Not just a little cheaper, faster, or better

Adam Burke wants potential customers not to pigeonhole his firm''s patented melt-phase forming process as "a bit like thermoforming, or blowmolding, or injection molding," because then they also assume the process has the same limitations as these more common ones.

This is a new plastics technology," explains the president of PBM Plastics. "This isn''t just about making things a little cheaper, or a little faster, or a little better." And though he says melt-phase forming is comparable in part cost to other plastics processes, his mission is not to simply snatch business from other processors. "We''re trying to work with customers to design and make brand-new products."

To date PBM''s tactics seem to be on target, with the firm in the midst of an expansion from its current stable of three commercial lines plus a prototype unit. Burke, formerly with GE Plastics (now GE Advanced Materials, says PBM (Newport News, VA) has several new lines under design. "We''re actually looking to add a number of new machines. Plus we''ve worked with GE Fanuc to automate the ones we have," increasing productivity, "and we''ve gone from a five-day to a seven-day workweek." The firm is also on the search for a new business sales manager and a sales representative; so far most customers have approached PBM after the processor was recommended by other customers. "I cannot think of a product [where] we''ve had to bid against [another processor]," he says. "In fact, most of our discussions are not with purchasing [departments of customers], but with marketing and design people who have new ideas they want to realize."

A bit like...

PBM''s patented process and equipment (made in-house) most closely resemble thermoforming, which makes rigid parts. But melt-phase forming is different-enough so that PBM''s first commercial part, a baby bottle liner, was awarded one of the Flexible Packaging Assn.''s top awards in 2003 (PBM distributes the Pumpmate Breast Milk Storage and Feeding Kit with liners via www.pumpmate.com). Indeed, melt-phase forming is fine for rigid or flexible parts, or both rigid and flexible sections in a single part, says Burke.

PBM''s process is similar to some developed in the past, such as the solid phase pressure forming (SPPF) process created by Shell Chemicals (November 1988 MP/MPI) and a billet forming process from Dow Plastics in the 1970s. At his website, www.foamandform.com, acknowledged thermoform expert Jim Throne writes that SPPF "was introduced in the 1970s as a way of pressure-forming thin-gauge homo-PP sheet into relatively simple shapes such as drink cups and unit dose cups." PBM''s process adds a greatly increased degree of flexibility and automation.

PBM sources sheet from two extruders, one a specialist in engineering thermoplastics and one in standard materials. PBM uses the sheet to punch billets with a die punch. These billets, in nearly any shape, are automatically conveyed through a heater into a tool with 30 to 50 cavities. The plastic billets are heated to their melting point, which enables forming with no vacuum required-a plug assist and air pressure suffice.

Burke highlights the billet punching step as key to the process''s advantages. "We can get scrap rates of only 15% to 18%," compared with much higher ones (30% or more) on standard thermoforming machines, "so the economics are a game changer." Thermoformers generally granulate and reprocess scrap, but Burke says PBM''s lower scrap levels as a percentage of virgin material enable it to form parts with much higher clarity since high scrap reuse can impact transparency. Also, PBM''s process can realize much thinner walls with less stress than either blowmolding or conventional thermoforming, producing material savings and more economical use of expensive plastics often too costly to use in thermoformed or blowmolded parts.

Output on a PBM melt-phase forming line is in the "hundreds of millions of parts per year," much higher than extrusion blowmolding equipment, he notes. A typical part for melt-phase forming includes a thin-walled, flexible, disposable tube with an integrated rigid flange, formed in a single step.

Even the parts themselves are special, with draw ratios of 1:8 possible. Since this spring, PBM''s website (www.pbmplastics.com) includes an E-engineer program that enables potential customers to determine in a few steps whether their parts can be made via melt phase forming. The program also lists the many options available in this process, including a near-endless choice of materials.

"We''ve validated polyure-thane, PET, nylon, ABS, polycarbonate, EVOH, all of the polyolefins," says Burke. As an example of the novel parts that can be formed, he cites PBM''s processing of polyetherimide (GE''s Ultem) into containers 4 inches square with 1-mm wall thickness that could be placed on a range for boiling water. One of the companies supplying PBM can process sheet to 11 layers; such coextrusions pose no problems, he says.

The very broad range of potential materials allows PBM to take advantage of high-end materials for parts that are pasteurizable, auto-clavable, retortable, or more. Burke says the firm''s E-development program and in-house prototyping capability are critical since designers have often written off some material combinations; or, a part design that might be considered too difficult, when, in fact, PBM can handle it.

Other options for melt-phase formed parts include threaded caps and something called inmold welding. "One of our customers wanted to attach another part to the bottom of one we processed for him," explains Burke. Rather than take the melt-phase formed part and reheat part of it to its melt phase again to attach the two, PBM developed the means to insert the other parts into the melt-phase forming unit''s cavities. It then formed the billets onto the parts so that a bond was created inmold-analogous to overmolding in injection molding. Melt-phase forming also facilitates any type of embossing or decoration as well as use of lenticular and holographic labels.

Beyond the milk bottle liners, Burke says he can offer few details on other commercial parts, other than to say that PBM is commercial in its five targeted markets of industrial, consumer, medical, food, and beverage.

"Most customers insist on non-disclosure agreements. They see it [the process] as such a game-changer that we can''t talk much," even being turned down when he''s offered discounts to customers if they allow him to publicize a project. One market being pursued is forming of flexible liners for blowmolded bottles for mayonnaise, ketchup, shampoo, and window cleaner.

Matthew Defosse

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