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REPRINTED FROM ASIAN PLASTICS NEWS - March 2001
Microcellular Moulding in AsiaThe MuCell microcellular process technology, developed by Trexel, has been widely licensed in North America and Europe. Silvia Wong looks at how the process is making waves in Asia's injection moulding arena "Office equipment and matrix trays are two of the most exciting applications for the MuCell in Asia," says Stephen Friend, Trexel's director of strategic marketing. "A number of Asian companies have already licensed the technology and are planning to go into production immediately." The semi-conductor matrix trays and office equipment components include printers, fax machines and photocopiers, and the plastics components inside these products are required to have improved flatness and dimensional stability. Much of the warpage and dimensional instability in these parts comes from the moulded-in-stress inherent to the traditional solid manufacturing method. The MuCell process, however, eliminates this moulded-in-stress, making it possible for the parts to stay flat as moulded and remain dimensionally stable, even when heated. In addition to improved flatness and dimensional stability, the Asian companies are attracted to the material cost savings and reduced cycle times, adds Friend. Two injection moulding machines equipped with the MuCell process are currently being installed in Singapore and will immediately be placed in the production mode. MuCell-equipped machines have also been scheduled for installation in Japan, Korea, Malaysia and Thailand. Trexel's first MuCell licensing agreement with a machine manufacturer in Japan was signed with JSW in April last year. It joins a growing list of leading European and North American machine makers which also have MuCell licenses. Under the agreement, JSW can offer MuCell technology on its new injection moulding machines as well as retrofit the MuCell process to its existing equipment. In November, JSW demonstrated the process at its open house in Hiroshima, Japan. The demonstration, watched by about 1,100 visitors, was performed on a J200 EL III injection moulding machine which was used to mould a semiconductor matrix tray using conductive polypropylene. The 200-tonne electric/hydraulic machine is a hybrid design that is well suited for high-speed thin-walled product applications. The moulding process was considered challenging and with the MuCell process it showed dimensional improvements, process advantages and material savings. The warpage of the tray was reduced to 0.07 mm, down from 2.6 mm when the part was solid, while the cycle time remained unchanged. An 8% weight reduction was also recorded. Another benefit provided by the MuCell process is reduced cavity pressure. Trexel's manager of process development, Levi Kishbaugh notes that MuCell's ability to eliminate the pack and hold also reduces the stress in parts, which means less warpage and distortion.
The MuCell moulding machines produced in Japan are now installed with Trexel's SCF systems, the first to be certified by the High Pressure Gas Safety Institute of Japan (KHK). The SCF systems were designed to pressurize supercritical fluids, not only for injection moulding but also for extrusion and blow moulding machines. The KHK certification programme is said to be one of the world's most demanding, and obtaining the certification on the SCF systems is expected to open up the market for MuCell machines to Trexel's partner JSW as well as make the technology readily available to its Japanese licensees. Through the Japanese Sanpho Group, Trexel provides local engineering support, training and other services to licensees, and supplies them with equipment and components integral to the MuCell process. A plastics development laboratory is presently under construction in Japan in support of these activities.
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"This reduction in cavity pressure is also beneficial in other areas," says Kishbaugh. "In insert moulding, for instance, there is less damage to the component being inserted. The same benefit holds true in other applications."