Extruder Barrel

It is generally a metal barrel made of alloy steel or composite steel pipe with alloy steel lining. Its basic characteristics are high heat and pressure resistance, strong wear resistance and corrosion resistance. Generally, the length of the barrel is 15 to 30 times its diameter, and its length is based on the principle that the material can be fully heated and plasticized evenly. The barrel should have sufficient thickness and rigidity. The inside should be smooth, but some barrels are engraved with various grooves to increase the friction with the plastic. The outside of the barrel is equipped with electric heaters, temperature automatic control devices and cooling systems for heating by resistance, inductance and other methods.
1. There are three structural forms of barrels:
(1) Integral barrel
Processing method - processed on the whole material.
Advantages - easy to ensure high manufacturing accuracy and assembly accuracy, can simplify assembly work, the barrel is heated evenly, and has more applications.
Disadvantages - due to the large length of the barrel, the processing requirements are high, and the requirements for processing equipment are also very strict. The inner surface of the barrel is difficult to repair after wear.
(2) Combined material
Processing method: Divide the barrel into several sections, and then connect each section with flanges or other forms.
Advantages: Simple processing, easy to change the aspect ratio, mostly used in situations where the aspect ratio of the screw needs to be changed.
Disadvantages: High processing accuracy is required. Due to the large number of sections, it is difficult to ensure the coaxiality of each section. The flange connection destroys the uniformity of barrel heating, increases heat loss, and is difficult to set up and maintain the heating and cooling system.
(3) Bimetallic barrel
Processing method: Inlay or cast a layer of alloy steel material inside the general carbon steel or cast steel matrix. It can not only meet the barrel's material requirements, but also save precious metal materials.
① Bushing barrel: The barrel is equipped with a replaceable alloy steel bushing. It saves precious metals, the bushing is replaceable, and the service life of the barrel is increased. However, its design, manufacturing and assembly are relatively complex.
② Casting barrel: A layer of alloy about 2 mm thick is centrifugally cast on the inner wall of the barrel, and then the required barrel inner diameter size is obtained by grinding. The alloy layer is well bonded to the barrel substrate and is evenly bonded along the axial length of the barrel. It has no tendency to peel off or crack, and has sliding properties, high wear resistance, and long service life.
(4) IKV barrel
1. Longitudinal grooves are provided on the inner wall of the barrel feeding section
In order to improve the solid conveying rate, solid conveying theory shows that one method is to increase the friction coefficient of the barrel surface, and another method is to increase the cross-sectional area of ​​the material at the feeding port that passes perpendicular to the screw axis. The longitudinal grooves are provided on the inner wall of the barrel feeding section and the inner wall of the barrel near the feeding port is made into a cone shape, which are the specific implementations of these two methods.
2. Forced cooling of the feeding section barrel
In order to increase the solid conveying capacity, there is another method. It is to cool the feeding section barrel, the purpose of which is to keep the temperature of the conveyed material below the softening point or melting point, avoid the appearance of melt film, and maintain the solid friction properties of the material.
After adopting the above method, the conveying efficiency is increased from 0.3 to 0.6, and the extrusion volume is less sensitive to the change of the die head pressure.