On track to achieving a 90% market share by 2013, that should add up to a lot of PET in circulation. According to research conducted on behalf of the International Bottled Water Association (IBWA), however, the average weight of a single-serve container has shrunk by almost a third over the past eight years, representing a saving of 1.3bn tonnes of resin.

Thin-wall preforms with lighter neck threads have paved the way for significantly reducing the weight of the finished bottle. For example, Canadian injection-moulding manufacturing systems supplier Husky has slimmed down the industry standard 500ml preform by 50% over the past 10 years. With preforms sold subject to weight, there is evidence of some disincentive among converters to invest in new tooling for relatively short runs only to sell less product; hence, the growing trend for some preform manufacture to be undertaken by packers and fillers.

Meanwhile, single-source manufacture integrated blow-moulding and filling lines are stripping time and cost as well as weight out of the process. Speed of production is primarily dependent upon preform weight, but an additional factor will be the number of cavities required to blow the bottle shape itself. For example, Sidel’s Combi (more than 300 systems installed worldwide) has an output rate of 60,000 units an hour for a standard construction. Blowing a more complex design, such as Norwegian brand Isklar’s award-winning multi-faceted PET bottle, on the same system necessitates a running speed closer to 36,000 units an hour.

Productivity has also been optimised by reducing changeover times between jobs. The MouldXpress Advanced semi-automatic system integrated into the blowing wheel on Krones’ range of Contiform blow-moulding machines has lowered the time taken from 3.5 minutes to less than a minute for each blow-moulding station. Makeready time is also cut by as much as 75%.

Much of the latest equipment offers a similar facility. Sipa’s mould opening system allows simultaneous access to more than one station – for example, on a 20-cavity SFR 20 rotary stretch blow- moulder up to three moulds can be changed at the same time.

Sidel was the first blow-moulding equipment manufacturer to commercialise a lighter-than-10gsm single-serve (500ml) PET water bottle, for Nestlé. Since then, other manufacturers have followed suit, with Krones’ Nitropouch taking lightweighting to the extreme with a 6.6gsm container. Meanwhile, Italian manufacturer SMI introduced its 9.94gsm 500ml bottle last year.

Sidel has more recently turned its attention to reducing the weight of hot-fill blow-moulded bottles for carbonated soft drinks. The Skyward and Curvy 500ml PET bottles not only weigh 18.9gsm – the lightest currently available – but have differentiated design possibilities in a category that hitherto has been characterised by a uniform shape and appearance.