Wire EDM vs Sinker EDM: The Differences Between the Two EDM Machining Process

What is Wire EDM?

Wire electrical discharge machining (Wire EDM) is sometimes called wire-cut EDM and wire cutting. It involves a thin single-strand metal wire like brass fed through the workpiece. And in this case, dielectric fluid is usually deionized water. In this method, thousands of sparks are shot at the metal workpieces to cut them. The workpieces must be able to conduct electricity, like metal and graphite. 

When it comes to wire EDM, the most concerned issue is nothing more than the wire EDM machine. Generally speaking, the components of the wire EDM machine include CNC tools, a power supply, wire (such as brass wires, zinc-coated wires, diffusion-annealed Wires), a dielectric medium, and electrodes. Common materials you can cut with the wire EDM machine include aluminum, titanium, steel, brass, and graphite.

In the wire EDM machine, a thin metal wire is held between two diamond guides, one above the workpiece and one below. These guides move along the X and Y axes based on instructions from the CNC. The upper guide can sometimes move along other axes to make more complicated cuts. Like other EDM processes, current discharges of wire EDM create sparks between the wire and the workpiece. This causes erosion of the workpiece.

How does Wire EDM Work?

Wire EDM operates in the same way as a cheese cutter, or a bandsaw cuts wood. In this process, the wire moves instead of the workpiece. A high voltage is fed via a metallic wire, commonly composed of brass or copper, allowing it to cut through the thickness of the workpiece. You can start cutting from the edge of the material, or you can make a hole in the piece so the wire can go through it. This makes cutting from the inside more convenient.

Deionized water is used in wire EDM to provide highly controlled conductivity. It can also cool the workpiece and washes away the particles that have been removed. Wire EDM delivers an extremely exact cut, allowing producers to create even the most complicated and delicate designs.

Pros and Cons of Wire EDM Machining

Pros of Wire EDM

1. It makes precise and accurate cuts eliminating the need for further processing and finishing of the workpiece.
2. The process is suitable for creating complex designs and shapes that are otherwise challenging to produce using traditional CNC machining.
3. Wire EDM machining is ideal for fragile materials and cannot withstand the stress of machining.
4. It is applicable in machining small parts and for cutting highly detailed items that would otherwise be too delicate for other machining options.
5. The machining process cuts continuously without interruptions. Even if the wire breaks when cutting, the process continues immediately.
6. With just one processing stage, the machine cuts materials and leaves no burrs or distortion.

Cons of Wire EDM

1. It is only compatible with materials that conduct electricity.
2. It has a high initial investment and maintenance cost.
3. An oxide layer may develop on the cut surface of some materials, such as aluminum. Therefore, this could necessitate additional finishing, which raises the cost.

Features and Applications of wire EDM

The following are some of the primary features and applications of Wire EDM.

• This method essentially creates two-dimensional cuts in three-dimensional parts. 
• Wire EDM allows for the creation of extremely fine and complicated structures. Furthermore, because of its high-precision machining and unique relaxation generators, it can achieve shape accuracies of roughly ±1 μm.
• This method is most typically employed in manufacturing molds and dies. Notably extrusion dies, and blanking punches.
• Wire EDM is primarily used for high-precision cutting and sample preparation.
• It’s a good deal for small production. Nevertheless, employing this approach necessitates the frequent movement of wires that cannot be reused, making it more expensive than other processes.

What is Sinker EDM?

Sinker EDM, also known as ram EDM, cavity-type EDM, or volume EDM, is mainly composed of an electrode and a workpiece immersed in an insulating liquid. The insulating liquid is usually oil but sometimes other dielectric fluids. The electrode is often CNC machined from graphite, copper, or tungsten and is pre-machined to have the required form.

Sinker EDM uses spark erosion to create workpieces with great precision. Here, spark erosion means producing cavities in metal workpieces using an electrode tool with an obligatory shape. The electrode is advanced progressively toward the workpiece until it almost touches it. A high-voltage spark develops between the electrode and the workpiece, melting away the material nearest to the electrode. Sinker EDM is perfect for making blind cavities in conductive metals.

How does Sinker EDM Work?

Sinker EDM necessitates the use of an electrode, an insulating fluid, and a power supply. The electrode and the workpiece are linked via the power supply. The electrode and the workpiece are alternatively either positively or negatively charged. When the electrode gets close to the workpiece, an electric spark jumps between them. This spark creates a localized temperature ranging from 8,000 to 12,000 °C. The high temperature vaporizes the metal in a specific region.

The Sinker EDM process, unlike wire EDM, does not cut entirely through the material. This enables our operators to make intricate shapes. At the same time, it does not induce material stress. As a result, Sinker EDM is a great way to create injection molds and stamping dies.

Pros and Cons of Sinker EDM Machining

Pros of Sinker EDM

1. Sinker EDM is different from other ways of machining because it doesn’t need a tool that is harder than the material being machined.
2. It may create features with irregularly shaped blind holes, such as hexagonal holes.
3. Sinker EDM can generate extremely accurate features if the electrode is machined precisely.
4. The process does not subject the tool to loads that might bend and deform it, as CNC machining does; as a result, features can be accurately controlled.
5. Sinker EDM may be used to machine any metal that is conductive.

Cons of Sinker EDM

1. Sinker EDM only machines conductive materials but cannot machine plastics or composites.
2. The sinker EDM technique removes extremely little material compared to other machining methods, such as CNC milling. Because of the extra time, the individual part cost is higher than if other machining methods could be used.
3. Sinker EDM machines use excessive electricity because of the high-energy spark erosion process. Conventional CNC machines use far less energy.

Features and Applications of sinker EDM

Sinker EDM’s primary features and applications are listed below.

• Sinker EDM allows the maker to produce complex forms without inducing stresses on an electrically conductive material.
• It’s a low-risk machining method.
• Sinker EDM is suitable for creating parts with unrivaled precision and dependability.
• Because it does not cut entirely (until required), it is employed in various applications, including cross-sections, thin walls, and blind cavities/keyways.
• Because of its versatility, it is an efficient and commonly utilized method. Sinker EDM has applications in the space travel sector, like developing parts for rocket engines, satellites, and other spacecraft.

What are the Similarities between Wire EDM and Sinker EDM?

Wire EDM and sinker EDM belong to the type of EDM process, and they have many similarities in some aspects.

1. Thermal Energy based Non-traditional Machining Processes

Wire EDM and sinker EDM are non-traditional machining processes using thermal energy. None of them is thought of as a hybrid process.

2. Use Dielectric Fluid

They all use a suitable dielectric fluid (deionized water or kerosene) to aid spark creation and debris clearance.

3. Spark Erosion

The material removal of wire EDM and sinker EDM is nothing more than spark erosion, or the melting and evaporation of work metal due to the spark’s tremendous localized temperature.

4. No Formation of Burrs and Residual Stress

None of them are related to the formation of burrs, residual stress, and so on.

5. An Appropriate Potential Difference

The presence of an appropriate potential difference between the tool electrode (cathode) and the workpiece (anode) is required for dielectric fluid breakdown.

6. Material Electrical Conductivity 

None depends on the work material’s mechanical properties, such as strength, hardness, ductility, etc. On the other hand, electrical conductivity is a required property of work materials.