Electrical discharge machining is a machining method primarily used for hard metals or those that would be very difficult to machine with traditional techniques. It is a manufacturing process in which the desired shape is obtained by using electrical discharges (sparks). Material is removed from the workpiece by a series of rapidly recurring current discharges (several hundred thousand sparks per second) between two electrodes separated by a dielectric liquid.
EDM has an accuracy of up to one-thousandth of a millimeter with no mechanical action. Furthermore, EDM can cut intricate contours or cavities in pre-hardened steel without the need for heat treatment to soften and re-harden.
By virtue of these properties, EDM is a key “non-traditional” advanced technology in mold and tool making. As opposed to the traditional processes of turning, milling, grinding, and drilling. However, because of the wear and tear brought about by these millions of electrical discharges, operations have evolved in very strategic ways.
THE WIRE-CUT EDM
This process avoids the erosion of material from the wire—which will ultimately cause the wire to break. The wire is wound between two spools so that the active part of the wire is continually changing. Only a small portion of the wire is engaged in the machining process at any given time.
THE DIE-SINKING EDM
Is a process that uses different sizes and shapes of electrodes during the same EDM operation (multiple electrode strategy). This involves “sinking” the blank in a single vertical direction into the dielectric liquid while the tool electrode carves out the shape. The corresponding machine is called sinker EDM. It moves the blank in multiple directions and rotations to complete the shape. These intricate designs are run via computer numerical controlled (CNC) plotters for precise accuracy.
EDM technology is best used for complex shapes that would otherwise be difficult to produce with conventional cutting tools. But also for tough materials with very close tolerances. But there are other instances where EDM technology is also suited by virtue that there is no direct contact between the tool and workpiece. These include very small workpieces that could be damaged from conventional cutting tool pressure. Such as delicate sections, weak materials, very fine holes (microscopic), tapered holes, and internal contours of pipes or containers.
Precision Group has a robust EDM equipment inventory across our three facilities, with expert machinists to run them. See our ad in Manufacturing News to learn more about Precision Group