Screw damage cause.

1. The temperature is low when the raw material is plasticized. 

2. There are many impurities in the raw material mixed with metal foreign material or raw materials.   

3. The operation time of the screw is too long.   

4. The selection of screw material is not reasonable.   

5. Low precision of screw manufacturing and low heat treatment hardness of thread working face. 

The disassembly sequence of the screw. 

Special tools should be used when the screw is removed. No heavy hammer should be used. The specific removal steps are as follows.   

1. Remove the connecting parts between the nozzle and the nozzle and the cylinder. 

2. Separate the rear key of the screw and the drive shaft. 

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

4. When the screw head is exposed to the cylinder, immediately remove the screw head connection thread (note: the thread here is mostly left).   

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

6. Remove the nozzle, check ring, sealing ring and screw, and use the copper brush and shovel tool to clean up the residual materials immediately.Special difficult to clean the sticky material, should be placed in the oven heating, the temperature is the minimum temperature which can soften the material, and then remove the residue.

7. Assemble the parts of the screw rod together, and the joints of each thread should be coated with molybdenum disulfide to facilitate the next removal.   

8. The unused screw shall be coated with protective oil after cleaning, and it shall be hung in the ventilated safety place. 

Repair and replacement of screw rod:

1. If there are slight abrasion or scratches on the working face of the screw, it can be used to grind and repair the damaged part of the oil stone or fine abrasive cloth. 

2. The screw work surface with serious abrasion, scars ditch is deep, should check this paper analyzes the reasons of screw wear, troubleshooting, in order to avoid again appear similar phenomenon, and then repair welding repair of deep scars.If heavily damaged the whole screw thread, screw and barrel of the fit clearance increases, there was a molten material work when leakage flow increases, injection quantity is unstable, the screw threads of the cylindrical should thermal spraying alloy, and then according to the actual size of barrel inner diameter, according to the requirements of the parts fit clearance for screw grinding. 

If the cylinder wear is serious, the diameter of the inner hole is increased after repairing, and after the spraying of the screw, it can not meet the requirement of the clearance size of the cylinder and screw, and the screw should be remanufactured.Screw thread outer diameter processing should be based on the clearance requirements of the two parts, and the actual inner hole diameter of the machine can be machined.