Predictive topography impact model for Electrical Discharge Machining (EDM) of metal surfaces
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.433
Predictive topography impact model for Electrical Discharge Machining (EDM) of metal surfaces Johan Bäckemo1,2, Matthias Heuchel1, Markus Reinthaler1,3, Karl Kratz1, and Andreas Lendlein1,2,* 1Institute of Biomaterial Research and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Kantstrasse 55, 14513 Teltow, Germany
2Institute
of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany
3Department
of Cardiology, Campus Benjamin Franklin, Charité Berlin, Berlin, Germany
* To whom correspondence should be addressed: Prof. Dr. Andreas Lendlein, email: [email protected]
ABSTRACT
Electrical discharge machining (EDM) is a method capable of modifying the microstructure of metal surfaces. Here, we present a predictive computer supported model of the roughness generated on the surface by this process. EDM is a stochastic process, in which charge generated between a metallic substrate and an electrode creates impacts, and thus is suitable for modeling through iterative simulations. The resulting virtual, modified surface structures were evaluated for roughness. Curvatures were analyzed using Abbott-Firestone curves. Three radii of impacts (10, 20, 30 μm) and two values for the depth to radius ratio (0.1, 0.3) were used as input parameters to compute a total of six simulations. It was found that the roughness parameters followed an inverse exponential trend as a function of impact number, and that the strongly concave curvatures reached equilibrium at an earlier impact number for lower depth to radius ratios.
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INTRODUCTION Electrical Discharge Machining (EDM) is a process in which a metallic substrate is brought into close vicinity with an electrode and subjected to repeated sparks, which iteratively removes material – ultimately creating a rough surface [1]. This process is commonly used for difficult-to-machine materials, tooling of complex parts and especially highly accurate micro parts [2]. The roughness of the surface is dependent on many variables such as electrical parameters (voltage, pulse duration, and dielectric influence [3]) and duration of treatment. EDM is a random process, and a probable statistical distribution governs the geometrical parameters and must be taken into account – but as a first approximation the parameters were fixed for each impact for a given simulation. The size of each individual impact is dependent on the charge built up before each spark [3] which is a function of the said electrical parameters, and the number of sparks is dependent on the duration of treatment. Thus, the size of impact and duration of treatment were considered for simulation in this paper. It is of interest to researchers who wish to creat
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