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RAPID CONTOUR TOOL FOR ELECTRICAL DISCHARGE MACHINING

IP.com Disclosure Number: IPCOM000239133D
Publication Date: 2014-Oct-14

Publishing Venue

The IP.com Prior Art Database

Abstract

The present disclosure relates to improved plunged-based Electrical Discharge Machining (EDM) tools.

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RAPID CONTOUR TOOL FOR ELECTRICAL DISCHARGE MACHINING

TECHNICAL FIELD

The present disclosure relates to improved plunged-based Electrical Discharge Machining (EDM) tools.

BACKGROUND

Electrical discharge machining (EDM) is a popular electrode machining process. Electrodes for EDM are usually machined from a conductive material such as copper or graphite. Since the shape of the electrode, or at least the working portion of the electrode must correspond to the geometry of the desired, finished part, the electrode manufacturing process can be time-consuming depending upon the required complexity of the part shape. That is, the formation of the EDM electrode increases the cost and turnaround time for creating complex parts such as gear molds. Such complexity is particularly troublesome in the area of involute gear formation.  Further, during electrical discharge machining, the electrodes are subject to wear. Therefore, electrode life and cost are significant factors in the EDM process.

In a typical EDM process, the electrode is brought into close proximity to an electrically conducting work piece creating a gap between the work piece and the electrode.  The gap is then flushed with a dielectric fluid as a pulse DC voltage is applied across the gap. The dielectric fluid is ionized at a localized spot as a current flows across the gap, vaporizing a portion of the work piece. Thus, to make an EDM electrode for creating a mold having a particular gear form, (i.e. tooth shape and orientation), the electrode must include and fully define the gear form.

Plunged-based Electrical Discharge Machining (EDM) tools are frequent used to remove metal and some ceramic based materials at an expedient rate, with limited tool wear when compared to mechanical cutting based material removal systems. Using plunge-based EDM, simple shapes such as holes and dovetails can be plunged into materials to cut a though hole feature. In contrast, when EDM plunge based material removal is not used to generate a "through" cut feature, the shape of the electrode must be machined to reflected the desired profile of the finished surface. As the "dressed" electrode is plunged into the working material it can erode at differing rates requiring the electrode to be re-dressed periodically to retain the final surface profile as the electrode approaches it final depth.

Profile based plunge tools made up of unitary electrodes require frequent redressing, as the edges of the profile surge wears more than the center of the profile surface due to edge based electrical conductivity and cutting fluid flushing characteristics. As a result, the whole face of the contour tool needs to be periodically dressed to re-shape the desired end profile. The redressing of the electrode tool may require the electrode to be physically removed from the EDM machine, which slows down the task time of the full EDM operation.

In the past EDM material removal operations have been set up in parallel jobs so that mo...