Re: [CAD_CAM_EDM_DRO] EDM retrofit

WGB wrote:

> Does anyone have any info or do you know of any links that will help
> me with this problem. I am thinking of buying an older wire edm
> machine and replacing the old CNC control with a Linux EMC
> controller. Has anyone done this? What are the issues with EDM. I
> really do not know much about wire edm but I would like to get one for
> my home machine shop, however I would prefer to use a commerical unit/
> with mods rather then build from scratch. Any help would be great.

EMC2 now apparently has the features to handle double XY UV
axes. As I understand it, the traditional way this is built is
with the UV axes riding along on the XY positioner, so that no
movement of the UV keeps the wire vertical. And, when the UV
moves, that tilts the wire.

But, there are a lot of gotchas that are handled by the
controller. It needs to know when the wire has welded, and have
a strategy for piercing the wire into the work and threading the
machine. There may be some shortcuts you can take that will get
you a working machine without solving all these problems
completely. For instance, one could make a rig that allows you
to mount a thick, stiffer wire for piercing, then manually
thread the cutting wire. EMC2, as far as I know, still doesn't
have an automatic way to retrace a path backwards if a bind-up
occurs. This may be a lot less important with wire than sinker.
Alos, a fair amount of strategy is in the CNC program, like
cutting conical things point up, so they don't jam the wire when
they drop. I think you are right that you can save a lot of
time with a commercial unit. But, you need to be absolutely
sure you can get manuals with complete schematics for the
pulser, and so you can decipher how the control programmed the
pulser for current, on- and off-time, etc. You could put in a
bank of switches to accomplish the same programming, or
interface it through HAL.

I hope you know EDM can be pretty expensive with consumables,
and may not be a great fit for a machine you only use once in a
while. The filters and de-ionizer beds are expensive, the fine
wire costs a bit, and the sapphire or even more exotic guides
can be a fortune.

Jon