The flat die pellet mill was the first pellet mill design at the turn of the 20th century based on flat dies. Generally, there are two types of flat die pellet mills in the market, the rotating die type and the rotating roller type. The former one has a stationary roller with the rotating die while the latter has a stationary die with a rotating roller. Adopting vertical principle, the raw materials drops down by the its own weight into the pelletizing chamber where they are compressed between the rollers and die to form pellets by going through the die holes.