What Is the Principle of a single screw fish feed making machine?

Jan 12, 2026

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Raw Material Conveying Stage: Continuous feeding is achieved using a spiral structure. The screw surface of the single screw fish feed extruder machine has spiral ridges. When the screw is driven to rotate by the motor, the spiral ridges generate axial thrust, continuously pushing the powdery raw materials (such as fish meal, soybean meal, corn flour, etc.) in the feed hopper into the extrusion chamber. The core of this stage is ensuring uniform feeding. The screw's helix angle and rotational speed directly affect the conveying efficiency-the larger the helix angle and the higher the rotational speed, the faster the conveying speed. It is important to note that the moisture content of the raw materials needs to be controlled between 12% and 15%. If the moisture content is too high, the raw materials will stick to the screw, affecting the continuity of conveying; if the moisture content is too low, it will increase the frictional resistance between the raw materials and the screw, reducing the conveying efficiency. This stage lays the foundation for subsequent compression melting and expansion processes and is a prerequisite for ensuring stable overall production.

Compression Melting Stage: Mechanical energy is converted into heat energy to melt the raw materials. As the screw advances towards the die head, the screw groove depth of the single screw floating fish feed machine gradually becomes shallower, the volume of the extrusion chamber continuously decreases, and the raw materials are subjected to continuous compression, resulting in volume compression. Simultaneously, friction between the raw material and the screw, the inner wall of the extrusion chamber, and the friction between particles within the raw material generate a large amount of frictional heat. Combined with an external heating device (electric or steam heating) for the extrusion chamber, the raw material temperature gradually rises to 100-130℃, achieving melting and plasticization. This stage is a crucial prerequisite for the raw material to expand; only when the raw material is fully melted can a stable pressure and temperature environment be formed during subsequent extrusion. For example, in the production of fish feed, the protein in soybean meal begins to denature initially at this stage, preparing for improved digestibility and absorption after subsequent expansion.

Extrusion Extrusion Stage: High-Temperature and High-Pressure Environment for Raw Material Modification. When the molten raw material is pushed to the die head, due to the small die orifice diameter, the raw material cannot be discharged quickly, creating a high-pressure environment (pressure can reach 3-5 MPa) at the end of the extrusion chamber, while the temperature continues to rise to 120-150℃. Under high temperature and pressure, the starch particles in the raw material are fully gelatinized, the protein further denatures, and the moisture inside the raw material instantly vaporizes, generating a large amount of steam, causing the raw material volume to expand rapidly, achieving the expansion effect. The single-screw extruder here essentially integrates the core functions of an extruder, achieving a unified "extrusion" and "expansion" process through mechanical structure design. Different feed types have different requirements for the degree of extrusion, which can be precisely controlled by adjusting the screw speed, die orifice diameter, and heating temperature-the faster the speed, the smaller the die orifice diameter, and the higher the temperature, the more significant the extrusion effect.

Forming and Discharge Stage: Pellet shaping is achieved through the die. Under pressure, the extruded raw material is extruded through different orifices on the die of the single-screw fish extruder machine, forming pellets of different specifications (e.g., 1mm fry feed, 3-5mm adult fish feed). The extruded pellets are at a high temperature and need to be cooled to room temperature by subsequent cooling equipment to stabilize the pellet structure and reduce the moisture content to 10%-12%, improving the pellets' water resistance and storage stability. The die orifice diameter and shape at this stage can be flexibly changed according to feed requirements. This characteristic of the single-screw extruder allows it to adapt to the feed production needs of different species and different growth stages of fish. For example, when producing floating fish feed, by precisely controlling the degree of expansion and the die orifice diameter, the extruded pellets can float for 8-12 hours, meeting the feeding habits of surface-dwelling fish.

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MIKIM's fish feed pellet production lines and supporting machinery offer excellent value for money. Not only are they affordable, eliminating middlemen markups and allowing small and medium-sized enterprises (SMEs) and fish farmers to purchase complete sets of equipment at reasonable costs, but they also boast exceptional efficiency. The fully automated process, from raw material crushing and precise ingredient mixing to extrusion pelleting and maturation, is completed in one continuous flow. This results in high starch gelatinization rates and uniform pellet formation, significantly improving production efficiency and feed quality, truly achieving "low cost, high output." Choosing a MIKIM fish feed pellet production line means enjoying comprehensive pre-sales and after-sales service, including 24-hour online customer support, a one-year warranty on the entire machine, professional on-site installation, commissioning, and maintenance, and a stable supply of spare parts. Customers can buy with confidence and use with peace of mind, with both excellent value and service quality!!!

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