puma 8s turret unclamping randomly

[Deano7/11]

Hello all. Hoping someone can help with an issue I have on my 1995 Daewoo 8s.

The problem is the turret will unclamp by itself.

This appeared recently during a 1 tool only program where I had to skim cut a diameter on 100 parts. No tool change was done for an extended length of time.

I noticed a change in sound during the cut and assumed the insert corner had died so I would replace and rerun the program. Next I heard the tool smashing into the chuck jaws and the turret plate bouncing around on each impact (tool finished cutting 2mm from the jaws).

I then estopped the machine and gathered by thoughts and noticed the turret plate was unclamped.

I then did some tool changes and all seemed well. Tool changing and clamping like normal.

I then did a couple of test that included .
Testing the solenoid coils
Checking hyd pressure and oil level.
Checking the signals coming from the plc to see when the instruction the unclamp was given.

This is what I have found so far but not got to the bottom on the issue.
Changing the solenoid with the tailstock solenoid didn’t help (yes they are the same, also used a 3rd solenoid off my Daewoo 10HC with no luck)
Removing the coils from the solenoid didn’t stop the problem from happening so hyd causing the unclamp and not electrical.
I am able to replicate the problem by manually activating the solenoid unclamp push plunger.
Starting the machine and letting it run idle for a period of time just sitting sometimes the issue will arise other times it has run idle all day with no issue
I did get a video of the turret slowly unclamping when it starts to move it takes about 9 sec to get to a full unclamp state (about 8mm of movement)
When the turret is unclamped I am able to do a null tool change and the turret will suck back in. this I think is important as it tells me the solenoid spool is in the wrong location. If the spool was located in the ‘clamp’ position and the turret plate was unclamping then doing a null tool change or activating the clamp side of the solenoid would not do anything as the oil should be directing to the clamp section of the piston.

I have looked at the signals going to the coils and the clamp signal is only on for a short amount of time then it turns off meaning there is not constant signal to the clamp coil.

In summary it seems that something hydraulic is causing the spool in the solenoid to slowly move to the unclamp position and directing oil to the unclamp side and venting the clamp side pressure.

I don’t understand the hyd circuit inside the turret that well but the only thing I can thing of is if the seals need replacing as maybe the piston seal is leaking a lot and the constant stream of venting hyd oil going through the solenoid and back to the tank is pushing on the spool in the solenoid causing it to move and with no constant energizing of the coil the spool can move easy enough.

This assumption is all I have left but wanted to bounce the issue off you all prior to breaking into the turret (last resort) and seeing what I can find.

Thanks in advance

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[lshingleton]

If i remeber right the turret had only one connection for unclamp forced with spring return so on power interput the Turret would clamp reguardless ?

[Deano7/11]

If i remeber right the turret had only one connection for unclamp forced with spring return so on power interput the Turret would clamp reguardless ?

It has 2 solenoids on it. One is clamp/unclamp the other is turret direction. There isn't a spring return on the clamp/unclamp it has no default position. The system relies on the spool in the solenoid staying in the correct position until the plc sends a signal to change states.

[lshingleton]

Sorry maybe was thinking of Okuma Howa from that era
Usually when we had turret issues would have been the other way not unclamping but to be honest been alone time and unless i pulled the motor stuff for it not so easy

[Deano7/11]

Sorry maybe was thinking of Okuma Howa from that era
Usually when we had turret issues would have been the other way not unclamping but to be honest been alone time and unless i pulled the motor stuff for it not so easy

all good thanks for your input.

doesn't look like anyone else has anything to suggest so i guess i will dive into the turret and see what i can find.