Re: PC based CNC system architecture

Jon Elson <jmelson@a...> wrote:

>
>
> > > For steppers, I think having an encoder with more resolution

than

> > the
> > > stepper could cause problems. But, we could put a dead zone in

the

> > > control loop to prevent fast hunting. (The planned design will
> > cause steppers
> > > to hunt at a rate of one step every .6 seconds, as that is as

slow

> > as the
> > > rate generator can go.)
> > >
> >
> > Wally K.
> >
> > For this dead zone in the control loop for steppers. Is this a
> > number in an EMC file. Or something on your control.

> Jon replys:
> I don't think EMC has a dead zone, but it could be put into the
> code that gets these numbers from the .ini file and passes
> them through to the real-time section. For now, it would have to
> be coded into the driver for the rate generator.
>

Wally K. replys

So for the time being you would have to code the numbers for the dead
zone into the driver for the rate generator. Does this mean what you
program in would be dependent on the encoder mounting position.
Either on the motor or ballscrew, encoder resolution, steps per rev
and belt ratio. And we would have to provide this information to you.

> > Wally K. wrote:
> > And, If i have a stepper system and want to add 1 spindle control
> > axis for my bridgeport to use for a VFD. Can your 4 axis servo

card

> > be populated for 1 axis and maybe even a cheap DAC put on board.

(i

> Jon Replys:
> There is no servo card. There is an encoder counter card and a DAC
> card. The DAC chip IS pretty expensive, close to $40 in small

quantity.

> But, at least, it does 4 axes with one chip.
> Now, for open-loop spindle speed control only, a much lower

resolution

> DAC would do just fine. Unfortunately, we don't really have plans

for

> one like that right now.

Wally K. replys:

Ok i forgot the DAC came in a single 4 channel package. And i did
not understand if you can run an axis in open loop if you want to for
rough spindle control.


Wally K.