Corrugator makers still chase blowmolding market

Processors of difficult blowmolded parts—for example, those with high length- to-diameter ratios—can expect to see a competing technology aggressively vie for their business in the next months as a number of North American machinery manufacturers actively target these and other blowmolded applications with vertically oriented corrugating machinery. The idea is not new, as corrugator manufacturers Cullom Machine Tool & Die and Corma both have worked to develop vertical corrugators for such parts (February 1999, MP/MPI, p. 50).

But progress has been slow, says Gerry Sposato, director sales and marketing at extruder and injection molding machinery manufacturer HPM (Mt. Gilead, OH), and "No one has taken it past the point of concept." In a bid to do so, last June HPM hired Chris Turner and Hal Minderman, former Cullom employees, to drive development of what HPM calls its vacuum forming system (VFS). The firm is also hiring sales agents with blowmolding experience, says Sposato. A prototype system should be ready early next year.

Cullom''s physical assets were acquired by Scion Technologies in March, and Scion president Gary Karr renamed the combined firms Modern Machine Corp. (Columbus, OH). Scion made corrugator tooling and downstream automation equipment for extrusion lines, and following the acquisition it is actively working to expand use of continuous vacuum formers beyond pipe processing to other applications, Karr says, noting that the competition has some ground to make up. "We''re actually making machines and selling them for these applications," says Karr, with a prototype vertical corrugator now running for potential customers at the firm''s headquarters and one machine sold and being built for a processor of neoprene automotive boots.

To form corrugated pipe, corrugators-oriented horizontally-are placed after extruders, with forming realized using molds on chains or tracks that move continuously. By orienting a corrugator vertically, a process similar to continuous extrusion blowmolding is created, except that corrugated tooling is so close together that there is little to no flash.

"When manufactured in a continuous ribbon, part-to-part separation is greatly reduced and in many cases products can share a common pinch off," explains Turner. Once the parison is captured, all molding is done in a straight line with continuous motion. Parts are formed using vacuum to draw the parison to mold walls, rather than using internal air pressure as in blowmolding, a point both Turner and Karr say will reduce processing costs. Parts are removed continuously as an interconnected ribbon and then trimmed.

Corma (Toronto, ON) did not return phone calls, but the firm actively markets its vertical corrugator via its website as an alternative to blowmolding machines. At HPM, "We''ve a number of different processors that want to work with us on prototype projects," says Sposato. The system is not patented, but the way HPM designs it may eventually be patented instead. HPM acquired no machinery or intellectual property from Cullom.

Turner says the VFS requires neither hydraulics nor water cooling, leading to further saving during operation. Part cooling is accomplished using ambient air, as the molds have internal air flow with the vacuum source. The equipment from Modern Machine Corp. is understood to be similar. Capital equipment investment will likely be competitive with extrusion blowmolding equipment, says Turner of the VFS. He says tooling will cost less than blow molds, making low-volume projects feasible.

As the process is continuous, output is based on length extruded divided by part height rather than cycle times. At HPM, the first machine series will have a linear speed of 20 to 40 ft/min, but the firm is developing units with 200 to 400 ft/min throughput. Karr says machine size will be determined by individual customer projects.

Matthew Defosse

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