Standard injection molding unit becomes PET stretch blowmolding machine

By admin
Published: June 30th, 2007
A unique invention from a longtime materials and machinery distributor in Cyprus may soon turn the world of injection stretch blowmolding on its head. Called the Cypet process, and developed and patented by Costas Sideris, managing director of Cypet Technologies, it essentially starts with a standard injection molding machine (clamp force from 200-550 tons) and converts it into a single-stage stretch blowmolding unit suitable for small-to-medium volume bottle and jar production.

The big deal? Such a processing cell may cost substantially less than the established single-stage and 1.5-stage machines marketed by better-known manufacturers, while exceeding their output.

Cypet is a newly formed subsidiary of longtime Cypriot distributor M. Sideris & Son Ltd. MPW spoke with Sideris during the PETnology packaging conference in Munich in March; in April a website about the development, www.cypet.eu, was online. He is the first to admit that the Cypet process concept is a simple one?therein lies its charm.

The most difficult part, which required some trial-and-error, was to determine what shape (wall thickness and form) a preform requires for proper blowmolding, as preforms are not?as in standard two-stage units?reheated after molding, but rather move directly from injection mold to blowmold. A second issue was managing the transfer of preforms to the blowmold cavities, but in fact this proved easily managed, says Sideris.

How does it work? A standard injection molding machine, preferably with wide spacing between tiebars, molds preforms on a standard two-stage injection mold design (with naturally balanced hot runner). Upon mold opening, preforms are grabbed by a transfer device and transferred to blowmolds mounted adjacent to the injection mold, within the machine’s clamping unit. The movements of the injection molding machine clamp opens and closes both the injection and blowmolds simultaneously, so that cycle times are coordinated, and the clamping force is sufficient to hold all the cavities (injection and blow) firmly closed. The number of injection cavities matches the number of blowing cavities, as in standard one-stage injection blowmolding.

However, Sideris says Cypet’s cavitation can be much higher, possibly up to 48 cavities, versus eight or 16 with existing one-stage technologies. A Cypriot blowmolder has tested a prototype, and so far has had no difficulties. Cypet intends to offer commercial machines by this September, initially on a 300-ton injection molding machine, in three versions (refer to machine models table).

Output of 1-L, 80-mm neck diameter jars is about 2000/hr on the eight-cavity unit, and about 250 10-L bottles/hr output is possible with two cavities. Sideris reckons output on a Cypet system running a 48-cavity mold set, for example for small shampoo bottles as found in hotels, could be 15,000 bottles/hr. He says a conditioning station (as used in some single and 1.5-stage injection blowmolding units) could also be integrated into the Cypet work cell if required.

According to Sideris, Cypet should be advantageous to PET bottle and jar processors on the basis of lower machine cost and higher output. It retains all the advantages of the one-stage process, while stretching the production output range to that of the two-stage process, at a favorable investment cost.

Sideris has patented the technology in the U.K. and has patents pending for most of the plastics processing world, and remains open to the possibility of licensing the technology. Cypet Technologies, Dhali, Nicosia, Cyprus; +357-22-610-700; www.cypet.eu

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