Progress in blow molding keeps plastic containers popular: advancements in container-making equipment are behind innovation and extreme output

Food & Drug Packaging, August, 2004 by Deirdre Sokol

Makers of plastic containers will be pleased to know that demand for their products keeps growing. According to a June 2004 study by research firm The Freedonia Group, Americans can't get enough polymers. Demand is so high that, in the U.S. alone, plastic container production is expected to rise 5.3% a year to $17 billion by 2008.

The pressure to produce product has manufacturers not only ramping up production speeds and output, but also making huge capital investments in new, cutting-edge technology to fill orders. Freedonia estimates that plastic's popularity parallels another trend: a surge in demand for plastic processing machinery, which industry watchers expect to reach $2.8 billion in 2005. In processing plants, that number equals 15 billion tons of product annually.

The introduction of more sophisticated equipment is in part responsible for this growth. Low production costs, design flexibility, light weight but sturdy, make plastic appealing to container manufacturers. On the retail shelf, its aesthetic qualities endear it to consumers.

Inject, extrude or stretch?

Blow molding is the primary method to form hollow plastic objects, with three basic techniques: extrusion, injection and stretch. Injection blow molding is the most popular method. For one, there is no scrap from the container. Second, the three stations of the process allow for the formation of a thick treaded neck with a thin container wall, and a third advantage is the ability to mold multiple containers.

Extrusion blow molding is usually used for large runs--over 50,000 to 60,000 output an hour. The plastic container typically weighs over 12 ounces and is ideal for packaging food and laundry products.

Injection blow molding is used to achieve accurate wall thickness, high-quality neck finish and to process polymers that can't be extruded. Typical applications include pharmaceuticals, cosmetics and single-serve items weighing less than 12 ounces.

Stretch blow molding is only used for difficult-to-blow crystalline and crystallizable polymers, such as polypropylene and polyethylene terephthalate.

The next generation

Behind every plastic container is machinery that costs millions, but has workhorse power and sophisticated functionality that keeps getting better with every new generation.

Machines that were once considered state-of-the-art 10 years ago, are probably no longer show pieces on the plant floor. And machines today have even shorter life-spans. Like personal computers, extruders and blow molders, for example, are considered obsolete in just a few years thanks to rapid-fire technical improvements.

Moreover, plastic processing machinery continues to evolve as long as market competition keeps growing. Competition is so fierce that consumer packaged goods companies (CPGs) have to devise clever, eye-catching ways to increase brand appeal. In turn, it's up to the container manufacturers to execute these new designs. Extruding or blow molding at Mach 2 line speeds no longer gives manufacturers a leg up on the competition. It's merely standard operating procedure.

Recapitalize, stay competitive

Higher out-put machines encompass much more than faster rotation speeds. Today's integrated injection lines, for example, have multi-cavity blow molding functionality, can index several platens at once and are able to blow mold multiple pieces of plastic, or "parisons," at once. "There's no waiting," explains John Denner, director of product development at Graham Packaging. "Instead of just one platen, you have a rotary index so you can injection mold quicker. While you're cooling one cycle you're injection molding another."

Just as end users pass requirements onto manufacturers to keep them ahead of the curve, so do manufacturers, who constantly raise the bar on machinery makers to give them a competitive advantage. German manufacturer Uniloy introduced a new blow molding machine that can be configured for single or double stations, with one-, two-, three- or four-parison bottle molds ranging from 0.2 to 1.5 liters. The BW F4 also features in-machine trimming and labeling. An advanced control panel with a color touch-screen user-friendly operator interface, Ethernet connectivity and tele-diagnostic capability, while not unique to Uniloy, is evidence of how hi-tech computing functionality is now a staple on processing lines.

Machines are also versatile enough to accommodate product design tweaks, making full-blown system replacements down the line unnecessary. Sometimes all that's required is a minor retooling.

Graham Packaging had to make some manufacturing adjustments to its production lines when it introduced Simple Eloquence, a panel-free hot-fill polyethylene terephthalate (PET) bottle. Graham's Denner says, "The primary benefit is being able to have a container with no geometry in the side walls. No seams, no rings, no ribs."

The proprietary method, Graham's Active Transverse Panel (ATP) technology, enables 100% of the vacuum to be removed from the package without the use of traditional panels. As a result, the plastic container looks like glass.