[turbo bob]

hi been a member a while and found the forums a great help,
but can not find any liks for this problem
i have a old fanuc 3000c control fitted on a 3 axis 344 amarda punch
problem i am getting is the Z axis show a alarm light on the drive (A06B 6035-H315/H316)once or twice a day, it drives a getty motor
the motor and drive have been repaired
with a full set of thrysiter
and the motor with a full overhall
was blowing the 32a supply fuses
any ideas?
thanks
bob

[alliedeng]

Could there possibly be a tightness in the axis? is the axis vertical, if so does the brake function ok?

[turbo bob]

no there is no tightness in the axis. the alarm is OVC led,
only comes on when ref machine runs ok in auto very odd?
sounds as i am getting AC on the motor by switch machine on and off serival times clears the fault might be the control card?

[alliedeng]

If you have had the motor and drive repaired and you still are getting overcurrent alarms, you may need to reset the variable pots on the card again, try giving them a tweak once in either direction to start with. I'm not sure which pot relates to what, but I allways have started at the furthest to the right!

Thats if your drive has these on it?

[Dan Fritz]

The Fanuc 3000C on the Amada machines used 3-phase full wave thyrister drives, and it also used resolvers for positioning feedback. Each motor will also have a tach-generator inside.

There are MANY things to adjust on these machines to get the servos to run smoothly. If you're blowing fuses, here are some things to check:

On the back of the servo amplifier, you will see 3 cartidge fuses and nearby you will see 3 black plastic "indicator" fuses. Each cartridge 30A cartridge fuse has a 1.3A indicator fuse wired in parallel, so if the cartridge fuse blows, the indicator fuse blows also. The indicator fuse has a set of contacts inside that close and put the servo into an alarm state. I've seen situations where a pair of fuses will blow, but the little contact inside the indicator fuse would get stuck inside the plastic enclosure. This prevents the servo from alarming out, but the servo can then run with a phase missing (single phasing). This can cause all kinds of trouble. It's best to remove each cartridge fuse and check it with an ohm-meter. Also, remove the plastic cover from each of the indicator fuses and be sure that one of them isn't blown. A blob of solder on the fuse wire can cause the indicator fuse to stick.

When you turn on the Fanuc control and the servo contactors kick in, the motors should not "jump". If they do, then some adjustments are in order to set the "drift". Drift is compensated by adjusting pots on the 3000C "analog" board (the bottom board in the rack). I'm not sure of the pot number, but it may be labeled "offset". There would be one for each axis.

The 3-phase power in most shops is not always the same. When a machine gets moved from one shop to another, the servo transformer should be checked to be sure that it matches the line voltage. The big 3-phase multi-tap transformer in the bottom of the servo cabinet should have jumpers that let you set any line voltage from about 190v to 460v. Be sure that these jumpers are set to match your line voltage.

If you have an oscilloscope, use it to look at the current pulses on CH11 of the Z azis servo amplifier board. Use CH3 as a ground reference. You should see 180 "bumps" per second (one bump per phase). These bumps represent the actual DC current going to the motor. Each time a pair of thyristers fire, they send a pulse of DC current through the motor. If one pair of phases has a higher line voltage than the other phases, then you'll see that one set of "bumps" will be higher than the others. By adjusting RV13a, b, and c, you can equalize the current pulses so that all 3 phases are sending the same DC current to the motor. This will smooth out the motor and reduce the possibility of blown fuses.

The OVC alarm usually only happens when the load on the motor is too high, the line current is not correct, or when something is wrong inside the motor itself. If the axis moves easily, look for worn brushes, carbon dust inside the motor, coolent goo inside the motor, etc. Sometimes these motors just need to be disassembled and cleaned, and the commutator needs to be cleaned up and a new set of brushes installed. Carbon dust from worn brushes is a big culprit.

Also, in the back of the motor you will find a resolver (a little can with a shaft, driven by a tiny gear on the motor shaft). If you remove the resolver, be sure to "load" the little spring-loaded split-gear that drives it when you reassemble it. This keeps backlash out of the resolver gears.

Directly attached to the motor shaft is a tach-generator, which has a pair of very small brushes riding on a tiny commutator. Be sure that these tach brushes are OK, and that the tach commutator is clean. A dirty tach can cause the motor to jump around like crazy. You can clean the tach commutator by jogging the motor while holding a pencil eraser against it.

Hope this helps.

[turbo bob]

thanks for the information, the getty motor had a full stripdown and new brushs fitting i think the same way that it is just setting the drive card up,
i try and adjust the control pots you suggested
thanks
bob

[bbrreid]

Hi,
I have a yamazaki microturn 15L by Mazak with Fanuc 6t control circa 1980
with a similar problem on the X axis.when I fire up the machine and release the Allstop the X axis motor gives a quick turn and sets of the alarm 401. each time I press the reset button to clear the alarm the X motor turns (or jumps).the red led(ov) on the drive board comes on some times.I have not had the machine very long and I know older machines do not like moving around from one workshop to another but it was working for the first 2 weeks after its arrival.I dont know much about electronics but I looked at one of the main brushes and it looked ok (maybe worn by a quarter ).
anyone have any ideas for fixing this problem.I have a job waiting to go on it
thnaks
Brian.
if I get it running I will post the info.