Sinker EDM, which goes by many names including conventional EDM, plunge EDM and ram EDM, produces parts by eroding materials in the path of the EDM tool using electrical discharges, or sparks that can generate heat anywhere from eight to twenty thousand degrees. One of the two major types of EDM, sinker EDM differs from its counterpart wire EDM in terms of the type of electrode used and because sinker EDM has 3D capacities while wire EMD can only produce 2D parts. Common sinker EDM electrodes include machined graphite, copper tungsten and brass. Die sinking EDM is ideal for applications such as injection mold tooling, micro hole drilling, keyways, washers and scientific research apparatus. Industries served include aerospace, medical, tool and die, automobile and military.
Sinker EDM is used for more complex geometries where electrodes are used to erode the desired shape into the part or assembly. A pre-drilled hole is not required for the electrode, unlike wire EDM. Consisting of an electrode and a workpiece (the material being processed), the electrode is used to generate a series of sparks and is connected to the workpiece through a power supply. There is no actual contact between the electrode and the work piece, but rather a conductive path that is established between the electrode and the material. The "tool electrode" forms an arc to the "workpiece electrode" as the two are brought closer together, creating the intense electric field which is responsible for removing material. This process takes place in a bath of dielectric fluid, which prevents premature sparking and flushes away debris, conducts electricity between the electrode and the work piece and then flushes out the melted material. CNC machines are used to guide, monitor and control the EDM process, as well as CAD and CAM software.
Sinker EDM can be applied to hard materials including stainless steel, copper, graphite, and exotic metals that would cause difficulties during conventional machining. In addition, sinker EDM is advantageous due to its ability to create complex and intricate parts with a high degree of accuracy. Also, while using this process, the work piece is not deformed from impact because there is no direct contact between the electrode and the material, and likewise the work piece is burr-free after completion and saved from heat damage because very little material-damaging heat is generated during the procedure. Sinker EDM has an advantage over wire EDM as well, because sinker EDM does not cut all the way through the material, thus producing parts that wire EDM cannot.