Solutions for 14 Kinds of Injection Molding Machine Clamping Problems

The injection molding machine consists of three main parts: clamping unit, injection unit and machine bed.

The mold clamping unit is used to close the mold against the force generated by injection unit during the injection and holding pressure. After that, the platen open and eject the plastic product out from the mold cavity.

If the clamping unit has some problems, the whole injection molding machine will stop.

Injection Mold Clamping

1. No clamping action


  • Check the limit switch of the front safety door and repair it.
  • Check the 24V-5A power supply in the electric box of the machine bed, replace the fuse and the power box.
  • Check whether the valveis stuck, and clean it.
  • Check whether the I/O board has output and whether the solenoid valve is energized.
  • Check whether the hydraulic safety switch is pressed and whether the mechanical safe device is open.

2. Clamping unit opening and closing with abnormal noise.


  • Check whether the lubricating oil pipe is disconnected. If so, the oil pipe must be reconnected again.
  • The dose of lubricating oil is small, increasethe dose of lubricating oil. It is recommended that 50 molds per dose or manually add enough lubricating oil.
  • Clamping force too strong, check whether the mold requires such a strong clamping force, and reduce the clamping force accordingly.
  • The electrical current of the amplifier board is disturbed. Check whether the current parameters meet the acceptance criteria, and readjust the current value.
  • The parallelism is out of tolerance, use a dial indicator to check whether the parallelism of the platens (the moving platen and the stationary platen ) is greater than the acceptance standard. Then, adjust the parallelism.

3. The clamping unit open with few seconds waiting


  • The starting speed is too slow. Check whether the screw damping is too large, and adjust the screw damping hole.
  • The middle hole of the damping screw is too large. Check whether the damping of the Y-hole screw is too large. Replace the damping screw with a thin center hole.

4. Crawling during open


  • The moving-plate brush and column are worn out. Check them. Then, replace the copper brush of the moving plate andthe column, and add more lubricating oil.
  • Improper adjustment of speed and pressure in open/clamp. When at the settingof 20 flow rate and 99 pressure, the moving plate of mold clamping should not crawl. Adjust the flow proportional valve hole or pilot valve hole and adjust the linear current value of the proportional valve.
  • There is air in the hydraulic oil hose and cylinders.

5. The clamping unit can't be opened


  • Increase the mold opening / clamping speed. If the pressure flow is too small and not adjusted properly, check whether the mold opening / clamping speed and pressure is appropriate. Increase the mold opening / clamping pressure and speed.
  • The zero position of the mold-locking electronic linear changes. Check at the clamping moment of the clamping toggle straightening, whether the linearends at the zero position. And then readjust the zero position of the electronic linear.
  • Check whether the toggle is reversed.

6. In automatic model for the production, mold adjustment becomes tighter or looser.


  • Internal leakage of the mold adjustment solenoid valve.Check whether the solenoid valve is “O” type.
  • Check whether there is any mold adjustment action in the manual model. And check whether the valve is stuck.

7. After the mold clamping, the mold is opened slowly and automatically while other actions are applied.


  • If the hydraulic manifold block is leaking, check the high speed clamping valve and replace the hydraulic manifold block.
  • If the mold opening valve leaks, turn on the oil pump and terminate the mold clamping. Apply the action of the injection unit or injection to check whether the moving platen moves back, and replace the mold opening valve. Normally, it does not move when opening and locking the mold.

8. There is only mold opening action when clamping.


  • Wrong wiring, check if there is 24V DC to the valve. Besides, check the wiring and connect the wiring.
  • If the valve is stuck or the wrong installation, check them. Then, reinstall the valve or clean it. Under normal circumstances, the mold opening and clamping action is immobile.

9. Poor clamping


  • Improper adjustment of holes A and B. When the system flow rate is 20 and the pressure is 99, observe whether the clamping action is crawling. If so,readjust or change the valve.
  • There is air in the hydraulic oil circuit, hearwhether there is air in the oil circuit. Check whether there are air bubbles in the oil. If so, then it needs to be exhausted.
  • The ramp-up and ramp-down adjustment of the amplifying board is improper. Observe whether the current value of the ammeter is proportional to the rise and fall or the speed, and adjust the amplifying board.

10. Clamping can not afford high pressure and exceeds the stroke


  • If the limit switch exceeds the limit, check whether the mold adjustment is appropriate. Then, adjust the proper mold thickness. Also, check whether the motor is in a normal state.
  • If the hydraulic limit exceeds the stroke, whether the stroke position of the electronic linear is appropriate. Check whether the mold adjustment is appropriate, and adjust the mold forward appropriately.

11. Manual model has termination, but without semi-automatic model.


  • If the mold opening valve leaks, move back the injection unit in manual model. Then, observe whether the moving platen moves backward, and replace the mold opening valve.
  • Check the maximum stroke of the electrical linear and pressure flow.

12. No ejector action


  • The ejector limit switch is broken. Use a multimeter to check whether the 24V proximity switch is lit. Replace the ejector limit switch.
  • For the stuck valve, use a hexagonal key to press the spool of the ejector to see whether it can be moved. If so,clean the pressure valve.
  • The ejector limit rod is broken. After stopping the machine, take out the limit rod by hand and replace it.
  • The ejector switch is short-cut, check the 0 voltage of the ejector switch to ground with a multimeter, and replace the ejector switch.
  • The position of the electronic linear is set improperly.

13. The ejector is out of control in semi-automatic model.


  • The ejectorboard is broken, check whether the circuit is normal. The normal voltage is DV  Repair the ejector board.
  • If the cableis broken, check the switch connection line and I/O board connection  Check the wiring and rewire.
  • Check whether the mold moves.
  • Whether the sealing ring of the piston rod of the oil cylinder is damaged.

14. Loud sound when opening mold


  • Poor proportional linearity, poor adjustment of pressure and flow at the time of mold opening and closing. Check and adjust the ramp up and ramp down in the parameters.
  • The lubrication of the toggleof the clamping machine is poor. Check the lubrication of the column, the moving platen slippery foot, and the toggle of the machine. Increase the lubrication and the number of oil dose.
  • If the mold clamping force is too large, check the clamping force when the mold is stressed. Then, reduce the clamping force according to the plasticproduct condition. Check whether the time position is appropriate.
  • The deviation of the parallelism of the stationary platenand moving platen, check the parallelism of these two platens.  Adjust the parallel error.
  • Slow to fast mold opening setting position is too small and speed is too fast. Check whether the position of slow mold opening to fast mold opening is appropriate, and whether the slow mold opening speed is too fast. Lengthen the slow mold opening position and reduce the slow mold opening speed.

Leave a Comment

Contact Us