Series Six APM (Axis Positioning Module)

This is definitely an old-timer's sort of question


We're having difficulty with a servo that:

1) Sometimes it runs right.

2) Sometimes it goes nuts in the homing cycle and bottoms out.

3) And sometimes just runs for the hell of it.


The symptoms are:

1) When it runs ok, all three LEDs are on.

2) Bottoming out (overtravel) results in the loss of the "Drive Enabled" LED (as one would expect).

3) When it takes off unexpectedly, it actually turns ALL of the LEDs off, including the "Board OK" LED. When this happens, it requires cycling power to the rack to clear the fault.


The fault codes coming back from the APM are:

1) 02h (when it runs right). Meaning everything's okay.

2) 15h (when it goes into overtravel). Meaning that somebody requested a move while the servo was homing (which we did not do).

3) 52h (when it takes off by itself). Meaning that the system RAM is corrupt.


We've done the obvious, changing the card and the rack to no avail. Any suggestions?


Thanks!

I used an APM once, and it was a LONG time ago...

rootboy said:

We've done the obvious, changing the card and the rack to no avail. Any suggestions?

Click to expand...

Damn... and I was just going to suggest changing the backplane. That's the item most often overlooked... :nodi:

I highly doubt the CPU would be an issue, as the APM has it's own program (er, memory). Encoder problems shouldn't cause these errors either. Really, the only thing left is the power supply.

Of course, you can't rule out a defective servo amp. If a new power supply doesn't do the trick, that would be the next thing to look at.



-Eric

Yeah, this is a wierd one


Where we are now:

The servo drive seems to be working fine, so no worries there.

We replaced the servo motor with a rebuilt one - which doesn't work at all. Typical...

Tomorrow we are going to pull the encoder off of the new servo and mate it to the old motor. Here's hoping that at least the encoder works.



Other than that, how have you been? Good to see your avatar again

Is that really Phil's voice on the opening page? Is he doing that to cull out the faint of heart?

I see we are going to get a working PLC simulator, does it come with a free traffic light program as well?

Inquiring minds and all that...


Thanks,

John

Is there any external HMI writing to the Series Six? If so, has anything in it been changed recently? Could it be writing to a register that's mapped to an AI or AO address (or some other channel) used by the logic controlling the APM?

The faults seem to point to something flaky coming over the backplane. Since you've already changed the rack, try changing the logic controller module. I'm pretty sure that's the module that writes the state of the outputs onto the backplane. If it's writing bogus values, the APM will go nuts trying to follow the bogus command.

What else is in the rack with the APM? The troubleshooting section of the manual says that the 'Board OK' LED goes out on "Hardware failure or board is not in a high capacity I/O rack or a CPU rack". Could some other module in the rack be dragging down the power supply?

It turned out to be the servo motor that was causing all of the problems. We replaced that (and took the opportunity to do some serious mechanical repairs as well), and it's now working.

That was really, really wierd.


Thanks for the help guys

Sorry I didn't see this sooner, I had the same problem twice on two different axis over the past year, and like your problem the first we had to replace the motor/encoder since the encoder is a none replaceable item in our motor. The second time this happened it was the Encoder Cable. We found it by going into the program and monitoring the encoder values as we manually moved the the motor.

Thanks anyways, it was a learning experience