How Does the Flat Die Sawdust Pellet Making Machine Work?

Dec 26, 2025

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The core working logic of a flat die wood pellet machine is "extrusion molding." Through the relative movement of the pressure rollers and the flat die, pre-treated wood chips are extruded into the die holes to form high-density pellets. The entire process is divided into four key stages. The first stage is raw material feeding and pre-compression. Pre-treated wood chips (moisture content 12%-15%, particle size 2-5mm) enter the equipment through the feed hopper and are uniformly pushed between the pressure rollers and the flat die by a screw feeder. The screw feeder's speed is adjustable to ensure that the feeding speed matches the subsequent pressing speed, avoiding material accumulation or insufficient supply. Simultaneously, a feed plate at the feed inlet evenly distributes the raw material on the surface of the flat die, preparing for subsequent uniform pressing.

The second stage is extrusion heating and lignin softening, which is the core of pellet forming. The flat die remains stationary, while the motor drives 2-4 pressure rollers above to rotate at high speed through the transmission system. A strong extrusion force (typically 10-15MPa) is generated between the pressure rollers and the flat die. Under extrusion pressure, the wood pellet raw material is not only compressed and densified, but also generates heat due to friction between particles and between particles and die holes, raising the temperature to 70-90℃. This temperature fully softens the lignin in the wood pellets. Lignin, acting as a natural binder, binds the dispersed wood pellets together, laying the foundation for subsequent molding. It's important to note that the temperature generated by friction is sufficient to soften the lignin, so most flat die machines do not require additional heating devices, making them energy-efficient and highly effective.

The third stage is die hole forming and cutting. The softened and bonded wood pellets are forcibly pushed into the evenly distributed die holes on the flat die under the continuous pressure of the pressure rollers. The die holes are cylindrical or conical, with the diameter selected according to requirements (commonly 4-8mm). The wood pellets are further compressed and densified within the die holes, forming continuous columnar shapes. When the columnar shape is extruded from the other side of the die hole, the cutter on the flat die wood pellet making machine cuts it according to the set pellet length, forming uniformly sized wood pellets. The cutting speed is adjustable, and the particle length is generally controlled at 2-4 times the aperture diameter to meet different combustion or usage requirements.

The fourth stage is finished product discharge. The cut wood chips fall naturally through the discharge port, completing the entire processing. Some flat die machines are equipped with a simple cooling device at the discharge port to quickly cool the hot particles to room temperature, preventing them from deteriorating due to moisture absorption at high temperatures. Throughout the entire process, the coordination of core components is crucial: the anti-slip texture on the pressure roller increases friction with the raw material, preventing slippage; the inner wall of the die hole in the flat die is polished to reduce resistance to material passage and improve particle surface smoothness. Understanding this working principle allows users to more accurately control raw material pretreatment parameters and equipment operating parameters, improving particle quality.