News & Events

What is the screw removal and repair method

Update:31 Jan 2019

Cause of screw damage 1. The temperature of the raw mat […]

Cause of screw damage

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

2. The raw material is mixed with metal foreign matter or the raw material contains many impurities.

3. The screw running time is too long.

4. The choice of manufacturing screw material is unreasonable.

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

Screw removal sequence

Special tools should be used when disassembling the screw. It is not allowed to strike with a heavy hammer. The specific disassembly steps are as follows.

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

2. Separate the screw joint at the rear of the screw from the drive shaft.

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

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

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

6. Remove the nozzle, check ring, seal ring and screw. Immediately use hot copper brush and shovel tool to clean the residual material. Specially difficult to clean the adhesive, should be placed in an oven to heat, the temperature is the lowest temperature to soften the material, and then remove the residue.

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

8. The screw that is not used temporarily should be coated with protective oil after cleaning the surface, wrapped and hung in a safe place.

Repair and replacement of the screw:

1. If there is slight wear or scratch on the working surface of the screw, use oil stone or fine sand cloth to grind and repair the damaged part.

2. When the working surface of the screw is seriously worn and the groove is deep, the cause of the screw wear should be checked and the fault should be eliminated to avoid a similar phenomenon, and then repair the repair of the deeper groove. If the thread of the whole screw is seriously worn, the matching clearance between the screw and the barrel increases, the leakage of the melt increases during operation, and the injection volume is unstable. The outer circumference of the thread of the screw should be thermally sprayed with wear-resistant alloy, and then according to the barrel The actual size of the inner diameter is subjected to screw grinding according to the matching clearance requirements of the parts.

If the barrel is seriously worn, the diameter of the inner hole is increased after the repair, and the grinding after the spraying of the screw can not meet the matching gap requirement of the barrel and the screw, and the screw should be remanufactured. The thread outer diameter of the screw should be machined according to the actual clearance of the barrel according to the fit clearance requirements of the two parts.