EN
How do manufacturers cut intricate profiles into hardened tool steel, tungsten carbide, or titanium without the cutting tool ever touching the part? In most cases, the answer is wire EDM. This non-contact process has become essential for producing precision metal parts with complex geometries, fine details, and tolerances that conventional cutting tools simply cannot hold. This article explains what wire EDM is, how it works step by step, which materials it handles, what accuracy you can expect, and when it makes more sense than milling or turning.
Wire EDM (wire electrical discharge machining), also known as wire-cut EDM or WEDM, is a machining process that removes metal through controlled electrical sparks rather than mechanical cutting. A thin wire, usually brass or zinc-coated brass with a diameter between 0.10 mm and 0.30 mm, acts as the electrode. The wire is fed continuously from a spool, so the "cutting tool" is always fresh and never wears down in the way an end mill or turning insert does.
The defining feature of the process is that the wire never physically touches the workpiece. Material is eroded by a rapid series of electrical discharges jumping across a microscopic gap. Because there is no physical contact, there are no cutting forces, no tool deflection, and no mechanical stress introduced into the part. That is exactly why wire EDM can hold extremely tight tolerances on delicate, thin-walled, or ultra-hard components that would be distorted or damaged by conventional machining.
Although the machine does the work automatically once it is set up, every wire EDM job follows the same fundamental sequence:
Two design details keep the process stable over long cuts: the wire is under constant, monitored tension so it cannot bow or wander, and the dielectric water is temperature-controlled to prevent thermal expansion of either the machine or the part. Together with real-time servo feedback, these measures keep dimensions consistent from the first part to the last.
The rule is simple: if a material conducts electricity, wire EDM can cut it, regardless of how hard it is. Spark erosion does not rely on mechanical shear, so a 62 HRC hardened tool steel cuts almost as willingly as soft aluminum. The most common materials for wire EDM machining include:
The main limitation is that non-conductive materials such as plastics, ceramics, and glass cannot be processed on standard wire EDM equipment. Parts that combine conductive and non-conductive features are typically split between wire EDM and CNC milling or turning within a single production plan.
Achievable accuracy depends mainly on the number of passes. A single roughing cut typically holds around ±0.02 mm. Adding skim passes progressively refines both dimension and finish, and a well-tuned machine with three or four skim passes can reach single-digit microns. The table below shows what each stage delivers:
| Pass Type | Typical Tolerance | Typical Surface Finish | Purpose |
|---|---|---|---|
| Rough cut (1st pass) | ±0.02–0.03 mm | Ra 2.5–3.2 µm | Bulk material removal |
| First skim pass | ±0.01–0.015 mm | Ra 1.0–1.6 µm | Dimensional refinement |
| Second skim pass | ±0.005–0.01 mm | Ra 0.4–0.8 µm | Fine tolerance and finish |
| Third / fourth skim pass | Down to ±0.003 mm | Ra 0.2–0.4 µm | Tightest tolerance, near-mirror finish |
On production equipment such as the Sodick wire EDM machines used in our shop, tolerances as tight as 0.003 mm and perpendicularity of 0.001 to 0.002 mm are routine, with start holes as small as 0.07 mm in diameter. Wire diameter, part thickness, material stability, and dielectric temperature all influence where a given job lands within these ranges, so they are dialled in for each project rather than treated as fixed numbers.
Wire EDM is not a replacement for milling or turning; it is a complement. Choosing correctly between them is largely a matter of material hardness, feature geometry, and tolerance requirements:
| Factor | Wire EDM | CNC Milling / Turning |
|---|---|---|
| Material hardness | Any conductive metal, any hardness | Best below ~45 HRC; tool wear climbs sharply above it |
| Feature type | Through-profiles, narrow slots, fine internal contours | Pockets, 3D surfaces, open cavities, threads |
| Mechanical stress | Virtually zero; ideal for thin walls and fragile features | Clamping and cutting forces can distort delicate parts |
| Speed on simple shapes | Slower; erosion removes material gradually | Much faster for bulk removal |
| Internal corner radius | Limited by wire radius, roughly 0.05–0.15 mm | Limited by cutter radius, usually larger |
| Partial-depth cuts | Not possible; wire EDM is a through-cut process | Fully capable |
In practice, wire EDM is the clear winner for hardened steels and carbides, intricate internal profiles such as keyways and gear tooth forms, tolerances tighter than about ±0.01 mm, and thin-walled parts that cannot survive clamping and cutting loads. Conventional machining remains the faster and cheaper choice for bulk stock removal, blind pockets, and non-conductive materials. Many precision parts use both: milling for the primary shape, then wire EDM for the features no cutter can reach.
Because it combines hardness independence with fine detail, wire EDM shows up across nearly every precision industry:
Wire EDM cuts precision metal parts by eroding material with controlled electrical sparks between a continuously fed wire and the workpiece, all without physical contact. The process handles any conductive metal at any hardness, holds tolerances down to a few microns through skim passes, and leaves surfaces smooth enough to skip secondary finishing in many cases. When a drawing calls for hardened material, intricate internal geometry, or accuracy beyond the reach of conventional tools, wire EDM is usually the right answer.
ANOK Precision Manufacturing has provided wire EDM machining services from Shenzhen, China since 2007, operating Sodick wire EDM machines under an ISO 9001:2015-certified quality system. Our shop holds tolerances as tight as 0.003 mm, cuts workpieces up to 500 mm in diameter and 400 mm thick, and machines everything from hardened steel and titanium to carbide, graphite, and copper without thermal damage. If you have a part that demands this level of precision, send us your drawing for a free, no-obligation quote.