Fundamental Investigation of EDM Plasmas, Part I: A Comparison between Electric Discharges in Gaseous and Liquid Dielectric Media

Wiessner, Moritz; Macedo, Felipe T.B.; Martendal, Caroline P.; Kuster, Friedrich; Wegener, Konrad

doi:10.1016/j.procir.2017.12.073

Cited by 25 publications

(12 citation statements)

References 11 publications

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“…The emission spectra of a 32 µs discharge is seen in Figure 5. Even though many characteristic lines of metals (Ti, Al, Cu) are visually dominant in the spectra, the plasma has a high amount of carbon and hydrogen, which can be calculated with plasma simulation as shown by (Wiessner et al, 2018). Prominent peaks originating from the dielectric elements can be observed at high spectra resolution with Hα at 656.28 nm, C I at 658.8 nm and C II at 658.3 nm.…”

Section: Resultsmentioning

confidence: 99%

Analysis of Eroded Ti-6al-4v Single Craters and Surfaces in Oil by Electron Microscopy and Optical Emisson Spectroscopy

Wiessner¹

2019

Proceedings of the 25th International Congress of Mechanical Engineering

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The comprehension of the metallurgical transformations of the workpiece can contribute with valuable data for simulation models and for a better understanding of surface creation in electrical discharge machining (EDM). This is necessary to improve the process in the scope of zero defect manufacturing. This work aims to investigate the influence of EDM on the often used but difficult to machine alloy Ti-6Al-4V. Single and multiple sparks in oil are performed and subsequently analyzed with advanced electron microscopy methods and optical high-speed emission spectroscopy. The microscopic analysis of recast layer and heat affected zones in addition to the plasma analyses provides deep insight into the process and contributes with new information about EDM. Results showed that, with the employed machining conditions, phase transformations occur at the surface of the material. Also, a superficial carbide layer was observed exclusively during multi sparks experiments. The performed analyses of metallurgical and topographic aspects of EDM describe its surface integrity, i.e., the condition of a surface generated by this manufacturing process. The emission spectroscopy analysis shows that the erosion plasma consists mostly of the dielectric elements with a high amount of hydrogen, which comes from the breaking of the dielectric hydrocarbon chains. This spectrum suggests the plasma takes part in the formation of the carbide layer.

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Section: Resultsmentioning

confidence: 99%

Analysis of Eroded Ti-6al-4v Single Craters and Surfaces in Oil by Electron Microscopy and Optical Emisson Spectroscopy

Wiessner¹

2019

Proceedings of the 25th International Congress of Mechanical Engineering

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“…This situation is explainable by the occurrence of the hot anode vacuum arcs (HAVA) at the machining area [10]. Micro-breakdown mechanism (subsection 3.2) explained by the modified Paschen's law is actually similar to the vacuum breakdown when the gap distance between the electrodes is less than 5 μm [30,34,38,41,43]. The phenomenon is caused by the electrons from the field emission [10,30,38,41].…”

Section: Polaritymentioning

confidence: 99%

“…distance between the electrodes (pd) as declared by the classical Paschen's law [10,[28][29][30][31][32][33][34]. However, in this situation, the gas pressure is essential since the airflow from the compressed air with 0.0345 MPa pressure assists in maintaining the ideal gap distance between the electrodes (workpiece and wire electrode).…”

Section: Dielectric Fluidmentioning

confidence: 99%

“…3, when 0.0345 MPa dielectric fluid pressure is used, the machining process is much more stable (machining length ≥ 225 μm) with intact wire. It is due to the formation of the micro-breakdown mechanism which is influenced by the gap distance between the electrodes (d) as stated by the modified Paschen's law [28][29][30][31][32][33][34] (Subsection 3.1). When modified Paschen's law is applied in micro-breakdown mechanism, then ion-enhanced field emission plays a crucial role in generating the microplasma [10,28].…”

Section: Dielectric Fluid Pressurementioning

confidence: 99%

“…Thus, ion-enhanced field emission escalates the generation of microplasma [28]. This brief explanation justifies the formation of the μDWEDM microplasmas that lead to the formation of a specific type of vacuum discharge known as HAVA [10,30,[33][34][35]. Hence, the workpiece as the positive polarity while the wire electrode as the negative polarity would be the best option for a stable and smooth machining operation.…”

Section: Polaritymentioning

confidence: 99%

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Stability of micro dry wire EDM: OFAT and DOE method

Banu

Ali

Rahman

et al. 2020

Int J Adv Manuf Technol

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Micro dry wire electrical discharge machining (μDWEDM) is an environmental-friendly machining process where gas is used as the dielectric fluid instead of liquid. In this process, certain modifications of wire electrical discharge machining (WEDM) are required during the machining operation for stable machining. In μDWEDM, the process is considered stable if the machining is continuous without any interruption due to wire breakage or wire lag. However, in the present state of the arts, stable and smooth machining process using μDWEDM remains a critical issue. Hence, the objectives of this research are to establish a stable μDWEDM process using two different experimental approaches: one-factor-at-a-time (OFAT) and design of experiment (DOE) method. The investigation was performed on a stainless steel (SS304) with a tungsten wire as the electrode using integrated multiprocess machine tool, DT 110 (Mikrotools Inc., Singapore). Types of dielectric fluid, dielectric fluid pressure, polarity, threshold voltage, wire tension, wire feed rate, wire speed, gap voltage, and capacitance were the controlled parameters. The machining length of the microchannels was measured using scanning electron microscope (SEM) (JEOL JSM-5600, Japan). Analysis based on these two experimental approaches shows that stable μDWEDM process is achievable when the types of dielectric fluid, dielectric fluid pressure, polarity, threshold voltage, wire tension, wire feed rate, and wire speed remain as the fixed parameters while the capacitance and gap voltage remain as the controlled parameters.

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