Overview Of The Analysis Of The Use Of The Twin-screw Extruder Barrel

The barrel of a twin-screw extruder is an important part of the extruder in extrusion and compression molding systems. The barrel and the screw work together, the barrel accommodates the screw, and the screw rotates in the barrel. When the screw rotates and pushes the plastic to move forward in the barrel, the outside of the barrel is heated and conducts the heat to the plastic in the barrel, and the volume of the thread on the screw gradually shrinks, so that the plastic groove in the thread is squeezed, turned over and sheared . After various forces such as cutting, it is uniformly mixed and plasticized. As it moves to the front end of the barrel, it gradually melts into a viscous flowing state to complete the plasticization of the plastic. The normal cooperation between the barrel and the screw ensures the continuous extrusion of the raw material of the extruder.

The commonly used hopper structures for the barrel feeding of the twin-screw extruder are ordinary hoppers, forced feeding hoppers and vibrating feeding hoppers.

1. Ordinary hopper

Ordinary hopper. This kind of hopper has simple structure and low cost, and is mostly used for feeding the feeding barrel of small extruder. The feeding method of this hopper is to rely on the weight of the particles to fall freely into the barrel. Therefore, attention should be paid to avoid the phenomenon of "bridging" of raw materials in the hopper during work, which will affect the continuous feeding of the extruder.

2. Forced Hopper

Forced hopper feeding is mostly used in large extruders or when the extruded raw materials are powdery. After the screw is decelerated by the worm gear, it is driven by the motor to rotate, and the upper spring exerts a certain pressure on the screw, so that the raw material is pressed into the barrel when the screw rotates. When the material in the barrel is full, the back pressure of the pressed material pushes the screw upward, so that the barrel stops feeding. When there is no raw material in the barrel, the screw is pressed down by the spring force, and the feeding barrel continues to rotate.

This forced feeding method avoids the "bridging" phenomenon caused by the raw materials in the hopper, and can ensure the continuous feeding of the machine hopper and the continuous feeding of the extruder.

3. Vibrating hopper

The structure of the hopper for vibrating feeding is relatively simple, only an electromagnetic vibrator is added to the ordinary hopper. When the material in the hopper needs to be fed, the vibrator is started to vibrate the hopper in the horizontal direction, so that the material in the hopper overcomes the frictional resistance with the hopper wall and the material and the material, and slides down in the hopper. Shake and get into the barrel.

The vibrating hopper feeding is suitable for powder or granular materials.

The structure of the twin-screw extruder barrel is relatively simple. In large extruders, the structure of the twin-screw extruder barrel can be composed of several parts. Since the barrel is divided into several sections, the length of each section of the barrel is reduced, which brings convenience to the processing of the barrel. However, it is difficult to achieve the same inner diameter size and concentricity accuracy of the inner hole of the multi-section barrel after processing this kind of barrel composed of multiple sections; in addition, the barrel of the segmented twin-screw extruder is heated and cooled in the barrel The layout of the equipment will also bring some difficulties, and the temperature control will not be too uniform. In order to save more expensive alloy steel, the barrel of some large extruders adopts the method of adding a bushing in the inner hole or casting a wear-resistant alloy layer. This barrel casing can be cast from ordinary steel, which reduces the cost of barrel manufacturing.