[sorin_paul]

Swapped already, with a drive from another OKUMA LB15. No difference. Those bearings came in pairs, and I think you can't over preload them.

[underthetire]

Yes, you can, remember, okuma stretches the ballscrew to compensate for thermal growth. Too much, and you'll wipe out the bearings quick. Do you have another motor to swap then?

[sorin_paul]

Not on LB15. It has two TAC bearings on the end of the ballscrew, fixed on a bearing block, and on the other end, where is the pulley, the bearing can move longitudinally on his case, to compensate for thermal expansion.
The motor seems fine, but after removing the excess grease, if the problem persists, I will try to swap the servomotor. I have one LB15 without SDU, that will became an organ donor soon for the other LB15's that I have, because the price of a VAC drive is higher than the price of a LB15.

[sorin_paul]

Thank you all.
Changed the motor and now it's working.
Now, I have one question: The defective motor jumps like a stepper when I turn it by hand. 36 steps.
Does anybody have a clue?

[underthetire]

Yes, seen that quite often. rotor becomes magnetically coupled. usually caused by heat or a shorted winding. A mega ohmer would check that.

[sorin_paul]

It can be repaired or is scrap?

[underthetire]

Not too many places ive found that can rebuild Okuma motors, is this the sanyo denki type ot the true okuma BL series?
Okuma repair - Accu Electric Motors Inc.

[sorin_paul]

Okuma BL-120E-20.
Do you know what type of VAC unit was on '89 OKUMA LB15? I bought one at an auction without VAC unit.
Thank you.

[underthetire]

You mean the spindle drive?
'89 had a Fanuc spindle drive believe it or not. Later machines had the VAC type A
I have an 89 or 90 LB15 on site, if it hasn't gone to salvage yet, ill take a look and see if i can grab the fanuc part number, it was a pretty generic fanuc drive from that era.

[koch.Cnc]

Hi @Geserteg, were you able to solve your Issue? I have an Okuma LB15-IIM,
Two days ago had an X-Axis Diff Alarm, some weird sound was coming out as if something was stuck? or broken..anyway its not there anymore.
Turned machine off, turned again...All ok..then after about 5 mins error came again..Reset..then All ok.

Today turned it on, and i´m not having any problems. Everything is smooth.
Im not actually using the machine right know, but It has been on for about 4 hours, and no problem.

The load display on the axis on X is about 22% when resting, it goes up to 74% when I go rapid manually in X+ and in X-
Load on Z axis is 3%.

I also thought it was the X, Z drive..tried swapping Ux, Vx, Wx, with the Uz, Vz, Wz, and changed the blue dipswitches (2) on the E4809-770-065B board, but I had a Door Interlock alarm,
changed it again, and the machine was ok again. (Maybe someone knows what I did wrong here)

I already visually checked the PCB drive, if anything was blown...(all Ok)
Lubrication (all Ok)
Checked the manuals on the machine, and there is no X axis brake, I guess the X- Axis servo motor does the brake function.


I still haven´t checked out the bearings etc.. maybe the turcite is already gone bad.
Im trying to discard any simple problems without having to take the machine apart.
Maybe someone has an Idea what this might have been? Or where I can keep on looking?

Thanks in advance!

Update: I just came back to the machine, I only left it turned on.. and It started making some weird noices in the X axis..It was still, without jogging the Load on the X- Axis was going up to 0% to 211%.. then it Stabilized, measured the x, z drive with a temperature scope at it was about 38-40 degrees celsius?..(Working temp)

[sorin_paul]

My problem was a demagnetized servo. With the belt removed, trying to rotate the servo by hand feels jumpy, like a stepper motor.
Changed the servo and everything was ok after that.

Check also the bearings on the ballscrew.

[deadlykitten]

salut sorin check al tau praivat email