edm machines

[noel shelleyParticipant @noelshelley55608]

RIGHT ! Guildford was Maurice Fagg. Dilectric fluid parafin ! I bought the only 2 books on the subject available at the time and took the bits I liked from both to build a powerful EDM. Drilling holes in tungsten carbide with copper wire was a party piece ! Most of what was used was what was found lying about, apart from a few £s for electronic components. The 2 transformers gave me 66v at 6A and came from old 1arm bandits, before the days of LED ! Jeff is spot on ! The over cut is about .004" and brass makes good electrodes. If you can file the shape you can EDM it. I used a draw slide with 12v DC motor/gearbox and leadscrew. Speed is goverened by volume of metal to be removed. As the oft talked of removal of broken taps goes, small ie under 1/4" use thick copper wire or brass to take out the middle. For BIG ones use copper tube and just cut off the "legs" and it all falls in the middle.

I'd better get out the books and draw up my circuit diagram, for those who may find it interesting.

More later. Noel

[Jeff DaymanParticipant @jeffdayman43397]

I use a Valvoline dielectric oil specifically made for EDM, sold by a large oil dealer in my area (Ontario Canada).

I suggest calling a local oil dealer to you and ask what they recommend. Or call a mouldmaking shop for injection moulds, they use it out of 45 gallon drums.

Rustlick is another USA brand I have tried but I find it smells unpleasant, where the Valvoline one does not. Virtually no smell and almost clear transparent in colour with the Valvoline product. Great stuff.

I would not recommend any paraffin / kerosene unless it is specifically formulated for EDM. Lighter kerosenes can catch fire under some EDM conditions, ie work submerged less than an inch deep. Kerosene also smells strong, and EDM smoke is oily and sticks to curtains, clothes etc. so if it smells bad it can be a big issue in the household.

Edited By Jeff Dayman on 06/05/2021 20:29:18

[Frances IoMParticipant @francesiom58905]

Noel – look forward to circuit details – always meant to build one based on Maurice’s very simple model but like so much else never seemed to get around to it.

[noel shelleyParticipant @noelshelley55608]

The second book I bought was HOW TO EDM by Robert P. Langrois. One design used a dc motor/leadscrew, the other a stepper motor/leadscrew.. I found the dc motor easier and less complicated to make. Noel

[Robert Atkinson 2Participant @robertatkinson2]

Liquid paraffin may be a suitable dielectric fluid. Chemists don't seem to sell it any more due to limited practical use an some abuse (not going into detil as this is a searchable forum). It is howeve used for horses so equine suppliers sell it in useful quantities. Called "mineral oil" in the USA. It has good dielectric and thermal properties and not highly flammable. It has low volatility and high purity. It's used in temperature controlled baths in standards labs.
EDIT: If liquid paraffin is too viscous you could try odourless white spirit. This is of course a lot more flammable

Robert G8RPI.

Edited By Robert Atkinson 2 on 06/05/2021 22:00:44

[noel shelleyParticipant @noelshelley55608]

I can buy parafin from a local motor factor in 20 or 25L drums, though it's dearer than petrol. I have heard it said that de ionised water will work, though I've not tried it. Noel

[CirclipParticipant @circlip]

"I can buy paraffin from a local motor factor in 20 or 25L drums, though it's dearer than petrol."

When did that happen? Used to trip down to the local Esso Blee Dooler for a gallon for the room heater.

Regards Ian.

[CirclipParticipant @circlip]

When the above posting is modded due to the "Overlap", this seems to occur when you add the " and then insert a cut and paste quotation instead of the "Norm" of adding the whole posting and wasting space.

Didn't get this with the old system, DOH!

Regards Ian.

P.S. Spline chunk still don't work.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Circlip on 07/05/2021 08:27:31:

When the above posting is modded due to the "Overlap" […] instead of the "Norm" of adding the whole posting and wasting space.

.

I find the best compromise is to quote and then edit the quotation … as demonstrated ^^^

… that way you properly reference whomever you are quoting.

MichaelG.

[noel shelleyParticipant @noelshelley55608]

Clambered about in the spare bedroom this evening and Got out the EDM ! So long since I last saw it, I had even forgotten how I'd built it. Due to the transformers I had used I had 2 voltages, 66v at 8A and 100v at 3A It also gave me 12V at ample current for the cutting head positioning and 5V for the control circuits. The 2 bridge rectifiers + other handy bits, like the transformers came from gaming machines, when all the flashing lights were proper bulbs and needed quite some power. I had added a bank of capacitors in increasing values to 2200uf, all switchable so almost any value could be used. The heavy resistor that was going to be expensive, I used a NOS electric fire element cut down to give the required ohmic value. I used VERO(strip) board to build the circuit, no fancy PCB. An old metal box was adapted to make a good solid case to contain all the bits, and a cooling fan from something kept everything from breaking into a sweat as the resistor could get quite hot. The cutting head is a readily available small 12v motor/ gearbox unit, the accurate verticle movement is achieved using an ordinary ball draw slide and the tool holder is an old 3/8" drill chuck. An old fridge drawer served as a tank and a small machine vice was the work holder. To remove some of the debris an old speaker magnet laid in the bottom of the tank. It was built as 2 parts, the power supply and controls and the cutting unit. I will try to post some pictures in the near future. Noel

[noel shelleyParticipant @noelshelley55608]

Today weather has stopped me cutting the grass, so I have used the time to look at the issue of an EDM. ME carried an article by C.R. Amsbury in july 1976 and an update in October 1981. There appear to be several errors, one being the switching transistor in Fig 3 of the update which should read 2N3055. The dearest part of making an EDM is going to be the power transformer. Anything above 40V at 4A on the secondary will be good up to about 100v and 6 or 8A., if it also has 12v and 5v you are laughing. Capacitors of 400v rating will be good. For simplisity the capacitor discharge system and a DC motor is best – and cheapest. What you build and what circuit you use will largely depend on what you have or can get cheap or for free, making friends with the maintanence man at an amusment arcade may pay dividends. Noel.

[noel shelleyParticipant @noelshelley55608]

I have dismantled the EDM today,it was built in 5 parts, The case, front panel with all the controls, the power supply, capacitor bank and control board. I have included some pictures of the parts.to give an idea of how it was built. The control circuit board is based on Ben Flemings circuit but built on strip board. The 2 ic s that were used were mounted in holders to avoid the risk of damage due to static or heat and make testing or repair simple. The front panel starting top left, mains fuze 5A, mains switch, to the right 5 switchable capacitors, & the 66V or 100V switch. Bottom left,cutting head motor switch on/off, centre off, up or down. A bicolour LED to indicate up or down movement, this is a failure & will be changed for 2 separate LEDs. Set voltage pot and voltage spread pot. Red and Black power output sockets. Lower left is the cutting head indexable socket. Whilst the ampmeter was fitted, I have not got round to fitting the Voltmeter – yet ! I Suppose you want me to draw up the strip board layout and cutouts ?

The cutting head I have yet to find, it's in one of the sheds, there is as much work in making this as the power supply and is the real key to good operation and results. One thing I found vital was to be able to obsereve the rotation of the leadscrew, this was achieved by sticking a strip of barcode round the shaft. Steady fore and back movement, but more fore indicated cutting, constant fore indicated you were through, hold motor up, job done !   Noel.

Edited By noel shelley on 09/05/2021 14:26:47

[EDMGuruParticipant @edmguru]

Actually a commercial grade EDM machine can be easy and cheap to build, the problem is there is a misconception that there’s some sort of manufacturer’s design secret to these machines which makes people overcomplicate their home build designs usually by using some sort of code to control the actual burn. There's no need to buy a book or anything like that, the electronics are simple and mainly use "off the shelf" parts and the resulting machine performs, in my opinion, better than any DIY build I've ever seen online.

It might be worth you having a look at the video that I posted on YouTube a few days ago in response to other people having design problems, showing a simple machine that I built a few years ago, which I think you will agree proves my point

https://youtu.be/I6EgTPVLrwU.

[HuubParticipant @huub]

That looks pretty usable, promising and "doable" .

Thanks for sharing

[noel shelleyParticipant @noelshelley55608]

Whilst I will agree that many on line machines are complicated and there is no need for them to be so, that your machine was cheap, that term is relative ! Neither of the 2 books I'm aware of on the subject use code and many who build will use parts they have to hand and adapt things to achieve the desired result, rather than buy ready made parts and just wire them up. It really depends on why your building an EDM, what you want it to do and how much you want to spend.

Your machine looks good and seems to work well, that it was easy to make – may be ! That it was cheap, is less clearly proved. Noel.

[Jon LawesParticipant @jonlawes51698]

Posted by noel shelley on 01/03/2022 00:52:26:

Your machine looks good and seems to work well, that it was easy to make – may be ! That it was cheap, is less clearly proved. Noel.

The gentleman is a Guru, I'm sure we will find out shortly.

[EDMGuruParticipant @edmguru]

I agree that the term cheap is relative to what parts you already have in fact if you have all the parts to build this then technically your machine is free! I already had some of the parts and the rest were either second hand or the cheapest available at the time (the D C geared motor was from a child’s toy).

The reference to using code was in response to other people online getting frustrated over how an EDM machine actually works so they end up going down the mystical code route which is unnecessary for a DIY build but ultimately is the way to go as manufacturers of EDM machines do. This is because if you know exactly where the z axis is at any given time you don’t have to wait for a voltage feedback control to work so you can have incredibly fast z axis travel speeds without fear of the electrode hitting the work piece, which is what’s required for the flushing “pump” action when using deep thin web electrodes etc.

Finally I use the name Guru online mainly as a wind up just to further frustrate those who can’t figure out how these machines work when all the time the answer, to me at least, is obvious but then again I’ve always been known for thinking outside of the box and someone had to be the first to discover this type of machine build and, on a quick note, my latest stepper motor EDM machine with anti arc circuit, when finished, so far looks like it could be a real game changer to DIY builds. Also I have compiled over 45 years of working on these machines, mainly as a business, a lot of technical information, which you won’t find anywhere online, for different electrode and work piece material at different Amp, pulse frequency and duty factor settings for spark gap sizes, metal removal rates, electrode wear, surface finish etc so maybe the name Guru is true?

[Les Jones 1Participant @lesjones1]

I have only built an EDM based on Ben Flemming's capacitor discharge design. I have modified the servo design to allow it to work with either electrode polarity. I have done this by adding a precision rectifier circuit to the input so that it works with either polarity sense input.

This is the schematic.

This is the power supply part so you can see the attenuation and filtering of the sense signal from the electrode.

Les.

[Jouke van der VeenParticipant @joukevanderveen72935]

Youtube video mentioned by EDMGuru is not available anymore?

[Frank.N StormParticipant @frank-nstorm18349]

Hi Jouke, I suppose you copied the point/full stop at the end of the link, which does not belong there.
A bit stupid from a Guru, don't you think so?

Regards,
Frank

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Frank.N Storm on 01/03/2022 20:06:27:

[…]

A bit stupid from a Guru, don't you think so?

.

With friends like you, who needs enemas ?

MichaelG.

[Jon LawesParticipant @jonlawes51698]

I don't think I'll ever know everything about a subject. However if I did I'd never proclaim I did for fear of being considered obnoxious. The only subject I know definitively is the Dunning-Kruger effect.

[noel shelleyParticipant @noelshelley55608]

Jouke, If you look for EDMguru on youtube you will see his EDM ! Noel.

[Michael GilliganParticipant @michaelgilligan61133]

**LINK**

[Jouke van der VeenParticipant @joukevanderveen72935]

This works, Thank you.

I tried to open the link given by EDMguru on my iPad but it said the video did not exist anymore.

[Author]

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