Injection blow continues to gather speed

No scrap, tight tolerances, and fast cycles are the main reasons injection blowmolding, still a niche process, continues to gain converts.

Injection blowmolding (IBM) is a near-ideal process for forming small hollow packaging of less than 1 liter volume-the smaller the package, down to about 1 ml, the better IBM fits. Typically IBM is a three-stage process. Preforms are molded, rotated while warm to a blowing station, and then rotated once more so that finished parts can be removed from core rods. Parts formed-usually for packaging but also for automotive parts such as CVJ boots-feature tight tolerances comparable to injection molded ones, excellent appearance, and the process creates no scrap.

Small sized packaging such as that formed with IBM equipment is often marketed in Asia, one reason that Asian-no surprise here, mostly Chinese-IBM machine manufacturers have sprouted up like mushrooms after a spring rain. Using the Google search engine and "injection blow" as a search term, seven of the top eight hits are for Chinese manufacturers of IBM machinery and equipment; not only are they plentiful, but their marketing efforts are aggressive.

But most of the genuine technology developments are taking place at more established machinery manufacturers. For instance, Uniloy Milacron (Magenta, Italy) worked with coinjection technology specialist Kortec (Beverly, MA) to develop an IBM that is able to form multilayer preforms. The machines are targeting the medical packaging market, according to Uniloy, but other uses may be found in cosmetics and perfumes that contain oils or aromas.

The Uniloy/Kortec development takes the sting out of one of extrusion blowmolders'' best arguments against IBM that the latter process cannot process multilayer containers.

Tooling is the most costly aspect of injection blowmolding; the standard math says processors should expect two sets of molds will cost as much or more than a machine. The per-cavity cost of injection blow tooling is approximately three times the cost of extrusion blow tooling, making the initial investment a steep one for processors keen to add the process to their stable, notes Bill Petrino, president of Jomar Corp. (Pleasantville, NJ), one of the leading IBM machine manufacturers. He notes the move to larger machinery in U.S. markets is continuing as processors strive to generate more output in limited floorspace. More machines in the 135- and 175-ton range are running molds of as many as 36 cavities. This trend will likely also occur in other markets.

In recent IBM tooling developments, Wentworth Technologies Inc. (Hamilton, ON), which claims to be the world''s largest independent manufacturer of blowmolds for packaging, in April 2005 closed its Jersey Mold & Tool business in Millville, NJ, where the firm had manufactured IBM tooling as well as PET preform molds. Most of this work was transferred to another Wentworth subsidiary, Electro Form, in Vandalia, OH.

Another moldmaker and hot runner supplier, R&D Tool and Engineering (Lee''s Summit, MO), in mid-2005 expanded its Genesis hot runner system so that it also is suitable for IBM. Previously, these hot runners had found use in a related process, injection stretch blowmolding. R&D also supplies tooling for IBM. Many injection moldmakers now offer tooling for IBM, so that availability has increased and the competition has pushed prices lower, say sources.

Though it likely will remain a small niche even within the blowmolding market, injection blowmolding''s benefits make it a very viable alternative.

Matthew Defosse [email protected]