920 Watch Dog Timer Alarm

[gearmachinist]

Good Morning!

Okuma & Howa Act2SP-2 with a Fanuc OT Control. We are getting a 920 Watch Dog Timer alarm. However, the alarm is very intermittent. Once the alarm occurs, we can power the machine down and bring it back up and the alarm goes away. The machine may run a few minutes or a few hours.

Has anyone encountered such a problem and if so, what would you suggest? The manual suggests that the problem is a servo system problem but it doesn't really help in pinpointing if the problem is in the drive or in the main control.

Any help would be appreciated.

Thank you,

Gary

[der_fisherman]

Usually, a Watchdog timer is used to make sure that a CPU is still active. The CPU needs to go and reset the timer every few milliseconds, or it times out, and shuts down the process.....or restarts its program or something similar.

The reason being is that if the CPU stops working, it can be quite dangerous to certain hardware and the people around....

There is a reasonable explanation on Wikipedia here:-

http://en.wikipedia.org/wiki/Watchdog_timer

that might help you further....

Bad programming is usually the problem, a function simply takes too long to happen, or interrupts are badly set up.....

You may find that doing a particular job causes the problem.....

Best wishes.

[xavierdemoura]

Gearmachinist,

Here i do maintenance in Yang machines ans we have a lot off problem´s like that here. 3 machines, 1 machine only solve the problem when FANUC change the motherboard the other 2, the eletric gabinet is very hot, one we open the door of eletric gabinet and never more stops (4 years) and the other machine we put an fa with door open and never stops more (3,5 years).

Best Regards,

Daniel

[memogrr18]

My god!, i just had this alarm and almost died when i saw that i had to change master pcb! i just have replaced two demagnetized servos.

it happened while making a hole and there was a lot of vibration. then this alarm triggered.

rebooting didn't help.

i oppened the master pcb door and pushed all the microcontrollers to their holder. some of them clicked. then i turned on the system and it is running now.