How to clean the barrel and preheat the insert before injection molding?

(1) Clean the barrel

1) Purpose of cleaning. If the cylinder is not cleaned, the molding operation will have a greater impact on the quality of the plastic parts, in order to ensure the quality of the plastic parts. The barrel must be cleaned.

2) Cleaning method

  1. If the injection molding machine wants to produce several plastic parts, it should first produce light-colored plastic parts with low melting temperature and poor thermal stability, so that refueling and washing are more convenient and easy.
  2. If the molding temperature of the new material is higher than the remaining material temperature in the cylinder, the temperature of the cylinder and nozzle should be raised to the lowest processing temperature of the new material, and then the new material should be added for continuous air injection until the remaining material is drained, and then the material temperature should be increased until the nozzle temperature reaches the required temperature, and then the new material should be added to continue production.
  3. When the molding temperature of the new material is lower than the remaining material temperature in the cylinder, the temperature of the material nozzle should be raised to make the remaining material in the best flow state, and then cut off the heating power supply, add the new material to clean when the cylinder is cooled, and wait until the new material falls to the processing temperature of the new material, and then continue to produce.
  4. For the cylinder cleaning with heat-sensitive residual materials, such as PVC, POM, PCTFEF3, etc., in order to prevent plastic decomposition, a two-step process should be adopted, first with good thermal stability of plastic, such as PS, LDPE and other raw materials for transition recharging cleaning, and then replace the transition cleaning material with the processed new material.
  5. Cleaning agent cleaning. Whether it is direct refuelling or transitional refuelling, it consumes a lot of raw materials and causes waste. The effect of cleaning with cylinder cleaning agent is not only good, but also saves money. It is suitable for the cleaning of injection molding machine materials of various thermoplastics in the processing temperature range of 180 to 280 degrees Celsius.


3) The way of cleaning

1 Plunger injection molding machine cylinder cleaning, because the cylinder memory amount is large, and not easy to turn, cleaning is more difficult, must be disassembled and cleaned or use special materials.

2 Screw injection molding machine cylinder cleaning, usually using direct refuelling cleaning, cleaning should be understood in the material sheet remaining material and new material molding temperature range, thermal stability and different compatibility of various plastics, in order to develop specific cleaning methods.


(2) Preheating of inserts

1) Purpose of preheating. After the insert is preheated, the temperature difference between the molding and the molten material shrinks, so that the cooling rate of the molten material around the insert slows down, the shrinkage rate is more uniform, and a certain hot material feeding effect occurs, which reduces the internal stress around the insert, is conducive to reducing the crack generation around the insert, and does not reduce the strength.

2) Range of preheating. Not all inserts need to be preheated when forming, such as smaller parts, easy to be heated by molten material in the mold, can not preheat; For larger inserts and plastics with rigid molecular bonds, such as PC, PS, PSF, PPO, etc., they are prone to stress cracking, and such pieces generally need to be preheated.

3) Preheating temperature. The preheating temperature is limited to the lock layer on the surface of the metal parts, which is generally 110~130C for coated inserts, and the preheating temperature can be increased to about 150C for aluminum alloy or copper inserts without surface coating.

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