When do you need EDM?

Modern Machine Shop, Feb, 1995 by Harry C. Moser

If you're making a part or product with a material that tends to leave tough burrs when traditional machining is used, EDM can solve the problem for you. With traditional machining, burrs are typically left along workpiece edges. In contrast, the EDM process leaves no burrs and the vaporized material is flushed away by the dielectric. By eliminating the deburring process, EDM eliminates extra operations and the potential of causing dimensional changes that may occur during the deburring process. As a result, EDM is often used to make surgical tools and copper electrodes.

Another time to consider using EDM is when you are making a part with accuracies that are difficult to maintain after heat treating. With EDM, you can cut conductive material of any hardness.

No Rotation

Another area where EDM shines is producing sharp internal corners. Conventional machining has problems with internal radii less than or equal to 1/32 inch that are parallel to the tool axis. The internal radius cut by an EDM is as small as the spark gap, plus the radius of the wire or the electrode corner.

In milling and turning, tools or workpieces rotate. The smallest workpiece radius is equal to the tool radius. In contrast, EDM electrodes generally don't rotate and since there is no force, very small, long tools can be used. The minimum EDM wire diameter is 0.0012 inch versus the minimum production milling cutter diameter of about 0.1 inch.

The minimum dimensions of features that can be EDMed are approximately:

Features                Wire             Ram