Comprehensive Guide of Electric Discharge Machining(EDM) Types

Table of Contents

Electrical discharge machining is a non-traditional specialized form of machining that uses electrical discharges instead of mechanical force to remove material from a workpiece. It is used to achieve part precision to produce desired cuts, such as sharp internal corners or a deep complex cavity. 

However, EDM manufacturing only works for electrically conductive materials. The process involves creating a path of electrical discharge between an electrode and workpiece. The intense heat generated by the electrical sparks melts and evaporates the material and separates it from the workpiece.

To get a better understanding on electric discharge machining (EDM), we will look into the different types of EDM that exist and where they are applicable.

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Electrical Discharge Machine (Image Source: Shutterstock) 

Types of EDM

We have three common types of electric discharge machining. These include die Ram EDM, Wire EDM and Hole drilling EDM. Let’s have an in-depth look into the three!

Die Sinking EDM (Ram EDM)

Also known as conventional EDM die, sinking EDM is used for creating parts with complex cavities and sharp internal corners.This method makes use of a dielectric fluid, electrode and an electric spark induced between the electrode and the workpiece.

The electrode is produced in the reverse shape of the required cavity part, which forms the die. An electric discharge is introduced between the die and the workpiece while submerged in a dielectric fluid. The die is lowered slowly towards the workpiece.

This evaporates and melts material from the workpiece. The dielectric fluid then carries any ejected particle away. As the sparks remove material from the workpiece, the desired shape and precise cut out starts to take shape. Every aspect of this process is controlled through precision machining to ensure dimensional accuracy.

Through its ability to produce complex shapes and cutouts, die sinking EDM finds various applications across different industries.

Medical Device Components

Die sinking EDM is used in the production of medical device components such as dental prosthetics and surgical instruments to meet the precision requirement of the medical industry.

Automotive Parts

This method is used for producing dies and molds used in the manufacture of automotive parts to ensure dimension accuracy of the final component. It helps create intriguing features that are very complex.

Aerospace Components 

Turbine blades and structural elements of planes are manufactured through this method due to their need for precise machining to meet performance and safety standards. This enables them to meet strict aerospace standards for quality and reliability.

Injection Molds for Plastics Parts 

Die sinking EDM is used in production of molds for plastic components such as consumer electronics that require precise cavities. These molds require precise cavities with proper corner radii to produce high quality parts with intricate details.

Wire EDM (Wire Erosion)

It is the best type of EDM for complex Geometries. This process is commonly used to produce extrusion dies. In this case the die is replaced with a fine electrically charged wire which works as an electrode controlled within a deionized water environment. The wire is usually very thin. 

To ensure precision, cutting a fresh wire is automatically spooled throughout the machining process. The wire electrode is guided along a defined path while maintaining a small gap between the wire and workpiece. 

A spark discharge occurs vaporizing a small portion of the workpiece material. The control system regulates various parameters such as wire tension, speed and spark distance to ensure precise material removal. Here are some of the application for wire EDM:

Automotive Manufacturing

It is used for machining precision components such as gears and other engine components with complex geometries and fine surface finishes requirements.

Aerospace Industry 

Wire EDM is applied in the manufacture of critical components to produce complex shapes with high tolerances ensuring optimal performance in aerospace systems. These components include turbine blades and structural components.

Electronic Industry  

Used  in production of electronic devices and microelectronics that require precise dimensions to ensure high accuracy and reliability. It is used for machining components such as connectors and microelectrodes.

Mold Repair and Maintenance 

Wire EDM is employed in the repair and maintenance of molds and dies in various industries. It allows for precise machining of damaged sections extending their life cycle and reducing downtime in production.

Semiconductor Industry

It is used to produce micro tooling and molds for semiconductor manufacturing. These include water dicing, die bonding and wire bonding.

Hole Drilling EDM

This is a specialized machining process that is used to create precise, high quality holes. This is achieved by utilizing a small hollow tube electrode that rotates and advances into the workpiece. This tube acts as a cutting tool and a means to flush away eroded material. 

The small diameter and hollow nature of the tube electrode allow for drilling holes of various sizes with high precision.The electrodes’ small sizes enable for the creation of fine features and details in parts. As the electrode rotates it helps penetrate the workpiece more efficiently.

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Hole Drilling EDM (Image Source: Shutterstock)

This spinning ensures consistent material removal and enhances the accuracy of the hole drilling process. One of the main advantages of hole drilling EDM is establishment of clean and precise holes without the formation of burrs. 

As a result additional deburring operations are reduced saving time and reduced production cost. Here is how hole drilling EDMis utilized in various industries:

Aerospace Application 

It is used to create cooling holes in turbine blades to enhance heat dissipation. These holes need exceptional precision and consistency to ensure uniform cooling across. 

Critical engine components such as fuel injector nozzles and combustion chambers use this process to create precise holes with high tolerances for optimal engine performance. High precision holes are drilled for fastener installation to ensure structural integrity in challenging aerospace environments.

Medical Application 

Hole drilling EDM is used in production of orthopedic implants to facilitate screw insertion allowing for accurate fixation and alignment of implants. 

Devices such as pacemakers and neuro stimulators require precise holes drilled for lead placement and electrode insertion. This technique ensures that these requirements are met with efficiency.

Considerations for Using EDM

Several key factors should be taken into account when considering the use of Electrical Discharge Machining. These consideration include:

Surface Finishing vs. Cutting Speed

These two properties impact the outcome of each other. Increasing the cutting speed results in rougher surface finishes while lower cutting speeds produce finer surface finishes. 

For applications that require high precision going for finer surface over cutting speed is necessary. It is important to establish a balance between cutting speed and surface finishing to meet the application requirements.

Material Selection 

This greatly impacts the machining outcome. Conductive materials are well preferred for EDM processes. You should consider the material conductivity, hardness and thermal properties when selecting for high precision application. Harder material may affect the cutting speed and surface finishing quality.

Electrode Selection 

This plays an important role in achieving desired machining outcome. Graphite electrodes are used for finishing due to their ability to produce finer surface finishes. Copper electrodes are used for roughing operations due to their high conductivity. Selecting the appropriate electrode should be based on application requirements.

Project Suitability 

Applications such as aerospace components, medical implants and injection molds that require high precision and complex geometries are well suited to use EDM. Put into consideration the project’s complexity, dimension tolerances and surface finish requirement to establish its suitability for EDM. 

You will need to also consider the cost effectiveness of EDM for the project. Factors such as machine setup time, electrode wear and machining time can greatly impact the cost effectiveness.

Choosing the Right Type of EDM Machining

Choosing the appropriate type of EDM machining can significantly impact the quality, efficiency and cost effectiveness of your machining process. Below are some tips to consider when selecting appropriate EDM techniques!

Consider Part Complexity and Geometry

This plays a crucial role in selecting the right EDM technique. Some techniques excel in cutting intricate shapes while others are suitable for creating cavities and molds. Put into account the suitability of each technique based on your parts design requirements.

Assess Precision and Tolerance Requirements

These properties should align with the capabilities of the chosen EDM technique. Some methods offer higher precision and can achieve tight tolerances while others may be better suited for roughing operations.

Evaluate Material Compatibility

Different techniques work best with specific materials .You need to consider properties such as material conductivity, hardness and thermal properties to ensure optimal performance.

Cost Considerations

cost is a crucial aspect to consider when choosing an EDM technique. Put into account the overall cost expenses including,equipment cost, tooling, electrode wear and maintenance requirement. Consider the cost effectiveness of the technique chosen in relation to your application requirements.

Analyze Production Volume and Efficiency

Some techniques are more efficient for high volume production while others may be better suited for low volume production. Evaluate the speed and overall productivity of each technique.

By carefully considering these factors,manufacturers can determine the most appropriate type of EDM machining that meets their needs.

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Wire EDM Machining (Image Source: Depositphotos) 


EDM presents a unique set of capabilities for precision machining, allowing for the creation of intricate shapes and high quality finishes. By understanding the different types of EDM available which include, wire, die sinking and hole drilling EDM, manufacturers are able to choose the best suited technique for their project. 

Other considerations to account for include considering key factors such as project complexity, material properties and cost budget for manufacturing. Overall EDM offers significant advantages in terms of precision, flexibility and efficiency in operation making it a crucial technology in various industries such as aerospace, automotive and the medical industry. 


Gary Liao

Gary Liao

Gary Liao is the Engineering Manager of TDL Company and has more than 20 years of mold design experience.

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