EDM (or electrical discharge) machines are one of the most popular CNC machine tools around. They belong to the class of machines capable of starting with raw material, like a block of steel, and making very complex parts with precise tolerances and amazing repeatability.
EDM machines are used for many different types of metal fabrication and for cutting various materials from soft iron alloys to steels. The EDM process itself is relatively straightforward, but there are things to consider before deciding if an EDM machine is suitable for your shop or business.
EDM Machines Work By Using Electricity To Cut Metal
EDM is a common machining method often reserved for difficult-to-machine materials such as hardened steels and superalloys. It’s used to produce parts from these materials when conventional methods are too costly or impractical.
EDM machines use electricity to cut metal by plasma cutting, which involves a thin wire being charged with electricity and placed into a spool called an electrode. The wire is then fed through the spool to discharge into whatever material needs cutting—plastic or steel.
The EDM process relies on an electrical charge to create a spark that cuts metal. To do this, the machine uses electrodes or metal parts with wires coming out of them.
The electrodes are placed in a cutting fluid and connected to an electrical power source, usually a standard outlet. EDM works by placing the workpiece into an electrically conductive bath (called an electrolyte) which contains metal ions. When a small electrical current is passed through the electrolyte, it creates an electric field that attracts the negative ions in your material (i.e., iron).
A high-voltage electrode will then create an arc between itself and your workpiece, removing those positive charges to make room for more negative ones on your part while simultaneously melting its surface layer. The result is a clean circular groove around its circumference where only solid material once existed.
Turning on the machine creates a circuit between the electrodes and the ground (called a “return”). To make sparks, electricity must flow from one electrode through the cutting fluid and back through another electrode so there’s a complete electrical circuit between them. This happens when you turn on your EDM machine: Electricity flows from one electrode through your workpiece (your metal piece) and back into another electrode so there’s now current going around two circular paths within the metal at once.
How Fast Do EDM Machines Operate?
EDM machines are some of the fastest machine tools in the world, capable of cutting up to 250 inches per minute. Many factors determine the speed at which an EDM machine operates:
- Material type
- Cutting length and thickness
- Tooling and setup
The Roles Of The Electrodes In The EDM Process Are Reversed
In the EDM process, a positive electrode is replaced with a negative one and vice versa. This switches the roles of the electrodes in the EDM process. When an electric current passes through your motor, it generates heat. The heat causes carbon to melt, forming an arc between the wire and electrode. The melted carbon then floats away from its original location, where it creates your groove or whatever shape you’re trying to create in metal.
EDM cutting fluid, or dielectric fluid, serves several purposes during the process. It cools the workpiece to prevent thermal shock as it passes through the cutting zone. The dielectric fluid also cleans the surface of your workpiece, removing any dirt or debris on it.
If you were to look closely at a spark discharge between two wires, it would appear like they were burning off excess material from one wire onto another. If no dielectric fluid were present, this would happen immediately and cause damage to both wires (and possibly even damage to your machine). The dielectric fluid prevents this from creating an insulating barrier between the two wires until enough buildup has occurred for current flow through them to happen again.
Because the cutting wire never makes contact with the workpiece throughout the EDM process, no stresses are added to the component. As a result, less stress may be used for creating slots, grooves, and eyelets in machined items using EDM.
The coolant also lubricates both wires to move smoothly past each other without getting stuck together or overheating due to friction caused by poor lubrication.
EDM’s superior finish is one of its additional advantages. With tight tolerances, the wire cutting process produces surfaces that are burr-free and smooth. In fact, wire EDM can be used to create through-slots and very thin eyelets for medical devices—features that are inaccessible to traditional centers.
How Noisy Are EDM Machines When Operated?
When comparing the noise level of an EDM machine to other machining methods, it’s essential to remember there are many different types of EDM machines on the market. Some are pretty loud, while others are much quieter. For example, you might think a plasma cutter would make a lot of noise because of all its sparks, but it’s significantly quieter than an electric motor running at full speed.
Similarly, although an EDM machine may use electricity for power instead of air pressure like with a milling machine or router bit (and therefore produce less heat), this doesn’t necessarily mean it’ll be quieter than these other options. It depends on how well built your particular unit is and what kind of material you’re working with; certain materials are naturally noisier than others when being cut into or drilled through (for example, metal tends to be louder than wood). In general, most EDMs tend not only to produce less heat but also require less airflow around them during operation, resulting in lower overall noise levels due to reduced air turbulence generated by their cutting action.
What Are The Maintenance Requirements On An EDM Machine?
EDM machines are more complicated than other machining methods, requiring more maintenance. There is a weekly, monthly and yearly maintenance recommendation. These recommendations are located in the machine tool’s manual which is supplied with the machine.
As part of operating an EDM machine, you’ll need to clean and lubricate it regularly. You may also have to inspect and maintain it regularly, as well as calibrate it from time to time. Sodick offers service and maintenance for the machines it sells.
How (Or When) Is An EDM Machine Better Than The Alternatives?
Regarding precision, speed, and ease of use, EDM machines have few rivals. The machines allow you to create complex shapes—even ones that would be impossible by any other means.
As for what an EDM machine can’t do: They’re not good at cutting soft metals like aluminum or copper. However, they aren’t really meant for those materials anyway (in fact, most EDMs won’t even work on them).
It is best to consult a professional when deciding which machine is suitable for you. The variables involved in choosing an EDM machine include the material being cut, its hardness, and how much material to remove. Sodick is here to answer all of your questions.