Re: EDM retrofit

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Stephen Wille Padnos
<spadnos@...> wrote:

>> >
> At the moment, I believe reversal is the only thing keeping EMC2 from
> being fully capable of doing EDM control. It's a pretty big thing,

so I

> don't expect full support for it any time soon. We usually try to make
> any implementations generically usable rather than single-purpose,

which

> sometimes means features take a while to get implemented. For EDM, you
> only need to reverse for a few thousandths of an inch. To remove a
> broken dovetail cutter, you may need to reverse inches, through

multiple

> G-codes. A simple solution to back up a few thou would be - err -
> simple :) A general solution to allow you to reverse as far as you

want

> (possibly to the beginning of a program, while properly handling G2/G3,
> cutter comp, other modal codes, etc) isn't so easy.
>

Thanks for some further info on what EMC can and can't do. Mach3 can
also do feedrate override, you can also pause and even reverse however
I think the reverse takes a straight like back to the end of the last
move before following the g-code.

I had the idea of recording step and direction pulses to memory with a
microcontroller, then either the whole program could be played back
according to gap conditions (including full reversal if needed). The
other idea which is probably neater is to just pause the CNC control
program and use a small buffer for reversal over short distances.

However all of this is probably the easy part with a retrofit, you
have to work out how the machine works, the generator, feedback etc
etc I think it could be quite difficult without support. And that is
before you consider 4-axis cutting.

Graham