16 Solutions for the Failures of Injection Molding Machine Plasticizing Unit

Problems of injection molding machine plasticizing unit and solutions

1. Unable to shoot glue

  • There is someforeign matterclogged in the nozzle. Check whether the nozzle is blocked and clean or replace the nozzle.
  • The glue nozzle is broken. Disassemble the flange to check whether the glue nozzle is broken, and replace the glue nozzle.
  • The injection directional valve is stuck. Check whether the directional valve has 24V voltage and the coil resistance is 15-20 ohms. If it is normal, then it’s very likely that the valve is blocked. Clean the valve or replace the directional valve.
  • The piston rod of the injection rubber is broken. Loosen the rubber-injected piston rod nut. And check whether the piston rod is broken, and replace the piston rod.
  • The barrel temperature is too low. Check whether the actual temperature reaches the required melting point temperature of the material, and reset the barrel temperature.
  • The piston oil seal of the injection rubber is damaged. Check whether the piston oil seal is broken and replace the oil seal.

2. Loud start-up sound when shooting glue

  • The injection speed is too fast. Observe the start speed change of the injection speed, and adjust the flow rate of injection.
  • There is air in the oil circuit. Observe whether there is vibration in each movement.

3. The sound is loud when the glue is stopped when the glue is injected

The movement conversion speed is too fast when shooting glue. Check whether the injection glue has increased the holding pressure. Then, increase the holding pressure, adjust the injection level, and add the melt glue to delay.

4. Unstable injection volume

  • The oil seal of the oil cylinder is worn. Observe the pressure retention of the pressure gauge and replace the oil seal.
  • The glue nozzle and rubber ring are worn out. Detect with 2 shotsand replace the three-piece glue nozzle.
  • The barrel is worn. Use the nozzle twice to detect, Disassemble the material to check the wear condition, and replace the glue cylinder.

5. Semi-automatic action without glue injection.

  • The advancement of the shooting platformis not terminated. Check whether the injection stationand the mold clamping limit switch is normal. And check the wiring and travel switch.
  • Disconnected. Check the wiring and rewire.
  • Reset mode clamping. When the machine hinge is straight, the position is 0, readjust the zero position of the electronic ruler.

6. When working in semi/automatic mode, the barrel temperature gradually exceeds the set value.

  • The melt speed is too fast. Use a tachometer to test whether the screw speed is too fast, and reduce the melt speed.
  • Excessive back pressure. Observe the product, the back pressure gauge value, and reduce the back pressure as much as possible.
  • Friction between the screw and the barrel. Disassemble the screw and barrel, check the wear condition, and replace the barrel or screw.
  • Improper temperature setting. Check whether the actual temperature is too low and reset the temperature.
  • The shear heat of the plastic is too large. Check the temperature rise in the front and middle sections, reduce the speed of the melt, and the back pressure.

7. The screw sounds when melting glue

  • Improper installation of the drive shaft. Separate the screw rotation to check if there is any noise. If there is any, remove the flat bearing and reassemble it.
  • The plane bearing is broken. Separate the screw and check that the rotating part. If there is noise,then replace the flat bearing.
  • The screw is bent. Remove the screw for inspection and replace the screw.
  • The screw has iron filings. Disassemble the screw to check and clean the screw.
  • Use a dial indicator to check the concentricity of the adjustment screw. The beating around 0.05mm is normal.

8. Unable to melt glue

  • Burnt bearings or bursting of the drive shaft. Separate the screw and melt the glue.Then, observe the soundand replace the bearing.
  • The screw has iron filings. Separate the screw and the barrel, then check the screw for iron filings. And remove the screw for cleaning.
  • The melt valve is blocked. Use the hexagon key to top the spool to see if it moves, and clean the solenoid valve.
  • The glue motor is damaged. Separate the meltingmotor. When the melt does not turn, replace or repair the meltingmotor.
  • Burn out the heating coil. Check whether it is normal with a multimeter and replace the heating coil.
  • The plug is loose. Check whether the molten glue oil plug is in poor contact.Connect the plug tightly, and check whether there is a 24 power supply.

9. The back pressure cannot be adjusted when melting glue.

The back pressure valve is broken. Increase the back pressure when cutting the material. Check whether the screw retreats, and clean the back pressure valve.

10. The product has black spots.

  • The screw has carbon deposits. Check the cleaning screw and barrel.
  • There is carbon deposit in the barrel and the auxiliary machine is not clean. Check whether the feederhasdust, polish the barrel and clean the auxiliary machine.
  • Corrosion of glue nozzle components. Check the glue nozzle and replace the glue nozzle assembly.
  • Flanges and nozzles have carbon deposits. Clean up and replace.
  • The raw materials are dirty. Check raw materials and replace them.
  • The temperature is too high and the back pressure of the melt is too large. Check the temperature of each section and reduce the back pressure.

11. Poor screw color mixing

  • Material issues. Check the toner quality and replace the material.
  • The temperature is too low. Check the actual temperature and the required temperature of the material, and increase the temperature.
  • The back pressure is too low. Check the back pressure and increaseit.
  • Short mixing time. Extend the mixing time or replace it with a mixing head.
  • The speed is too low. Check the screw speed and increase the screw speed.

12. No glue pulling action

  • High back pressure. Check the nozzle spraying speed when meltingglue by manual, and reduce the back pressure.
  • Disconnected. The pumping valve is disconnected.
  • The spool of the directional valve is not flexible. Press the spool with an Allen wrench to check whether it is free to move, and clean the spool.

13.When melting glue, the motor vibrates abnormally

  • The bearing is broken. Observe whether there is any abnormal sound when melting the glue, and replace the bearing.
  • Improper adjustment of oblique ball bearings. Observe whether the drive shaft swings, and readjust the gap.
  • Deformation of the screw. Separate the screw to observe the rotation of the drive shaft, and replace the screw.
  • The copper sleeve of the rear plate of the shooting table is worn out. The 2 guide rods are deformed or the fixing screws are loose. Observe whether the second plate copper sleeve is ground out of copper powder, and the copper sleeve needs to be replaced in time.

14. Shoot glue twice

  • The nozzle aperture is too small, and the resistance is too large when shooting glue.
  • The nozzle heating ring is broken, check the heating ring or replace it.
  • Check whether the pressure and flow output is changed.

15. Reasons for screw fracture

  • The shooting movement is not synchronized. Then, adjust the shooting movement synchronization at the range of ±0.05.
  • The injection cylinder is not synchronized, adjust the injection cylinder to synchronize at the range of ±0.05.
  • The raw material and the screw performance of the injection molding machine do not match.
  • The temperature has not reached the melting point of the material used.
  • Turn the screw as soon as the temperature is reached.
  • If the heating tube is burned out, it will not be heated. Check for the anti-cold function and replace the heating tube.

16. Unable to adjust the mold

  • The mechanical level and parallelism are out of tolerance. Check with a spirit level angle ruler to adjust the parallelism and level.
  • The gap between the pressure plate and the die-adjusting nut is too small. Measure with a feeler gauge, adjust the gap between the pressure plate and the nut. Besides,adjust the gap between the die nut and the pressure plate (gap ≤ 0.05 mm).
  • Burn the nut to check whether the nut can be turned to generate heat and iron powder is coming out. Replace the nut.
  • Adjust the upper and lower support plates. Remove the lock nut of the expense board to check and adjust the nut.
  • The I/O board is broken. Check whether there is a signal at the output point on the computer page, and repair the electronic board.
  • The mold adjustment spool is stuck. Remove the valve to check and clean the valve.
  • Die adjustment motor is broken. Check the oil motor. Replace or repair it.

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