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    Controlling short circuiting, oxide layer and cavitation problems in electrochemical machining of freeform surfaces
    (Elsevier Science Sa, 2018) Demirtas, Hasan; Yilmaz, Oguzhan; Kanber, Bahattin
    Freeform surfaces are widely used in the design of complex parts to satisfy aesthetic and functional requirements, particularly in automotive, aeronautics, and die-mould industries. Traditional machining of freeform surfaces is gradual and involves significant manual interactions. Non-traditional machining processes such as electro-chemical machining (ECM) enable to increase productivity and cost effectiveness when machining of freeform surfaces as well as hard to cut materials in large scale production. However, some manufacturing problems may be arisen during ECM process and the control mechanisms for preventing such problems (short circuiting, oxide layer and cavitation problems) are very critical for achieving correct form of freeform surfaces and a complete process without any faults in ECM process. This paper firstly investigates possible causes of the ECM drawbacks such as short-circuiting, cavitation, and oxide-layer formation while ECMing of freeform surfaces and then proposed solutions in order to prevent these drawbacks are discussed. A closed-loop control system was developed using a micro-controller board in order to control short-circuiting. Flow analysis was carried out using an ANSYS (R) Workbench and four different types of apparatus were designed for preventing the cavitation formation. The conducted experiments showed that the voltage feedback was alone insufficient to prevent shortcircuiting during high feed rates. In addition, it was observed that the velocity distribution prevented the cavitation when the velocity was adequate within the gap domain. Additionally, it has been showed that the oxide layer generation was associated with the amount of contamination in the electrolyte solution.
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    A simplified mathematical model development for the design of free-form cathode surface in electrochemical machining
    (Taylor & Francis Inc, 2017) Demirtas, Hasan; Yilmaz, Oguzhan; Kanber, Bahattin
    High-performance machining of free-form surfaces is highly critical in automotive, aerospace, and die-mold manufacturing industries. Therefore, electrochemical machining (ECM) process has been used in such cases in that sense. The most important challenges of using ECM process are the lack of accuracy and difficulty in designing proper machining tool (cathode) surfaces. In this article, a simplified mathematical model is presented to obtain a cathode surface for ECM of free-form surfaces which have high curvatures. In this theoretical approach, the finite-element method (FEM) is used to solve the 3-D Laplace equation and to determine the potential distribution between the anode (workpiece) and cathode (tool) surfaces. A compact and simple program was developed to obtain a proper cathode surface that only requires some nodal coordinates on the anode surface and boundary conditions. In this work, a trial cathode surface is constructed for a given gap distance. For the determined ECM parameters, cathode shape that satisfies the boundary conditions is obtained for the 45(th) layer. The results are compared with the literature and ANSYS Workbench for verification. The developed theoretical approach benefits simpler and faster FEM solutions, accurate cathode surface, and consequently correct form of machined surface.