Re: [CAD_CAM_EDM_DRO] Accuslide was "Re: Disappointing Lathe CNC Software"

dougrasmussen@... wrote:

> Matt,
>
> --- In CAD_CAM_EDM_DRO@egroups.com, "Matt Shaver" <mshaver@e...>
> wrote:
> >
> > > Servo Dynamics (the maker of my amps) tells me Upgrade doesn't
> > > connect the amps correctly so as to provide motor over current
> > > protection. Duh??
> >
> > It should be settable (the max motor current) by tweaking a pot on
> the edge
> > of the amp card. The amp's manual from SD will show how to do it.
>
> I don't quite understand why Upgrade didn't do this. The simple
> answer would be that they're too stupid, but I think there must be
> some other reason.

I'm guessing the real problem here is not current limit, but overcurrent
shutdown
of the entire system, including spindle drive and all servo axes. In
other words,
any amp going into fault status should cause an emergency stop
condition.
All you need is a relay contact in each amp, which practically all of
them have.

This is a real safety issue, as a runaway servo axis can be a
heart-stopping
event! I put a doubly fail-safe emergency stop system on my mill. It
not only
notifies the CPU to go to e-stop, but commands all servo amps to shut
off,
and then interrupts servo power to the amps. The E-stop system can be
tripped by manual switches, the computer detecting an out of position
condition, or any amp getting an overcurrent. Even though the amps have

a current limit, a sudden transient, such as a crash, encoder
malfunction
or some other disturbance can upset the fine balance of the servo loops
and cause motor current to rise very rapidly.

Jon