Microcellular foaming reduces cycles, costs, and quotes

Injectronics, a growing $50 million Tier One molder, is the first custom molder to license the microcellular foam molding process trademarked MuCell by its developer, Trexel. Injectronics officials believe the productivity improvements provided by MuCell will help them meet the belt-tightening price pressures of their customers, including the likes of DaimlerChrysler, Ford, and Valeo.

“When you’re looking at 3 to 5 percent per year givebacks, you can’t quote with a lot of fat in there,” explains Paul A. Nazzaro, Injectronics president. “This kind of technology is just about the only thing we can use to get to the givebacks and still leave us room to make some decent margins.”

Invented at MIT, the MuCell process uses EPA-approved supercritical fluids of atmospheric gases, CO2 and N2, to create uniformly sized, evenly distributed microscopic cells in molded plastic parts (see Figure 2). It can be used even in thin-wall parts molded from high-temperature engineering resins and in structural foam molded parts. But none of the chemical or physical blowing agents, nucleating agents, or reactive compounds used in structural foam is used in MuCell (see related article from December 1998 IMM).

MuCell technology reduces part weight up to 50 percent depending on product design, an important matter in automotive applications. Less plastic is used, so material costs can be cut and cooling is quicker. Injectronics has already been able to cut the cycle time for a glass- and mineral-filled nylon part from 23 seconds to 13 seconds.

MuCell can also reduce injection pressure and clamp tonnage requirements by half. So when Injectronics ordered its 200-ton Engel equipped with the MuCell options, it ordered it tiebarless. Shortly after it arrived, it was running a valve-gated mold that normally runs in a 500-ton press.

Injectronics—with production facilities in Clinton, MA, and Burlington, NC—has already begun investigating other leading-edge processing technologies to improve the splayed surface finish of MuCell molded parts. This will allow MuCell molding of appearance parts, not just for automotive, but for Injectronics’ medical, IT, telecommunications, consumer, and industrial customers as well.

Meanwhile, the company is running trials in nonappearance automotive parts like intake manifolds, engine covers, and HVAC components, like that shown in Figure 1. It is also investigating ways to improve mold cooling to cut even more fat out of cycle times.

Injectronics is also moving its design and engineering center into a new 14,000-sq-ft facility in Farmington Hills, MI. It will be ready by this November and will have injection molding presses installed by Q1 2000.

There’s plenty of room for improvement, but Injectronics officials are excited about the potential in their investment. Nazzaro says the 200-ton tiebarless with the MuCell software, special injection unit, and gas delivery package costs about $270,000. Without these options, it would have cost around $150,000. Trexel licenses MuCell technology based on machine clamp tonnage and resin type. A 200-ton machine has a license fee of $7500 for commodity resins and $15,000 for engineering resins. Regardless, Nazzaro believes the MuCell premiums are a small price to pay for the potential payback.

“Long-term, we expect to retrofit MuCell systems on our existing equipment,” he concludes. “I can’t say now that we will be a 100 percent MuCell shop, but who knows?”

Engel was the first machinery maker to license the process, but Milacron Inc. has also licensed the technology, first for structural foam molding and more recently for straight injection molding and blowmolding.