Sinker EDM vs Wire EDM: What is the Difference?
The typical workshop comprises many machines, sometimes in the hundreds. The versatility of these machines varies a lot. Some are for specified jobs while others can handle many jobs. In any particular job, the user will switch from one machine and tool to the other. They will end up using dozens of tools by the time the job is completed. One machine that suits these dynamics of a shop is the electrical discharge machining (EDM) machine.
Some users call it the spark machining tool. Using spark generation to machine the workpiece, this innovative machining process is available as sinker EDM and wire EDM machines.
Each of these EDM machining processes performs metal removal differently. Therefore, the processes have their place in the industry. Despite the application differences, the fundamentals of the processes are the same. They use thermal energy to machine even the hardest metal with impeccable precision.
Before we look at each of these EDM machining methods in detail, it would be consistent to understand the EDM machining process more clearly.
What Is EDM Machining?
Electrical discharge machining (EDM) is a metal removal method that is highly accurate and able to machine in ways the conventional machining processes are unable to. As we have mentioned, you can also call it the spark EDM machining process. Yet another name for EDM machining is the arc machining process.
The concept of the spark machining process is simple. An electrode produces a spark and directs it to a workpiece. There is a dielectric fluid between the electrode and the workpiece. This setup generates a spark that creates an erosion process. Therefore, thermal energy causes the machining process on the workpiece.
EDM technology relies on the conduction of electricity. That’s why electric discharge machining only works with conductive materials. As long as the material is a good conductor of electricity, the EDM process will deliver an accurate cut.
Note that the hardness of the material is not a big issue for EDM processes. This means that hard materials including Tungsten carbide are candidates for EDM processes.
Apart from the hardness of the material, the need for complex shapes is another reason engineers may opt for EDM machines. For instance, where milling and other conventional machining processes cannot produce deep holes, cavity-type EDM comes in handy.
How Does the EDM Machining Process Work
The EDM machine setup comprises the following parts:
Power supply
Electrically conductive workpiece
Dielectric fluid
Tool or electrode
These major components of the EDM process coordinate to cut the desired shapes and profiles in the workpiece.
The secret to the EDM process is the electrical discharge concept. It is based on the generation of a plasma between the workpiece and the electrode material. The plasma heats, melts, and evaporates the material.
When the voltage between the workpiece and the electrode surpasses the voltage that the dielectric fluid needs to break down, the fluid ionizes. The result of this ionization is plasma, which generates a path in the spark gap – a small gap of 0.01mm to 0.50mm in size.
This path allows for the formation of a spark. Consequently, the spark has a high temperature, so it heats the dielectric fluid in the vicinity. In its superheated form, this dielectric fluid erodes a portion of the workpiece. The channel disappears once the spark ends. Since the rest of the dielectric fluid is cool, it cools the area, and the metal solidifies. It also carries away the eroded and solidified waste material.
Factors Affecting the Material Removal Rate
Many factors are at play when the EDM process is happening. Although a single spark removes an insignificant amount of metal, it is the cumulative amount that matters. That said, these elements can determine the material removal rate:
Pulse Time – This is the time in every cycle that the current flows. The amount of energy that the setup provides during the pulse time is directly proportional to the material removal rate.
Voltage (V) – The voltage for an EDM machine is typically in the range of 50-400 V
Dielectric Fluid – Various properties of the dielectric fluid can affect the material removal rate – viscosity, thermal conductivity, etc.
More on the Dielectric Fluid
The dielectric fluid plays an irreplaceable role in the EDM process. Here are more details about the importance of this fluid:
Heat Dissipation – The EDM method generates significant heat, especially in the area around the electric spark. The dielectric fluid is instrumental in the removal of heat from the area. This is an important exercise that not only allows for material solidification but also prevents damage to the electrode material.
Insulation – The workpiece and the electrode should not touch each other during the electric discharge machining process. The dielectric fluid provides the necessary electrical insulation. With the insulation in place, the material removal rate is controllable.
Debris Removal – Material removal leads to the formation of debris around the machined surface. It is important to continually remove this debris. The fluid also acts as a waste removal medium. The EDM machine has a design that circulates the fluid, filtering away the debris and cooling the fluid.
2 Common Types Of Electrical Discharge Machining
Arranging the different components of EDM differently and altering the shape of the electrode gives rise to different types of electrical discharge machining. The two most popular types of EDM are sinker EDM machining and wire EDM machining.
In the following section, we delve into the details of these two EDM machining processes.
Sinker EDM Machining
Sinker EDM machining utilizes a die that is a negative shape of the intended part. By bringing the die into close contact with the workpiece in the presence of dielectric fluid, machining takes place. The name comes from the fact that the die “sinks” into the electrically conductive material.
It is akin to when you press a screwdriver into a piece of bar soap. The soap assumes the shape of the screwdriver. It is the same concept in die-sinking EDM. It acts like a ram, hence yet another name for the machining process – ram EDM.
Die sinking EDM tends to be more popular than the other EDM machining process, wire cut EDM. Being a conventional EDM process, this cavity-type EDM is more common in industries.
How Does the Sinker EDM Machining Work?
Enabling the sinker EDM machining process is a system comprising these components:
Electrically conductive workpiece
Dielectric fluid
Ram-held electrode
Servo motor controller
Voltage and current generator
Feedback mechanism
The sinker electric discharge machining process begins when the power switch is on. An electrical charge of high voltage goes to the gap between the workpiece and electrode, forming a gap voltage. The resulting spark machines or erodes the metallic workpiece and forms a negative shape of the electrode.
The spark can be as much as 12000°C hot. However, sinker EDM machines have a mechanism to control the power of the spark. The parameters that contribute to this control include the current level and pulse duration. The process removes very tiny particles of the workpiece for every spark.
As the machining process is proceeding, the dielectric fluid is moving around the machining area. It prevents the metals from arcing and removes waste material. Since the machinist will have the desired surface finish and other machining parameters, the control keeps everything in check. Usually, it switches the electro discharge machining process on and off.
The finish by sinker EDM may be mirror-like, but it may still require extra finishing in some applications. Here are some of these finishing options:
Painting
Drilling
Deburring
Assembly
Types of Sinker EDM
There are several types of sinker EDM namely small hole drilling EDM, orbital sinker EDM, multiple electrode sinker EDM, and Pulse Power Sinker EDM. Others are cheese cutter EDM and conventional sinker EDM.
Each of these versions of sinker EDM has its pros and cons. Therefore, the user needs to analyze their specific project requirements before settling on any particular version. It is also worthwhile to seek the advice of the manufacturer on the capabilities of the sinker EDM machines.
Advantages of Sinker EDM Machining
Let us now briefly look at the advantages and disadvantages of the sinker EDM process.
The advantages of this electrical discharge machining process include the following:
It is a precision machining method that you can use to create intricate shapes
It is suitable for all electrically conductive metals
The tool does not have to be harder than the workpiece
It is an ideal machining method for irregular shapes and sharp internal corners
Disadvantages of Sinker EDM Machining
It consumes more energy as compared to CNC machining processes
The longer machining time and the higher cost can be challenging
Cannot be used on non-conductive materials, for instance, plastic
Wire EDM Machining
Wire electrical discharge machining (Wire EDM) is a popular metal machining process that uses a non-contact concept. Its cutting capability comes from a spark. This machining method is capable of cutting very hard materials.
Conventional machining processes find it difficult to machine carbide and harder steels. However, wire EDM machines remove material from these metals easily. The surface finish from this method is also excellent. Wire-cut EDM also gives tight tolerances.
Of course, the machining technology has its drawbacks. However, these don’t deter the method from finding use in a wide range of industries.
How Does the Wire EDM Machining Work?
The cutting action of the wire EDM machine emanates from a thin wire of brass or copper. This wire is the electrode material in this process. It conducts electricity between the workpiece and the power supply.
A spark forms due to this interaction, leading to the machining of the substrate material. The formation of the spark and the consequent removal of material is repetitive. To maintain the spark gap, the wire electrode and the workpiece remain in the dielectric fluid.
Due to the movement of electric current between the workpiece and the electrode, a temperature of up to 10,000° C forms. This extreme heat machines the workpiece through vaporization and melting. On stopping the power supply/current, the wire-cut EDM machining process also stops.
For wire EDM machining, you want to use the right cutting parameters. These parameters and the speed have a direct effect on the quality of the cut. When the wire is moving extremely fast, it tends to bend, hence affecting the cut accuracy of the electro discharge machining. It is better to operate the electrical discharge machining EDM machine at a slower speed.
Advantages of Wire EDM Machining
When you compare the wire EDM machining method to conventional EDM or other machining processes, you notice a few advantages. One that comes out is the cost-effectiveness in accurate machining of a wide range of machining. This includes even the hardened steel and other hard materials you can think of.
This electrical discharge machining EDM method cuts the intricate shapes relatively fast too. Let’s look at a breakdown of these and other advantages of wire-cut EDM:
Cost-effective
Through its accurate cutting action, this electrical discharge machining method does not use expensive cutting tools and mold setups like other conventional methods. It is ideal for hard and soft materials alike, yet it does not produce a lot of waste.
Super accurate
If you are looking for some of the most accurate cuts, consider wire-cut EDM machines. The thin wire is so good at creating precise cuts that you can use it to create virtually any complex shapes. The wire erosion is fine and measured, so it provides tight tolerances.
Fast manufacturing process
As long as you have the requisite expertise, setting up and programming the wire EDM machine is simple. You save more manufacturing process time by the cuts being precise. The lead time is minimal because the need for surface finish is minimal.
Produces small complex shapes
This unique manufacturing process is perfect for producing tiny and intricate parts. Many advanced industries need such parts. Examples of such industries are aerospace and medical.
Low damage to tool and workpiece
By design, the thin wire-based machining process easily machines hard materials and soft materials with unmatched effectiveness. It is effective in many respects, one being the longevity of the cutting tool (wire).
Disadvantages of Wire EDM Machining
Wire-cut EDM has its shortcomings also. One, this machining technology is only applicable to electrically conductive materials. You cannot use this method to machine non-conductive workpieces such as plastic and wood.
The other challenge of wire EDM is that it is relatively slow. Due to this, the per-part machining cost for this method can be higher than other machining methods.
Also disadvantageous is that the consumables of the EDM machine can be costly. Note that the thin wire is non-reusable. You have to replace the wire after some time. While the frequency of replacement can vary depending on several factors, some shops may need replacement in a few hours.
Difference Between Sinker EDM and Wire EDM
Cutting Process
The main component in sinker EDM is a tiny wire electrode that cuts through the material. The wire produces sparks that aid in material removal. On the contrary, sinker EDM utilizes a specially shaped electrode. The shape of the electrode is comparable to the intended shape of the machined area. As the electrode presses into the workpiece and produces sparks, material erosion takes place.
Machining Speed
For sinker EDM, the machinist has to create a custom-shaped electrode. This adds to the machining time. For wire-cut EDM machines, the thin wire is standard. Therefore, the wire-cut EDM process can be significantly faster than the sinker EDM manufacturing method.
Applications
Since the two electrical discharge machining processes have differing functionalities and capabilities, their applications are also usually different. You can approach a workpiece from any angle if you are using die-sinking EDM. However, this may not be possible for the wire EDM process. Therefore, die-sinking EDM is better suited for producing fresh holes or cavities. As for wire EDM, the best applications are where you need sharp contours, precise 2D shapes, and so on.
Precision
Talking of precision, we can agree that both methods are applicable in precision machining. However, if you must pick one for precision cutting and extremely tight tolerances, choose the hole drilling EDM or any other wire EDM method. However, die-sinking EDM is great at producing accurate cuts on harder materials.
Conclusion
Selecting either wire EDM or sinker EDM will depend on the specific project and its requirements. Both electric discharge machining methods are accurate and precise. However, they may not achieve the same level of intricacy.
Depending on your project requirements, the able team at Aria Manufacturing can guide you on which process to use. Do you need professional input in the entirety of the manufacturing process? We are also experts in that aspect.
FAQ
How deep can a wire EDM cut?
The depth of a cut from wire EDM varies because it depends on several factors. One such factor is the capability of the specific EDM machine. Generally, the electric discharge machining can cut several inches across a diameter and up to 450 mm across the length of a workpiece.
Can wire EDM make holes?
Yes, wire EDM can make holes. You can use this process to create small, accurate, and accurate holes in any electrically conductive material. Experts call this form of making holes wire EDM drilling. Holes from the wire EDM process are present in the electronics industry, automotive industry, aerospace industry, and medical industry, among many others.
Can you cut aluminum with wire EDM?
Yes, you can cut aluminum and its alloys using this machining process. Aluminum is an excellent electrical conductor, so it meets the basic criteria for this type of metal machining. However, you want to restrain yourself to the less complicated aluminum parts. Make sure you use a brass wire electrode due to its good electrical conductivity.
What is the difference between sinker EDM and wire EDM?
The two types of electric discharge machining are different in several ways. Generally, the difference emanates from their different operating principles. Sinker EDM uses a custom-shaped electrode while wire EDM uses a thin wire to machine metal. Due to these setups, sinker EDM is ideal for 3D geometries while wire-cut EDM suits 2D patterns and profiles. Because the surface finish and accuracy differ, the applications for the two are also different.
Author
Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.