Firstly the mash that has been formulated and pulverized should be conveyed into the anti-bridging bin. When the extruding machine is working, the material in the anti-bridging bin is continuously fed into the different diameter cylinder conditioner by the feeder. On the other hand, metered steam, water and other liquids should be added evenly and continuously into the conditioner while the material is entering the conditioner.
Material being conditioned for a certain period will flow into the feeding section of the extruder chamber. In the feeding section, the material is primarily compressed and conveyed to the kneading section. In the kneading section, the material is gradually ripened or dissolved under the comprehensive effects of strong agitating, mixing and shearing. After entering the final ripening section, the pressure as well as the temperature rise gradually, which will enable the material to be ripened further, resulting in further gelatinized starch, denatured fat and protein, and homogenized non-crystal texture. Finally, the material will be extruded out of the die and then cut into pellets.
The three sections of extruding assembly can be adjusted depending on the production requirement. The extruding screw pushes material to pass through the whole extruder machinery chamber. And mechanical energy generated by the rotating screw will be transformed into heat energy through the frictional interaction between the material and extruder parts as well as the frictional interaction of material particles.
When this doughy material is extruded to pass through the die holes at the end of the extruder chamber, it is processed to a certain shape. Due to the great pushing and mixing effects of the screw, the material in the chamber is at a certain pressure and temperature, which will evaporate water to make material expanded momentarily when extruded out of the die holes. The more the water evaporated the larger expansion of extruded product, and vice versa. So the product expansion is controllable, and the required expansion extent can be obtained through adjusting each operation parameter strictly. The production of low-density products depends on material composition and the processing conditions. In such case the product will be greatly expanded and kept in a corresponding shape and dimension.
When producing products with high density, the products will be slightly expanded depending on the pressure relief opening provided on the extruder machine barrel as well as the processing conditions (including increasing water content, reducing extruding strength and temperature).
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