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

--- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:

> 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

Hi Jon,

Thanks for the reply. I havn't signed into the group for a while
since I installed Windoze XP upgrade that was not suposed to wipe
out all of the files it wipped out. (anyway that's another group...
backup, backup, backup}

The mill was complete and all of the wires were connected with the
exception of some broken solder joints in socket connectors and
tarnished contacts showing some resistance. Wires were resoldered
and the contacts are nice and clean. I was lucky enough to get a
line drawing of how the different components of the system connect
together. I've trace everything down and it all looks good. I've
recieved a lot of great advice. It sounds like next step to take is
to input my own +/- voltage into the amp and see how the motors
respond. I'll post the results.

Thanks,
Jim