All About Electrical Discharge Machines (EDMs)

The topic of Electrical Discharge Machines (EDMs) comes up now among machinists and technicians despite being a completely different technology than CNC (Computer Numeric Control) for removing material from a workpiece. Rather than remove material using cutting tools, Electrical Discharge Machines remove material using electrical flow between two contacts and a liquid that aids in removing shavings. The process used generates sparks between the two contacts that energize the material being processed and removes a small amount of material with each spark. Sparking rapidly creates a thermoelectric flow that pulls molecules away from the workpiece. Dielectric fluid is used to enhance the sparking and remove material.

What’s the Diff?

CNC machines are all about cutting and removing shavings using tools that slice small pieces of material away to achieve the desired results. Electrical Discharge Machines don’t actually touch the surface of the workpiece. The electrical discharge touches the part to remove unwanted material so the entire process is the opposite of what traditional CNC machining can accomplish. Material is removed until the desired specification is achieved without any follow-on grinding or smoothing of the part necessary. Both types of machines can do the job, but the EDM never touches the workpiece.

Different Strokes for Different Folks

There are three types of Electrical Discharge Machines:

Die Sinking – This type of machine conducts the entire removal process while submerged in a conductive liquid. It’s like working underwater.

Wire – Considered the most accurate, this type of EDM uses a small (0.05mm to 3.0mm) wire drawn across two pulleys close to the workpiece,

Micro – Recently developed, the Micro EDM machine works with the Wire EDM process and enables operators to “drill” holes.

What Is It Doing?

Making different types of “cuts” in materials with accuracy is what parts machining is all about. The EDM process can make a variety of cuts in many different materials like steel, carbon, ceramics, and other heat-treated metals. Some of the shapes and cuts that can be achieved are:

• Circular
• Conical
• Helical
• Orbital
• Vertical
• Spherical
• Polygonal
• L-spin
• Indexing

Why and Why Not

The “why” is pretty simple to figure out. An EDM can often work faster with less downtime and input from operators. That saves money and if you’re running a large production floor with multiple CNC machines, you might want to consider this alternative. Everything from heavy metal to delicate and thin workpieces can be machined with high accuracy and productivity. The EDM process leaves no burrs or other unwanted material after machining so there are no follow-on production costs to be incurred. If a workpiece is made out of a softer material, like plastic or silicone, the EDM process won’t work. The workpiece must be able to conduct electricity or else the system fails.

Who, What, Where

With fewer moving parts than a traditional CNC machine combined with the ability to produce more types of “cuts’ than most traditional CNC machines, EDMs are making a big splash in manufacturing plants and machine processing floors. As the technology evolves, there will be a greater emphasis on more and more complex shaping capabilities. This is an excellent technology for brand new machinists to learn about as it appears to be here to stay for the long term.