How to Disassemble the Extruder Screw? How to Repair It?

Ⅰ. Reasons for damage to the extruder screw

1. The temperature of raw materials is low when plasticizing.

2. The raw material is mixed with metal foreign matter or there are many impurities in the raw material.

3. The extruder screw is running for too long.

4. Unreasonable selection of screw materials.

5. The screw manufacturing precision is low, and the heat treatment hardness of the thread working surface is low.

Ⅱ. The disassembly sequence of the extruder screw

Special tools should be used when the screw is disassembled, and no heavy hammer is allowed. The specific disassembly steps are as follows:

1. Remove the nozzle and the connection between the nozzle and the extruder barrel.

2. Separate the key connection at the rear of the extruder screw elements from the drive shaft.

3. Remove the connecting flange and move the screw of the extruder forward.

4. When the screw head of the extruder is exposed to the barrel, immediately remove the screw head connecting thread (note: the threads here are generally left-handed).

5. Remove the check ring and sealing ring on the screw.

6. The disassembled nozzle, check ring, sealing ring and screw should be cleaned immediately with copper brushes and shovel tools while it is still hot. The special hard-to-clean sticky material should be heated in an oven at the lowest temperature that can soften the material, and then remove the residual material.

7. Assemble the parts on the screw of the extruder together, and apply molybdenum disulfide heat-resistant grease to each threaded connection part to facilitate the next disassembly.

8. After cleaning the surface of the screw that is not in use, apply protective oil, wrap it well, and hang it in a ventilated and safe place.

Ⅲ. Repair and replacement of extruder screw

1. If there is slight wear or scratches on the working surface of the extruder screw, you can use oil stone or fine emery cloth to grind and polish the damaged parts.

2. When the working surface of the screw is seriously worn and the scar groove is deep, the cause of the screw wear should be checked and analyzed, and the fault should be eliminated to avoid similar phenomena again, and then repair the deep scar groove.

If the thread of the entire extruder screw is severely worn, the matching gap between the screw and the barrel increases, the melt leakage increases during operation, and the injection volume is unstable, the outer circle of the screw thread should be thermally sprayed with wear-resistant alloy, and then According to the actual size of the inner diameter of the barrel, the screw grinding is carried out according to the requirements of the fitting clearance of the parts.

If the barrel of the extruder is seriously worn, the diameter of the inner hole increases after repair, and the grinding of the screw after spraying can no longer meet the requirements of the matching gap between the barrel and the screw, the screw should be remanufactured. The thread outer diameter of the screw should be processed according to the matching clearance requirements of the two parts and the actual inner hole diameter of the barrel.

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.

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