Electrical discharge machining removes metal with a spark rather than a cutting edge: a discharge jumps between the electrode and the part through a dielectric and vaporises a tiny volume of metal. There are no cutting forces, so the hardness of the part does not matter — hardened steel, carbide and heat-resistant alloys machine just like mild steel. There is one limitation, and it is a hard one: the material has to conduct electricity.

Three processes, three different jobs

Process	What cuts	What you get	When to choose it
Wire cutting	wire of Ø0.1–0.3 mm	a through contour over the full height of the part, tapered if needed	dies, punches, templates, tooling parts
Sinker EDM	a shaped electrode	a blind cavity in the shape of the electrode, with sharp internal corners	moulds, ribs and slots a cutter cannot reach
EDM drilling	a tubular electrode of Ø0.2–3.0 mm	a hole in hard material, at an angle if needed	start holes for wire cutting, cooling channels

The processes do not replace one another, they complement one another. A wire cuts all the way through — it cannot make a blind cavity, which is the sinker machine’s job. And to thread the wire inside a contour that does not reach the edge of the blank you need a start hole — drilled by EDM, because the material is already hardened. That is why the three machines often stand side by side in a shop.

What you will be asked when selecting

Material and heat treatment. The alloy and its condition after hardening set the parameters. And the first check is whether the material conducts at all — ceramics and plastics cannot be machined by EDM.
A drawing of the contour or cavity. For wire — minimum radii, taper angle and part height. For sinking — depth, radii and electrode shape. For drilling — diameter, depth and exit angle.
Size and weight of the blank. They are checked together with the fixture: a part that fits by size may not pass by weight or by the way it is lowered into the tank.
Tolerance and surface finish. They drive the wire diameter, the settings and the number of passes — and therefore the time. Finishing in several passes costs time that has to be allowed for.
How many parts per shift. This decides whether you need automatic wire threading, automatic electrode changing and unattended running overnight.

What it is not

EDM is slower than milling — and that is fine, because it does what milling cannot: it machines a part after hardening, takes carbide, gives a sharp internal corner with no cutter radius, and cuts thin ribs and narrow deep slots without the tool deflecting. If a part can be milled, it is milled. EDM goes where nothing else works.

The equipment in this section comes from the Taiwanese maker CHMER. The range is wide: wire machines run X/Y travels from 360×250 to 1200×800 mm with workpieces up to 5000 kg, sinker machines from 300×200 to 3000×750 mm with workpieces up to 16,000 kg, and drilling machines from 300×250 to 600×800 mm.

EDM machines in the catalog

Model	Type	X / Y travels	Z travel	Workpiece, max.	Weight
CHMER RQ3625L	wire	360 × 250 mm	200 mm	450 kg	—
CHMER RQ4025L	wire	400 × 250 mm	200 mm	550 kg	—
CHMER RQ5030L	wire	500 × 300 mm	200 mm	600 kg	—
CHMER RQ6040L	wire	600 × 400 mm	300 mm	1000 kg	—
CHMER GV5043L	wire	500 × 400 mm	310 mm	800 kg	—
CHMER NV432L	wire	400 × 300 mm	250 mm	500 kg	—
CHMER NV643L	wire	600 × 400 mm	310 mm	800 kg	—
CHMER UA432L	wire	400 × 300 mm	250 mm	550 kg	—
CHMER GLX432	wire	400 × 300 mm	250 mm	450 kg	—
CHMER GLX643	wire	600 × 400 mm	310 mm	650 kg	—
CHMER GX430L+	wire	400 × 300 mm	220 mm	350 kg	—
CHMER GX640L+	wire	600 × 400 mm	300 mm	600 kg	—
CHMER G32S	wire	360 × 250 mm	220 mm	300 kg	—
CHMER G43S	wire	400 × 300 mm	220 mm	350 kg	—
CHMER G64F	wire	600 × 400 mm	300 mm	600 kg	—
CHMER G64S	wire	600 × 400 mm	300 mm	450 kg	—
CHMER RX853F	wire	800 × 500 mm	300 mm	2000 kg	—
CHMER RX853S	wire	800 × 500 mm	300 mm	1000 kg	—
CHMER RX1063F	wire	1000 × 600 mm	300 mm	3000 kg	—
CHMER RX1063S	wire	1000 × 600 mm	300 mm	1500 kg	—
CHMER RV653L	wire	600 × 500 mm	350 mm	2000 kg	—
CHMER RV853L	wire	800 × 500 mm	300 mm	3000 kg	—
CHMER RV855L	wire	800 × 500 mm	500 mm	3000 kg	—
CHMER RV1063L	wire	1000 × 600 mm	300 mm	5000 kg	—
CHMER RV1065L	wire	1000 × 500 mm	500 mm	5000 kg	—
CHMER RV1283L	wire	1200 × 800 mm	300 mm	5000 kg	—
CHMER RV1285L	wire	1200 × 800 mm	500 mm	5000 kg	—
CHMER AW3L	wire	370 × 270 mm	260 mm	500 kg	—
CHMER AW5L	wire	560 × 360 mm	300 mm	600 kg	—
CHMER AW6L	wire	650 × 450 mm	300 mm	800 kg	—
CHMER AW8L	wire	800 × 500 mm	300 mm	3000 kg	—
CHMER AW10L	wire	1000 × 600 mm	300 mm	3000 kg	—
CHMER AW12L	wire	1200 × 800 mm	300 mm	5000 kg	—
CHMER AW4E	wire	400 × 300 mm	260 mm	500 kg	—
CHMER AW5E	wire	500 × 300 mm	260 mm	600 kg	—
CHMER AW6E	wire	600 × 400 mm	300 mm	700 kg	—
CHMER D322CL	sinker	300 × 200 mm	250 mm	300 kg	—
CHMER D433CL	sinker	400 × 300 mm	300 mm	350 kg	—
CHMER A6040L	sinker	600 × 400 mm	350 mm	1500 kg	—
CHMER CM A43C	sinker	400 × 300 mm	350 mm	1000 kg	—
CHMER CM A53C	sinker	500 × 350 mm	350 mm	1000 kg	—
CHMER CM A64C	sinker	600 × 400 mm	350 mm	1500 kg	—
CHMER CM323C	sinker	300 × 200 mm	300 mm	500 kg	—
CHMER CM434C	sinker	400 × 300 mm	350 mm	750 kg	—
CHMER CM655C	sinker	600 × 500 mm	500 mm	3000 kg	—
CHMER CM865C	sinker	800 × 600 mm	500 mm	4000 kg	—
CHMER CM1065C	sinker	1000 × 600 mm	500 mm	5000 kg	—
CHMER CM1265C	sinker	1200 × 600 mm	500 mm	7500 kg	—
CHMER CM1475C	sinker	1400 × 700 mm	500 mm	5500 kg	—
CHMER CM1675C	sinker	1600 × 700 mm	500 mm	5600 kg	—
CHMER CM1875C	sinker	1800 × 700 mm	500 mm	5800 kg	—
CHMER CM2076C	sinker	2000 × 750 mm	600 mm	6800 kg	—
CHMER CM3076C	sinker	3000 × 750 mm	600 mm	16000 kg	—
CHMER CM323Z	sinker	300 × 200 mm	300 mm	500 kg	—
CHMER CM434Z	sinker	400 × 300 mm	350 mm	750 kg	—
CHMER CM545Z	sinker	500 × 400 mm	500 mm	1500 kg	—
CHMER CM655Z	sinker	600 × 500 mm	500 mm	2250 kg	—
CHMER CM240R	sinker	300 × 200 mm	300 mm	500 kg	—
CHMER CM380	sinker	400 × 300 mm	350 mm	750 kg	—
CHMER CM545	sinker	500 × 400 mm	500 mm	1500 kg	—
CHMER CM655	sinker	600 × 500 mm	500 mm	2250 kg	—
CHMER DX655C	sinker	600 × 500 mm	500 mm	3000 kg	—
CHMER AD4L	drilling	400 × 300 mm	300 mm	900 kg	—
CHMER AD5L	drilling	500 × 300 mm	300 mm	1000 kg	—
CHMER AD6L	drilling	600 × 400 mm	350 mm	1200 kg	—
CHMER H32C	drilling	350 × 250 mm	400 mm	180 kg	—
CHMER H64CL	drilling	400 × 600 mm	400 mm	1000 kg	—
CHMER H86CL	drilling	600 × 800 mm	400 mm	1200 kg	—
CHMER H32Z	drilling	300 × 250 mm	345 mm	120 kg	—
CHMER H43Z	drilling	400 × 300 mm	345 mm	450 kg	—
CHMER H54Z	drilling	550 × 400 mm	345 mm	1000 kg	—
CHMER H75Z	drilling	700 × 550 mm	345 mm	2600 kg	—

Questions and answers

What materials can EDM machine?

Anything that conducts: steel in any condition including hardened, carbide, titanium, heat-resistant and tool alloys, graphite and copper. Ceramics, plastics and non-conductive composites — no.

Wire or sinker?

By the shape of what you are making. A through contour — wire: the wire passes right through the part. A blind cavity, a rib or a slot with a floor — sinker: the shape is set by an electrode, which has to be made first.

Why a separate machine just for drilling?

To thread the wire inside a closed contour you need a hole, and the material is already hardened — an ordinary drill will not take it. EDM drilling makes that hole in minutes. The same machine drills cooling channels and holes in carbide.

What about consumables?

In wire cutting the wire is consumed and not reused — it is a line in the cost of every part. Besides it you need dielectric and its filtration, and in sinker work the electrodes themselves, made from graphite or copper. Allow for this from the start.

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