A complete injection-unit package for liquid silicone rubber (LSR) molding that meets the special mixing and metering requirements of low-viscosity thermoset ingredients and can be readily retrofitted on standard injection molding machines has been developed by Nordson Corporation . The company will introduce the package at Chinaplas 2016.
The Xaloy® LSR Package includes a specially designed screw, barrel, seal, valve, and nozzle, along with other components where needed, such as a feed-pipe adapter. Nordson recommends the package for manufacturers of seals, gaskets, cushioning pads, medical devices, infant feeding items, ruggedized electronic devices, and such kitchenware as baking pans and spatulas. As a specialist in the engineering and manufacture of injection-unit components, Nordson can develop customized packages to meet specific customer requirements, according to Mark Colella, global product manager for the Xaloy brand.
“The low-viscosity liquid ingredients for LSR pose a very different set of mixing and metering requirements from those of thermoplastics, and their temperatures must be maintained below the curing point until homogenized material reaches the mold cavity,” said Mr. Colella. “Our LSR Package addresses these unique challenges yet can be retrofitted on a standard injection molding machine in what amounts to a bolt-on conversion.” The components of the Xaloy LSR Package are:
? Screw. A single-flight, wear-resistant, 12:1 to 14:1 L/D screw is designed to provide optimum homogenization of catalyst and crosslinking agents without increasing the temperature of the compound.
? Barrel. With a feed port moved downstream and two welded cooling jackets, the barrel is designed for a low L/D ratio and provides the intensive cooling required to hold the LSR compound below crosslinking temperature. The Xaloy X-800® barrel inlay is a nickel-based alloy with tungsten carbide, providing the abrasion and corrosion resistance posed by certain LSR compounds.
? Rear seal. This is installed on the barrel or as a seal ring on the screw shank.
? Valve. An Xaloy spring-loaded valve ensures immediate shutoff with low-viscosity LSR compounds.
? Shutoff nozzle. This component is provided by a partner company that is a longtime supplier to the LSR industry.