Are you an employee in an industry that uses machinery? Then you have come across the terms spark erosion, electrical discharge machining (EDM) or metal disintegration.
These terms refer to a machining process that uses electric currents to cut through metallic material to produce a particular product of a specific size and shape.
Reading this article will give you insights and knowledge on what machining is in general, how EDM technologies came to be and why they are critical processes and techniques in the manufacturing world.
In this article
- What is machining?
- Types of Machining
- What are machining tools?
- Machining tools – Types
- Electrical Discharge Machinery (EDM): Description, history (who, when, what, why, where), types, etc.
- What is spark erosion?
- How does spark erosion work?
- Uses of spark erosion
- Advantages and Disadvantages of spark erosion
- Conclusion
So, to set the ball rolling, let’s look at what machining is all about.
What is Machining?
Machining is a manufacturing term that refers to a wide range of technologies, techniques and machine-based manufacturing processes used in the controlled removal of material from a workpiece – such as a block of metal – to get the desired shape, size or form.
Machining processes create many parts and components of machines and devices. There are practical points for every EDM operator to adhere to.
The machining process removes material parts – like a sheet of fibreglass – to create an item. This is in contrast to additive manufacturing, which employs a function of the controlled addition of material to form an object.
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Types of Machining
The three types of machining are:
- Milling: Rotary cutters remove material from a workpiece using a feed motion during the milling process. This motion is perpendicular to the cutting tool’s rotating axis. Nowadays, milling is one of the most utilised types of machining.
- Turning: Also known as Lathing, turning is a machining process that involves the rotation of a workpiece on a machine while the tool used for cutting stays in a fixed position. It uses a single-edged cutting tool in the cutting process. The tool moves slowly parallel to the rotational axis of the workpiece in the machining process. The cutting tool removes material from the work piece as it moves.
- Drilling: The drilling method involves using a cylindrical tool parallel to the rotation axis of the workpiece, to create a hole. The cutting tool creates a hole equal in diameter to the diameter of the tool.
Machining Tools
Numerous machining tools can be used to accomplish a wide range of tasks that require machining processes. A machining or machine tool is a tool that is used to machine or handles metal or other hard/rigid materials. The process usually involves cutting, boring, grinding, shearing or other forms of deformations.
The main types of machining tools include:
- Turning tools: These tools are specially created for the turning machining process where the workpiece or raw material is spun against a blade or cutting tool that is stationary.
- Milling tools: As the name also suggests, these tools are used in the milling machining process for cutting distinct shapes and designs from a workpiece or raw material.
- Grinding tools: These are tools are used in a machining process known as grinding. This is related to turning but focuses more on cleaning than shaping. Materials that require deburring and fine finishing require griding.
- Cutting tools: Cutting instruments such as shears and saws (manual or electric) enable straight lines through difficult material when precise cuts are required.
- Drilling tools: Machinists use drilling tools to finish all drilling operations; drill presses and a variety of other drilling devices enable precise hole drilling through any material.
- Boring tools: Boring is a technique for enlarging already drilled holes and expanding them to the correct size.
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A computer system manages the machining process through a process known as Computer Numerical Control (CNC). The computers are responsible for controlling the movement and operations of the cutting machines which include mills and lathes. These systems increase efficiency in the machining process while reducing labour costs for machining companies or businesses.
Such advancement of technology in the manufacturing world has led to the development of advanced machining techniques such as spark erosion or electrical discharge machining (EDM).
Now that we have the foundation, we can build a good understanding and appreciation for Spark Erosion or Electrical Discharge Machining (EDM) and its processes and tools.
Spark erosion or Electrical Discharge Machinery (EDM)
It is essential to manufacture parts and components of machines to the most outstanding quality. Spark erosion is one of several machining technologies that can help you process and manufacture the piece of an exemplary element that is aiming at.
Assume you’re working on a massive manufacturing machine on the assembly line. All looks like it’s working perfectively fine until disaster strikes; a tap breaks off somewhere in the machine.
You have two alternatives if you are unable to extract the shattered piece without harming the machine or removing the threads of the casting:
- replace the damaged equipment, which is expensive and inhibits output, or
- you can use spark erosion, which solves the problem in seconds rather than hours or days and costs a fourth of the price.
Spark erosion or EDM can be used to get damaged bolts, taps, studs and drill bits out of machine castings without destroying the threads or the casting itself.
But what exactly is spark erosion or EDM?
What is spark erosion or EDM?
Also known as spark machining, wire erosion and wire burning, spark erosion or electrical discharge machining (EDM) is a non-conventional machining method used in the fabrication of metal objects that are applied in the machining of very hard materials that may not be machinable through the use of conventional machining methods.
If you remember some of your geography lessons, you may recall learning what soil erosion is, how it occurs and the types of soil erosion. Spark erosion follows the same principle.
How does spark erosion work?
As the name suggests, spark erosion or EDM utilizes electrical current to perform its machining functions. This is how it all works:
Every machining process requires two things, to begin with. First and foremost, you will need the workpiece or the metallic material you will be eroding to produce your desired shape or item. Secondly, it requires an electrode (an object that conducts electricity and allows electricity to enter or leave an object, substance or region).
The process
To begin with, the machinist(s) soaks both the workpiece and the electrode in a fluid known as dielectric fluid (this fluid facilitates the process of controlled electrical discharges to remove material from the gap between the tool or electrode, and the workpiece during the EDM process).
Next, a positive current passes through the workpiece to make it an anode. The tool becomes the anode.
When the workpiece and machining tool come into close contact, they create an electric arc. At the point of contact, the resulting spark creates a lot of heat and this causes some of the metal to melt and evaporate.
In the case where the cathode and anode are made of the same material, the positively-charged anode experiences erosion faster than the cathode. Thus, the workpiece to be machined is normally made the positively-charged electrode.
The spark that causes the workpiece to erode occurs when the tool and the workpiece are closest to each other. Thus, in general, the machine keeps a gap of about 0.005 or 0.05mm between the workpiece and the tool. Dielectric fluid fills the gap between the two electrodes.
When the spark is generated, the particles of the dielectric fluid become ionized and concentrated. This forms a path for the current to flow from the tool (cathode) to the workpiece (anode).
The workpiece is eroded as a result of the intense arc created at the interface of the tool and the workpiece. Some amount of the tool is also eroded in the process. Watch this here to understand how the EDM machine works.
The tool moves back and forth to create the spark for the erosion process and this is controlled by the servomotor mechanism which keeps the gap between the workpiece and the tool.
Uses of spark erosion
The application of spark erosion or EDM cuts across a number of industries. Machinists in the tool die, and mould-making industries use this common machining method. However, it is fast becoming a go-to method for creating prototype and production parts for industries such as the aerospace, automobile and electronics industries.
Other applications of spark erosion include:
- Micro hole drilling in nozzles.
- Creation of slots, gear wheels, or fine holes in hard materials.
- Cutting the blades used for manufacturing turbines, compressors, etc. )
- Thread cutting
- Engraving operation on hard materials
- Rotary form cutting
What are the advantages and disadvantages of spark erosion?
Spark erosion has many advantages for the manufacturing industry or sector.
Advantages of spark erosion
- It produces complex shapes and forms. These shapes would have been very difficult to produce with conventional machining processes.
- It achieves a tolerance of +/- 0.005 microns in the machining process.
- It helps to achieve a great surface finish in an economical way.
- Since there is no physical contact between the workpiece and the tool, it prevents distortion and vibration in either part.
- Spark erosion machines are relatively:
- simple to operate
- lightweight and easy to manoeuvre
- easily set up and taken apart
- easy for single-person usage
- Cost-effective to run with little-to-no maintenance; it only requires fresh coolant.
Disadvantages of spark erosion
Even though this machining process is very innovative and helpful, it certainly has some drawbacks.
Some of the disadvantages of using spark erosion or EDM include:
- The high rate of electricity or power consumption due to the need to generate a large amount of electrical energy to remove material from the workpiece. Read more on the hidden cost of using EDM machine.
- The tool experiencing excessive wear and tear during the process.
- Spark erosion only works with materials that are metallic or capable of conducting electricity.
- The slow rate of material removal from the workpiece.
- Finding expert machinists is difficult. What is an EDM operator and how to become one?
Conclusion
The advances in technology in the manufacturing industry have produced innovations such as spark erosion. There is no doubt that the quickest and most cost-effective way to recover machinery that has broken tools is by spark erosion.
In the coming years, advancements in spark erosion or EDM technologies will enable greater manufacturing feats and possibilities.
