Eurospark H425 Die Sinker EDM reborn

[awemawson]

I've had my Eurospark H425 Die Sinker EDM for many years - bought it as a non worker and fixed a few problems probably about twelve years ago. Then about (guessing) eight years ago (*) the tank bellows split and I replaced them. Well about six months  (*) ago they split again so this job has been outstanding since then.

First delve in and remove the bellows, so first the table has to come off. This is a mighty heavy chunk of cast iron!

Andrew

(* later correction. First changed Bellows October 2005, and they failed September 2013 )

[awemawson]

Then the old bellows need to come off. This involves removing the tank as it's seal is trapped between the hydraulic cylinder and the tank

[awemawson]

Then we need to inspect the hydraulic ram and check for blemishes. Note that the central pillar holding the table stays stationary, and the outer part raises bringing the tank up around the table.

[awemawson]

Now comes the tricky bit. Putting in the new bellows without damaging them. Various hazards, for instance the cap screws that hold the tank onto the ram are under a fold of the bellows, so don't slip and tear the new ones. They were only £280 so no pressure 

Turns out that the replacement has ten convolutions whereas the old one had fifteen. Quick call to Eurospark who confirm that this is correct 

[awemawson]

Now to get the table back on. There's an electrical connection to it (it's isolated from ground as it can be negative or positive) and the 'free length' is so short to make it very fiddly.

[awemawson]

So does it work. In short no 

Firstly, to remove the tank I had to raise the vertical slide further than the screw that moves it.Lowering it back I ended up with a burr on the phosphor bronze nut. Had to remove the nut with the slide precariously balanced on cribbing timber, mill off the burr and re-install in - all a bit of a drag but then it was mechanically back together.

So does it work. In short (Still) no 

All the servos work but we have no spark. I'd had enough by then so clean up and have supper and a couple of cans of 'Old Speckled Hen'

A bit of prodding this morning and I find that one contactor was a bit sticky, clean it up, re-wire a few bits I wasn't happy with and off she goes 

Lets do a quick and dirty test. Stubby bit of copper tube as an electrode with a block of EN8 steel as the victim

[awemawson]

So what was the result. Well in about two minutes we've sunk the copper in 70 thousandths of an inch. So we're back in business and maybe now I can make that 5/8 UNC x 2" grub screw with a hex recess that I needed for my Edwards folder re-build.

Lets hope these bellows last longer than the previous ones as it was an unpleasant messy and dirty job.

Andrew

(* later correction - it's a 5/8 BSF x 2" grub screw)

[Pete W.]

Hi there, Andrew,

It's good to read your post - that's a result!          

I remember that the green soup was part of the problem but I've forgotten how you needed to resolve that part.

[Meldonmech]

Hi Andrew
                          It really is amazing what that Old Spreckled Hen can do for you. Just shows job fixed.

                                                                Cheers David

[awemawson]

Hi Andrew
                          It really is amazing what that Old Spreckled Hen can do for you. Just shows job fixed.

                                                                Cheers David

Only bettered by Harvey's Best Bitter, but that's not available in cans only barrels - (polypin ordered for Christmas  )

Andrew

[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 

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 

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

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 

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 

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 

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 

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  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 

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

[AdeV]

Hi Andrew,

Next time you want EDM fluid (which I would imagine would be never, if you've got 60 litres of the stuff now!), try Lube Tech Shop: £57ish or £62ish for 25 litres... + delivery I expect: http://www.lubetechshop.co.uk/index.php?cPath=25_48

Slightly less bankruptcy inducing!

I was lucky, my EDM machine came with a 3/4 full 205litre barrel of fluid, and I've not even had to break that open yet, there seems to be plenty in the machine. My machine is obviously a lot older than yours, it doesn't have an fancy dancin' raising/lowering tanks; just a door on the front that I can presumably take off to access the table. I haven't tried it yet, in case I break a seal...

One day, I need your expert presence to strip the machine down & find out why the vibrating table doesn't vibrate, and why the middle power setting trips the fuse every time I try it... 

[awemawson]

Hi Ade,

It was tempting to change to a cheaper fluid - in extremis I could use neat paraffin after all that's what it was designed to use originally and paraffin costs peanuts, but stinks the workshop out and is highly inflammable. The IONOPLUS is very low odour and I have failed to set a rag dipped in it on fire by applying a match 

To change would require a comprehensive flushing and I suppose I took the easy option !

[AdeV]

Mine is full of some fluid from one of the major petrochemical companies (BP or Shell, I forget which), it's not quite as lurid green as yours, it doesn't seem to smell either, other than a bit paraffinny if you get it on your hands.

Must admit, I hadn't considered using graphite as an electrode - how does that wear compared to copper?

[awemawson]

Ade, I have reams of pages of tables detailing cutting rates for copper and graphite at differing currents, and the allowance needed for the side burning effect, but I confess never to using them.. I just suck it and see !

[awemawson]

Today I put things like the electronic touch sensor through it's paces and convinced myself all was well with the machine 

Then I started the Herculean task of shifting the machine to it's spot in the workshop - but where ? Where it came from is very close to the lathe, and I suspect that flying swarf had accelerated the demise of the bellows 

Much pondering later I realised that where it was was really the only practical option - so it had to go back with some sort of swarf shield. In the end I decided to use a sheet of 18 mm OSB board that I had on hand (all be it on the other side of site in our domestic garage  ) Not very subtle, rather 'in your face' but seems effective

So cutting some 36" lengths of scaffold tube, and using levers I got the beast raised onto the rollers, and bit by bit eased it across the workshop and round two 90 degree bends, amazingly finishing the job with all fingers and toes intact leaving me able to type this 

Connecting it up and doing a quick test cut it still seems to work (phew!) and I only lost perhaps a litre of fluid (=£5) on the journey 

. . . .so that's probably that . . . . .until the next time !

[Noitoen]

Maybe you could try a stainless steel bellows to solve the problem.

https://huntvac.com/products-catalog/section-9/vacuum-bellows/

[awemawson]

A nice bit of lateral thinking 

Also I suppose I could silver solder the ends to create the correct flanges - food for thought if / when the need arises again. I had thought of turning up a former and painting / brushing / dipping it in one of the proprietary liquid rubbers but buying a bit of suitable stainless bellows and fabricating the ends sounds do-able.

[Noitoen]

Some thin stainless disks and tig welding could do the trick.

[RotarySMP]

Interesting thread on a less common type of machine. Do you use it often?
Mark

[awemawson]

Not very, but this morning I cut a 15 mm o/d 13.5 mm i/d circular slot 15 mm deep in some tool steel.

Why you may well ask  Only because I wanted to do a full current (25 amp) test on the machines electronics and the first electrode that came to hand was a short length of copper plumbing pipe. Oh and the machine passed the test 

I've used it to sink all sorts of irregular holes in things, to remove broken taps and bolts, cut holes in HSS tool steels, and modify the holes in index-able carbide threading tips - a very handy tool albeit not often used - it digs you out of difficult situations