The Three Types of EDM Machining and How They Differ

What is and why do we use Electric Discharge Machining

EDM, or Electrical Discharge Machining, serves as a substitute for traditional machining methods when dealing with tough materials, particularly refractory metals and intricate shapes that are challenging to cut. Wire EDM enables the attainment of precision cuts with tolerances that would otherwise be unachievable, while hole drilling EDM excels in achieving precise diameters and roundness.

Overall, EDM ensures exceptional precision and exceptionally low Ra levels, resulting in high-quality surface finishes. This characteristic reduces the need for extensive post-processing, ultimately lowering costs associated with manufacturing components that are notoriously difficult to produce.

Technique 1: Hole Drilling EDM

Hole Drilling EDM, also known as EDM Hole Drilling or EDM Micro-Drilling, is a specialized variant of Electrical Discharge Machining (EDM). We specifically designed it to create precise and accurate holes in various materials, including metals and alloys.

In Hole Drilling EDM, a small-diameter electrode, typically a rotating brass or copper tube, is used to generate a series of rapid electrical discharges. These discharges occur between the electrode and the workpiece, creating controlled erosion and gradually drilling a hole through the material.

The process involves flushing a dielectric fluid, such as deionized water, through the electrode to flush away debris and cool the workpiece. The dielectric fluid also acts as a conductor for the electrical discharges.

We value hole Drilling EDM for its ability to create highly accurate holes with tight tolerances, even in materials that are difficult to machine using conventional drilling methods. It is commonly used in industries such as aerospace, medical, automotive, and electronics, where precision holes are required for applications like cooling channels, fuel injection nozzles, or turbine blades.

Technique 2: Sinker Discharge Machining

Electrical discharge machining (EDM) is a type of procedure used for shaping and machining conductive materials. We refer it to as sinker discharge machining, sinker EDM, or conventional EDM.

In Sinker Discharge Machining, a tool called a "sinker electrode" is used, which is typically made of graphite or copper. It shaped the sinker electrode to match the desired form or cavity that needs to be created in the workpiece.

The process involves placing the sinker electrode close to the workpiece, with a dielectric fluid, such as oil or deionized water, acting as a medium between them. A series of electrical discharges, or sparks, are generated between the sinker electrode and the workpiece. These electrical discharges create controlled erosion, gradually removing material from the workpiece and shaping it according to the geometry of the sinker electrode.

Sinker Release Intricate and complicated forms, such as molds, dies, and tooling components, are frequently made using machining. Because it does not need mechanical effort and doesn't create any noticeable heat-affected zones, it works especially well for cutting tough materials. Sinker EDM is capable of high accuracy and precise surface finishes, making it suited for sectors such as aerospace, automotive, tool and die manufacture, and medical device manufacturing.

Technique 3: Wire Cut EDM

Wire Cut EDM, also known as Wire Electrical Discharge Machining or Wire EDM, is a specialized kind of Electrical Discharge Machining (EDM) used for the precision cutting and shaping of conductive materials.

A sequence of electrical discharges, or sparks, between the wire and the workpiece, are produced throughout the operation. The substance melts and evaporates because of the controlled erosion produced by these electrical discharges. The wire advances continuously, guaranteeing a continuous cutting action and enabling the machining of intricate forms and curves.

Tight tolerances may be achieved, and wire-cut EDM is highly accurate. Cutting complex forms, thin sections, and contours in a variety of materials, such as metals, alloys, and conductive ceramics, is a popular use for it. Producing dies, molds, and tooling components for the precise engineering, automotive, aerospace, and electronics sectors is very helpful.

Wire Cut EDM offers advantages, such as the ability to cut materials regardless of their hardness, minimal heat-affected zones, and the ability to achieve fine surface finishes. It is a flexible machining technique that allows for the high repeatability manufacturing of intricate and accurate components.

Materials and Applications in EDM Machining

EDM primarily handles materials that pose challenges for conventional machining methods, including tungsten, molybdenum, and hardened tool steels. Additionally, materials like titanium and austenitic stainless steels, which demonstrate significant work hardening during mechanical machining processes, are well-suited for EDM. As these materials harden while being machined, they become increasingly difficult to cut. Consequently, this hardening phenomenon often leads to a reduction in the accuracy of the machined part features.

Electric discharge machining finds application in the production of molds for plastic injection molding and metal die casting. It is utilized to create intricate cavities in pre-hardened materials, showcasing its proficiency in achieving precise and complex cavity shapes, as well as executing deep cuts. Industries such as aerospace, automobile, and electronics also rely on EDM for fabricating prototypes and manufacturing various components.

Differences between these three techniques

Different types of EDM are classified based on their operations and applications. One example is wire EDM, which utilizes a linear feed wire electrode to make primarily two-dimensional cuts. We position the electrode wire on a guide made of diamond or sapphire, and the dielectric fluid used is typically deionized water. Brass or galvanized brass is commonly employed for the electrode material.

In contrast, sinker discharge EDM allows for the utilization of intricate electrode shapes to create equally complex cavities. Graphite or copper electrodes are pre-machined into the desired shape and then eroded into the workpiece, resulting in holes that mirror the shape of the electrode.

Drilling EDM is capable of producing smaller and deeper holes compared to traditional drilling methods. This enables precise diameters, roundness, excellent surface finishes, and eliminates burrs. Electrodes in drilling EDM can have intricate cross-sectional shapes. Drill tools often incorporate cooling channels through which dielectric fluid is circulated to aid in the removal of chips.

Sinker discharge machining stands out as the most suitable type of EDM for fabricating components with intricate cavities. It enables the creation of complex cavity shapes frequently needed in the design of plastic and die-cast parts. While there are limitations to the range of cavity shapes achievable through sinker discharge EDM, these restrictions do not significantly affect its effectiveness as a tool for mold-making. The concept of the "line of the draw," which restricts EDM from producing undercuts, also applies to plastic molded and die-cast parts. These parts enter the tool cavity in liquid form but solidify as they exit.

Conclusion

To conclude, this article described the many forms of EDM machining, their differences, and when to utilize them. As a subsidiary of JLCPCB, we provide an industry-leading online 3D printing & CNC machining service by utilizing cutting-edge manufacturing technology to create affordable functional parts out of many different industrial-grade materials that can be used in the automotive, medical, and consumer electronics fields, among others.