Re: [CAD_CAM_EDM_DRO] cheap edm tap buster?

Mark Vaughan wrote:

>Yes Jon, Paraffin is Kerosine, over there, aviation fuel, what they fly jet
>aircraft on, though I prefer Avgas in my car what they fly the old prop
>planes on.
>
>Nice cheap and readily available. As a liquid in a bucket you have to get it
>really hot to vaporise before you can burn it, or you use a wick to vaporise
>it.
>
>I suppose for EDM use, it's either keep the amount small so that if it
>catches on fire, it's one puff and all burnt up, or keep a large quantity so
>it keeps cool.
>
>On the commercial sinkers they pump the kerosene through filters and a
>complete cooling plant. If you push the current up too much you can get
>quite some nasty smoke puffs.
>
>AS you know they also have quite fancy power generators and automatically
>withdraw the probe on a short, a probe like yours they actually rotate and
>bump up and down, the current controlling the rate they bump at.
>
>I have never worked on any of the old simple sinkers, as an electronics
>engineer I was dumped in on CNC stuff, 'hey mate can you fix my machine
>cheaper than the manufacturers engineers'.
>
>I am amazed at how simply you manage to pull this off. I don't have the need
>or room for a full CNC EDM machine, but I do get broken taps and things
>where I could do with a better codge to get it out. When the mill is
>finished and running as a mill, I am going to have to make up a simple EDM
>rig and play I think. May even reserve an input on my G100 to control short
>circuit lift off.
>
>

Well, it may appear simple,. but that was because I already had a
Bridgeport mill that
I CNC'd, and it has a ballscrew on the Z axis with .000025" encoder
resolution.
(That's not a typo, 25 micro-inch per encoder count.) The .001"
backlash in the
quill coupling is a major annoyance, you have to back out quite a while
before actual
motion breaks the short. I usually feed at roughly .0001" per second,
and I do rotate
the electrode with the machine's spindle.

Jon