Twin-screw wet type extruders are commonly used in the production of extruded feed. There are many factors affecting the expansion of the material, but it is mainly related to the quenching and tempering conditions, the operating conditions of the extruder and the properties of the material. Changing the extrusion conditions can control the ups and downs of the extruded feed.

1. The role of conditioning is particularly important in the production of sinking extruded feed. When producing extruded sinking feed, it is necessary to weaken the strong effect of extrusion and enhance the effect of conditioning. Water and steam are added during conditioning, and there is enough conditioning time to fully soften and mature the material, creating conditions for the material to achieve better plasticity in the next step in the puffing cavity under weaker conditions. In this way, the material continues to mature without a large degree of expansion, and a sinking feed is obtained. Sufficient tempering has a good effect on improving feed digestibility, product water resistance, and improving extrusion stability, that is, product uniformity.

2. Lower screw speed should be used for extruded sinking feed, which can not only provide the required extrusion and shearing effect, but also avoid excessive pressure, so as to avoid the sharp increase of material energy, and the excessive expansion after passing through the die hole is not easy become sinking feed.

3. The control of machine cavity temperature is another important aspect of material energy control. In the feeding section of the extruder chamber, in order to ensure the good conveying performance of the material, heating may not be required; in the melting section of the machine chamber, heating must be carried out. The temperature of the machine chamber is 120-125°C, which should not be too high. Shearing and kneading, etc., promote the maturation of the material and improve the plasticity; go to the homogenization section at the end of the machine cavity to cool the machine cavity (the temperature of the machine cavity is 40-50°C), reduce the energy of the matured plastic material, and reduce the material The supersaturated state of water in the medium prevents the material from puffing too much when it is extruded from the die hole into the atmosphere.

  4. The expansion degree of sinking feed is usually less than 1.3, which is different from floating feed which can reach 2 or even more than 3. The pressure in the machine cavity is related to the screw configuration of the extruder, the properties of the material, the opening ratio of the template, and the amount of feed. The opening ratio of the template affects the pressure of the material in the machine cavity. The larger the opening ratio of the template, the larger the discharge flow rate, and it is not easy to accumulate high pressure at the template. During the trial production, the number of die holes can be changed according to the situation to obtain a suitable extruded sinking feed.

Due to the low maturity of traditional granulated hard pellets, the extruded sinking fish feed has successfully solved this problem. In addition, extruded sinking fish feed has high stability in water, does not need to add artificial binders, and does not collapse or disperse. Therefore, it has been widely used in fish farming and is gradually replacing hard pellet feed.