Re: [CAD_CAM_EDM_DRO] Re: Please help!!! I have run away servos on X and Y

Jim Montgomery wrote:

> OK, It's starting to sink in but, now let me show you how little I
> know about servo systems. It seems like if I reverse polarity on only
> the motor, that the position loop would get a huge error count and
> shut things down. I won't know till I try.
>
> Also, there are six trim pots on the amp AUX, SIG, TAC, TC, CLM, and
> BAL. First what do they do and second, If any one or more of these
> pots are "out of wack", Could this be causing run away.

Aux is probably not used, it is an extra input. Sig is a gain setting for
the velocity command signal from the CNC control. TAC is the gain
control for the tachometer. TC is most likely "tach compensation",
to adjust the high frequency gain for the velocity control loop.
CLM is current limit. BAL is a DC offset, to allow the servo amp to
produce zero voltage to the motor when the CNC control is requesting
zero velocity. If TAC is set to zero, it may cause a runaway, as the
amp has no velocity feedback.

Has this machine been disconnected from the control or servo amps?
If you did not have to reattach wires when you reinstalled it, then it is
unlikely that wires are reversed. IF you DID have to reattach the wiring,
then it is entirely possible that wires have gotten swapped. Are you
absolutely sure that the encoder, tach and motor wires are all hooked
up to the right axes? if you had the encoder from one channel connected
to the input for another, or the tach from one axis connected to the servo
amp
for another, then wierd things would be expected.

The servo amps ought to have a command input (might be labeled SIG
to match the trim pot). If you apply voltages between +10 and -10 Volts
on this input, it should command the machine to move at a constant
speed. There is probably an amp enable signal also provided by the
CNC control. You might start with a 1.5 V battery, which would move at
about 15 % of maximum velocity.

Jon