The Craftmans Shop > New from Old
Eurospark H425 Die Sinker EDM reborn
awemawson:
Well this certainly is reviving an old thread, but this is the logical place for the info so here goes !
Some months back I noticed that the EDM fluid in the Eurospark H425-P25 Die Sinker EDM machine had drained away :bang:
Now the construction of this machine is quite strange. There is a central steel column about 7" diameter, on top of which is mounted the Tee slotted work table. Up and down the column slides a fixture that mounts a tank that can be raised hydraulically to submerge the work in EDM fluid, or lowered to give access to the work for setting up. To seal the tank to the fixture is a set of concertina bellows.
The received wisdom is to leave the tank raised when the machine is idle, so that the bellows are compressed rather than stretched for longevity, so one would expect to walk past and see fluid in the tank . . . . but there wasn't :bang:
Now logically this means that the bellows had once more failed and would need replacing, but I'd been putting the job off as the new Tractor Shed had been taking most of my spare time. As that is now finished I decided to move the machine (only 1.25 metric tons!) to the centre of the workshop where I could get all round it and have proper access - not a luxury that I enjoyed last time four years ago.
By the time I got round to looking at it, the sliding fixture that holds the tank was firmly jammed in the 'up' position and no cajoling, pleading or even violence would shift it.
So today I had dismantled the machine far further than ever before, drained out the hugely expensive EDM fluid, removed the radiator and fan motor( that previously I've never been able to get at) - taken off the table, and the tank, and then the column itself.
Having got the column (which is far too heavy for me to lift - probably 60 -70 kgs ) out of the machine and on the floor I could apply a bit of heat and gentle persuasion with a wooden drift and lump hammer removed the sliding fixture :thumbup:
On the bench I cleaned up both the column and the bronze bearings of the slider, greased them and proved that now they moved freely - phew ! Then I replaced the column in the machine.
Now as sinker EDM machines use graphite (or copper) electrodes the machine was hideously grubby, so during this process I took no photographs - however here are some 'after the event' ones to be going on with
awemawson:
Now today is Saturday so I can't open negotiations to buy new bellows until Monday - (last time they were £280 !!!! ) but there is a pile of stuff I need to clean up before then.
The radiator is utterly choked with carbon dust - it always has been in the 20 years I've had the machine, but that side has always been against a wall. Also the fan motor doesn't work - I disconnected it 15 years ago as it wasn't spinning, but similarly it wasn't accessible. Also the table and tank need cleaning but they are trivial fixes.
awemawson:
Quite good progress today :thumbup:
Apart from other distractions (animals and half-term grand-children) I spent the day cleaning decades of oily carbon build up off the radiator and it's associated fan mount. Now unclogged, amazingly the fan motor is working fine :med:
Before breakfast I set up a livestock drinking trough and put a couple of gallons of Red Diesel in, and left the radiator and it's mounting bracketry soaking for an hour or so to loosen the muck - a bit of scrubbing with an old sink brush followed by good blow off with an airline seemed to do the trick. (I had blanked off the entry and exit from the radiator first to keep the diesel out of the EDM fluid passages)
Then I re-fitted the column slider and it's safety brake along with the double acting hydraulic cylinder that raises and lowers it with the tank.
Just as somewhere to put it, I temporarily re-fitted the tank - (it will have to come out again when I get the new bellows)
awemawson:
The hugely expensive new Bellows arrived yesterday, so after super I took my heart in my hands and fitted them :bugeye:
It's a trivial job EXCEPT for the fact that they are very delicate, have to be manoeuvred around and through sharp objects, and the hex socket clamping screws that trap the bellows and their seal through the tank bottom to the raising collar are on a pitch circle that puts them firmly under the lowest corrugation of the bellows. This means that not only is it impossible to see the screw (everything has to be done by feel) it is virtually impossible to avoid scraping the allen key on the bellows material and that brings the risk of tearing them :bang:
Anyway after a very controlled and slow approach to it I finally got everything tightened down, and was able to re-mount the work table. This is insulated from the central support pillar by a fibreglass ring, and sealed with Blue Hylomar against leaks of EDM fluid.
Then this morning, on went the radiator and fan and I changed the main fluid filters while I was at it.
So the big test - fill her up. With the tank half raised I poured fluid directly into the tank as per instructions until it poured over the weir that sets the level, then the remainder went into the base which acts as a reservoir.
Glad to say that the tank fluid level has stayed unaltered all day BUT I don't have enough fluid to cover the lowest extremities of the filter housing. Consequently the pump is drawing in air not fluid. I knew that the level was marginal, and having drained and cleaned things up I must have lost the odd litre in the process.
Order placed for more - it's £5 per litre - minimum container size is 60 litres so you can do the maths yourself :bugeye: Scheduled to arrive on Friday.
awemawson:
This afternoon as promised, the 60 litre drum of bankruptcy invoking EDM fluid arrived, and I promptly topped up the reservoir :thumbup:
Glad to say that now the pump is no longer sucking air, as the level has risen above the skirts of the filters, the tank is being correctly filled and level maintained with a good cross flow.
Now I just need to find time to prove out the workings of the machine and correct any foibles that may have crept in as it's been disturbed
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