Pellet machines, also known as pellet presses or granulators, come in several types. The most commonly used are flat die pellet machines and ring die pellet machines, as well as multi-function pellet machines and soft feed pellet machines.

1. Flat Die Pellet Machine and Its Working Principle: Its main components are a flat circular steel die and a set (2–4) of freely rotating grooved rollers. Raw material falls from above into the gaps between the rollers, is pressed into the die holes by the rotating rollers, extruded from beneath the die holes as long cylindrical strands, and cut into pellets by the cutter. Drive modes include roller-driven, flat die-driven, and dual-drive configurations.

The flat die pellet machine is characterized by its simple structure, ease of manufacture, low cost, and suitability for pressing fibrous materials. However, during pelletizing, the linear speed (circumferential speed) at the inner and outer diameters of the flat die is not equal, and the material on the flat die is subjected to different centrifugal forces, resulting in uneven load distribution on the working surface. Therefore, the diameter of the flat die should not be too large, otherwise it will affect the uniformity of the finished product.

2. Ring Die Pellet Machine and Its Working Principle: Its pressing die is a multi-hole cylindrical drum that rotates via transmission. Inside the drum there are 2–4 grooved rollers (pressure rollers) that either rotate freely or are driven. The raw material enters the steel die, is pressed into the working chamber by the rotating rollers, embedded into the die holes, extruded from the outer wall of the steel die, and cut into cylindrical pellets by the cutter.

The main feature of the ring die pellet machine is that the linear speed at every point on the ring die and press rollers is equal. There is no additional friction, and all pressure is used for pelletizing, resulting in higher efficiency.

3. Multi-Function Pellet Machine: It primarily uses mechanical crushing, mixing-extrusion, and frictional heat generation to gelatinize the starch in raw materials. At the same time, it utilizes the moisture content of the raw materials themselves to make the feed plastic and capable of being formed, dried, and cut—all operations completed in one pass.

4. Soft Feed Pellet Machine: Used for processing raw materials with a moisture content of 20%–30% or more. It can pulp green fodder or mix it with powder materials and press them into pellets. Generally, it is processed and fed simultaneously. If storage and transportation are needed, drying is required. Soft pellet machines come in three types: screw type, impeller type, and roller type. The screw type is most commonly used, primarily composed of the barrel, screw, and die holes.