Flat die pelleting machine
A flat die pellet mill is a dry forming equipment used for pelleting coarse fibers, mainly applied to the pelleting of feed pellets, wood pellets (biomass fuel), and organic fertilizers. This equipment uses a low-temperature extrusion cutting process, eliminating the need for drying and crushing raw materials before pelleting. It features no material return, high pelleting rate, high pellet strength, uniform roundness, and wide applicability. Flat die pellet mills can be classified into three types according to the movement of their actuators: moving roller type, moving die type, and double-moving die roller type; and according to the shape of the pressure rollers: conical roller type and straight roller type. The equipment has a relatively simple structure, small footprint, is easy to operate, and can be used for both dry and wet processing, making it particularly suitable for small and medium-sized farms or feed processing plants.
Component composition and functional zoning

From a production process perspective, a flat die pellet mill can be divided into the following functional units:

(I) Feeding Unit: Includes a feeding hopper and a distribution device. Feeding relies on the material's own gravity, requiring no additional assist devices and effectively preventing blockages.

(II) Forming Unit: Includes a flat die and pressure rollers. The flat die and pressure rollers utilize a threaded clearance adjustment device, which extends service life compared to traditional shim methods. The pressure rollers are evenly distributed, ensuring smooth operation.

(III) Cutting Unit: Includes a rotary cutter and a scraper device. Used to cut the cylindrical strip from the extrusion die into pellets of a certain length.

(IV) Discharge Unit: Includes a sweeping plate and a discharge port. Employs a unique tangential discharge method to prevent pellet breakage after forming.

(V) Transmission and Control Unit: Includes a motor, reducer, transmission mechanism, and screw pressure regulating device.

Production line roles and processes

Flat die pellet mills play a core role in the pelleting process of organic fertilizer and feed production lines. The complete process flow is: raw material pretreatment (fermentation/crushing) → ingredient mixing → flat die pelleting → cooling → screening → packaging.

In organic fertilizer production, fermented and decomposed livestock manure, straw, and other raw materials can be directly fed into the flat die pellet mill without prior drying or crushing. The equipment uses a low-temperature extrusion process, resulting in a high one-pass pelleting rate and no material return during production. The resulting cylindrical pellets can directly proceed to subsequent cooling and screening processes. In feed production, crushed materials such as corn, soybean meal, and straw are mixed and directly pressed into pellet feed.

 Granulation process and stages

The pelleting process of a flat die pellet mill mainly includes the following stages:

Feeding Stage: Biomass raw materials are fed into the feeding chamber and evenly spread on the flat die under the combined action of the distributor and scraper.

Extrusion Forming Stage: The pressure rollers driven by the main shaft continuously roll over the material layer, extruding the material into the die orifice. The material is subjected to high pressure in the extrusion forming zone at the front of the die orifice and is compacted into shape.

Shaping and Setting Stage: The initially shaped material enters the shaping section of the die orifice. In this section, residual stress that is detrimental to shape retention is eliminated, and the pellets are finally shaped.

Cutting and Discharge Stage: After the formed cylindrical material is extruded from the die orifice, it is cut by a rotating cutter to form pellets of a certain length, and finally discharged from the machine by a sweeping plate.

Pre-fermentation and material preparation
The flat die pellet mill itself does not directly participate in the fermentation process, but it has specific requirements for the degree of fermentation of the feed materials. In organic fertilizer production, organic raw materials (livestock manure, straw, etc.) need to undergo aerobic fermentation and secondary aging first, during which fermentation bacteria are added to decompose crude fibers. The moisture content of the fermented and decomposed material is generally between 20% and 40%, and it can be directly fed into the flat die pellet mill for pelleting. The equipment adopts a low-temperature extrusion process, resulting in a low pelleting temperature rise, which can better preserve the various nutrients inside the raw materials. For feed production, various feed raw materials need to be crushed first to achieve a suitable particle size before entering the pelleting process.

Operating procedures and key control points

The standard operating procedure for a flat die pellet mill is as follows:

Pre-start preparation:Check the gap between the flat die and the pressure roller (ideal gap 0.1-0.3mm, measured with a feeler gauge); check the transmission system (belt tension, gearbox oil level); ensure the raw material moisture content meets requirements (28%-35% for organic fertilizer pelleting, 12%-18% for biomass fuel); check the raw material particle size (must be crushed to 2-5mm) to prevent large impurities from entering; run the mill under no-load for 3-5 minutes to check for any abnormal noises.
In-operation control:Monitor the motor current (must be stable at 80%-100% of the rated value); sample and check the pellet quality every 10 minutes; immediately shut down the feeder if die blockage is found.
Post-shutdown handling:After shutting down the motor, continue running the feeder for 1-2 minutes to empty any residual material; manually clean any residual material from the die holes; apply lithium-based grease to the pressure roller bearing and die plate bearing.

Application effectiveness and industrial contribution
Flat die pellet mills have demonstrated outstanding application effects in small and medium-sized organic fertilizer and feed production. The equipment has a simple structure, low investment cost, and lower energy consumption than ring die pellet mills with the same capacity. No drying or crushing of raw materials is required before pelleting, saving significant energy. The equipment can operate continuously for 24 hours. The single-pass pelleting rate is over 90%, the pelleting rate is greater than 95%, and the pellet compressive strength is greater than 8 Newtons. The pellets have low moisture content, are easy to store, and can maintain their original shape for a relatively long time in water. Overall, flat die pellet mills, with their comprehensive advantages of low investment, small footprint, low energy consumption, and wide applicability, have become the preferred equipment for pellet forming in small and medium-sized production enterprises.