The Working Principle Of The Extruder:

The working principle of the extruder:

The extruder has a pair of screws and a screw sleeve, which have the functions of mixing and kneading. After the raw material enters the extruding cavity, the material is subjected to extrusion, friction, shearing, and other effects between the screw sleeves, and the internal pressure continues to rise, up to 4Mpa, and the temperature continues to rise, up to 140 degrees Celsius. Within 3-7s, the temperature and pressure rise sharply, and the tissue structure of the material changes, which further gelatinizes the starch, denatures the protein, destroys the crude fiber, and kills harmful bacteria such as Salmonella. The high-temperature and high-pressure material come out of the discharge port, and its pressure is suddenly released in an instant, and the moisture is partially flashed.

The structure of the extruder:

1. The feeder is to ensure uniform and stable feeding and adjust the feeding amount according to the rated current value of the extrusion motor. Generally, an electromagnetic speed regulating motor or a frequency converter is used for speed regulation to change the feeding amount of the feeder. The outlet of the feeding hopper is usually fed by a screw auger to the extrusion and puffing section.

2. The expansion cavity is composed of the screw, screw sleeve, template, card bone, etc. The screw and screw sleeve are combined in sections, and the degree of compression can be adjusted according to the type and requirements of the extruded feed, and the extruded degree of the extruded feed can be changed.

3. The puffing mechanism is divided into 3 sections in terms of collapse degree according to function and position:

Feeding section: This section has a large screw pitch, which mainly conveys and compresses the material so that the material fills the spiral groove.

Compression section: The screw groove of this section changes from deep to shallow along the material moving direction to compress the material.

Extrusion section: the screw groove is shallower, the pitch gradually becomes smaller, the extrusion force can reach 3.0-10Mpa, and the temperature can reach 120-150 degrees Celsius. This section has the highest pressure and highest temperature, so the wear of the screw and screw sleeve is also the highest. severe. The outlet of the extrusion section is a template. The shape of the template is designed with different die holes according to the needs of different feeds. The material is extruded from the die hole of the template and enters the atmosphere. The pressure and temperature drop sharply, causing its volume to expand rapidly and moisture Rapid evaporation, dehydration and solidification become extruded materials.

The working principle of extrusion puffing:

The raw material is evenly fed into the screw extrusion cavity by the feeder, the space volume of the extrusion cavity gradually decreases along the advancing direction of the material, and the expansion force received by the material gradually increases. At the same time, the material moving in the extrusion cavity is also accompanied by strong shearing, rubbing, and friction. Sometimes, according to the need, an electric heating sheet can be added outside the puffing chamber for auxiliary heating. As a result of this joint action, the temperature of the material rises sharply, and the starch in the material is gelatinized. The entire mass becomes molten plastic jelly. At the moment when the material is discharged from the extrusion die hole, the pressure suddenly drops to 0.1Mpa, the water quickly turns into steam and increases the volume, so that the volume of the material also expands rapidly, and the water vapor further evaporates and escapes to reduce the water content of the material. also dropped quickly. The material coagulates immediately, and many micropores appear in the coagulated colloidal material. The continuously extruded columnar or sheet puffed products are cut by a rotary cutter and then cooled, and sometimes post-processing steps such as drying and spraying additives (such as oils, vitamins, etc.) are required.