No slowing the speeds of stretch blow machineryNo slowing the speeds of stretch blow machinery

Stretch blowmolding is a high-volume affair, and new machinery developments only serve to underline that point.

There is much involved in the stretch blowmolding of packages, of course, but with quality a given, one area where processors best can compete is by simply out-supplying the competition. Generally, stretch blowmolding machines are divided into two categories: those using the one-step "hot parison" method and those using the two-step "cold parison" method.

Two-step machines, in which preforms are molded elsewhere and then fed to the stretch blowmolding unit, are generally high-output, and each year it seems the output climbs. For instance, in 2005 at the Interpack exhibition, stretch blowmolding machine maker Sidel (Le Havre, France) brought its SBO Universal units to market. The manufacturer claims these can help blowmolders increase productivity by 23%. SBO is Sidel''s established machine range, but changes to the basic SBO model, made for the Universal units, have increased output to 1800 bottles/cavity/hr, with units available holding from six to 20 molds. Only three years ago, 1600 bottles/cavity/hr was leading edge.

Sidel says processors require less compressed air to run these machines, reducing an upfront capital expense-that of the air compressor-that can cost as much as the processing machine, as well as operating expenses. Improvements to the preform feeding system keep preforms from jamming; if preforms are too numerous, they are automatically ejected onto orienting rollers and returned to the hopper.

Competitor SIG Corpoplast (Hamburg, Germany) remains hot on Sidel''s heels, and says its own Blomax 24 Series III (24 blowing stations) also is good for up to 1800 bottles/cavity/hr, and in the floorspace that used to only hold the firm''s 20-station machines. Corpoplast introduced this machine during the K show in October 2004. Corpoplast says its machines also do not require as much compressed air as preceding models, and that molds can be changed in 25% less time. Corpoplast has extended its upgrades to the entire Series III range of machines, regardless of mold cavitation.

Two-stage stretch blowmolding machines are most likely to be found at very large internationally active bottle processors, or at beverage bottlers; few of these find their way to "normal" processors. In comparison, single-stage machines, with preform molding and bottle blowing integrated into a single unit, generally are more suitable for processors tackling the small-to-medium volume projects found in the medical, personal care, and cosmetics markets, as well as many food applications.

Nissei ASB (Nagano, Japan) promotes its four-station method as offering extreme process flexibility. The stages on the machine include preform injection, preform temperature conditioning, blowmolding, and finally ejection.

With more than 500 machines and 10,000 molds sold, Nissei ASB claims to be world leader in this machine market. It recently opened offices in Dubai and Pennsylvania to extend its reach, and in May 2005 began marketing an improved version of its PF8-4B machine for generic bottles sized to 1.5 liters. Competition in this market is especially tough, with Italy''s Sipa, Magplastic in Switzerland, and numerous other manufacturers competing for business.

As a result of the fluctuating pricing for polyethylene terephthalate (PET), practically every leading machine manufacturer has gone to great lengths to promote its ability to process other materials. Polypropylene has become a viable alternative to PET in many applications, based on its clarity and processability, though PP does not offer the gas barrier inherent in PET.

Matthew Defosse [email protected]