A MuCell market incubator

Editor's note: By now, it's rare to find a molder who is unaware of microcellular foaming technology, or MuCell, as its developer, Trexel Inc., has named the process. Its advantages in reducing plastics use and cutting cycle time have been documented by devoted licensees (see "Microcellular Foaming Reduces Cycles, Costs, and Quotes," October 1999 IMM, pp. 100-101). Yet, there are still questions to be answered that will allow MuCell to become more widely accepted. Following are two articles that cover efforts on that front; one hopes to answer nagging questions while the second, "Micropores in MIM Provide Material Savings," unlocks a new frontier for MuCell development.

Purchasing agents listen to the promises of lower material costs, faster cycles, and lower machine rates in a MuCell molder's sales pitch and welcome it with open arms. Ever-skeptical engineers are a tougher sell. What, they ask, does microcellular foaming do to my part's properties? There's little information yet—it's too new. This is the biggest thing holding back wider marketplace acceptance of the process. So says one MuCell licensee, Kaysun Corp. of Manitowoc, WI, a molder who intends to be among the first to find the answers. 

Like others, Kaysun is a MuCell newcomer. Word of MuCell's developer, Trexel Inc. (Woburn, MA), licensing its first molding machine only came out late in 1999. Using supercritical fluids may be new to Kaysun, but Kaysun is no newcomer to molding. 

This $40 million, UL/ISO/QS-registered, full-service contract manufacturer has been molding since 1947. Its specialty is decoupled/scientific molding and CNC machining of functional, tight-tolerance parts—mostly nonappearance parts—in ETP compounds, primarily for fluid transfer, business equipment, lawn and garden, and electrical applications. 

It puts all of its molding know-how into its tooling, which it began building in the mid-'80s. And it knows reinforced ETPs as well as it knows molding and tooling. Kaysun is often called on by customers to specify and qualify materials. The company also designs parts and molds, and supplies turnkey production systems. 

Kaysun began investigating MuCell after attending a Trexel presentation at the Molding 1999 conference and exposition that March in New Orleans, LA. The 310-ton Magna toggle equipped for MuCell molding that Ferromatik Milacron displayed at NPE 2000 belonged to Kaysun. Another MuCell press, this one a 150-tonner, is on order. Most of the 40 other 1990s-vintage machines (35 to 500 tons) at its molding plants in Wisconsin (82,000 sq ft, including a 32,000-sq-ft technical center) and Kentucky (20,000 sq ft) are from Toyo (Maruka USA, Lombard, IL). 

Its Magna T310 has transformed the company's two-year-old technical center in Manitowoc into what it calls a MuCell incubator. Relying on its time-tested materials, design, and molding expertise, this self-styled "engineering intensive" company is incubating a new marketing tool—a MuCell process database. 

Hatching Understanding 
Kaysun's MuCell research project is focused on materials and design. Rick Spindler, manager of new product development, explains, "The bottom line is that people want to save money and MuCell allows them to do so. If you can reduce the part price by 25 percent, maybe you can use a better resin, or modify your part design to take better advantage of the improved dimensional stability this stress-free process provides." 

Both Spindler and Bruce Wendt, Kaysun's president and general manager, agree that there is a considerable learning curve involved in getting the most out of a MuCell investment. "You can't just buy a press, turn it on, and say, 'Now I'm a MuCell molder,'" cautions Wendt. "It's going to take some work." 

Kaysun has learned that MuCell involves low-pressure packing. It is basically a short-shot process. Flow length is critical, so shot volume is a more important variable than melt pressure. Backpressure control is also key. Foaming pressure is what packs the tool, not melt pressure. 

These factors have a tremendous influence on such considerations as gating, hot runner balancing, cooling, cavity pressure sensing, mold cavitation, screw design, and fiber orientation. Determining how these and other changes in the process affect material selection, part mechanical properties, and part design is the purpose of Kaysun's R&D. 

Wendt believes that all the work Kaysun is putting into mapping the data will smooth its customers' learning curves. "Marketers have been taught that splay is bad. With MuCell, splay is OK. There are many, many misconceptions about MuCell and many customers don't have the time to do their own R&D. There is considerable skepticism. But engineers were skeptical about glass-filled resins when they first came out, too." Kaysun's been around for 54 years. It ought to know.