Lightweighting plastic bottles for packaging

By Stephen Barter MAIP
Wednesday, 22 January, 2014

Reducing the plastic component of the overall package is a great environmental initiative; however, in today’s competitive market the opportunity to save money in the actual packaging cost is very appealing. There is a need to understand this opportunity; quick savings in plastic could end up costing much more in other areas like filling and function failures.

Extrusion blow moulding (EBM) for plastic bottles is a very flexible process and of all the moulding processes offers the most cost-effective method to reduce packaging costs by way of tooling and process adjustments.

Effective weight reduction projects should start with an analysis of the bottle sales volumes.

High-volume production bottles should be targeted for 5% or less weight reduction immediately. In most cases this can be achieved with little effort and the impact on the supply chain maybe non-existent. The key to achieving quick weight loss is to ensure that the process(es) remain stable; if the process becomes less stable at 3%, choose this as the benchmark. It’s a small percentage value; however, on large-volume products, it will add up.

For example, a 60 g bottle with a volume of 2 million units per year can save 6000 kg of plastic with a 5% reduction in weight.

Low-volume products require a more substantial percentage target to achieve savings that are worth the effort and - in many cases - the investment.

A change in the bottle weight of more than 5% will potentially impact the structural performance of the bottle and this may be an ideal time to re-evaluate the expectations of the pack. Is this expectation overstated? The bigger percentage changes become more technical and the impact on each of the processes will vary based on the shape and size of the bottle and design features.

Bottles can be redesigned to reduce the weight while maintaining and even improving the structural and physical performance. For example, a bottle that is relatively square with a single radius corner can be greatly improved by a series of compound curves around the perimeter of the bottle and a conical shape to the panels.

Such design enhancements on high-volume products can pay for the capital investment. The resin saved in a package redesign will quite often pay for the associated tooling components and the impact on the shelf appeal can be very minimal or even prove to be a style upgrade.

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