Re: stepper-servo system

--- In CAD_CAM_EDM_DRO@yahoogroups.com, John Dammeyer <johnd@...> wrote:

>
> Hi all,
>
> As I recall, measuring the arc voltage is described in several DIY EDM
> projects. As Dave says, run that into a comparator and the digital

output

> could be fed into an Electronic Leadscrew Module with slightly different
> software. One could even program how deep it's supposed to go.
>
> Cool. Yet another possible project for ELS hardware. <GRIN> I

already use

> a comparator now, to test the threshold for the spindle encoder.

I'll have

> to dig deeper and see if that same circuit couldn't be used for

testing the

> 'gap height'.
>
> The real question is how quickly does a system like this need to

respond?

>
> John Dammeyer

The logic of the whole thing is one op-amp. the stepper or servo
pulse generator can be one other device, or possibly other parts of
the same op-amp. the stepper driver can be anything. or you could
use a DC motor.

the speed required is conditional.

to feed from the clearance height to the part needs a rapid.

once cutting is established, and the axis has no side to side play,
and the electrolite is flushing well, then the feed is only a step
every now and again.

A better circuit would drop the voltage when a short occurs and do a
very short wait to see if it was just the odd electrolite/chip
problem. if one moves too close, and does not touch, then a lower
voltage will cut till the gap opens.

if the retraction has any sideways movement of the axis, then a short
will be caused, followed by full retraction and then by full extention.

a memory of the last good position would great so it could rapid to
near that, then slowly advance to cutting.

Dave