Factors Affecting the Service Life of Extruder Screw and Barrel and Processing Requirements

Ⅰ. Factors affecting the service life of the extruder barrel and screw

1. Working conditions of extruder barrel and screw

When working in a relatively harsh environment, the temperature is generally above 200 °C. The extruder barrel screw must not only accept high pressure, but also accept the abrasive effect of the melt and the frequent load starting during pre-molding, and also accept a lot of pressure and torque during the operation.

2. Failure mechanism

The main reason for the failure of the extruder barrel and extruder screw due to wear is "abrasive wear". When plastics and fillers are plasticized at high temperatures, corrosive media are often disassembled, which will corrode the surface metal of the barrel and screw, and the corrosion products are easy to It is carried out by the plastic, which then leads to the loss of material. The combined effect of wear and corrosion aggravates the failure of the barrel and screw.

3. Factors of production

The design, material selection of the barrel and screw, surface metal plating such as Cr, Ni, nitriding, spraying or spray welding hardened alloy, as well as materials (such as plastic particle size, masterbatch function) and operation (speed, back pressure, etc.) will affect extrusion. The service life of the barrel screw. It can be seen that the service life of the barrel screw is mainly related to the raw material of the screw, especially various surface treatment technologies.

4. Selection basis

When selecting the barrel and screw, first select or plan the structure of the barrel and screw according to the nature of the plastic to be processed. Such as aspect ratio, compression ratio, pitch, edge width, etc. The second is to select the material of the barrel screw and the corresponding surface treatment method. Only by selecting the extruder barrel screw suitable for the application scenario, it is possible to prolong the service life of the barrel screw.

Ⅱ. Processing technology requirements of extruder screw and barrel

1. The screw and barrel of the extruder should be made of anti-corrosion and wear-resistant alloy steel. China is currently mostly made of 38CrMoAl, 400 or 45# steel;

2. The screw barrel blank should be forged;

3. The screw barrel should be quenched and tempered after rough processing, the hardness is HB=260~290;

4. After the extruder barrel is machined, the wall thickness should be uniform, and the machining accuracy of the inner hole should meet the standard;

5. The surface of the inner hole should be nitrided, the depth of the nitrided layer should be in the range of 0.40~0.70mm, and the surface hardness HV≥950;

6. The roughness of the surface of the inner hole of the extruder screw barrel should not be greater than 1.6pm after finishing;

7. The extruder screw blank is forged with 38CrMoAl or 40Cr alloy steel;

8. The extruder screw should be quenched and tempered after rough processing. Hardness 118=260~290;

9. The outer circle accuracy of the screw after finishing should meet the h8 level accuracy requirements in GB1801-79;

LESUN is a leading extruder spare parts manufacturer in China, providing screws element and screw barrels. The extruder screw types include conveying screw element, kneading screw element, mixing screw element, etc;  Screw barrels include extruder closed screw barrel, extruder closed screw barrel, extruder feed barrel, extruder side-feed barrels, etc. Custom service is available. Meanwhile, we also provide surveying and mapping business as well as processing business for accessories made by major extruding machine companies. Feel free to contact us.

10. The roughness Ra value of the thread part of the screw barrel is not more than 1.6um on both sides of the thread, and the bottom groove surface and outer circle of the thread are not more than 0.8/um.

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