to deliver added efficiencies to the manufacturing process.
In addition, manufacturers are beginning to focus on the “traceability” of plastic. Much like the farm-to-table concept in restaurants — where consumers know where their food is grown — plastic manufacturers are working to ensure both brands and consumers know exactly where the plastic in their containers and bottles came from. Whether it’s been collected from a landfill, picked up by municipal recycling companies or rescued from the ocean — traceability is another marketing tool brands can use when promoting their products.
By embracing the digitalisation of manufacturing, companies like Graham Packaging are delivering products that offer greater sustainability while helping to lower their carbon footprint and contribute to a more circular economy throughout the supply chain.