30 Questions and Answers About Ejection of Injection Molding Part 2

For this issue, it is divided into two parts, this is the second one and the first part is in the following link:

30 Questions and Answers About Ejection of Injection Molding Part 1

16.  One injection molding machine, in the semi-automatic and fully automatic model, the ejector can forward and retreat back. But it can’t realize in the manual model. No input signal indicating in the controller. After inspection, the controller’s panel button are not broken.

(1) Has the controller connection line between the screen panel and the main board been checked?

(2) Is there an input signal sent to the main board? Is there a core-pulling chain?

(3) Is there a problem with the input on the I/O board?

(4) When the ejector is opened in the manual model, whether it is carried out at the stop position of the mold opening.


17.  When the ejector retreat,the alarm is always over-limitation(the tolerance has been adjusted very large). The situation doesn’t change after replacing the electronic linear and electrical board.

(1) The pressure speed setting of the ejector pin retraction is too large.

(2) It may be a problem of origin point of the electronic linear. The other is whether the fixing screws of the electronic ruler are loose.

(3) Check whether the P/Q output is linearity.

(4) Change the computer board.

(5) Adjust the ejector electronic linear to a new one.


18.  A 400T machine is set to eject one time. During production, there are multiple ejections back and forth from time to time, and no problem can be found at a time.

(1) If the CPU computer board is broken, then replace it.

(2) If the vibration demoulding method is used, then reset the ejection method.

(3) The spring mold is not in place, causing multiple ejections.


19.  The ejection force of the ejector pin of a machine is too small. After the pressure is increased, the ejection force still does not change. But the ejection pressure is high and the speed is fast.

(1) The oil seal of the ejector cylinder may broken.

(2) Check the ejection solenoid valve.

(3) Check the set parameters and P, Q, pressure and flow output values.


20.  Press and hold the ejector forward button, the ejector can’t stop when it moves forward. And it runs back a little, and then moves forward again. Why?

The mold ejector spring is too strong and the top is not in place.


21.  Why do the ejector push several times continuously? The number of ejector is adjusted to twice.

(1) If the vibration pallet is not used, reset the data.

(2) If it is an old machine, there may be a problem with the dialing code.

(3) Check if the O-valve, or check valve is worn and leaking oil.

(4) In this case, the upper mold ejector spring has a strong force, it is possible to push the ejector back. And the computer cannot sense the final position and has to go back and forth.

(5) Computer program.


22.  The jacking stop switch still has jacking action after being short-circuited. Why? How to eliminate it? We have inspected the following points:

(1) The switch has been confirmed to be good, because after the short circuit, the top stop light on the control board is on.

(2) When pushing in, unplug the electronic valve coil and the action stops.

(3) The top back stop switch is fine.


(1) The solenoid valve always outputs, it is very likely that the output transistor of the I/O board has broken down.

(2) In the manual state of shutdown, press the jacking stop switch while pressing the jacking button to see if there is an output signal.

(3) The action of unplugging the coil will stop, and it can be determined that the solenoid valve is good. Please confirm whether the input and output are normal, and then make a judgment.


23.  There will be no ejector after the mold opening is terminated. The ejector indicator isn’t light up and there is no signal output. But there is no problem with the oil circuit. So what are the problems with the circuit?

(1) Is the mold opening terminated? If there is a termination, the ejector will have a signal.

(2) Check the ejector control circuit for it may be broken.

(3) When the ejector moves, does the ejector solenoid valve have electricity? Is there any response when pushing the spool ejector tubing with a screwdriver?

(4) It may be the problem of light perception. Generally speaking, when the mold is opened in place, the ejector lightly sensor light up to output a voltage signal. Also, when it is in place, use an object to approach the light sensor to see if the light is on and if there is a voltage signal output.

(5) Can it be operated in manual mode, and whether the input conditions are met.


24. It returns to the position without pressing down the stroke switch. And the ejector pin is too short, causing the product to be unable to be taken out.

(1) Check the ejector stroke switch! Then check the ejector cylinder seal.

(2) Try to lower the stroke switch with half-removal, if it is normal, then increase the jacking pressure.

(3) Whether the ejector control oil valve was wrong in the last repair. And whether the valve with differential quick opening was installed there.

(4) Whether the ejection vibration mode is set. And the mold is pressed back because the ejector spring return device is not pressed against the switch.


25.  For a 1380T plastic machine, the ejector is often set to eject for 3 times, but it  only ejects 2 times.

(1) Is the ejector position set too long and the top is not in place?

(2) The time may be wrong.

(3) It is recommended to replace the top-retraction stop and the front safety door travel switch. If the internal contact of the travel switch is jittered, the situation will appear.

(4) Please re-adjust the position, pressure speed of jacking and retreating.

(5) Computer failure.


26.  The manual ejector output has pressure. But there is no pressure when it is semi-automatic. The pressure, flow, and ejection indicator lights are all on, and they are OK in the manual state.

(1) Check the interlocking action switch or ejection time control system after mold opening, pre-molding stop switch, etc.

(2) The manual ejector action is okay, but there is action output in the semi-automatic state. And there is no pressure in the oil circuit, check whether the two proportional solenoid valves have current output during the action. It is estimated that the computer system has malfunctioned. Check if the computer system can be restored.

(3) Check the pressure leakage, shooting platform, mold opening and closing.


27.  Why can’t it be pushed back in production?

(1) The mold needs to be maintained, and the ejector rod is not lubricated enough.

(2) The length of the ejector rod is different. Or the pulling back of the structural screw (the length is also important) is loose on one side and not locked. Or the screw of the machine supporting template is loose, etc.. It may cause an imbalance in the return position. What’s worse, it may cause the ejector to jam.

(3) Mold loading problem. The ejector pin may be unbalanced when loading the mold.


28.  In the semi-automatic mode, the ejector still has a little movement after the mold is locked.

(1) Will the ejector move a little if with another action? There may be a problem with the ejector valve.

(2) Is it a push-in or push-back action?

(3) Check the oil seal of the ejector cylinder.

(4) In the manual state, open the table to see how it reacts.


29.  Why does the ejector stay but not stop? Could it be a problem with the ejector valve?

(1) Make corresponding settings. If not, it may be that the cylinder seal or the reversing valve cannot be locked.

(2) What is the structure of the ejector on the mold? Is there a spring on the mold?

(3) The piston oil seal of the ejector cylinder should be damaged.

(4) First, check if there is any problem with the setting. And then see if there is a signal waiting for the ejector to advance? If so, it should be a cylinder problem.

(5) If it is a rapid return, it may be a setting problem. If it is a slow return, it should be the internal leakage of the directional valve.


30.  There is a machine that fails to top when the ejection speed is set to 60, but it can be ejected when the set speed is 61. Why?

(1) The built-in computer set 30% as a pressure and flow conversion point. 31 is the beginning of a new conversion point. Re-adjust the linearity of P and Q values.

(2) It is possible that one pump is broken. A speed of 61 is used to rotate another pump. Many machines are controlled in this way.

(3) There is also the parameter setting of the computer. One of them is to set the flow rate of the pump.

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