Re: software for EDM maschine

The garden of CNC stuff is an untested project as far as I can tell.

You can find everything you need to know in patents on pulse
circuits or more importantly control circuits. For home use you can
copy it till the cows come home.

As has been said the control of gap in wire or sinker is a closed
loop thing, you try to maintain certain conditions and to do this
the electrode is moved. In the sinker I used, the head was
controlled with a dc servo and ballscrew. So in your servo feedback
loop is something related to the gap. Away from the workpiece the
eletrode simply drops slowly depending on the knobs you tweak.

Now for a homebrew system based on step and direction you should be
able to do the same thing it is just that the software has to be
able to keep track. Now whether or not the head has to back up an
entire move or a few steps is irrelevent as the event may happen on
the boundary between moves so it has to be a little clever at the
very least.

One possilbility might be to have something that stores a certain
number of step/direction pulses in a sort of cache. When the gap
appears to be too small then the cnc program supplying the pulse
train would be paused and the pulse train played in reverse until
the conditions were ok again, then it would be played forward again
and the program restarted. How well this worked would be down to
how quickly the software could be started and stopped. It would not
be as good as the servo based feedback of a sinker or no doubt of a
commercial wire machine. But we are talking about DIY machines or
at least we should be.

For an even dafter idea you could play the entire cnc program as
steps and directions into memory and just run through them flowing
back and forth as required depending on gap voltage etc. That
*might* be a quick and dirty solution for a pic programmer. The
cutting rates would be dictated by the cutting conditions as normal.

Graham