What is Electrical Discharge Machining (EDM)?

This type of machining process, sometimes referred to as spark machining, die sinking or burning, is when an electrical discharge is used to shape materials. In some ways it can be a very versatile and accurate way to prototype and produce parts with hard metals or materials that are electrically conductive. Here's how.

How EDM Works

EDM works by removing material through recurring electrical discharges that form a spark between the tool and the workpiece, sometimes separated by a liquid electrical insulator to flush waste.

The entire EDM systems is composed of a tool or wire electrode and the part, which is connected to a power supply and is typically CNC controlled. This mechanism will also control the cutting pattern. There are two main types of EDM: wire and die-sinking.

• Wire-Cut EDM- A single, thin strand of metal wire is fed through the workpiece while submerged in dielectric fluid. The upper and lower diamond guides that hold the metal wire are CNC controlled. While the wire never actually touches the material, the spark that forms between the wire and material cuts the piece into the desired shape.
• Die-Sinking EDM- An electrode tool connected to an electrical current is lowered to a workpiece and submerged into a dielectric liquid. When the two pieces are brought closer together, thousands of sparks fly across the pieces causing the material to melt away. This process creates a negative impression of the electrode tool on the workpiece.

Pros and Cons of EDM

Advantages of using EDM:

• Can be used with small workpieces that can be damaged from conventional cutting tools since there is no direct contact between tools and material
• Surface finishes can be aligned with the machining process
• Can create complex shapes that may be otherwise difficult to produce
• Can work with very hard materials and metals

Disadvantages of using EDM:

• Additional time is used to create electrode tools for die sinking which could mean extra costs
• Continually creating electrical currents which means power consumption can be higher than other methods
• Can only be used with conductive materials, and non-conductive materials have to use a custom setup process that could be more expensive
• Process can be slower than other machining methods

EDM vs Milling

EDM is used in specific cases but which is the best to use will more than likely be determined by your machine shop based on shop experience, machines available, and materials. EDMs are better used for complex surfaces that are difficult for mill cutters to reach, and where deep cutting is required. Milling is better used when high accuracy is necessary and when programming needs are more robust.

Your machine shop will know what processes are best for your materials and design. Call Texas Metal Tech at (281) 893-0411 to get more information on how we can help create your next part or prototype!

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