Re: [CAD_CAM_EDM_DRO] motor sizing vertical slide EDM

Hi Tom:
Are you sure you want high ram speeds at the expense of high positioning
resolution on a sinker EDM?
You need to be able to maintain a very small spark gap to exquisite levels
of precision if you want to do any fine burning.
My CNC sinker has very SLOW rapids...of the order of 10 IPM, and its
feedrate is maybe one tenth of that.
Retract rate is the same as rapid rate.
Believe me, this machine crawls when I'm tramming across a job, but I can
jog in 0.0001" increments that are exactly 0.0001".
My machine has DC servos and ballscrews.

Are you planning servos or steppers?
If you're looking at a stepper system, you have not even a faint prayer of
getting the resolution you need and the rapids you want.
With a servo system you've supposedly got a wider range of speeds to play
with, but if you heat the ballscrew while Z cycling the ram, you'll be
forever shorting the trode to the job from thermal expansion of the screw.
I'd check this whole thing out to be sure of what you want, before getting
in any deeper.
I do know that Sodick makes a sinker that uses a linear motor (no ballscrew)
and is supposed to be blazing fast for ram response, but I have no idea what
"Blazing Fast" means on a sinker.

This must be the mother of all sinkers if it has a 700 lb ram on it!
My machine has the ram cored out all over the place to reduce its weight,
and has a pretty wimpy electrode weight limit too (35 lb I think)
My old hydraulic sinker, on the other hand, has a massive load limit...300
lb, so it's ram is much less responsive than the ram on the CNC machine.
It is capable of fairly fine burns, though...and can maintain a spark gap of
0.0002" with the right EDM oil and good flushing.
All this leads me to believe that ram speed is not so terribly important on
a sinker unless you want to burn deep skinny ribs and other horrid
geometry.(this is supposed to be the Sodick's claim to fame)
If that's your aim, you need a fuzzy logic control and all the other high
end goodies too.
Cheers

Marcus