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billyboy
10-25-2005, 12:27 PM
hi all, ive heard a lot about edm machining, what is it?

bill

SGW
10-25-2005, 12:52 PM
Electrical discharge machining. Undoubtedly others know a lot more about this than I do, but here's my take on it.

Two main types: "sinker" and "wire." Sinker EDM uses a formed electrode to cut a particular shape into a part. For instance, for a simple case, you could use a square electrode to cut a square hole through a piece of steel. This was the first type of EDM, I think, and there have been plans published in HSM and elsewhere on how to build a home shop version.
Sinker EDMs are also good for burning out broken taps....

Wire EDM uses a wire -- the movement of which is computer-controlled -- to cut an arbitrary shape. You can start cutting from an edge, or you can drill a hole, thread the wire through the hole, and cut an internal shape.
The shape on the top of the hole doesn't need to be shape on the bottom of the hole, either. For instance, I once saw a sample block about 2" or 3" thick that had a slug cut out of it. The top of the slug was in the shape of a "3" and the bottom of the slug was in the shape of a "D".

Oh -- all this occurs with the work submerged in a vat of liquid of some kind.

[This message has been edited by SGW (edited 10-25-2005).]

jkoper
10-25-2005, 01:03 PM
bill,
EDM stands for elctrical discharge machining. It is a process of removing metal by spark erosion. If you have ever dropped a wrench across the terminals on a car battery, that big crater that get burned in the wrench is edm on a grand scale. EDM machines use an electronic circuit that generates millions of tiny sparks that jump between the electrode and the workpiece, each one makes a small crater in the workpiece. Eventualy a cavity is created in the workpiece the same shape as the electrode. The process was first developed durring the 40s to remove broken taps. Tap disintergrators eventualy evolved into the die sinker edm.

Jim

------------------
Jim Koper
J&R Machining

[This message has been edited by jkoper (edited 10-25-2005).]

Rich Carlstedt
10-25-2005, 07:03 PM
Bill , There is a group of Hobbiests that get together at
http://groups.yahoo.com/group/EDMHomeBuilders
Thye are building small home units that were published in a book by Ben Fleming

Herm Williams
10-25-2005, 08:23 PM
go to google type in"electro arc", to get a lot of information on the disintegrators they sell
re

Dave Burnett
10-25-2005, 08:47 PM
I have worked in Mold shops for the last 35 yrs. and I know 5 EDM operators that have died from cancer. The oil will get you sooner or later. They are not good machines for the the hobbyist as the oil is a real problem. Trying to just get rid of the used filters is a nightmare. The shock can also be a killer along with being a hell of fire hazard. If you need EDM work done take it to a job shop and have them do it for you.

Dave Burnett
10-25-2005, 08:50 PM
Oh I forgot to mention machining the carbon electrodes. Now that is a real treat getting carbon dust all over everything.

billyboy
10-25-2005, 09:11 PM
i originally posted this thread because i bought some ground flat stock from my steel supplier (cromwell tools)england, in the catalog it states that this steel can be edm machined, i was just wondering what edm was, thanks for the replies,

bill

Mcruff
10-25-2005, 09:30 PM
Dave I have run one for more than 20 years, its not the oil that gets you, its the heavy metals that are eroded away and deposited in the oil. Most shops do not change the oil or filters on a proper schedule. Not to mention alot of shops use copper tungsten for elctrodes, I always used electro-glove to protect my skin from the oil and heavy metals.
Grinding carbon is not messy if you use a vacu-guard on the grinder or mill. I have literally ground tons of carbon in 24 years and burnt 1000's of cavities. I ran 2 machines for 10 hours a day for more than 10 years, a 100 amp Elox and a 30 amp Eltee Pulsitron and also ran a 25 amp Hansvedt. Some guys hate this job others love it, I loved it and got payed handsomely for my knowledge of the machines and the process, probably more than 1/2 of the guys running ram type machines really know nothing of what they are doing, they are working in the dark and getting by.

Dave Burnett
10-26-2005, 07:42 PM
Mcruff, I was pointing out that EDM machines are not good machines for the hobbyist because of the problems involved in getting rid of the waste and the mess from the oil. I have run EDM machines, and they really are the only way some forms and shapes can be machined, this is really true in mold work. I would not want one in my small shop.