Wire EDM achieves a level of accuracy in mould production that is not attainable with conventional machining processes, even with hardened steels. Wire EDM operates without mechanical contact forces, allowing thin walls and hard materials to be machined without distortion. Tolerances of ±0.002 to ±0.005 mm are routinely achievable for mould components such as punches, die inserts, and guides. The combination of wire EDM with precise surface finishing makes the process suitable for complex mould geometries with sharp internal corners.
Wire EDM (Electrical Discharge Machining) is een niet-contact bewerkingsproces dat een elektrische ontlading tussen een draadelektrode en het werkstuk gebruikt om materiaal te verwijderen. Het is relevant voor matrijsfabricage vanwege de nauwkeurigheid en precisie die het biedt. Met draadvonken kan men complexe vormen en interne hoeken creëren die met traditionele bewerkingsmethoden moeilijk of onmogelijk te realiseren zijn. Dit is cruciaal voor de productie van hoogwaardige matrijzen die specifieke en gedetailleerde onderdelen moeten produceren. Daarnaast kan draadvonken worden gebruikt op harde materialen zoals gehard staal, wat vaak wordt toegepast in matrijzen, zonder dat de materiaaleigenschappen worden aangetast. Dit betekent dat matrijsdelen hun sterkte en duurzaamheid behouden na het bewerkingsproces. Kortom, draadvonken is essentieel voor de matrijsindustrie vanwege: * **Precisie en Nauwkeurigheid:** Het maken van complexe en gedetailleerde vormen met hoge toleranties. * **Bewerking van Harde Materialen:** Het verwerken van materialen zoals gehard staal zonder de prestaties te beïnvloeden. * **Mogelijkheid tot Fijne Details:** Het creëren van scherpe hoeken en kleine features die cruciaal zijn voor de matrijsfunctie.
Wire EDM (Electrical Discharge Machining), also referred to as sinker EDM, is an electrical discharge machining process in which a thin metal wire acts as the electrode and removes material through controlled electrical discharges.
The wire, typically brass with a diameter of 0.1 to 0.3 mm, moves continuously from a spool and never physically contacts the workpiece. The sparks generated between the wire and workpiece remove material in microscopic particles. This occurs entirely within a dielectric fluid (deionised water), which cools the process and flushes away eroded particles.
For die production, this is important for several reasons:
- The dies are manufactured from hardened tool steels such as 1.2379 (D2), 1.2842 or 1.2083, which are difficult or no longer dimensionally accurate to machine after hardening using milling and turning.
- Wire EDM works after hardening, so that thermal dimensional changes caused by the hardening process no longer affect the final dimensions.
- The absence of cutting forces eliminates springback and deflection in slender die profiles
- Sharp internal corners with a radius of 0.05 mm are achievable, which is not possible with milled work.
What tolerances are achievable with wire EDM?
With wire erosion of mould parts, positional tolerances of ±0.002 mm and surface finishes of Ra 0.2 µm are achievable without post-processing.
The exact accuracy depends on three variables: machine configuration, material, and the number of cutting passes. In practice, for die production, multiple cutting passes are standard:
- First cut (roughing cut)High material removal, lower accuracy, diametral oversize of 0.05 to 0.1 mm
- Second cut (skim cut 1)Improvement of straightness and surface quality
- Third and fourth cut (skim cuts 2 and 3)end size and surface finish, Ra reaches 0.2 to 0.4 µm
Each extra cutting pass increases machining time but reduces surface resistance and improves die-to-punch fit. For fineblanking dies, stamping tools for electrical connectors, or injection moulds with tight tolerances, three to four cutting stages are standard.
In addition to surface quality, straightness over the height is a critical parameter. For a die insert of 80 mm height, a straightness of 0.003 mm is achievable on well-calibrated machines with guidance of the wire above and below the workpiece.
Six applications of wire EDM in mould making
Wire EDM is used in mould making for all components requiring high dimensional accuracy, sharp contours, or machining after hardening.
Stamp and die inserts
The punch and its corresponding die insert must fit together exactly with a clearance that depends on the material being punched and the sheet thickness. Wire EDM makes it possible to define the fit down to the micrometer level, regardless of the hardness of the tool steel.
Conductor plates
Guide plates contain precisely positioned holes that guide the punch exactly during the stroke. Positional tolerances of ±0.003 mm are achieved at wire sparking achieved using precise reference points on the machine.
Ejector plates and bushings
For ejector plates, the holes for the ejector pins are precise in position and diameter. Wire erosion offers advantages over drilling, particularly for multiple holes with small centre distances.
Die-cutting contours
Fine die-cutting requires the smallest possible cutting clearance – sometimes less than 0.5% of the sheet thickness – which means that the punch and die must fit together with sub-micrometre precision. This can only be achieved using wire EDM.
Inserts for injection moulds
In injection moulds, cores and cavity inserts are spark-eroded from hardened steel to define the contour of the plastic part to be produced. The surface finish after several skim cuts is directly usable for glossy product surfaces.
Profile contours for progressive dies
In progressive stamping dies, multiple die stations are placed at precise intervals. Wire EDM enables the toolmaker to accurately produce complex profile contours in hardened steel, without the positional build-up of the tool to disturb you.
Bij draadvonken verwerk je materialen die elektrisch geleidend zijn. Dit omvat een breed scala aan metalen, zoals: * Staal (en gehard staal) * Aluminium * Koper * Messing * Hardmetalen (carbides) * Titaan * Edelmetalen
Wire erosion can be applied to all electrically conductive materials, regardless of hardness, making it ideally suited for hardened tool steels.
The most processed materials in die manufacturing via wire EDM:
- 1.2379 (D2)High carbon, high chromium tool steel, HRC 58 to 62, standard for blanking and forming dies
- 1.2842 (90MnCrV8)Oil-hardened tool steel, HRC 58 to 62, good dimensional stability after hardening
- 1.2083 (420 RVS type)corrosion-resistant tool steel, used in injection moulds for corrosive plastics
- 1.2344 (H13)Heat-resistant tool steel, HRC 44 to 52, for injection moulds with high thermal load
- Tungsten carbide (WC Co)extremely hard composite materials, wire erosion is one of the few machining methods that works
The machining speed of cemented carbide is considerably lower than that of steel and requires specific machine settings. However, the ability to machine cemented carbide after sintering at all is a unique property of EDM that no other machining process shares.
Wire EDM versus milling: when do you choose?
Wire EDM and milling are complementary processes in mould manufacturing. The choice depends on the geometry, the hardness of the workpiece, and the required tolerances.
In practice, a combined strategy is often used for die components: milling for the global contours and holes before hardening, and wire electrical discharge machining for the final contours, fitting surfaces, and critical features after hardening. This optimises both lead time and dimensional accuracy.
At Euro-Techniek, we assess which process, or combination of processes, will deliver the required dimensional accuracy within the shortest possible lead time for each mould component.
Wire erosion at Euro-Techniek
Euro-Techniek has wire erosion for the production and refurbishment of die components, stamping and cutting tools, and precision inserts.
We process hardened steels, carbide and corrosion-resistant tool steels, and work with reference systems for repeatable clamping of mould components. Each spark erosion programme is drawn up based on the production drawing and the material specification of the workpiece.
Ash contact Euro-Techniek for a technical assessment of your mould component or for information on workable materials and achievable tolerances with wire EDM.
Frequently asked questions about wire erosion in mould production
Yes, wire EDM can be applied to hardened steel.
Yes. Wire electrical discharge machining works independently of the material hardness. Hardened tool steel up to HRC 65 can be machined without any limitations. This is one of the main reasons for its application in mould making.
What is the minimum corner radius for wire EDM?
With a wire diameter of 0.1 mm, an inner corner radius of approximately 0.05 to 0.07 mm is achievable. For standard brass wire of 0.25 mm, the minimum inner corner radius is approximately 0.13 mm.
How many cutting passes are needed for a mould insert?
For most mould inserts, three to four cutting passes are required to achieve both dimensional accuracy (±0.002 mm) and surface quality (Ra 0.2 to 0.4 µm). For less critical parts, two cutting passes are sufficient.