Morning All, Im in the middle of an EDM build. The electronics are mostly done, and I have a start on the mechanics. I haven't however really considered the flushing/dielectric system. Is a normal suds pump ok for this? The usual suspects all sell self contained tank/pump systems which at first glance would be ok?
What other alternatives might there be?
Cheers Dave
Dave,
It rather depends on the electrolyte you propose to use. Originally die sinker machines would use paraffin. But personally I hate the smell and use this stuff:
It's horrendously expensive but mine so far has lasted ten years !
Obviously you need a pump whose innards are compatible with the electrolyte that you chose in terms of vanes and seals.
Andrew
No idea whether it would work, but I use Bartoline low odour white spirit when I want to use something like paraffin but without the smell. BnQ sell it.
Note, it's got to say "low odour white spirit" on the bottle else you get something else - I include that caveat because there are very different things for sale which have very similar labels.
On another point, what sort of pressure is needed for edm flushing? I'd have thought that it might need to be quite a lot higher than for suds.
-- Peter Fairbrother
I was sort of assuming that a suds pump would be ok with whatever dielectric was used. I that synthetic dielectric more likely to cause issues? From its data sheet it looks like its nice and stable, and not likely to.
Is there anyway, other than experimentation, to tell what is good/bad/indiferent?
I dont really know. The book (Ben Flemmings Pulse EDM design) suggestes 7-8psi as a minimum. I dont know what a suds pump generates?
My Diesinker has a metal vane vane pump with brass seals - I have no idea what pressure, but it's main purpose is to lift the fluid from the base reservoir up into the working tank about a metre above. From there is flows constantly over a weir and down to the base again. The work is of course totally submerged in the tank, and if the ram is programmed for reciprocation pumped flushing isn't strictly essential, though I usually use it. The reciprocation tends to flush the work but wherever possible I have a hole in the electrode through which I flush. (The hole incidentally is also very useful for approximate alignment of the work - I stuff a drill up it and lower it onto the mark on the work!) There is also a 'suck' facility plumbed from the input side of the pump allowing reverse flushing, though to be frank I've never used it. The dielectric passes first though what are in essence large lorry engine air filters to remove the debris.
There are many reasons for choosing a particular fluid, but high on my list were lack of nasty all pervading smells, and low flammability. My tank holds iirc 45 gallons and I didn't fancy a workshop fire very much.
Andrew
I don't think a suds pump will produce anywhere near that pressure. If I wanted something cheap and readily available that would give more than that pressure I would try a petrol fuel injection pump. I don't know about the flow but I expect that can be looked up. I've something like this in mind
Is it sort of like an engine oil pump arrangement then? I have a spare oil pump from the last time I built an engine. I guess I could see if it'll pump water, thats about as thin as I imagine a dielectric gets.
I have the Oil filter head off an A series engine standing by. Hopefully that ans some settling / weir construction will filter sucessfully
Im not certain what capacity Ill end up with, but the work tank will only about the size of a car battery, so I imagine the storage/filter tank will be about 3x that. I also dont want a fire, but my workshop is attached to the house...
Where did you get your dielectric from?
Dave
I was wondering about Facet fuel pumps, maybe I'll see what is in the spares box...
Dave
No it's a vane pump not a gear pump like (most) car oil pumps. Turns out my machines dielectric capacity is 19 gallons not 45 :) I rang Oelheld in the uk and they supplied me direct. If you buy the same stuff but don't need a full drum, I need a top up so we could split it.
Andrew
IIRC Facet fuel pumps suitable for carburetters provide maybe 3.5psi max, SU fuel pumps are in the range around 1.5 to 2.5 psi depending on application. Facet may make higher pressure pumps for fuel injection but you would have to look up the details.
Look in homebrew websites (search on 'goodlife' and you will find a fairly high capacity pump which is intended to be turned by an electric drill)
That _may_ ring your bell.
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