Re: [CAD_CAM_EDM_DRO] Re: EDM machine

Hi,

The original design by Langloise used quite big caps and was a fairly simple
and brutal machine. In one of the later articles (in HSM) he speculates on
an 'improvement' which adds in frequency chopping and pulse width control to
the spark. This allows much better control of the cutting and, at the same
time, a reduction in the size of the capacitors. Whilst he gives a basic
circuit for this addition which is an oscillator with control over the pulse
frequency and on/off timing driving a couple of FETs in series with the
spark electrode power feed (and can therefore be added into the basic
machine after construction), he doesn't specify component values and says
the design 'will be refined if there is enough interest shown'.

This is basically the way I am intending to go although I may need to seek
assistance with finalising this add-on circuit as my electronics skills
leave a little to be desired.

This whole basic design seems to be similar to commercial machines - as far
as I can tell from looking at the instruction/servicing books for a couple
and would seem to have potential for producing good clean parts - this,
however, remains to be seen!

So, to answer your question, a big capacitor will give a big, uncontrollable
spark while a smaller one will give better control and better finish,
particularly if combined with a chopped, frequency controlled supply.

As to electrolytes, I have read a lot of literature, none of which seems to
agree on the 'best' fliud. I have also tried hydrocarbons (Stoddart solvent)
on a basic EDM and scared myself silly! So, I am inclined to go with one of
two suggestions I have seen - either a mixture of water and antifreeze
50/50, or hydraulic fluid and completely cover the part being machined in a
deep bath of the stuff.
Ian
--
Ian W. Wright
Sheffield UK

----- Original Message -----
From: "marble here" <marble_h@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: 31 October 2000 21:14
Subject: Re: [CAD_CAM_EDM_DRO] Re: EDM machine


> I my self am making his EDM I just started looking for
> the caps Now are you saying the the should be lower
> instead of 100ufX150volts . So if one used 50uf X XXv
> would make a better spark
>