18 FAQ Of Injection Molding Machine Mold Clamping

This article summarizes 18 FAQs about injection molding machine clamping failure analysis and repair. I hope it can help those in need. If there are other FAQs, please comment at the end of the text, we will add them to the article, thank you.

Question1. Semi-automatic state, it is still in high-pressure mode after clamping in place.


1.1. There is no mode-locking(Lock mold components) termination signal feedback or the high voltage time is too long.

1.2. The limit switch for mold clamping termination is broken.

1.3. The mold-locking termination switch wire is broken.

1.4. Computer I/O check.

Question2. After the mold is locked, during the injection process, the crankshaft retracts a bit, causing the mold-locking termination switch to fail to sense, and the injection action cannot be continued.


2.1. Check if there is any problem with the clamping cylinder and its oil seal.

2.2. Cranks wear.

2.3. Adjust the origin of mold thickness.

2.4. Reset the position of the three clamping plates (connecting rod, shaft sleeve).

2.5. Lengthen the piston rod, the old machine has such a problem.

2.6. Check whether the low-pressure is too large and whether the low-pressure position is too small.

2.7. There is a gap between the piston rod of the clamping cylinder and the cross, add a washer.

Question3. The computer output signal light of the closed mold is on, and there is a buzzing sound, and the mold is not closed.


3.1. Check if there is any problem with the solenoid valve of the clamping.

3.2. Is the demoulding and withdrawal signal normal?

3.3. Check whether the actual position of mold opening has exceeded the set value.

3.4. Is the differential clamping valve stuck?

3.5. Whether the mold closing end travel switch is good.

3.6. Whether the hydraulic and mechanical safety valve is pressed and whether the safety valve is faulty

3.7. Check the mold-locking flow valve to see if there is a flow output (CPU output, proportional flow current).

3.8. Check if the piston of the clamping cylinder is loosened, check the oil seal, or check the oil intake when the mold is closed.

3.9. Check the clamping mechanism to see if the crank is jammed.

3.10 Check the circuit optical scale.

3.11. Press the lock button to see if the pressure and speedometer display are consistent with the set parameters.

3.12. The front and rear switches of the ejector pins are turned on at the same time.

3.13. Reverse the mold opening and closing tubing and install it again.

3.14. Whether the mechanical safety block is still in the down position and whether the safety screw is adjusted in place.

3.15. Neutron check.

Question4. The machine does not close the mold, the pressure is present, and the signal is output. The solenoid valve is also good, but the mold is not closed!


4.1. Is there a signal on the solenoid valve? (PC output,) mold clamping solenoid valve inspection

4.2. Check if the safety valve is stuck

4.3. Check whether the flow proportional valve is normal

4.4. First, see if there is an alarm display to reset the end of the mold to zero, and try to reset the mold position. What action is displayed on the page?

4.5. Checking the level switch of the end of the mold clamping (checking the position of the electronic ruler)

4.6. Piston cylinder inspection

Question5. The film is not tight, and there are always flashes


5.1. Check the pressure of the small pump

5.2. Whether the two pumps of high-pressure mold clamping work

5.3. Inspection of the wear and tear of the clamping mechanism

5.4. Check whether the fixed screws are loose

5.5. Whether the calculation of clamping force is correct, and the molded product does not match

5.6. The injection pressure setting is too small

5.7. Checking the oil seal of the closing piston

Question6. Manual or semi-automatic cannot close the mold. Replace with a new flow valve, and it can't be produced after half an hour


6.1. When the mold cannot be closed, are other actions normal? (The shooting seat moves forward and backward to open once)

6.2. Check the proportional pressure and flow valve, and see if there is a pressure display when the fault occurs

6.3. Inspection of mold closing oil seal

6.4. Inspection of push-back function, an inspection of push-back cylinder

6.5. Neutron check

6.6. Oil temperature check

Question7. The clamping force often drops during production, and the mold needs to be adjusted again.


7.1. The tension of the elbow column is unbalanced or the hinge is worn out, adjust the tension of the elbow column or the machine hinge for repair.

7.2. The mold opening valve, the mold adjusting valve has internal leakage, is there a phenomenon of turning the mold adjusting nut during the mold opening and clamping process?

7.3. Check Check whether there is any problem with all the parts of the hinge part of the machine.

7.4. Computer output check whether there is a modulating signal output.

Question8. Burr in the product

After the Haitian 180T machine is installed with a relatively large mold for production (note: this mold has also been produced on this machine before, there is no problem), and it is found that the high-pressure mold has been locked and closed during semi-automatic production.

After the mold termination stroke switch is pressed, the twist will be loose at the time of injection until the mold is closed, and the stroke switch will continue to move, resulting in a phenomenon of burr in the product.


8.1. When the oil seal is not broken, increase the closing delay time or adjust the termination switch again

8.2. Clamp the mold, adjust the mold, check whether the valve leaks, check whether the piston oil seal of the mold clamping cylinder has been broken

8.3. Is there a gap in the clamping frame?

8.4. Check whether the mold adjustment valve is loose and whether the mold adjustment pin falls off

8.5. Adjust the travel switch to make the clamping cross move forward a little bit. The shot glue will not return

8.6. What is the high pressure of clamping? What is the pressure of injection? Inspection of clamping origin

Question9. What is the reason for the sudden high-pressure mold locking alarm during production?


9.1. Check whether the electronic ruler has been locked to zero. This phenomenon is often caused by the electronic ruler’s zero-point running position, the fastening screw of the electronic ruler is loose or the electronic ruler is broken.

9.2. The proportional amplifier board IC is broken.

Question10. When the semi-automatic setting is set, the machine cannot be stopped in the high-pressure clamping state, and there is no response when pressing the stroke with a tool. Is the stroke switch broken? How should I repair it?


10.1. Replace the mold-locking termination switch and check its wiring.

10.2. The high-pressure mold clamping pressure sensor is broken.

10.3. Is there any problem with the pressure setting? Can the set clamping pressure be reached?

10.4. The solenoid valve has a fault signal that cannot be cut off

10.5. The mold clamping electronic ruler is broken or the zero position is incorrect

Question11. After the product is ejected, the mold will automatically move forward slowly for a certain distance before closing the safety door.


11.1. Check whether the machine has an output signal for mode-locking while walking forward.

11.2. Check the internal leakage of the clamping cylinder.

11.3. The hydraulic valve has a leak check.

11.4. Caused by gas in the oil circuit.

Question12. After the injection molding machine has been working for a period of time, the machine has a shortage of finished products or a mold clamping failure. It is invalid to adjust the origin of the mold support. It is okay to shut down the machine for one night and restart it. The above situation occurs again after a period of work.


12.1. Machine oil temperature check (oil temperature 35-55)

12.2. Check whether there is a frequency converter (interference) installed on this motor vehicle platform.

12.3. Check the internal parameter settings of the machine.

12.4. Check whether there is a bad contact in the relevant line of the thimble.

12.5. Check the electronic ruler and circuit of the supporting mold.

12.6. Clamp the mold, check and clean the solenoid valve or overflow valve of the mold support.

12.7. Inspection of mold clamping, mold supporting mechanism, and oil seal of injection cylinder.

12.8. There is a problem with the matching manipulator, that is, the clamping signal to the injection molding machine is delayed or not.

The other is that when the ejector pin moves back to the limit line, it is switched on and off, rearrange the line and check the limit system, and then check the set locking parameters such as low voltage time, cycle time, etc., and whether the safety door wiring is firm, generally from here The problem can be solved in several ways.

12.9. What needs to be judged is whether the mode-locking signal has started or not, the most important thing is what information is on the main screen when the mode-locking is not visible, which is very important to analyze the cause of the failure.

12.10. The three-core wire of the mold-locking electronic ruler of the machine is in poor contact, just replace it.

Question13. What is the reason why the optical decoder goes to the origin?


13.1. Is the positioning screw loose or broken?

13.2. Sudden power failure during the operation is also easy to occur and needs to be reset.

Question14. There is nothing in the mold, but there is a mold protection alarm.


14.1. The parameter setting of mold low-pressure protection time is too short, or the parameter setting of the mold closing position is abnormal.

14.2 The mold temperature during the production process is higher than the mold temperature at the beginning of production (increasing the gap).

14.3. Insufficient mold lubrication or mold movement, fixed mold failure, 4 low pressure, speed, time, and position settings are unreasonable.

14.5. The lubrication of the mold guide pin is not enough. Do some ejector pin oil or touch some butter.

14.6. Check the wear of the clamping mechanism, check the elbow and the large pin shaft.

Question15. When closing the mold, the hinge cannot be straightened.


15.1. The clamping pressure time is too short or the clamping pressure is too low, or the speed is too slow.

15.2. Check whether the front and rear door travel switches are in poor contact.

15.3. After opening the mold, look at the prompt, there is a problem that the door is not closed properly.

15.4. It is also caused by poor contact of the solid-state relay on the I/O board. Sometimes it does not operate when the mold is closed. Just replace it with a new one.

Question16. When setting semi-automatic, close the door first time and failed, if close the door again it will be ok. Fully automatic is no this problem. The other is to set the semi-automatic setting and do not open the door after ejecting. Press manual and then semi-auto.


16.1. ①The input signal is not ejected completely.

   ②The top-retract travel switch is not turned on or the circuit is faulty. The above two treatments should be recognized by the computer, and the computer will give a signal to force the ejector to return. Check the manual ejection switch, then the input board has an indicator light.

When the mold is not closed, the pressure gauge should be displayed, set different ejection pressures, and the pressure of the oil pressure gauge will change at this time

16.2. The condition to meet the mold closing is that the ejection is in place, the safety door opening switch signal is input to the computer, and the manipulator returns to the position signal is input to the computer, and the continuous door opening and closing actions can be used to close the mold.

It is possible that the mold closing safety protection stroke valve does not spring It starts to bounce when opening and closing again. Of course, some other machines do not have hydraulic stroke valves.

You can do not open the door twice when the mold is not closed for the first time. First, check the input related monitoring page to find out whether all input signals have been accepted by the computer. , And whether the output signal is sent from the computer level.

16.3. The production number set by the injection molding machine has arrived, reset.

Question17. There is an electric valve for manual mold clamping, and the system is under pressure but the mold does not close.


17.1. Confirm that the mold clamping process setting is correct

17.2. Confirm that the clamping mechanism is normal

17.3. Check the opening and closing mold cylinder

① Whether the oil seal is good or not

② Whether the piston falls off, whether the piston rod is broken

Question18. After the injection molding machine is locked, the mold suddenly expands when it starts to shoot. What is the reason?


18.1. The machine hinge is not fully straightened, and the self-locking point is not reached, re-adjust the origin position

18.2. It may be that the piston oil seal of the clamping cylinder is damaged! Because the pressure is easy to open the mold during injection

18.3. Adjust the lock confirmation switch!

18.4. The oil seal of the mold clamping cylinder is worn, and the mold is actually not completely locked

If you have other FAQs, please let me know, and you may also be interested in the below articles:

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