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More details are available on the FMC (Foam Microcellular Molding) Process from Negri Bossi of Italy (U.S. office in New Castle, Del.). FMC was introduced in Europe at the FIP 2017 show in France last year and in North America at NPE2018 in May. FMC is an alternative to the MuCell microcellular foam process from Trexel, Wilmington, Mass. (trexel.com), which Negri Bossi also offers. Whereas MuCell involves injecting nitrogen gas into the melt through a port in the injection barrel, FMC injects the gas into a channel in the center of the screw. Gas is introduced at the back end of the screw, behind the feed section, and enters the melt through a series of “needles” in the metering section of the screw during the plasticating stroke. Although a special screw is still required, no modification of the injection barrel is necessary. Negri Bossi also claims that FMC allows use of the full shot capacity of the machine and imposes no limit on the plasticating stroke.
As was demonstrated at NPE, Negri Bossi has applied FMC to foaming both thermoplastics and liquid silicone rubber (LSR). A ping pong paddle was molded with microcellular foamed PBT handle, overmolded with TPU, and the paddle faces were overmolded with foamed LSR. Foaming LSR offers potential savings of costly raw material and the possibility of achieving new levels of softness.
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