[WC56]

Hi, I have a problem with the spindle drive unit on my LB15. The other day when I started it up there was an unusual noise comming from the spindle & the speed seemed to vary up & down. I stopped it & turned the spindle over by hand...all felt good. I then tried it in reverse (M04) & it ran nice & quiet. I let run for a while before tying M03 again, this time an alarm came up on the screen: 201-4 Alarm A Servo AMP Z AXIS 4802A6 followed by: 110 - Alarm A SDU.

I was able to clear these by turnng the control off & then back on. I have the maintenance log for this machine & found an entry back in 1987 with exactly the same symptoms & alarms. They replaced the regenerative fuse (F5 top LH corner of control unit) & seemed to have solved the problem. There are two fuses located there so I checked them both with a multimeter & they seem ok.

I then pulled the drive belts off the sipndle motor & ran it, the noise is gone but:

M04 fine at all speeds in both M41 & M42.

When in M41 M03, the spindle load meter climbs into or close to the red & flickers up & down at around 300RPM
When in M42 M03 it does it around 2500RPM

Oh, forgot to say...it is fitted with the OSP5000L control

What do you guys think is going on?

[fordav11]

if the spindle has an issue it can only be the spindle drive (which Okuma calls VAC, you'll have either VAC II or VAC III). Servo problems are caused by the servo amp(s).
If cycling the power fixes it temporarily that's a sure sign it is on it's way out and will eventually die.
Unfortunately these old things are failing a lot nowadays. My machine (built in 1995) has 2 VACs and 7 servo amps and all of them have totally failed and have been replaced by newer units (at considerable cost!) over the last 6 years. there's not much you can do other than wait for it to fail completely then replace it, or get it repaired.

[underthetire]

Naw, those use a Fanuc spindle drive. lots of options available for rebuild. Needs transistor replacement and maybe the control board.

[WC56]

Thanks for the replies, I would really like to fix this old girl as she hasn't done much work so is in overall good nick. I started it up again today & couldn't get it to alarm although the spindle speed still varies once you get over half way in both ranges (M41, M42) & the load meter goes way up.

The spindle drive unit is a Fanuc A06B-6044-H018

What should I be checking first?

Thanks

[WC56]

Thanks for the replies, I would really like to fix this old girl as she hasn't done much work so is in overall good nick. I started it up again today & couldn't get it to alarm although the spindle speed still varies once you get over half way in both ranges (M41, M42) & the load meter goes way up.

The spindle drive unit is a Fanuc A06B-6044-H018

What should I be checking first?

Thank

Forgot to add...the spindle starts & brakes as it should.

[fordav11]

ah Fanuc on those. well, assuming it works (spindle starts/stops/runs), the fault is most likely on the top control board, not the big transistors below. fixing that yourself is generally impossible unless you happen to have inside repair knowledge of Fanuc drives (which as far as I know is no one on CNCZone) and/or are an experienced electronic engineer who deals with industrial electronics. its a very complex box of tricks.
easiest way is just send it out for repair or get Fanuc to visit and advise you of the next step. Won't be a cheap repair either way.

[underthetire]

That's actually a typical transistor module failure (the high load is a giveaway) they are pretty tricky to fix though. Me personally I would pull the drive and send it to FANUC World.com : Tennessee Industrial Electronics, Inc. if your is the US. Top board may be faulty causing the transistor failure, and they get expensive. Plan on $2500 for a repair BTW.

[WC56]

Ok, thanks. I will contact the previous owner...I am sure he said something about a new drive having been fitted recently, but will have to check. Will keep you updated.

[underthetire]

You did set the switch in the spindle drive right? If this machine has moved you do need to set the toggle switch for your voltage.

[WC56]

Oh, it was moved recently. I've got 244 volts per phase coming in so the switch should be in the upper position (220-242) correct?

[underthetire]

Your right on the upper limit! Yes, should be 220-242. Any spike in your incoming is going to get exiting.

[WC56]

Just flicked the switch up & it has made to problem worse. I'm guessing that is not a good sign.

[underthetire]

Nope. Check the voltage on r s t on the drive. Early okumas like those had built in transformers. I'm wondering if its taped correctly.

[WC56]

The voltage measures 118-119 on R,S,T. I have spoken with the previous owner & the SDU was repaired before he bought the machine. He hardly used the lathe as he downsized soon after but said it was running fine. He put me in touch with the guys who did the repair, have sent them an email...will wait & see what they come back with.

[underthetire]

I'm assuming you measured to ground? What is leg to leg?

[WC56]

Measuring between them is 208-209

[underthetire]

So the switch is supposed to be set on the lower setting. That's about perfect voltage for that machine. Time to see if they will fix the drive.

[ashby]

I have an issue on our LB-15. The main spindle is getting no power and I cannot get "A" to activate. I can find on shorts in wiring and when I try to activate it and it syncs with the live tool or tries to activate the live tool it goes to AL-12. I know thats possibly the worse alarm.... sorry if this isnt the right thread any guidance would be appreciated

[WC56]

Sorry ashby, can't help with that. Still working on solving my spindle problem...funny thing is I ran it for about 45min late last night & it was absolutely fine. This morning, no good again??

[WC56]

Hi underthetire, hope you are still reading this. A helpful tech sugested that I place a fan heater on the spindle motor for an hour or so, then try it again. Apparently there is some sort of temperature sensor on the back of the motor which he thinks could be causing my issue. I only have a small heater so it took around two hours to get any warmth into the fan area, but it seemed to work. The spindle ran fine in both dirrections

I turned the heater off & ran it though a test program for a couple of hours, then the issue started to creep back in. I shut the machine off & turned the heater back on for another 20 minutes & all was good again.

Do you or anyone else know whats going on?

Thanks WC56