turret wont stop rotating

[Paul in OK]

Hello, we got a Daewoo 12L-C. The turret started to index and wont stop rotating. Any one have any thoughts?
Thanks.
Paul in OKC

[9566317]

I would think you need to check the ladder and see if you are getting a tool counter signal. Generaly on the back side of the turret, Tailstock side, you will see a bunch of proximity switches and a "star" This is what counts the turret index/changer and when it see's the corect combination of switches it will pull back into place. You probably have one proximity switch that needs to be adjusted slightly or is bad or dirt and swarf is blocking it.. Use your ladder to see what switch is not counting. Machine should time out after turning for a short period of time giving a alarm that can help find your exact problem.
Hope this helps.

[Paul in OK]

It has an encoder. Went looking for prox switches and found it. Is there still a ladder to check?

[9566317]

This must be a fairly new machine, The information I gave was based off the 12 older ,and differant machines I have. Anyway , there must be an alarm you are getting , a time out alarm or turret zero not found something like that.
There still needs to be a switch for zero. If you use the alarm that should be generated you can use the ladder and trouble shoot your problem.
Daewoo generaly has very good books with their equipment and trouble shoots easily. When you power up this machine normaly do you need to zero the axis and the turret?

[Paul in OK]

The machine is about 12-13 years old. Been pretty much rock solid. The only alarms I get are a 'tool change over'. Will do a little more digging in the books. Have a call in for servise but am a couple af days out on their schedule, and naturally am running something that needed done yesterday.
And yes, the machine has to be 'homed' every timeit is powered up.

[emexcee380]

Paul,

Whether your machine uses multiple prox. switches or an encoder to detect turret position your problem is most likely that the control is not seeing the "finish" signal to detect the index is completed.

Look in your electrical manual and you will find a nifty chart that shows which signals should be ON for each turret position. Locate the diagnostic numbers for each turret position and see that they're all working as the turret indexes. If the turret fails to clamp regardless of which station is commanded, then most likely the "parity" bit common to all stations is missing. Fanuc encoders don't fail very often so check the amphenol connector at the top,rear of the turret box and make sure you don't have a broken wire.

If all the relevant input signals for all twelve stations are working you're problem is elsewhere.

Does the turret clamp at any position?
Doees the turret try to decelerate just before reaching the commanded position?
Is the behavior the same in both the cw and ccw direction?

Please advise.

emexcee380

[Paul in OK]

Service guy got here. Found a broken spring inthe clamping mechanism. He was sure that was it. Not. It does not slow down once it starts, and is the same in either direction. Hitting the e-stop is the only way it stops. Using the tool selection switch it will change directions when the hydraulics are powered back up and the tool index button is pushed. It does not try to to 'sit', or clamp at all. Looking for the electrical book now.

[emexcee380]

Paul,

By "broken spring in clamping mechanism" I'm assuming you're referring to a return spring in the "clamp" solenoid valve as clamping is purely hydraulic, not spring-assisted in any way.

If the diagnostic input signals are present for each of the turret positions (per the chart in the electrical manual) then it is likely that the "decel" valve is not working. Once you've located the chart in the electrical manual you can confirm the input signals for each turret position by rotating the encoder. The encoder is clamped to the turret casting with two small clamps and connected to the turret shaft by means of a small coupling. Release the screws on the turret-side of the coupling, remove the two small clamps at the base of the encoder, and gently pull the encoder and coupling off. Then hold it in your hand and rotate the shaft. Watch the input signals on the DIAGNOSTIC page turn ON and OFF (i.e. "1" or "0"). Each station position should generate an input for PARITY and another signal or two per POSITION per the chart. Re-install the encoder once you've confirmed all the signals.
(Plug the encoder and coupling onto the turret shaft, then rotate the coupling until the correct input signals are ON for the turret station currently in the cutting position. Tighten the coupling screws and then tighten the screws for the encoder base clamps.)

If all the signals work correctly the problem will likely be in the deceleration circuit.

"x"-degrees before the commanded position, a hydraulic solenoid valve is actuated to cause the rotation to slow down to allow the turret to get into position and clamp. A prox. switch input (refer to electrical manual) causes the output to be generated. Check the output signal for DECEL (refer to electrical manual) to confirm that this signal is being outputted. If the output is confirmed then I would suspect a problem with the solenoid coil or the valve itself. The solenoid coil should read approx. 70 ohms resistance across its terminals.

If the DECEL output is missing it will be due to a missing input signal from the near-position prox. sw.

Hope this helps.

Best regards,

emexcee380

[Paul in OK]

Thanks, emexcee380.
He pulled up parameter display on the screen, and it was not showing any number change as the turret rotated. Got an encoder ordered. Naturally this happens on a hot job. Has me and my cohort cranking handles to get the parts out. Haven't done this much handle jerkin' in a while!

[9566317]

Paul,
Are you sure its the encoder?emexcee380 is correct in that it does happen but not often that a encoder fails. Did you check the plugins and continuity of the wires? I have more problems with my older machines with wires and conections, not actual encoders. Might be worth a check instead of turning handles.This feedback wire is being flexed as the machine moves and after time the wires are known to fail from moving.

[Paul in OK]

We are going to see about taking it off and over to a local place to see if they can bench test it. I didn't see the guy check the sires. Ours doesn't seem to flex as it is all on the same saddle under a guard.
I appreciate all the replies, was hoping to save the boss a little money, but alas...Thing that agravated me is the way the machine went bonko in the first place and anything related to position sensing stuff is the last place the guy checked. I know there is an order to follow whne trouble shooting, but....

[emexcee380]

Paul,

As 9566317 agrees, encoder failures are much more rare than broken wires. Rarer still would be a condition where all the encoder signals were missing. (Entirely possible, but entirely unusual....)

The signal cable on your PUMA 12 does get carried by a section of flex-conduit and, as such, is subjected to flexing that can break the signal wires after multiple thousands of cycles. More likely is that the amphenol connector that connects this cable to the cable from the encoder would be disconnected. And this is more likely than a Fanuc encoder that has completely failed. Encoder failure is possible, but it just doesn't happen often.

Methinks your service man is not monitoring the signals correctly if he says that ALL of the encoder signals are missing. Be aware that the encoder signals are located on the DIAGNOSTIC pages, not the PARAMETER pages. (Or in the dynamic LADDER display.) I can dig in my archives for Daewoo turret encoder signal diagnostics but it's best if you can find your electrical manual and use the data specific to your machine.

Keep us posted on how this problem develops.

Best regards,

emexcee380