Feed Screws

Feed screws (feedscrews) are horizontally-oriented screws or augers placed in the bottom of a bin, silo, extruder, hopper, or molding machine to provide uniform flow. Feed screws with pitches varying along their lengths may be used to provide uniform flow. As the feed screw turns, process material is dispensed. Most feed screws are made of alloy steel, tool steel, or stainless steel and then heat-treated, annealed, hardfaced with tungsten, triple-plated with chrome, or otherwise strengthened or finished. Plastic feed screws may be suitable for some applications. Both metal feed screws and plastic feed screws consist of a helically-flighted shaft that rotates inside a barrel or cylinder to advance the process material. The barrel’s thick, outer wall provides strength and may contain an integrally-formed or replaceable liner. There are several barrel choices for feed screws. Twin barrels are designed to house two extruder screws side-by-side. Depending on the design, the feed screws may or may not intermesh. Two-piece barrels usually have an annealed, outer shell and a centrifugally-cast second section that provides added strength. Vented barrels are designed for two-stage feed screws used in hot melt processing. These two-stage screws are usually longer than standard feed screws.

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