[rotec]

Hi Guys,
I have an old Okuma LB15 L-G with a Fanuc spindle drive unit problem ( FANUC AC SPINDLE SERVO UNIT A06B-6055-H108). When your try and start the spindle the spindle jerks then throws an SDU alarm.

I actually have two drives (one spare) when I swap the top boards around I get Fanuc LED Alarm 2 on one board and LED alarm 12 on the other. Both spindle drives show the same alarms depending on what top board is installed.|

My lathe is based at the Tyabb airport VIC 3913. Australia

My number us 03 5977 3805 email: [email protected]

Regards, Paul

[cncmakers001]

Have you checked the spindle motor and its wiring?

[WGoyer]

Paul,
It looks like you have at least a top board problem. The board that gives the alarm 12 should not be used anymore until repaired as it can damage the high powered switching transistors inside the lower cage. Alarm 2 means that the drive didn't get up to commanded speed fast enough. I presume the parameters are all OK. I'm remembering that the parameters are stored on the top board in a 6055 unit. We repaired one of these last week that just had a blown green fuse on the top board. You might check for that if you haven't done that already.

[rotec]

I have checked the main motor wiring for continuity and obvious shorts there are none. The fault has been progressively getting worse over time. At first the spindle would hunt and show high amp draw on the panel. Sometimes it would alarm, other times after it warmed up it would settle down and run all day with out any issues. The hunting or surging would subside in about 30 minutes of running.

Today the spindle alarms as soon as it moves. As I said one top board gives Fanuc alarm 2 the other board gives alarm 12.

I cant be 100% sure but a suspect the AC motor is ok. Based on probabilities I suspect that both the drives power sections are ok too (IGBT) etc.

There is also a Fanuc tachometer module mounted to the motor, that could be in play also?

Thanks Paul

[phucrobusl]

Pm me [email protected]

[rotec]

I'm told the top board with AL 12 has some serious issues and should not be used due to is creating an over current state.

However top board with AL 2 is apparently repairable. I have the Fanuc manual and can see various tests that can be done in relation to alarm 2. So far I have check all the fuses and they are all ok.

There is also an adjustment able to be made on pots RV18 and RV19 which sets the speed feedback duty signal, supposed to be set at 50%.

I did read online a chap that was having similar issues to mine and the problem was the speed sensor mounted to the AC spindle motor. An oscilloscope would confirm that I guess. Never used one!

Attachment 505634

[WGoyer]

Here's a procedure for checking/adjusting the encoder feedback signals. In your case, if you can't get the spindle to run at all, try to spin the motor by hand in high gear. Some motion of the encoder is necessary to check this. I didn't mean to say that your alarm 12 board is not repairable - Continued use before it is repaired risks damage to the power section.
Warren

FANUC ANALOG SPINDLE ENCODER
ADJUSTMENT PROCEDURE
12/14/23

This procedure insures proper adjustment of the encoder signal in Fanuc A20B-0009-053 and 069 series of spindle drive boards.
The encoder signals for this drive unit need to be adjusted for proper operation.
The A channel is monitored on Check point CH7, the B channel is monitored on CH8 (see picture).
The signals can be monitored using an oscilloscope for 50% duty cycle, or a voltmeter set for DC volts.
While running the spindle at a low speed (100 RPM), measure the DC voltage on CH7. Reference the other meter lead to the 0V test point nearby. The voltage should read 2.5 Volts DC. Adjust this voltage by turning the small blue potentiometer labeled RV19. The voltages will be quite different when the spindle is stopped, so only make adjustments with the spindle turning.
Do the same for CH8, but adjust RV19.
When they both are adjusted, try some faster speeds (Half speed for the speed range). Check the voltages again - both should still be 2.5V.
Try top speed for the range - both should still be 2.5VDC.

[rotec]

G'day Warren,
Thanks for the tips, I will run those tests when I'm back in the shop Monday. The card with alarm 2 will jog ok but can not run at all on its own. It jerks a few RPM then alarms.
But I can have someone rotate the chuck it by hand while I measure the outputs on the check points. CH7 and 8. I don't have an oscilloscope, so I will have to measure the DC voltages on each CH and adjust pots RV18 and 19 until I get 2.5VDC on each.
I'll come back with my findings and outcomes shortly.
Thanks again!

[rotec]

Do you have a picture identifying the locations of check points CH7 and CH8?

[rotec]

I think I found em!

[pankniru]

If your controller is too old, let me retrofit it with new syntec controller contact me at [email protected]/ +918168294379 (whatsapp)

[rotec]

If your controller is too old, let me retrofit it with new syntec controller contact me at [email protected]/ +918168294379 (whatsapp)

Im well aware of various retrofit options, all are viable.

The downside is retrofits tend to devalue the machine and none can hold a candle to the original Okuma system anyway. Much work is involved in a retrofit, so for the sake of repairing or replacing one circuit board, I'd prefer to stick with Okuma.

Thanks.

[joeavaerage]

Hi,

The downside is retrofits tend to devalue the machine and none can hold a candle to the original Okuma system anyway.

Is that actually correct??? After all it is the original Okuma system that has failed. It might be valuable if it were working, but it its not working and the machine is idle as a result.......just
how valuable is it??


Craig

[rotec]

Hi,



Is that actually correct??? After all it is the original Okuma system that has failed. It might be valuable if it were working, but it its not working and the machine is idle as a result.......just
how valuable is it??


Craig

Craig, Lets say the senario is that the machine is currently commissioned to do payable work, its actually not, but let's say it was. Ok so the machine is down due to an Fanuc spindle drive fault. The objective in this case would surely be to get the machine back up and running as quickly and as reasonably affordable as possible right?

Assuming we are agreeable on this are you suggesting that completing a retro fit would be favorable in time and cost over repairing the OEM Fanuc spindle drive and leaving the robust and proven Okuma system in play?

At one time my shop ran this machine 24 / 7 along with many other cnc machines of various types. Over the 20 year period we had several machine break downs and back then we needed those machine fixed ASAP. Not once would we have ever considered a retro fit, due to time and cost.

Then there's also the issue of down the road who would you call to have a retrofit repaired? Where as Fanuc, Okuma, Heidenhain, Mazak for eg, all have techs who know their systems and are on the ready.

Please dont get me wrong I love the idea of retrofits and I have done them myself as a hobby. And they certainly have their place as when done well the modernization is nice, plus if you complete the work yourself you can repair the machine in the future yourself.

Lastly if I needed the machine running ASAP, I'd have a tech here in the afternoon. But that's not the case today, and so I play with the machine as a hobby, and part of the appeal is leaving the machine original.

Regards, Paul

[joeavaerage]

Hi,

Assuming we are agreeable on this are you suggesting that completing a retro fit would be favorable in time and cost over repairing the OEM Fanuc spindle drive and leaving the rubust a proven Okuma system in play?

No, I'm not suggesting that either path is favourable, but rather the residual value of the existing system is very much tied to whether its working or not.

At one time my shop ran this machine 24 / 7 along with many other cnc machines of various types

I'm sorry to say then that I rather think this system is obsolete, you evidently cannot get new parts, or you probably would have, and have yet to find any Tech brave enough to put up his/her hand.
Does that not sound like obsolete?

plus if you complete the work yourself you can repair the machine in the future yourself.

Agreed. This would be a distinct advantage but ONLY if you do it yourself, which may or may not be your thing.

Craig

[rotec]

I'm sorry to say then that I rather think this system is obsolete, you evidently cannot get new parts, or you probably would have, and have yet to find any Tech brave enough to put up his/her hand.
Does that not sound like obsolete?

Craig

Obsolete? Nah, spares and repairs are readily available for Fanuc AC spindle drives, even of this vintage. As I said earlier this machine is not commissioned, if it was I'd have a tech here in the afternoon. But instead I'd rather I tinker with this machine as a hobby, leaving it as is rather than retrofit.

Regards, Paul

[rotec]

Hi,



No, I'm not suggesting that either path is favourable, but rather the residual value of the existing system is very much tied to whether its working or not.



I'm sorry to say then that I rather think this system is obsolete, you evidently cannot get new parts, or you probably would have, and have yet to find any Tech brave enough to put up his/her hand.
Does that not sound like obsolete?



Agreed. This would be a distinct advantage but ONLY if you do it yourself, which may or may not be your thing.

Craig

Here's a procedure for checking/adjusting the encoder feedback signals. In your case, if you can't get the spindle to run at all, try to spin the motor by hand in high gear. Some motion of the encoder is necessary to check this. I didn't mean to say that your alarm 12 board is not repairable - Continued use before it is repaired risks damage to the power section.
Warren

FANUC ANALOG SPINDLE ENCODER
ADJUSTMENT PROCEDURE
12/14/23

This procedure insures proper adjustment of the encoder signal in Fanuc A20B-0009-053 and 069 series of spindle drive boards.
The encoder signals for this drive unit need to be adjusted for proper operation.
The A channel is monitored on Check point CH7, the B channel is monitored on CH8 (see picture).
The signals can be monitored using an oscilloscope for 50% duty cycle, or a voltmeter set for DC volts.
While running the spindle at a low speed (100 RPM), measure the DC voltage on CH7. Reference the other meter lead to the 0V test point nearby. The voltage should read 2.5 Volts DC. Adjust this voltage by turning the small blue potentiometer labeled RV19. The voltages will be quite different when the spindle is stopped, so only make adjustments with the spindle turning.
Do the same for CH8, but adjust RV19.
When they both are adjusted, try some faster speeds (Half speed for the speed range). Check the voltages again - both should still be 2.5V.
Try top speed for the range - both should still be 2.5VDC.

Hi Warren,

Today, using the information you kindly supplied I managed, via pots RV19 and RV18 to set the voltages to 2.5 VDC each, measuring at check points CH7 and 0V then CH8 and 0V. Unfortunately the spindle still gives me Fanuc alarm #2,

The video link below shows where I'm at.
https://youtu.be/JeEvOYESXsk?si=oqBOKHNMAzD1ykNy

[phucrobusl]

Check in igbt modules in power PCB base card , AL-2 also generates from defective IGBT modules & main conactor.

[rotec]

Check in igbt modules in power PCB base card , AL-2 also generates from defective IGBT modules & main conactor.

Ive done IGBT checks and replacements on other drives (Yaskawa) But these looked different than the Fanuc and I did have test procedures. Would you happen to have any test procedures or instruction for testing the Fanuc power modules?