Electrical Discharge Machining (EDM): A Comprehensive Guide

Electrical discharge machining (EDM) is a machining method primarily used for hard metals or those that would be impossible to machine with traditional techniques. One critical limitation, however, is that it only works with materials that are electrically conductive. This method is especially well-suited for cutting intricate contours or delicate cavities that would be difficult to produce with a grinder, an end mill or other cutting tools. Metals that can be machined with EDM include hastalloy, hardened tool-steel, titanium, carbide, inconel and kovar.

This method is sometimes called "spark machining" because it removes metal by producing a rapid series of repetitive electrical discharges. These discharges are passed between an electrode and the piece of metal being machined. The small amount of material that is removed from the workpiece is flushed away with a continuously flowing fluid. The repetitive discharges create a set of successively deeper craters in the work piece until the final shape is produced.

There are two primary electrical discharge machining methods: ram and wire. The primary difference between the two involves the electrode that is used to perform the machining. In a typical ram EDM application, a graphite electrode is machined with traditional tools. The now specially-shaped electrode is connected to the power source, attached to a ram, and slowly fed into the workpiece. The entire machining operation is usually performed while submerged in a fluid bath. The fluid serves the following three purposes:

• it flushes material away,
• it serves as a coolant to minimize the heat affected zone, thereby preventing potential damage to the workpiece, and
• it acts as a conductor for the current to pass between the electrode and the workpiece.

In wire EDM a very thin wire serves as the electrode. Special brass wires are typically used; the wire is slowly fed through the material and the discharges actually cut the workpiece. This method is usually performed in a bath of water.

If someone was to observe the wire EDM process under a microscope, he would discover that the wire itself does not actually touch the metal to be cut; the electricity actually removes small amounts of material and allows the wire to be moved through the workpiece. The path of the wire is typically controlled by a computer, which allows extremely complex shapes to be produced.

Perhaps the best way to explain this method is to use the example of a thin metal wire stretched between two hands, slid though a block of cheese, cutting any shape desired. The positions of the hands can be altered on either side of the cheese to define complex and curved shapes. Wire EDM works in a similar fashion, except that it can handle some of the hardest materials used in industry. In dragging a wire through cheese, of course, the wire is actually displacing the cheese as it cuts, but in EDM, a thin kerf is created by removing tiny particles of metal.

This form of machining is frequently used to make dies and molds. It has recently become a standard method of producing prototypes and some production parts, particularly in low volume applications.

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Discussion Comments

By rupert — On Aug 04, 2012

How do you operate a LQ1W Wire EDM machine?

By rupert — On Aug 04, 2012

does anyone know LQ1W - EDM

By rupert — On Aug 04, 2012

how do you program edm?

By anon258028 — On Mar 30, 2012

How do I design EDM? What are the design parameters required for EDM?

By anon251267 — On Feb 29, 2012

Why does the anode (the work piece) erode more than the cathode?

By anon241089 — On Jan 17, 2012

What is the wire which is used to cut cheese? I am doing some science coursework on the resistance of wire. Please help. I require some vocational text on it.

By anon162292 — On Mar 23, 2011

I worked in a machine shop that used pantographs to create electrodes that were then used as a "tool" in the EDM to create stamps. Typically the electrodes were graphite. In rare cases, we used brass. The workpieces were usually tool steel, but in we also used carbide.

By craftydonkey — On Feb 09, 2011

Good information. Please can you send me any and all relevant info on the process? Mech Eng student writing paper on the subject. Thank you.

By anon142003 — On Jan 11, 2011

what are different types of edm?

By anon125290 — On Nov 09, 2010

15/ mm armor plate can be cut but it is slow. The water will not shock you #4 #5 wrong brass and even copper make fine electrodes and will make a precision cut or hole through carbon steel hastelloy-w inconel #7 and many others.

By anon125288 — On Nov 09, 2010

the resistance can be regulated by adjusting the milliamperage and the servo speed.

By anon125286 — On Nov 09, 2010

the edm process can even be used on plastic, if you use a iron powder for conductivity and deionised water to carry away the waste

By anon122641 — On Oct 28, 2010

Dielectric fluid is also called insulating fluid which is non conductive!

By anon104592 — On Aug 17, 2010

why is the material removed from the workpiece more than the material removed from the wire?

By anon103523 — On Aug 12, 2010

I want to ask about EDM and arc welding. both are spark processes, but in case the EDM material removes from an anode, and in the case of arc welding is different material removed from the cathode? What's the region behind it?

By anon94777 — On Jul 10, 2010

anode always gets eroded more than the cathode.

By anon94617 — On Jul 09, 2010

can armored plate of 15mm be cut or not?

By raychar — On May 15, 2010

Can aluminum material be machined by EDM?

By kailim — On Apr 29, 2010

can you help me explain about the advantages and disadvantages, applications, and characteristics of edm?

By syafiqamanah — On Feb 21, 2010

I'm studying in edm. can you help me explain about the advantages and disadvantages, applications, and characteristics of edm? thanks for the information.

By anon40863 — On Aug 11, 2009

1.what type of tool materials are used in EDM?

2.What is the basic difference between EDM and other unconventional machining methods?

By anon30381 — On Apr 18, 2009

What is the difference between an eletro and an electric discharge machine?

By zackm0923 — On Jan 13, 2009

Can you please send me any and all relevant info on the process? Mech Eng student writing paper on the subject. Thx

By sudhanitw — On Sep 06, 2008

can you tell me what are the different workpiece that are used in edm especially managing steel

By anon13420 — On May 27, 2008

thank you for the info. Can youpleasesend me the full detail about how EDM functions. i am more interested in the mechanical part of it. I am a student doing industrial and manufacturing eng. How exactly do the mechanical components interact is my concern, also include the design if possible.

By Mazlan — On Apr 24, 2008

Question : What are the usual caused for a fine brass wire ( 0.10mm dia. wire ) to fail its functionality e.g wire frequents breakages and no sparks visible thus it can't cut through the fabricating parts, when used on an edm machine.

By bpage1147 — On Apr 02, 2008

what happens if I touch the water when the machine is running. Even though the water is deionized, will it shock me?

By anon7449 — On Jan 27, 2008

why does anode ie. the work piece erode more than the cathode ?

By ravi38 — On Jan 08, 2008

can you please tell me how can we give power supply to wire edm? i mean how we can design power circuit for that? Could you please help me in building smps for that

By anon6278 — On Dec 21, 2007

what is the critical resistance in EDM?