At its most basic, pellet production involves pressing a mixed feed material through circular holes in a piece of metal to form solid pellets. For example, drilling a single hole in a metal plate, placing feed on top, and applying pressure (such as rolling a heavy object like a car over it) would create a single pellet.
To scale this up, drilling multiple holes arranged in a circle, mounting the metal plate (called a “flat die”) on a shaft, and using a rotating wheel to continuously feed material into the die creates a simple flat die press.
However, flat die presses had a critical flaw: the roller moved faster along the outer edge of the die than the inner edge, which led to inconsistent pellet quality and uneven wear on the press itself. To improve this, manufacturers redesigned the die into a ring shape, with the roller positioned inside the ring.
Early versions of this ring die press used a powered roller and a passive ring that simply moved beneath it, but modern technology has reversed this: today’s ring die presses use the ring die as the driving force, with the rollers coasting inside. This design ensures more uniform pressure and extrusion, resulting in higher-quality pellets and less wear on the equipment.