Wire cut or die sinker EDM: which process suits your part
In electrical discharge machining a spark removes the material, not a cutting edge. Hardness is therefore irrelevant as long as the workpiece conducts electricity. Two machine types share the work:
- Die sinker EDM machines sink a shaped electrode into the workpiece. This produces pockets, cavities, internal contours and sharp internal corners that no milling spindle can reach.
- Wire cut EDM machines guide a thin wire as the electrode through the workpiece. Use them for through cuts, fine contours, cutting plates and dies with tight radii.
The simple rule: a closed recess means die sinking, a cut that goes right through means wire cutting. Many toolrooms run both processes because they complement each other.
Applications in toolmaking and mould making
Toolmaking and mould making are the largest field of use. Typical parts are injection moulds, die casting moulds, forging dies, stamping and blanking tools, dies and cutting plates. Small batch work in medical technology, aerospace and special machinery follows close behind. Wherever parts are hardened, contours are too fine for a cutter or an internal corner has to stay square, EDM is the process that fits. Broken taps and drills can also be released from a finished part without scrapping it.
Which materials can be spark eroded
The one requirement is electrical conductivity. That covers exactly the materials that are difficult to cut: hardened tool steel, carbide, titanium, Inconel and other nickel based alloys, stainless steel, copper alloys and aluminium, plus conductive ceramics and graphite. Hardness barely affects the result because no mechanical pressure acts on the part. You can therefore harden a tool first and bring it to final size afterwards. Materials that do not conduct, such as plastics, glass and ceramics without conductivity, cannot be eroded.
Electrodes and electrode materials
In die sinking the electrode decides the outcome. Two materials dominate:
- Graphite allows high removal rates and is quick to machine. It suits large areas and roughing.
- Copper and copper alloys wear less in fine detail and give better accuracy and finer surfaces. They suit delicate contours and finishing.
Many workshops combine the two: graphite for the bulk of the work, copper for the final pass. Electrode wear belongs in your costing, because roughing and finishing often call for several electrodes. The electrodes themselves are usually produced on a CNC milling machine, which is why erosion and milling belong together in a toolroom.
CNC control, accuracy and surface finish
EDM machines are numerically controlled, a purely conventional version does not exist. The control governs feed, discharge energy and flushing and keeps the spark gap constant. That gap is the distance between electrode and workpiece, measures a few hundredths of a millimetre and is allowed for as an offset when the part is programmed. High discharge energy removes material quickly and leaves a rougher surface, a fine finishing pass takes longer and delivers the finish you asked for. Erosion is not a fast process, it is an accurate one.
Dielectric fluid, EDM wire and consumables
The process runs in a dielectric fluid. It insulates, cools and flushes the eroded particles out of the gap. Die sinking normally uses an oil based dielectric, wire cutting uses deionised water. Running requirements include EDM wire, filters, ion exchange resin and guides. You will find these items under EDM consumables. Budget for consumables and filter changes from the start, in continuous production they take a noticeable share of the running cost.
Why KNUTH
KNUTH has been a supplier of machine tools since 1923 and carries both EDM processes. We do not build the machines ourselves: we select the series, test them in Germany against a documented checklist and deliver them from stock. Around 1,000 machines are held permanently at the European warehouse in Wasbek, and we confirm the availability of a specific size on request. The focus is on entry level and mid range machines, which fits workshops adding EDM alongside their cutting capacity. Every machine is inspected with documented results and delivered CE compliant, and the declaration of conformity and the full documentation are included in the delivery. If you are new to erosion, we will say which type fits the milling machines and grinding machines you already run.
Service, spare parts and availability
Service is handled by our own service engineers, with locations in the north and the south of Germany and partner organisations in the export markets. Common spare parts come from the central warehouse, special parts directly from the manufacturers of the components. A ten year spare parts supply commitment applies across the company. Service requests go to the service planning team at service@knuth.com or by phone, and we reply on any working day. Installation, commissioning and operator instruction are available on request, the scope is stated in the quotation. Contact us by email or phone if you are weighing up wire cutting against die sinking or two machine sizes against each other.
Further Machine Categories at a Glance
Here is an overview of our machine range. Select a category to learn more about individual machines and their technical data.
