Electrochemical Small Diameter Deep Hole Drilling of Powder Metal Steel

In this study, a new hybrid electrochemical drilling (ECD) method is proposed. The method makes use of a tubular tool capable of rotating and an electrolyte flushing through the inner hole at the same time. The designed and manufactured small size ECD machine’s most important features are the regulation of the tool feed rate via current feedback control and the use of a rotating tubular tool with internal electrolyte flushing. The powder metal (PM) FLN2 4405 steel was drilled by using a brass tubular tool with various combinations of machining parameters such as machining voltage, electrolyte concentration and flushing pressure, and tool rotation speed. The machining performance outputs, namely, material removal rate (MRR), average radial overcut (RADOC), conicity (CO) and hole geometries were calculated and compared in different machining conditions. The results have shown that the aforementioned variables had a direct impact on the machining performance outputs in ECD. In all experiments, MRR increased with an in increase in machining voltage, tool rotational speed, electrolyte concentration and flushing pressure. RADOC values decreased with the rotational speed of the tool. The present study shows that deep holes with precise geometries and dimensions can be drilled successfully by employing the proposed hybrid ECD method. The method is economical and environmentally friendly since it requires low machining current values (0.1 to 0.7A) and a small amount of non-hazardous halide salt solutions instead of acidic solutions throughout the drilling process

Computer aided evaluation and computer control of electric discharge machining (E.D.M.) process by using properties of pulse trains.

Ph.D. - Doctoral Progra

Experimental Investigation on Wire Electric Discharge Machining of Biodegradable AZ91 Mg Alloy

The AZ91 magnesium alloy, used commonly as a biodegradable material in biomedical applications, is generally formed by conventional casting method (CCM) and high-pressure die casting method (HPDCM). The AZ91 alloys exhibit poor machinability with conventional chip removal methods since they degrade at elevated temperatures. In this study, the wire electric discharge machining (WEDM) was presented as a candidate process to machine the AZ91 alloy since no cutting stresses and plastic deformations were applied by the cutting tool to the part causing elevated temperatures. In this context, the WEDM machinability of the AZ91 alloy samples produced by cold chamber HPDCM and CCM at different process parameters, was experimentally investigated. The machining performance outputs (the machining current (I), the machining rate (MR), the average surface roughness (R-a), and surface topography) were found for the varying process parameters [pulse time (t(s)), pulse-off time (t(off)), dielectric flushing pressure (P-d), and wire speed (V-w)]. The present study revealed that the I and the MR were significantly dependent on the density, the porosity, and the micro structure of the samples, and the HPDCM samples gave the higher MR and the smoother surface than that of the CCM

The comparison of performance of electrolytic cu and cube tool electrodes in electric discharge machining of ti6al4v alloy [Ti6al4v alaşımının elektro erozyon ile işlemesinde elektrolitik cu ve cube takım elektrotlarının performansının karşılaştırılması]

The most crucial cost element of Electric Discharge Machining (EDM) is the production of tool electrode (shortly electrode). Copper, its alloys, and graphite are the most commonly used electrode materials. Selecting the proper electrode material with low production and material cost, high workpiece material removal rate (MRR) and low tool electrode wear rate (TWR) is key to reducing machining costs with EDM. In this study, the EDM performance of CuBe tool electrodes in the machining of Ti6Al4V alloy was experimentally investigated in comparison to electrolytic Cu (E-Cu) electrodes for different pulse time (ts) and discharge current (I) settings. An increase in MRR and a decrease in TWR and relative wear (RW=TWR/MRR) were observed in machining with CuBe electrodes. However, the high raw material cost of CuBe alloy is an essential drawback in widely using these electrodes in industrial applications. A new performance index formulation is introduced for EDM applications that factor in the production cost of the electrode and its life (i.e., RW). According to our results, the CuBe could be used advantageously as the electrode material at medium current settings. However, at low and high current settings, the low raw material cost of E-Cu makes it more favorable. © 2021, TUBITAK. All rights reserved