Wire EDM: process, applications and when to choose it
What is wire EDM?
Wire EDM (wire electrical discharge machining) is a non-conventional machining process that uses a thin conductive wire to cut metal parts through controlled electrical discharges. The wire — typically brass with a diameter of 0.25 mm — passes through the workpiece submerged in deionised water (dielectric fluid), generating thousands of sparks per second that erode the material without mechanical contact.
The absence of cutting forces is the defining characteristic of this process: there is no workpiece deformation, no residual stresses and no limitation imposed by material hardness. Any conductive metal — hardened steel, tungsten carbide, titanium, aluminium, copper — can be cut with equal ease.
At MECVIL, wire EDM complements our CNC machining service for the manufacture of tooling, dies and high-precision parts that require geometries impossible to achieve through conventional milling.
Tolerances and surface finish
Wire EDM offers a level of precision that exceeds conventional CNC machining in specific applications:
| Parameter | Wire EDM | CNC milling | Grinding |
|---|---|---|---|
| Typical tolerance | ±0.005 mm | ±0.025 mm | ±0.005 mm |
| Maximum tolerance | ±0.001 mm | ±0.005 mm | ±0.002 mm |
| Ra finish (standard) | 0.8 – 1.6 µm | 1.6 – 3.2 µm | 0.1 – 0.8 µm |
| Ra finish (with skim passes) | 0.1 – 0.4 µm | 0.8 µm (with HSM) | 0.05 – 0.4 µm |
With multiple skim passes, wire EDM can achieve surface finishes of Ra 0.1 µm, equivalent to polishing, without the need for subsequent operations. This is particularly relevant in stamping dies and injection moulds where the tool's surface finish transfers directly to the product.
Do you need parts with tolerances of ±0.005 mm or complex geometries in hardened steel?
Request a quote and we will assess whether wire EDM is the optimal process for your project.
When should you choose wire EDM instead of CNC machining?
This is the key question for any technical director or procurement manager. Wire EDM does not replace CNC milling or CNC turning: it complements them in specific situations.
Choose wire EDM when:
- The material is hardened or tempered (>50 HRC) and conventional milling cannot cut it efficiently
- The part requires sharp internal corners that an end mill, due to its diameter, cannot produce
- The required tolerances are below ±0.01 mm and milling cannot guarantee them reliably
- The geometry includes complex closed profiles (die cavities, punches, gears)
- You need to cut difficult materials such as tungsten carbide, Inconel or titanium without generating thermal stresses
Choose CNC machining when:
- The part requires large volumes of material removal (EDM is slow: ~300 mm²/min)
- Tolerances of ±0.025 mm are sufficient for the application
- The material is not hardened and allows high cutting speeds
- Complex 3D surfaces are needed that require 5-axis milling
In practice, many tooling projects combine both processes: the CNC machining centre performs roughing and general operations, whilst wire EDM completes the precision profiles, closed cavities and fine adjustments after hardening.
Compatible materials
Wire EDM works with any electrically conductive material:
- Hardened tool steel (H13, D2, M2, A2): the most common application. It cuts after heat treatment without altering the hardness or metallurgical structure.
- Stainless steel (304, 316, 17-4 PH): with no risk of the surface hardening that occurs during milling.
- Tungsten carbide: impossible to machine efficiently by conventional methods; EDM cuts it without difficulty.
- Titanium and superalloys (Ti-6Al-4V, Inconel 718): without the cutting forces or heat of conventional machining.
- Aluminium and copper: achievable tolerances of up to ±0.001 mm thanks to their good conductivity.
- Graphite: used for sinker EDM electrodes, graphite can be shaped using wire EDM.
The main limitation is that it cannot cut non-conductive materials: ceramics, plastics or composites without a conductive filler.
Industrial applications
Wire EDM is indispensable in sectors where tooling precision determines the quality of the final product:
- Stamping dies: punches and dies for sheet metal stamping, with complex profiles and hundredths-of-a-millimetre fits
- Injection moulds: mould inserts with cooling channels, free-form cavities and parting surfaces
- Production tooling: at MECVIL we manufacture assembly jigs, CNC clamping fixtures for aluminium machining and inspection fixtures with dimensional control, all with geometries that require wire EDM
- Gears and splines: internal tooth profiles that are impossible to mill
- Aerospace components: turbine blade profiles, nozzles and structural components in high-temperature alloys
- Medical components: implants and surgical instruments with micrometre-level tolerances
Wire EDM within a turnkey project
Wire EDM is not a standalone process. In a turnkey project for special machinery, it integrates into the production workflow alongside other processes:
- 1.[Engineering](/en/servicios/ingenieria) defines the tooling geometry, optimising for manufacturability
- 2.CNC machining roughs the part and machines the accessible surfaces
- 3.Heat treatment hardens the material to the specified hardness
- 4.Wire EDM cuts the precision profiles on the already hardened material
- 5.[Assembly](/en/servicios/montaje) integrates the tooling into the machine or production line
- 6.Verification using coordinate measurement to confirm tolerances
At MECVIL we carry out this complete workflow in our 10,500 m² facilities, with a team of +110 professionals and ISO 9001 and EN 1090 certifications. The ability to combine CNC machining of parts up to 20 metres, industrial welding, wire EDM and electromechanical assembly under one roof allows us to optimise the workflow for each project and reduce lead times.
Do you need precision tooling that combines CNC machining and wire EDM?
At MECVIL we manufacture jigs, dies and fixtures with the combination of processes your part requires. Contact our technical team to discuss your project.