FDBusiness.com

Pär Andersson of Tetra Pak explains how the development of the world’s fastest injection moulding machine was instrumental in the launch of the world’s first aseptic carton bottle for ambient distribution.

A light bulb image is often used to signify that moment when the solution to a problem becomes apparent. However, in my 30 years of experience, breakthrough innovations are usually not marked by one ‘light bulb’ moment; instead, they are an evolution of thinking, founded in experience, technical expertise and creativity. That is certainly how the ground breaking injection moulding technology behind the world’s first aseptic carton bottle, the Tetra Evero Aseptic (TEA) came to be a reality

When we set about designing the TEA, we wanted to create a package with the opening and pouring functionality of a bottle whilst maintaining the environmental and operational efficiency of a carton package. However, to do this we needed to develop a plastic top which could fuse the bottle opening to a cardboard sleeve, whilst ensuring that the liquid was kept safe and secure.

Existing injection moulding technology would require large production units which are too slow and expensive to run. The cost implications of using traditional injection moulding technology would have been prohibitive for producers. So we set about trying to figure out how to use injection moulding technology in a completely different way, but which would still provide the robustness and reliability required to assure aseptic conditions whilst also minimising costs. That also meant coming up with a polymer to get the right properties for both the package and for protecting the milk inside it.

Injection moulding is one of the most common manufacturing processes in the world, used in manufacturing such products as mobile phones, computers, sports equipment and DVDs.  Simply put, materials are injected into a mould to produce parts of a product. We have 25 years of experience in this technology and have used in the production of packages such as the Tetra Top.

The concept

Drawing on our experience we came up with a concept for injection moulding which could keep production costs down and production times up: reduce the size of the injection moulding equipment and integrate it into the filling machine itself, simplifying the process as much as possible. To do that we decided to place the sleeve and closure in the mould before the injection moulding: We apply the closure on a rotating mandrel and in the next step we put the paper board sleeve on the mandrel. The mandrel is then transferred into a moulding tool where we inject melted plastic – in just 40 milliseconds. One injection moulding cycle is 1.44 seconds and that makes this the fastest injection moulding system in the world and the first that is integrated into the aseptic carton bottle filling machine.

To progress, we needed to test the concept and demonstrate its viability. We started by designing some very basic tests to validate the fundamental idea and then developed a test rig, a process which took many more engineers and man-hours.

Towards industrial production

Having overcome the initial challenge of coming up with an idea and testing it, we were faced with the more difficult design challenge: transforming the concept and test rig into a production process which could operate on an industrial scale and become incorporated within the filling machine.

Among the many design challenges were the physical characteristics required for the plastic top. We needed a thin top to ensure quick freezing of the liquid plastic after moulding, but it needed to be robust enough to withstand impact if dropped. In addition, we needed to find a new light barrier to protect the product. We usually use aluminium foil, but in the case of the TEA, the plastic top would also be performing this protective role to ensure the shelf life of the product. This required coming up with a new recipe of the polymer blend.

To bring the packaging sleeve and cap together on the production line, the closure is supplied to the packaging machine where it is placed on top of a mandrel, a type of spindle, which rotates step-wise. The packaging material is cut from a roll to form a sleeve and is also placed on the same mandrel as the closure. The mandrel with the closure and the cardboard sleeve is then placed in the mould and the plastic top is moulded. The melted plastic seals to the closure and to the edge of the carton sleeve before the top solidifies in the mould. The innovative difference compared to traditional injection moulding is that instead of a one cavity injection moulding system, we developed a system with four, four-cavity moulds.

Increasing customer value

We are constantly striving to push the boundaries of what is possible in an effort to increase production efficiency for our customers. However, in producing 10,000 packages per hour in four single-cavity moulds we are close to the physical limits of injection moulding technology. To go beyond this production capacity ceiling will require innovations in the materials we are using. For example, if we were able to use a thinner polymer which had the same physical characteristics as the polymer we currently use we could speed up the injection moulding process still further.

The injection moulding of the top is just one of the critical technologies for the capacity of the machine. We are also exploring other potential efficiency gains such as ways of decreasing the time needed to fill a package. For us, the development of this new injection moulding technology for the TEA is only the start of the challenge. We are developing new closures, exploring ways to minimise the amount of material with the aim of making the injection moulding process even more efficient.

Pär Andersson is a Tetra Pak specialist in plastic injection moulding