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Volume 29 (1995)
- Issue 62 Pages 1-
- Issue 61 Pages 1-
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Volume 29, Issue 62
Displaying 1-6 of 6 articles from this issue
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Koji YONEDA, Masanori KUNIEDA1995 Volume 29 Issue 62 Pages 1-8
Published: November 30, 1995
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSIn this paper, the authors propose a numerical method to analyze the machined shape in the Electro-Chemical Jet Machining (ECJM) by calculating the distribution of electric potential in the electrolyte using the Finite Element Method (FEM). In this ECJM, a high pressure electrolyte is jetted from a fine nozzle whose position is numerically controlled against the workpiece, and a pulsating machining current is supplied in the working gap for micro-fabrication.
At first, assuming the voltage drop in the electrolyte the theoretical machining current is calculated by means of integrating the current density, which can be obtained from the potential distribution, over the surface of the workpiece. Secondary, the assumed voltage drop is adjusted so that the theoretical machining current should coincide with the measured machining current. Then, the current density distribution over the surface of the workpiece is recalculated using the corrected voltage drop. Lastly, from the current density distribution the machined shape is found by taking the equivalent dissolution valence of the workpiece and the current efficiency, both of which are obtained from the measured relationship between the current density and the material removal rate, into account. It was found that the shape obtained by the numerical calculation coincided well with the experimental result.View full abstractDownload PDF (2826K) -
Yoshiyuki UNO, Akira OKADA, Izuru KAMEKAWA1995 Volume 29 Issue 62 Pages 9-17
Published: November 30, 1995
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSThe surface generated by electrical discharge machining (EDM) appears to be generally mat. However, the machined surface in EDM with silicon powder mixed fluid becomes glossier and has a smaller surface roughness than that in conventional EDM with kerosine type fluid, which leads to the omission of finish hand lapping of metal mold. The quality of machined surface significantly depends on the kind of workpiece material, but the surface generation mechanism has not yet been made clear sufficiently.
In this study, the effect of silicon powder mixing on the surface generation mechanism is experimentally investigated, analyzing the shape of crater generated by a single pulse discharge, the surface roughness, the machined surface and so on. Main conclusions obtained are as follows:
(1) The gap distance in EDM with silicon powder mixed fluid is larger than that with kerosine type fluid, because of the lower resistivity of the former and the influence of silicon powder arrangement in the gap.
(2) EDM with silicon powder mixed fluid leads to smaller undulation of a crater, because of the smaller impact force acting on the workpiece due to evaporation and expansion of machining fluid.
(3) The more the precipitated carbides in the workpiece are, the larger the surface roughness is, since the carbides come off because of crack propagation due to the frequent heat impact during EDM.
(4) EDM with silicon powder mixed fluid results in the stable machining without short circuit between the electrode and the workpiece.View full abstractDownload PDF (14283K) -
Influence of Atmosphere between Electrodes on Carbon Adhesion and Removal AmountHeng XIA, Masanori KUNIEDA, Nobuhiko NISHIWAKI1995 Volume 29 Issue 62 Pages 18-26
Published: November 30, 1995
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSIn this research, the variations of the tool electrode and workpiece removal amounts due to one discharge with the repetition of discharge are investigated experimentally, in order to find out the influence of the variation of atmosphere between two electrodes on the carbon adhesion amount onto the tool electrode surface. It is found from the experimental results that the removal amount of the tool electrode becomes smaller with the atmosphere variation due to the discharge repetition, which is considered to be caused by the increased carbon amount adhered onto the tool electrode surface. Also, the mechanism of carbon adhesion phenomenon, the influence of the electrode shape on the tool electrode wear, the phenomenon of a greater tool electrode wear at corner, and the reason for the variation of the anode and cathode instantaneous removal rate are discussed.View full abstractDownload PDF (1208K) -
Tatsushi SATO, Yoshihito IMAI, Koji AKAMATSU, Akihiro GOTO, Yoshio OZA ...1995 Volume 29 Issue 62 Pages 27-39
Published: November 30, 1995
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSIn die-sinking EDM, sensing a state of machining is important for both preventing surface damage and improving material removal rate. This paper describes how to sense a state of machining using voltage waveform between a tool electrode and a workpiece. By examining 8 characteristics of the waveform, it is found that the average and the variance of the discharge voltage change acccording to the state of machining. It is also shown that discharge pulses are discriminated into two groups with these two characteristics. In a very bad state of machining, the variance is found to be better sensing parameter than the average. For practical purpose, sensing with high frequency component of the discharge voltage is examined and it is found to have the same capability as sensing with the variance. With the high-frequency method, every pulse is classified into effective or non-effective pulse in realtime. It is shown that the accumulation of effective pulses follows the penetration depth. This proves that the proposed method is practical for sensing a state of machining.View full abstractDownload PDF (1352K) -
Simulating Procedure and ExamplesYasushi IWATA, Haruki OBARA, Tsuyoshi OHSUMI, Yuhji MATSUDA1995 Volume 29 Issue 62 Pages 40-48
Published: November 30, 1995
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSPrecisions of Wire-EDM are spoiled by a wire deflection and a wire vibration during the machining. Examples, these wire behaviors cause a smoothed corner or a smaller radius corner shape and a concave cut wall.
As well known, these wire behaviors are caused by a explosive pressure, a electrostatic force, a electromagnetic force by each discharge and a force caused by flushing of water during Wire-EDM.
In previous some papers, wire behaviors are measured and discussed. And other papers reported methods to solve problems of cutting precisions.
But in spite of these reports, wire behaviors and the influence of EDM conditions on them are not so cleared, also the relation between cutting accuracy and wire behaviors is not so well understood yet.
For these investigations, simulations of Wire-EDM will be useful. But the simulation of Wire-EDM is quite different from them of conventional EDM because all process and repetition from voltage supply to discharge, explosion, machining and wire movement should be considered.
In this report we mainly describe a simulating procedure and few nalyzed results of Wire-EDM.View full abstractDownload PDF (1011K) -
Akihiro GOTO, Takashi YUZAWA, Takuji MAGARA, Kazuhiko KOBAYASHI1995 Volume 29 Issue 62 Pages 49-58
Published: November 30, 1995
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSThis paper describes the phenomena caused by the EDMed sludge. When the electrode comes in touch with the workpiece through the EDMed sludge, the current flows through the sludge and the bridge of sludge is made. When this bridge is made, it brings about the concentration of discharge pulses and damages the machined surface.
In order to improve the machining performance, the method to prevent the formation of the bridge of the sludge and the damege to the surface is discussed. It becomes clear that, when the electrode and the workpiece are shorted, interruption of current is effective to improve machining performance.View full abstractDownload PDF (7359K)
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