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Meyrin, Switzerland

Maradia U.,Inspire AG | Taborelli M.,GF Machining Solutions | Boos J.,Inspire AG | Buettner H.,Inspire AG | And 4 more authors.
Procedia CIRP | Year: 2016

The low electrode wear strategy based on a carbonaceous layer formation on electrodes considerably increases resource efficiency in the conventional die-sinking EDM. However, the smallest electrode projection area Ap for using the strategy is limited to 0.1 mm2 and maximum pulse current 3A, possibly due to the pulse re-opening phenomenon. In this work, using a novel generator circuit, pulse re-openings have been restricted up to pulse durations 100 μs and a current of 1A. Hence, the performance of conventional electrode materials is evaluated in order to push the limits of the low wear strategy. However, when using graphite and copper infiltrated graphite microelectrodes, bending of the electrodes is observed, especially in the tip region. The simulation of temperature in the microelectrodes suggests abnormal carbonaceous build up process. This explanation is also concurrent to the observation of a process instability resulting in irreproducible electrode wear behaviour. For copper microelectrodes, another phenomenon is observed where overcuts are produced in the eroded cavities. These overcuts are produced by sparks with high discharge voltage. Sliding of the plasma channel from the electrode corners to the side surfaces is proposed to cause such discharges and overcuts. Thus, underlying mechanisms limiting the low wear strategy in micro-EDM are identified. © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license. Source


Klocke F.,RWTH Aachen | Holsten M.,RWTH Aachen | Welling D.,RWTH Aachen | Klink A.,RWTH Aachen | Perez R.,GF Machining Solutions
Procedia CIRP | Year: 2015

The demand for higher efficiency in aircraft propulsion engines leads to materials with increasing thermomechanical strengths. The intermetallic gamma titanium aluminides (γ-TiAl) are attributed a great potential in this field, but the machinability of γ-TiAl by conventional processes is challenging. One alternative manufacturing technology for these materials, especially for cavities with a high aspect ratio such as seal slots in turbine blades, is sinking EDM. Since the process stability in terms of a constant feed rate is not guaranteed for high plunging depths, this paper focuses on an experimental approach to investigate interdependencies between common process control strategies and process output parameters (e.g. feed rate, surface integrity) during the machining of cavities with high aspect ratios in the intermetallic alloy TNM-B1. © 2015 The Authors. Published by Elsevier B.V. Source


Caggiano A.,University of Naples Federico II | Teti R.,University of Naples Federico II | Perez R.,GF Machining Solutions | Xirouchakis P.,Ecole Polytechnique Federale de Lausanne
Procedia CIRP | Year: 2015

In the framework of zero-defect manufacturing, an advanced sensor monitoring procedure aimed at detecting the process conditions leading to surface defects in Wire Electrical Discharge Machining (WEDM) is proposed. WEDM experimental tests were carried out with the employment of a multiple sensor monitoring system to acquire voltage and current signals in the gap between workpiece and wire electrode at the high sampling rate of 100 MHz. In order to extract from the acquired signals the most relevant features that can be useful in the identification of abnormal process conditions, an advanced sensor signal processing methodology based on signal feature extraction for the construction of sensor fusion pattern vectors is proposed and implemented. © 2014 The Authors. Source


Giandomenico N.,University of Applied Sciences and Arts Western Switzerland | Gorgerat F.-H.,University of Applied Sciences and Arts Western Switzerland | Lavazais B.,GF Machining Solutions
Procedia CIRP | Year: 2016

Commonly, on Die Sinking Electrical Discharge Machining (DS EDM), a special generator enables current pulses in sinusoidal or triangular shapes, only in a single polarity. The duration and the amplitude are adapted to the machining sequence, allowing the achievement of different surface finishing. By using a new configuration, it is shown that if one applies pulses of current in both polarities, related together but with a certain ratio between the positive and the negative peaks current, machining results could be improved. The purpose of this new generator is the ability to control with great flexibility the generation of these pulses, in terms of durations, amplitudes and sequence. These parameters can be independently selected for the positive and negative polarity and modified during the machining. One can also choose a special predefined or settable sequence of pulses. The generator includes also the double polarity ignition and the high-speed gap breakdown detection. An embedded programmable circuit (FPGA) provides a high-speed control of the sequence. Machining tests have been performed in order to explore and quantify different sequences of pulses in terms of machining results and performances achieved, compared against the current situation. © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license. Source


Caggiano A.,University of Naples Federico II | Caggiano A.,Fraunhofer Joint Laboratory of Excellence on Advanced Production Technology Fh J LEAPT | Perez R.,GF Machining Solutions | Segreto T.,Fraunhofer Joint Laboratory of Excellence on Advanced Production Technology Fh J LEAPT | And 4 more authors.
Procedia CIRP | Year: 2016

Wire electrical discharge machining (WEDM) is investigated in the perspective of zero-defect manufacturing with the scope to detect anomalous process conditions leading to typical defects generated during WEDM, i.e. the occurrence of lines and marks on the resulting workpiece surface. A multiple sensor monitoring system is employed to acquire high sampling rate sensorial data relative to signals of voltage and current in the gap between workpiece and wire electrode. An advanced signal processing methodology is implemented to extract and select the most relevant features useful to identify the undesired process conditions through a cognitive pattern recognition paradigm. © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license. Source

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