Electronic Discharge Machining (EDM) Wire erosion is a process within precision engineering where a workpiece is cut through a strand of the wire creating electronic sparks that cut the workpiece.
A key benefit of this is that the process can be cost-effective and has great accuracy for thicker component parts. These wire cutting machines are excellent in that they can cut complex shapes even from tougher materials.
The process dates back as far as 1770 when Joseph Priestly, an English scientist, discovered that an electrical discharge can erode metals.
What is EDM?
Precision Wire Erosion and EDM Machining is a commonly used manufacturing process used for the creation of grooves, slots and cut-offs in processed parts. It does not require a high cutting force and instead creates slow stresses. This makes EDM an extremely useful tool for the manufacturing of medical parts.
Electrical discharge machining often referred to as spark machining or arc machining, is a manufacturing process in which materials are removed from a workpiece as a result of electronic recurring discharges. As part of this process, currents flow between two electrodes separated by a dielectric liquid. This removes materials from the workpiece in order to create accurate dimensions.
It is the accuracy of EDM that makes it so popular. The EDM process has become very common for creating prototype parts. Its use can be seen across many industries including the electronic and automobile industries.
Additional use of EDM is that it can craft medical device components with critical tolerances. The reason for this is that the process does not implement vibration or cutting pressure.
It may also be used for small hole drilling across different applications. This process is carried out by using a different EDM head which is placed on a wire cutting machine. This allows for the machine to drill small and precise holes in components. This is ideal for materials that are not compatible with other types of machining.
CNC wire EDM uses an electrically charged wire which cuts workpieces that are submerged in deionized water. The wire is often made of brass and erodes conductive materials in its way while the deionized water cools and takes away any debris created through the cutting. This process creates a nice smooth finish that holds considerably close tolerances.
CNC wire EDM may be programmed to cut delicate and intricate shapes making it the perfect tool for manufacturing medical device components.
Advantages and Disadvantages of Precision Wire Erosion and EDM Machining
Firstly, a key benefit of the EDM process is that the cutting wire does not touch the workpiece and therefore doesn’t introduce any stresses to the part. As a result of this, manufacturers can use the process to generate grooves, slots, eyelets in machined parts with very minimal stress.
Additionally, another strength of EDM is that it produces a high-quality finish. The process produces smooth with close tolerances. Wire EDM can be used to build even very slim eyelets/ through-slots in medical devices which cannot be achieved using conventional methods.
On the other hand, the process does have a few disadvantages as well. Firstly, the wire cut EDM process removes material with electrical charges meaning it can only be compatible with electronically conductive workpieces. This means that the process cannot be used for the machining of composite/dielectric materials. The process may also create a layer of oxide on the surface of the cut when they are used with particular metals. These must be cleaned in order to maintain the best quality.
A second disadvantage is that the process may struggle with components that cannot be held without a compromise in its shape. This can be an issue for delicate tube parts as they can be deformed while being secured for cutting which can cause additional quality problems and disruption to your workflow.
In short, some advantages of EDM wire erosion may include:
- Being able to achieve intricate detail.
- No additional complications as a result of the use of hard materials.
- It can handle very small workpieces that traditional cutting tools would cause damage.
- There is no contact between the workpiece and the tools, which can benefit weaker materials as they are less likely to break.
- You can use the process to drill fine holes.
- The wire erosion does not leave burrs.
A couple of disadvantages include:
- The materials need to be conducive in order to use EDM wire erosion.
- Can be a more expensive option compared to some other options such as CNC milling.
Dielectric Fluid For Wire EDM
To increase cutting speed and to ensure a perfect finish and accuracy, it is essential to ensure that microscopic particles made during this process are removed to get the best results. This is where dielectric fluid becomes very useful.
Dielectric fluid refers to any liquid that has high dielectric strength and high electrical resistance. Furthermore, it is an electrical insulator in the form of a liquid. Common forms of dielectric fluid include plant-based oils and mineral oils as they are easy to obtain and cheap. However, other fluids such as fluorocarbons and silicones may sometimes be used in instances where a non-flammable or high-temperature fluid is needed.
With regards to wire cutting EDM, the dielectric fluid that is used is known as deionized water. This water acts as a flushing agent to wash any debris away that’s created during the cutting process. It also acts as a semiconductor between the wire and the workpiece. This maintains a controlled and stable condition for ionization within the spark gap.
Deionized water can also be chilled which ensures that the worktable, workpiece, wire and fixtures stay at a steady temperature and limit the thermal growth of the machine and workplace in order for them to hold tight tolerances.
What Materials are Suitable?
There is a range of different metal types that you can use in precision wire erosion and EDM machining. The typical options used for wire erosion may include:
- Brass has a high rate of wear. However, this material is now used more often for EDM hole drilling.
- Tellurium Copper as the removal rate of the wear is reasonable.
- Silver Tungsten because of the high conductivity level that silver can offer. This can be a more expensive option though in comparison to copper tungsten.
- Copper Tungsten may be used when safety is needed. That being said this material has a far greater wear resistance as a result of its high melting point.
- Tungsten may be used although it is not a common choice. It may be used when not under strict time constraints as it will work slower than other metals. It can also be more expensive than other metals.
Other Types of EDM
One additional type of EDM is die-sinking EDM. Die sinking and Ram EDM can be attractive options for the machining of complex cavities. A graphite electrode is produced in the reverse shape to the cavity which forms the die. The process works by inducing a voltage between the workpiece and the die while being submerged in a dielectric fluid. The die is then lowered to the workpiece until electric breakdown occurs and a spark jumps the spark gap. In doing so, this vaporises the material and the dialectic fluid carries any ejected particles away from it. Material is then repeatedly removed from the piece using high-frequency sparks, cutting out the shape needed.
Another variation of EDM is hole drilling EDM. In this method, accurate holes can be drilled that are extremely small and do not require deburring. This method is similar to that of die-sinking EDM but the cut is made with a pulsing cylindrical electrode that moves deeper into the workpiece. This method is essential for the advancement of high-temperature turbine blades. This is because it allows for the manufacturing of intricate cooling channels to be manufactured inside the turbine blades.
Precision Wire Erosion and EDM machining Overview
EDM machining is a great solution for creating complex shapes within electrically conductive materials such as carbide, titanium and tungsten carbide, hard metals and alloys. EDM uses multiple axis movement capabilities that allow for the cutting of delicate and precise shapes with close tolerances. As a result of its accuracy, the process allows for more complex medical components which can be impossible to create with traditional machining systems.
How can Epal Engineering assist you?
Our team of engineers are equipped with all of the skills to take on jobs both large and small. We’re comfortable working with the toughest metals down to the most delicate materials. So, no matter what sort of project you’re looking for, we can help every step of the way, from initial ideas all the way through to finishing and quality checks.
This even includes design services and precision calculations. We always strive to get things right the first time, so we do not skimp on measuring twice and cutting once. With plenty of industry knowledge and experience, you can rest assured we won’t make any of those common mistakes. To learn more about us and how we can help you, please visit our website by clicking here, or why not give us a call on 01903 74435?
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