Sensing a State of Machining with the Voltage Waveform in EDM.

Sato, Tatsushi; Imai, Yoshihito; Akamatsu, K.; Goto, Akihiro; Ozaki, Yoshio; Kobayashi, Kazuhiko

doi:10.2526/jseme.29.62_27

Cited by 3 publications

(4 citation statements)

References 3 publications

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“…It has been reported that the effective discharge contributing to machining is when the discharge voltage during EDM is above 20 V, and when the discharge voltage is less than 19 V, the voltage is abnormal and does not contribute to machining. 16,17 The authors are measuring the effective discharge frequency based on the AND of discharge current and discharge voltage based on this report. 18 In this study, the authors also measured the effective discharge frequency using this method.…”

Section: Resultsmentioning

confidence: 99%

Study on electrical discharge machining for cemented carbide with non-flammable dielectric liquid: Influence of form of oxygen supplied to dielectric liquid on machining

Yoshida

Ishii

Ueda

2017

Proceedings of the Institution of Mechanical Engineers, Part B:

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One of the problems faced in the finish electrical discharge machining of cemented carbide is the slow machining speed due to frequent abnormal discharges and concentrated discharge. To resolve this problem, in this study, attempts were made to supply oxygen to oil-type non-flammable dielectric liquid used in finish electrical discharge machining. First, the effects of the form of the oxygen when it is supplied to the dielectric liquid were investigated. As a result, it was found that when oxygen is supplied to the machining gap in the microbubble state, machining is not affected at all. When dissolved in the dielectric liquid and supplied, machining speed was seen to improve. Next, machining experiments were conducted, varying the percentage of 35 wt% hydrogen peroxide water mixed with the dielectric liquid to change the amount of oxygen in the dielectric liquid. As a result, the following were clarified. (1) The machining speed was six times faster than normal dielectric liquid when 15 wt% of oxygen was mixed; (2) at this time, the tool electrode wear had decreased to one-fifth that of normal dielectric liquid; (3) the surface roughness obtained was below Ra 1 mm regardless of the mixed percentage of hydrogen peroxide water; and (4) better machining characteristics were obtained when the workpiece was set as the positive electrode.

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Section: Resultsmentioning

confidence: 99%

Study on electrical discharge machining for cemented carbide with non-flammable dielectric liquid: Influence of form of oxygen supplied to dielectric liquid on machining

Yoshida

Ishii

Ueda

2017

Proceedings of the Institution of Mechanical Engineers, Part B:

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“…Consequently, as the frontal gap distance at the start of machining is narrow less than 4 μm, this is thought to cause frequent abnormal discharge. Frequent abnormal discharge causes open voltage, ignition delay time, and discharge voltage to become low, 10,11 resulting in low average working voltage, as shown in equation (1). To prevent this, the frontal gap distance is increased, but because the debris concentration at the start of machining is low, even the slightest rise of the Z -axis will disable discharge.…”

Section: Effects Of Differences In Working Voltage Detection Methods Omentioning

confidence: 99%

“…It has been reported that the voltage waveform of the abnormal discharge does not rise to the preset open voltage, 10 as shown in Figure 5(a), thereby enabling differentiation between normal and abnormal discharge because the discharge voltage of abnormal discharge is lower than that of the normal discharge. 11 Thus, in preliminary experiments, the discharge voltage waveforms of abnormal discharge and normal discharge were compared. The results revealed that for abnormal discharge, the discharge voltage is less than 19 V, lower than that of normal discharge, which is 22 V (Figure 5(a)).…”

Section: Experimental Systemmentioning

confidence: 99%

Study on improvement of unstable discharge at start of electrical discharge machining using external high-voltage superimposition method: Comparison of external and internal superimposition methods and influence of externally superimposed voltage on machining characteristics

Yoshida

Ueda

Nagoya

2014

Proceedings of the Institution of Mechanical Engineers, Part B:

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In this study, attempts were made to resolve the problem of unstable discharge at the start of electrical discharge machining using the external superimposition method. In general, electrical discharge machining (EDM), the frontal gap distance is controlled by detecting the working voltage. Electrical discharge machining experiments were thus conducted to compare conventional power supplies for electrical discharge machining machines, which superimpose high voltage on the detected working voltage (internal superimposition) with a power supply that superimposes high voltage externally so that no superimposed voltage is added to the detected working voltage (external superimposition). Differences in abnormal discharge rate, discharge frequency, frontal gap distance, and machining characteristics between the two superimposition methods were also investigated. The results showed that external superimposition is better than internal superimposition in that it widens the frontal gap distance immediately after the start of electrical discharge machining, which decreases the abnormal discharge rate to more or less 0 and increases the discharge frequency in a very short time, and that machining characteristics are better with the external superimposition method. Consequently, the effects of the superimposed voltage level on the machining characteristics of electrical discharge machining applying external superimposition were also investigated. It was found that (1) the discharge frequency increases with increasing superimposition voltage, thereby improving the machining rate; (2) the frontal gap distance increases and the surface roughness of the machined surface improves with increasing superimposition voltage; and (3) the tool electrode wear ratio is the smallest when superimposition voltage is around 200 V.

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“…In many electrical discharge machines, the discharge waveforms are monitored to distinguish the gap phenomena which cannot be seen directly, to control the pulse conditions adaptively to obtain higher machining speed and stability 6) . In this section, we investigated the discharge waveforms when multiple discharge occurred, and attempted to identify the discharge state from them.…”

Section: Discharge Waveformsmentioning

confidence: 99%

Direct Observation of Multiple Discharge Phenomena in EDM using Transparent Electrodes

Mori

Kitamura

Kunieda

et al. 2015

IJEM

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In this paper, multiple discharge phenomena in electrical discharge machining were observed directly through a transparent electrode using a high speed video camera. Multiple discharges occurred with a probability of about 2% in a steady state of normal sinking EDM. The probability was high when the gap width between electrodes was narrowed by the servo feed control and where debris particles were densely-distributed. Moreover, we investigated the change in gap voltage and discharge current waveforms and relative distance between the locations of consecutive discharges, when multiple discharges occurred.

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Sensing a State of Machining with the Voltage Waveform in EDM.

Cited by 3 publications

References 3 publications

Study on electrical discharge machining for cemented carbide with non-flammable dielectric liquid: Influence of form of oxygen supplied to dielectric liquid on machining

Study on electrical discharge machining for cemented carbide with non-flammable dielectric liquid: Influence of form of oxygen supplied to dielectric liquid on machining

Study on improvement of unstable discharge at start of electrical discharge machining using external high-voltage superimposition method: Comparison of external and internal superimposition methods and influence of externally superimposed voltage on machining characteristics

Direct Observation of Multiple Discharge Phenomena in EDM using Transparent Electrodes

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