Browsing by Author "Opoz, Tahsin Tecelli"
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Article Citation Count: 27An Experimental Study on the Geometry of Microholes in Microelectric Discharge Machining(Taylor & Francis inc, 2009) Öpöz, Tahsin Tecelli; Erden, Abdulkadir; Erden, Abdulkadir; Department of Mechatronics EngineeringShape and dimensional geometry of blind microholes produced by microelectric discharge machining (micro-EDM) is investigated experimentally to explore the relational dependency with respect to machining time. For this purpose, microholes are machined with machining times ranging from 1-80min on plastic mold steel samples using tungsten carbide tool electrode and hydro carbide dielectric liquid composed of mineral and synthetic oils. All other operational machining parameters such as pulse time, gap voltage, average current, and so forth, are kept constant during machining. Depth, diametric expansions, end-tip shape, wall side parallelisms of holes were analyzed both on surface and cross-sections of the samples. Consequently, nine different end-tip shape formations were observed, and these shapes discussed on basis of dielectric liquid circulation and sparking conditions during machining. Enlargement in hole diameter was predicted by defining a band-width of 20 mu m hole expansion. Moreover, parallel wall-side length was expressed as the microhole depth where 5% reduction in entrance diameter was measured at the tapered section.Article Citation Count: 39Geometry and surface damage in micro electrical discharge machining of micro-holes(Iop Publishing Ltd, 2009) Öpöz, Tahsin Tecelli; Erden, Abdulkadir; Opoz, Tahsin Tecelli; Erden, Abdulkadir; Department of Mechatronics EngineeringGeometry and subsurface damage of blind micro-holes produced by micro electrical discharge machining (micro-EDM) is investigated experimentally to explore the relational dependence with respect to pulse energy. For this purpose, micro-holes are machined with various pulse energies on plastic mold steel samples using a tungsten carbide tool electrode and a hydrocarbon-based dielectric liquid. Variations in the micro-hole geometry, micro-hole depth and over-cut in micro-hole diameter are measured. Then, unconventional etching agents are applied on the cross sections to examine micro structural alterations within the substrate. It is observed that the heat-damaged segment is composed of three distinctive layers, which have relatively high thicknesses and vary noticeably with respect to the drilling depth. Crack formation is identified on some sections of the micro-holes even by utilizing low pulse energies during machining. It is concluded that the cracking mechanism is different from cracks encountered on the surfaces when machining is performed by using the conventional EDM process. Moreover, an electrically conductive bridge between work material and debris particles is possible at the end tip during machining which leads to electric discharges between the piled segments of debris particles and the tool electrode during discharging.