Need Help!- Fanuc Series 15 SV003 alarm on two axes

[killywigs]

Hello everyone, I have a Nakamura Tome CNC lathe, with a Fanuc Series 15 controller, that has recently started giving the SV003 abnormal current in servo error on both axes.

The problem happened halfway through cutting a part, and strangely on both axis at the same time with both a20b-1003-0081 servo amplifiers having the HC led on.

I have already changed the a16b-2200-0080 dual axes positoning module, but the two SV003 alarms still occur straight after power up. I have also checked the +5, +15,-15 voltages on the PSU and they are all within in +/- 5%.

Could this really be both servo amplifiers or motors failing at the same time?

I appreciate any help with this, Thanks.

[MysticMonkey]

have you checked the lubrication of the axis ?

[killywigs]

Yes, I have checked the lub and all seems fine. I think I will have to replace both drives.

Thanks,

Killywigs.

[fanucman]

Originally Posted by killywigs Yes, I have checked the lub and all seems fine. I think I will have to replace both drives. Thanks, Killywigs.

NO dont replace any drives.. do this..

check incoming ac voltage to amplifier... needs to be balanced and not high

remove motor cables from bottom of amplifier and turn on machine, if any axis is a verical axis block it with some wood so it dont drop..

power up machine and see if problem comes back.. if it does than it probably is going to be a problem with the amplifier and i would recommend to call fanuc, they can send you a procedure on how to check the transistors inside...

if ur not up to it have them come in and do it for you.. i WILL be cheaper than ordering a new amplifier..

[killywigs]

Ok, sorry for not been able to post for a while. I have checked incoming voltage to amplifiers and I'm getting between 200v and 203v.

With motor cable disconnected the problem does not occur when the machine is powered up. This would make it seem like both motors are faulty, but I am getting a resistance to 1.8ohms on each winding, which I belive to be good.

I will call fanuc. Getting them to come will be a very costly exercise, as I will have to pay flights and hotels as well as hours.

Thanks again.

[CNCZILLA]

Hello. I am assuming your 1.8ohms is checking from winding to winding, I.E. U,V,W and that would be good but you need to meg the motor and check for a breakdown in the insulation. I think Fanuc's spec is at about 100 megs. Under that replace over that ok. you can also check each leg to ground with a standard multimeter and if this shows a short then of course the motor is bad. It would be unlikley that both motors went bad at the same time but in the machine world maybe not imposible. The procedure for checking the drives is pretty simple and can be done before you spend the expense for Fanuc to come out.

[fanuc-support.c]

There is always a cheaper option.

This guy is based in Belfast.

Google: Machine Tool Maintenance

[killywigs]

Ok, MTM are going to come have a look.

In the meantime I'm going to keep testing. Going to do IR test on friday. I made a mistake reading the input voltage to the drive, I'm actually getting 208-211vac, so I'm going to try powering them up from another machine transformer, incase the above is too high.
I took the drive off and tested the dc rectifier, transistor power pack and braking transistor and they are all ok. So if its the amplifiers, it is the PCB on top. However I ready think the drives are fine, as when I disconnect the motor UVW, the error does not occur.
again thanks for your help, I'll keep you posted.

[fanuservicetech]

seen this a few times. Problem is the CNC power supply (A16B-1211-0890), the black box mounted to the master board. Basically, the +/-15 volt DC is low on that power supply. +/-15V is used in the comparator circuits and this give a false HC alarm. Good luck and keep us posted.

[killywigs]

Originally Posted by fanuservicetech seen this a few times. Problem is the CNC power supply (A16B-1211-0890), the black box mounted to the master board. Basically, the +/-15 volt DC is low on that power supply. +/-15V is used in the comparator circuits and this give a false HC alarm. Good luck and keep us posted.

fanuservicetech, I did originally think it was this power supply, but after taking a closer look I realised that each of the A06B-6058-h005 amplifiers generate their +/- 15 and +5v onboard and do not seem to use the power from the master board PSU. There is only one cable coming from the dual axes positoning module to each amplifier, and I don't think It contains the above control voltages, as when I unplug it, leaving only r s t supply voltage, I can still measure +/- 15v and 5v at the test pins on the amplifier. Still can't rule anything out yet, as I have no spares to do trial and error fix.

I can't figure out what voltage I'm supposed to get supplying the amplifiers as I see 185v 200v and 220v stated in different places.

[fanuservicetech]

Did you check the +/-15 V on the CNC power supply itself? (not on the servo units). There are check pin on the PSU. A lot easier to check if you remove the cover off the power supply.

[killywigs]

Yep, checked that too. Didn't remove the front cover to access the test pins though, just got into an awkward position. Can't remember exactly what they were, just know that they were within a few tenths of a volt, and were on the high side.