Electrical discharge machining

Unlike conventional machining processes, electrical discharge machining uses electrical sparks to remove the material and shape the workpiece. It is usually applicable for shaping conductive and hard materials. However, on special consideration, EDM can work with non-conductive materials, such as composite and ceramics. Furthermore, EDM creates complicated shapes and contours, which are not possible with CNC milling & turning. 

You can get multiple options of EDM machining types like wire and sinker EDM. But, choosing the right types of EDM for your project is essential to ensure optimal results and cost-effectiveness. With several EDM techniques available, it can be challenging to determine which one suits your specific requirements.

This article will discuss the process, types, applications, advantages, disadvantages, and other aspects of EDM machining. It will also guide you through which EDM technique suits your project!

 

What is Electrical Discharge Machining (EDM)?

What is EDM? Like the laser cutting technique, EDM, also known as spark machining, is a non-contact subtractive manufacturing approach. It utilizes thermal energy (concentrated sparks) to cut, engrave, and shape the material generated by electrical discharging. It is based on a scientific discovery made in the 18th century, the erosion effects of electrical discharge. Then, in the 1960s, the EDM process underwent additional development. Since then, it has undergone a tremendous change (B.M. Schumacher, 2013).

The EDM process manipulates the erosion on a designated workpiece’s area with electrical discharging to create required cuts and shapes. Spark causes the local melting or vapourization of material and removes it from the workpiece. The limit of EDM is far beyond other traditional manufacturing processes in terms of small-cuts capability.

When is EDM a Best Machining Choice?

First, it is a go-to option when you have micro-level features in your parts, such as a hole with a diameter of 1 mm. It can create tiny features with extremely tight tolerances and an excellent surface finish. The following are the four scenarios for which it is wise to choose the EDM process.

• When materials are extremely hard and difficult to process with traditional manufacturing, such as tungsten carbide.
• When you have complex shapes and need highly tight tolerance.
• For thin or delicate parts that can be damaged or affected by cutting force.
• When you need to create complex internal features, such as holes and channels.

 

How Does Electrical Discharge Machining (EDM) Work?

The working principle of an EDM process involves creating a series of electrical discharges (sparks) between two electrodes, one is the shaping tool, and another is the workpiece itself. The sparks come from the contact of two electrodes eroding material from the workpiece and creating an intended form or shape.

Before discussing the details steps, here are the key components of the EDM system that work together to create the desired geometry.

1. The power supply: This provides the electrical energy necessary for the process. It controls the current, voltage, and pulse duration to facilitate precise material removal.
2. The electrode: In wire EDM, the electrode is a thin, conductive wire, while in die-sinking EDM, the electrode is custom-shaped to match the desired geometry of the workpiece. The electrode’s material is chosen based on its conductivity, wear resistance, and compatibility with the workpiece material.
3. The workpiece: This is the material being machined, which must be electrically conductive. Common workpiece materials include metals, alloys, and certain types of conductive ceramics.
4. The dielectric fluid: This fluid acts as an insulator and a cooling agent, preventing premature sparking and regulating the temperature during the EDM process. It also flushes away eroded material, maintaining a clean working environment.
5. The CNC controller: This computerized control system guides the electrode’s movement, ensuring precise and accurate material removal according to the programmed design.

Working in EDM (Ved Prakash, 2018)

Furthermore, the following are the stepwise descriptions of the steps involved in the EDM process.

Step 1: Arrangement of dielectric medium with electrode and workpiece.

The workpiece and electrode are placed in a dielectric fluid, usually kerosene or deionized water. Generally, the electrode (or shaping tool) is connected to a negative terminal and the workpiece to a positive power source terminal. As previously mentioned, it is a non-contact manufacturing approach; the gap between the shaping tool and workpiece with the dielectric medium is maintained.

Step2: Introduction of current

A high-voltage power supply generates the current between the workpiece and the electrode. As the electrical current passes through the dielectric medium, it ionizes the fluid and creates a plasma channel. The collision between electrons from the electrode (shaping tool) and dielectric medium molecules is responsible for the ionization of fluid.

Step3: Plasma channel and erosion

The ionization generates a plasma channel that creates a series of sparks or electrical discharges. These sparks erode material from the workpiece and create the desired shape or form, while dielectric liquid flushes away the eroded material. This process is repeated, and erosion occurs continuously until the desired shape or form is achieved.

The correct positioning of the workpiece and shaping tool is essential for a precise result. Therefore, positioning with computer numerical control (CNC) equipment is very accurate because it allows for precise control over the shape and location of the machined features.

Related to: Electrical Discharge Machining: An Essential Beginner’s Guide

Types of Electrical Discharge Machining

There are four types of EDM machining based on electrode shape and specific process, each with unique advantages and applications. 

• Wire EDM
• Die or sinker EDM
• Hole Drilling EDM
• Rotatory EDM

Wire EDM (Wire-Cut EDM) uses a thin wire as the electrode and is ideal for cutting intricate patterns and fine details. Sinker EDM (Ram EDM), on the other hand, uses a custom-made electrode that “sinks” into the workpiece to create a mirror image of its shape in the workpiece. Hole Drilling EDM, also known as fast hole EDM, uses a tubular electrode specifically designed for drilling small, deep holes.  Furthermore, the rotatory EDM uses rotating electrodes in multiple directions that erode the material from a workpiece.

Sinker, wire, and drilling EDM

EDM is cutting-edge manufacturing technology. There are several ways to cut and shape conductive materials using the EDM principle. Based on electrode shape and specific process, EDM can be categorized into four types;

• Wire EDM
• Die or sinker EDM
• Hole Drilling EDM
• Rotatory EDM

1. Wire EDM

As the name suggested, wire EDM uses a hair-thin, wire-shaped electrode to cut and shape the workpiece. Cooper, brass, or tungsten wire are popular wire materials. The standard diameter of the wire is 0.25mm. Although, it can range from 0.020 to 0.15 mm, depending on part features, such as corner radii, slot widths, and thin-wall (Devin Wendorf, 2009).

When the current passes to the wire, it creates a spark and erodes the targeted area through the ionization of the dielectric fluid. It can create micro-level shapes, such as needles and stents. Additionally, wire EDM is also useful in creating molds and dies. The capability of manufacturing tiny shapes with great detail and accuracy makes wire EDM a unique process in manufacturing.

Prolean’s Wire EDM workshop

2. Plunge or Sinker EDM

The Sinker EDM refers to the machining process that involves an electrode with a negative shape of the desired geometry. While applying the electrode onto the workpiece generates the negative version of the original geometry. Therefore, sinker EDM is also called die EDM.

It is especially used in creating complex cavities and addresses the sharp internal corner issue with CNC machining. Sinker or Die EDM is widely used in manufacturing die casting or injection molding devices, which is not accurate with CNC machining operation. It has the ability to micro-machine mold cavities with extremely fine details without applying any machining or impact stress on the mold.

Besides die and mold making, Sinker EDM is applicable in producing intricate and delicate parts, such as those used in the aerospace, medical, and electronics industries. Since sinker EDM can create a very smooth surface finish on the workpiece, it is frequently employed as a finishing technique along with other manufacturing approaches, such as CNC milling.

3. Hole Drilling EDM

The Hole drilling EDM is a specialized EDM process that creates very small holes with high accuracy. The wire EDM technique utilizes an electrically charged wire as an electrode that creates the holes using a series of electrical discharges to the workpiece. Furthermore, the hole is typically drilled from both ends to ensure accuracy.

It can drill holes as small as 0.0650 mm in diameter and depths up to 1m. However, it depends on various factors, such as workpiece material, electrode material, current magnitude, and many more (Kuppan, 2008).

4. Rotatory EDM

Movement in rotatory EDM (About Rotatory EDM)

In the rotatory EDM process, an electrode is mounted on a rotary axis, which allows it to move in a circular path around the workpiece. The top wire portion of the wire EDM machine can move in the U and V directions. Due to this multi-axis machining process, various shapes can be machined (About Rotatory EDM).

The table below shows the objective difference between types of EDM processes;

Table: Types of EDM

Criteria	Wire EDM	Sinker EDM	Hole Drilling EDM	Rotatory Drilling
Precision	High, ±0.0001 inches	High	Moderate,  ± 0.0025 Inches)	Moderate to High, ± 0.001 inches
Surface Finish	Excellent	Excellent	Good	Good
Material Waste	Low	Moderate	High	Moderate
Speed	Moderate	Slower	Fast	Fast
Geometry/Shape	Complex shapes and intricate patterns	Complex shapes based on custom electrode	Mainly used for drilling holes of varying depths	Primarily for cylindrical holes
Electrode Type	Thin wire	Custom-made	Tubular	Rotatory drill bit
Electrode Wear	Low	High	Moderate	Low to Moderate
Applications	Electronics, jewelry, medical, aerospace	Tool and die, aerospace, plastics	Aerospace, pre-process for wire EDM, automotive	General machining, automotive, aerospace
Setup Time	Moderate	Long (due to custom electrode)	Short	Short

 

How to Choose the Right Type of EDM  for My Project?

When choosing the right type of EDM for your project, several factors need to be considered. These factors will help you determine the most suitable EDM technique that aligns with your project requirements. Otherwise, inappropriate choices can significantly impact the quality, efficiency, and cost-effectiveness of your machining process. 

Here is the step-wise elaboration to guide you through the selection of EDM type; 

1. Understand Your Project Requirements

Before deciding on the types of EDM, it’s crucial to have a clear understanding of your project requirements. Consider factors such as the material to be machined, part complexity, precision requirements, production volume, and surface finish specifications. This understanding will guide you in selecting the most suitable EDM technique.

2. Research and Compare Different EDM Techniques

There are several types of EDM machining available, each with its unique capabilities and limitations. Research and compare the various EDM techniques, such as Wire EDM, Sinker EDM, and Hole Drilling EDM. Understand their principles of operation, applications, advantages, and limitations.

3. Evaluate Material Compatibility

Different EDM techniques work best with specific materials. Evaluate the compatibility of your chosen EDM technique with the material you intend to machine. Consider factors such as material conductivity, hardness, and thermal properties to ensure optimal performance and accurate results.

4. Consider Part Complexity and Geometry

The complexity and geometry of the parts you need to machine play a crucial role in selecting the right EDM technique. Some techniques, like Wire EDM, excel in cutting intricate shapes and contours, while others, like Sinker EDM, are more suitable for creating cavities and molds. Assess the suitability of each technique based on your part’s design requirements.

5. Assess Precision and Tolerance Requirements

The precision and tolerance requirements of your project should align with the capabilities of the chosen EDM technique. Some techniques offer higher precision and can achieve tight tolerances, while others may be better suited for roughing operations. Consider the level of accuracy needed for your specific application.

6. Analyze Production Volume and Efficiency

Consider the production volume and efficiency requirements of your project. Some EDM techniques are more efficient for high-volume production, while others may be better suited for prototyping or low-volume production. Evaluate the speed, automation capabilities, and overall productivity of each technique.

7. Factor in Cost Considerations

Cost is a crucial aspect to consider when choosing an EDM technique. Evaluate the overall cost implications, including equipment cost, tooling, electrode wear, and maintenance requirements. Consider the long-term cost-effectiveness of the chosen technique in relation to your project’s specific needs.

8. Seek Expert Advice

If you are unsure about which type of EDM technique is best suited for your project, seek advice from experienced professionals or EDM service providers. They can provide valuable insights and recommendations based on their expertise and industry knowledge.

9. Perform Test Runs and Evaluate Results

Before committing to a specific EDM technique, perform test runs on sample parts to evaluate the results. Assess surface finish, dimensional accuracy, material removal rate, and overall quality. This will help validate the suitability of the chosen technique for your project.

Factors to Consider:

In short, you can consider the following factors;

• Type of workpiece Material and its properties
• Design Complexity and Tolerances
• Production Volume ( Prototypes, mass production, etc.)
• Required Surface Finish Quality (functional or aesthetic needs)
• The cost associated with each EDM type
• Expertise in Operator and available equipments

 

When to Choose Wire EDM?

Wire EDM is the go-to choice when cutting intricate designs or complex shapes with high precision in hard materials. This method is particularly advantageous for projects requiring:

• High-precision cuts with tight tolerances
• Small kerfs or OK slots
• Complex shapes or intricate patterns

Some typical applications for Wire EDM include creating components for the aerospace, electronics, and medical industries.

Here’s a table that summarizes the types of projects best suited for Wire EDM:

Wire EDM is the go-to choice when cutting intricate designs or complex shapes with high precision in hard materials. This method is particularly advantageous for projects requiring:

• High-precision cuts with tight tolerances
• Small kerfs or OK slots
• Complex shapes or intricate patterns

Some typical applications for Wire EDM include creating components for the aerospace, electronics, and medical industries.

Here’s a table that summarizes the types of projects best suited for Wire EDM:

Project Type	Reason for Suitability
Intricate designs	Wire EDM can create OK slots and intricate shapes
Hard materials	Capable of cutting hard materials with precision
High-precision components	Offers high precision and consistency

 

When to Choose Sinker EDM?

Sinker EDM, Ram EDM, or Plunge EDM is the preferred choice for creating intricate, 3-dimensional shapes in a workpiece. This process is ideal for:

• Projects requiring cavities or molds
• Intricate details in hard materials
• Forming complex shapes

Sinker EDM is commonly used in tool and die making, plastic mold manufacturing, and fabricating components for the aerospace industry.

This table summarizes the types of projects best suited for Sinker EDM:

Project Type	Reason for Suitability
Mold and die manufacturing	Sinker EDM is perfect for creating intricate molds
Complex 3D shapes	Capable of producing 3-dimensional shapes with precision
Detailed features	Ideal for detailed features in hard materials

 

When to Choose Hole Drilling EDM?

Hole Drilling EDM is a fast and efficient way to drill deep holes, particularly in hard metals. It is especially beneficial for:

• Rapid drilling of holes in hard materials
• Deep hole drilling (diameters as small as 0.065 mm and depths up to 1m (or 250 times the hole diameter))
• Pre-processing for Wire EDM

Typical applications of Hole Drilling EDM include fuel system components for the aerospace and automotive industries.

The table below highlights the types of projects best suited for Hole Drilling EDM:

Project Type	Reason for Suitability
Fast drilling of holes	Hole Drilling EDM is designed for rapid hole drilling
Small hole drilling	Capable of drilling small diameter holes
Pre-processing for Wire EDM	Often used for start-holes in Wire EDM processing

 

What are the Advantages of Electrical Discharge Machining (EDM)?

EDM has several advantages in precise machining. It allows the creation of micro-level shapes with high accuracy and repeatability. The following are the key advantages of EDM process;

• EDM creates parts with extremely tight tolerances and excellent surface finishes.
• It can produce parts with complex shapes and features.
• Hard materials like tungsten carbide, Inconel, cobalt chrome, and Stellite can be machined with EDM, which is difficult with traditional approaches.
• There is no risk of failure due to stress since it is a non-contact manufacturing approach.
• It can create very small-scale features, such as internal corners, tiny holes, engraving, etc.
• It is cost-effective compared to traditional methods that require the use of diverse & expensive tooling.

 

Applications of Electrical Discharge Machining (EDM)

EDM’s precise micro-level machining capability makes it a suitable manufacturing technology for various industries. It applies in a simple tool-making process to advanced aerospace parts, whether for prototyping or full-scale production.

Parts created with EDM.

Automotive Industry

EDM machining produces high-quality components that meet strict performance and durability requirements of motorbikes, trucks, cars, or other vehicles. Common materials used in automotive applications include steel, aluminum, and specialized alloys.

First, the significant application of electrical discharge machining in automotive is the manufacturing of fuel injectors. It requires extremely precise holes and shapes, and EDM allows manufacturers to achieve the necessary levels of accuracy and finish. Other electrical discharge machining applications in automotive are internal threads, helical gear, engine components, and transmission parts.

Other examples include the manufacturing of engine components, such as pistons and injector nozzles, transmission components, and suspension parts. Additionally, EDM creates high-precision molds for plastic components, such as interior trim and exterior body panels.

Aerospace and Defense Industry 

EDM machining is widely used in the aerospace and defense industries due to its ability to produce complex shapes and geometries in difficult-to-machine materials, such as titanium, Inconel, and high-strength steel alloys. These materials are commonly used in aircraft components, missile systems, and satellite structures, requiring high precision and accuracy.

Different types of EDM play significant roles in producing aircraft turbine blades because it enables the required levels of precision and polish. Additionally, it is commonly utilized to produce aerospace-grade fasteners like screws, bolts, and nuts that must adhere to strict dimensions and surface finish specifications. The Panels, wing components, nozzles, engine components, and structural parts are examples of further uses.

Medical Manufacturing

Micro-level precise machining is mandatory in the medical industry to produce intricate, high-precision components. These components often have complex geometries and tight tolerances, making EDM a suitable solution for their manufacturing. Common materials used in medical device manufacturing include stainless steel, titanium, and specialized alloys.

Some application  of electrical discharge machining examples include;

• Surgical instruments, such as scalpels and forceps
• MRI machines and CT scanners
• Manufacturing or repair of molds for medical devices, such as catheters and stents.
• Dental implants and prosthetics
• Surgical needles
• Medical-grade tubes

Die and Mold Manufacturing

EDM machining creates highly accurate dies and molds for plastic injection molding, metal stamping, and die-casting operations. Its ability to machine hard materials and create intricate shapes makes it an ideal choice for producing these precision tools. Examples of die and mold applications include the manufacturing of injection molds for plastic components, progressive dies for metal stamping, extrusion dies, and die-casting molds for complex metal parts.

Electronics and Semiconductor Industry

The electronics and semiconductor industries also benefit from the precision and accuracy offered by EDM machining. The process produces components with intricate shapes and tight tolerances, crucial for the reliable operation of electronic devices and semiconductor equipment.

Examples of electronics applications include the manufacturing of connectors, switches, and sensors. In the semiconductor industry, EDM is used to produce components for wafer processing equipment, such as masks, dies, and electrodes. Additionally, EDM is used to create molds to make plastic and metal components used in electronic devices.

Read More:

• EDM (Electrical Discharge Machining)  in Medical Device Manufacturing
• Comparing Electric Discharge Machining and Laser Cutting in Modern Manufacturing

 

How Can You Select a Reliable EDM Machining Service Provider

When selecting an EDM machining service provider, it is essential to consider several factors to ensure the quality and precision of the finished product. Here are some tips to help you choose the right EDM service provider:

1. Expertise and experience: Look for a service provider with extensive experience in EDM machining and expertise in your industry. They should have a proven track record of delivering high-quality components and meeting tight tolerances.
2. Equipment and technology: Choose a service provider with state-of-the-art equipment and technology to ensure precision and accuracy. They should have a range of EDM machines capable of handling various materials and geometries.
3. Quality control and inspection: Ensure that the service provider has a robust quality control and inspection process to verify the accuracy and precision of the machined components. They should have a dedicated quality control team and use advanced inspection equipment to ensure compliance with specifications.
4. Customer service and communication: Choose a service provider that values customer service and communication. They should be responsive to your inquiries and provide regular updates on the progress of your project.

 

Precision Yet Affordable EDM Solutions At ProleanTech

ProleanTech is a leading provider of precise EDM services, specializing in all EDM solutions, including wire EDM, die-sinking EDM, and hole-drilling EDM. Additionally, we have extensive experience in various industries like medical device manufacturing and automotive.

We use CNC EDM machines for precision and accuracy. Meanwhile, ts quality control and inspection process ensures compliance with specifications. Additionally, We prioritize customer service and communication, providing regular updates and personalized support throughout the project. If you need any EDM services, you can upload your design and mention the detailed requirements also. We can deliver accuracy, efficiency, and superior quality in every component.

 

Summing Up 

EDM process involves creating a series of electrical discharges between two electrodes that create sparks and erode material from the workpiece to convert into the desired shape or form. It can create various parts and features, making it a versatile manufacturing process for various industries, including aerospace, medical device manufacturing, and automotive. 

Understanding the distinct types of EDM – Wire, Sinker, and Hole Drilling – is crucial to the success of your project. The choice depends on your specific needs, the material, the desired shape, complexity, budget, and the required level of precision. By considering these factors and consulting with EDM experts, you can determine the optimal EDM process for your project.

 

FAQ’s

What is Electrical Discharge Machining (EDM)?

EDM is a non-conventional form of machining that uses electrical sparks to erode material from a designated position to cut and shape the workpiece.

Can EDM machine non-conductive materials?

No, EDM requires the workpiece to be electrically conductive.

What are the precision levels of EDM?

EDM can achieve very high levels of precision, often up to micrometers, depending on the types of EDM and specific machine used.

What are the types of Electrical Discharge Machining?

EDM can be categorized into four types: Wire EDM, Die or sinker EDM, Hole Drilling EDM, and Rotatory EDM. Each of the EDM processes has its unique ability and electrical discharge machining applications.

Which type of EDM is best for complex geometries?

The best type of EDM for complex geometries is Wire EDM (WEDM). It allows for intricate and precise cuts in complex shapes and contours, making it ideal for applications that require high precision and intricate detailing.

What kind of materials can EDM process?

EDM can process a wide range of materials, including steel, aluminum, titanium, and many other hard metals.

What are the advantages of EDM over traditional machining methods?

EDM offers several advantages over traditional machining methods, including the ability to machine hard materials, create intricate shapes and designs, and produce high-quality components with tight tolerances.

Is EDM suitable for heat-sensitive materials?

EDM is suitable for heat-sensitive materials as it is a non-contact machining process that does not generate significant heat in the workpiece. However, certain precautions may be necessary to manage the heat generated during the machining process, such as using appropriate dielectric fluids and optimizing the machining parameters.

 

Bibliography

1. (n.d.). About Rotatory EDM. Relaiable EDM, from https://reliableedm.com/.
2. M.Schumacher, R. J. (2013). Historical Phases of EDM Development Driven by the Dual Influence of “Market Pull” and “Science Push.” ELSEVIER.
3. Devin Wendorf, M. M. (2009). Things to consider when wire. EDM notes, from https://www.xactedm.com/.
4. Kuppan, P. (2008). Influence of EDM process parameters in deep hole drilling of Inconel 718. The International Journal of Advanced Manufacturing Technology.
5. Ved Prakash, P. K. (2018). Surface alloying of miniature components by micro-electrical discharge process. ResearchGate.