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technology | PET preforms


Injecting competition into PET preform production


Sipa believes its Xtreme injection compression moulding technology – which offers material savings of up to 15% – takes PET preform production to a new level


Italian packaging machinery maker Sipa unveiled an injection compression moulding technology for preform production at the Drinktec show last month that it believes will enable produc- tion of lighter bottle designs at higher output rates. The 72-cavity Xtreme


system offers a production output of 55,000 preforms an hour, up to 15% greater output than could be achieved by a current 72-cavity injection moulding system. However, it is the potential to reduce weight that Sipa claims is the key differentiator. “The machine has the potential to go even faster – maybe 65,000 from the 72-cavity. But the benefit is not really the speed but the opportunity to reduce the packaging cost dramati- cally,” says Stefano Baldassar, global sales manager for preform systems . Injection compression moulding overcomes the problem of filling thin wall moulds by maintaining the mould slightly open when injection starts, and then closing it as dosing finishes. Sipa claims its Xtreme technology can produce preforms with length to thickness ratios of 80:1,


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compared to 60:1 for the best injection moulding systems and less than 50:1 for most current production. The demonstration system


was producing a 500ml preform weighing 6g, a weight saving of around 15%. While some of the saving comes from the ability to thin the wall, the bulk is attributed to the thinner base. In conventional injection moulding, base thickness is typically deter- mined by the mould filling requirements rather than the physical need of the package, Sipa claims. Baldassar says the injection


compression technology also places less stress on the PET, which results in lower AA levels in the preform and a smaller IV reduction during processing. At first glance, the Xtreme


system appears similar to the compression moulding machines used in the closure


INJECTION WORLD | October 2013


industry (see a video of the system in operation here http://bit.ly/1fkYAdD). The 72 moulds are mounted in blocks of three on a high speed carou- sel which rotates continually, with the moulds running through the closing and opening sequence on each rotation. However, rather than dropping dosed ‘slugs’ of molten polymer from above the open mould, the Xtreme system introduces the charge from beneath the mould via an injection point in the base. Baldassar is reluctant to go


into much detail on the moulding process. However, he says polymer is fed from a continuously-rotating extruder thorugh a rotary union and via a dosing valve into the mould prior to the final compression stroke. There is no conven- tional screw or piston, and no hot runner. “The construction is similar to what we have in our stretch


blow moulding machines. We fill the cavity at much lower pressure and the stress on the material is only during the compression phase,” he says. “In terms of weight


variation we believe we can be comparable with existing [injection] technology. The absence of the hot runner also enables us to treat the material in a more gentle way. IV drop is consistently lower than with traditional technol- ogy,” Baldassar says. Sipa is launching the


Xtreme technology initially in a 72-cavity version, although a 96-cavity system is planned. It will be marketed alongside the company’s own XForm 500 96-cavity preform injection systems and the XForm 150 48-cavity and and XForm 300 64-cavity systems developed with Canada’s Athena Automa- tion (and on show at K). “Our strategy is to


differentiate our product range by application – we don’t think that one preform platform can fit every business case perfect- ly,” he says. As the Xtreme technology is


more costly than a conven- tional 72-cavity injection system, Baldassar expects it to prove most attractive to high volume producers of smaller preforms – up to one litre – where the weight saving potential is the greatest. He says the first production system will be installed early next year. ❙ www.sipa.it


www.injectionworld.com


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