Screw barrel damage cause and disassembly sequence

Update:07-12-2018
Summary:

1) Causes of damage to the injection screw of the injec […]

1) Causes of damage to the injection screw of the injection molding machine

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

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

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 face has low heat treatment hardness.

6 The selected screw does not match the material being formed. For example, PVC molding needs corrosion resistance.

(2) Disassembly sequence of injection molding machine injection screw manufacturers

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 back joint 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 Disassembled nozzles, check rings, seal rings and screws should be cleaned immediately with copper brushes and shovel tools 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 Screws that are not in use should be coated with protective oil after cleaning the surface, wrapped and hoisted in a safe place.

(3) Repair and replacement of injection molding machine injection screw manufacturers

1 If there is slight wear or scratch on the working face 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 fitting 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 screw is unable to meet the matching gap requirement of the barrel and the screw, the screw should be remanufactured. The thread outer diameter of the screw should be processed according to the actual clearance of the barrel according to the matching clearance requirements of the two parts.