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Damage reasons and repair methods of injection screw of injection molding machine

Update:12-11-2020
Summary:

Injection screw of the injection molding machine, bette […]

Injection screw of the injection molding machine, better screw barrel, what is the reason for screw damage, disassembly and maintenance method?     

  (1) Injection screw of injection molding machine, better screw barrel, reason for screw damage
      ①   The temperature is low when the raw material is plasticized.
      ②   Metal foreign matter is mixed in the raw material or there are many impurities in the raw material.
      ③   The screw idling time is too long.
      ④   The selection of materials for manufacturing screw is unreasonable.
      ⑤  The screw manufacturing precision is low, and the threaded working surface has low heat treatment hardness.

 
  (2) Injection screw of injection molding machine, better screw barrel, disassembly sequence of screw manufacturer
       When removing the screw, special tools should be used, and heavy hammers are not allowed. The specific removal steps are as follows.
      ①   Remove the nozzle and the connection between the nozzle and the barrel.
      ②   separate the key connection at the rear of the screw from the drive shaft.
      ③   Remove the connecting flange and move the screw rod forward.
      ④   When the screw head is exposed to the barrel, immediately remove the screw head connecting thread (note: the thread here is generally left-handed).
      ⑤   Remove the non-return ring and seal ring on the screw.
      ⑥  The nozzle, check ring, sealing ring and screw rod that have been dismantled should be cleaned up with copper brushes and shovel tools while they are hot. Special sticky materials that are difficult to clean should be heated in an oven at a lower temperature that can soften the materials, and then remove the remaining materials.
      ⑦  Assemble the parts on the screw, and each threaded connection part should be coated with molybdenum disulfide heat-resistant grease to facilitate the next disassembly.
      ⑧   The screws that are not in use should be coated with protective oil after the surface is cleaned, wrapped, and hung in a ventilated and safe place. 


  (3) Injection screw of injection molding machine, better screw barrel, repair and replacement of screw manufacturer
      ①   If the working surface of the screw is slightly worn or scratched, use oil stone or fine emery cloth to grind and polish the damaged part.
      ②   When the working surface of the screw is severely worn and the scar groove is deep, check and analyze the cause of screw wear and troubleshoot to avoid similar phenomena again, and then repair the deeper scar groove. If the threads of the entire screw are 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 barrel The actual size of the inner diameter shall be ground on the screw according to the fitting clearance requirements of the parts.
       If the barrel is severely worn, the diameter of the inner hole increases after repair, and the grinding of the screw after spraying cannot meet the requirements of the clearance 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.

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