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Volume 24 (1990 - 199･･･
- Issue 48 Pages 1-
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Volume 24, Issue 48
Displaying 1-5 of 5 articles from this issue
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Reduction in Residual Stress and Improvement in Degenerated Layers by Heat TreatmentIsao OGATA, Yoshitsugu MUKOYAMA, Masahiko HIHARA1991 Volume 24 Issue 48 Pages 1-13
Published: March 20, 1991
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSAs reported previously, on surface of a workpiece by EDM, serious working defects arise such as residual stress and unusual structurs caused mainly by severe thermal actions and the existence of working fluid, due to EDM.
These degenerated layers are a harmful influence on the mechanical and physical properties; for example, a reduction in the fatigue limit, impact property of materials, thermal fatigue characteristics and various other machine elements. Hence, the quality of products (workpiece) largely depend on the treatment methods of products after EDM.
It is difficult to perfectly remove the working defect in EDM, because the working mechnism of EDM is mainly based on thermal action. Accordingly, it is important to control the generation of working defects by selecting more adequate working conditions, and decrease or remove unusual structures.
However, there are few reports on the reduction and improvement of working defects that ganerate on the surface of workpieces by EDM.
This paper deals with the improvement for degenarated layers on surface of a workpiece. Exactly, behaviors or changes in the residual stress and other unusual structures are investigated by tempering the workpieces after EDM, using X-ray methods.
Consequently, it was proven that the effect of a reduction for residual stress occurred during two-cycle tempering in the case of the low temprature(250°C) condition, and a great reduction occurred when tempering in high temperature (550°C) condition.
Furthermore, it became clear that the stresses due to structure transformation and precipitation of carbides such as Fe3C, M7C3 (M; Fe or Cr) take part in the generation of residual stresses as well as thermal stress which have been suggested as being normal.View full abstractDownload PDF (2752K) -
Development of Wire Electrodischarge Grinding MethodTakahisa MASUZAWA, Masatoshi FUJINO1991 Volume 24 Issue 48 Pages 14-23
Published: March 20, 1991
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSProduction of various micro-spindles is now an urgent problem in relation with the rapid change of industrial parts and tools towards miniaturization. A new micro EDM application is proposed to realize the formation of micro-spindles of which the diameter is between 0.5mm and several micrometers. The principle of the method consists in using a travelling wire as an electrode to form the spindle by EDM. Differently from known WEDM, the wire is guided by a single guide and machining takes place at a guided part of the wire. An extreme precision is guaranteed by this mechanism. According to the similarity to a grinding process, the method is named wire electrodischarge grinding (WEDG). Experimental results proved the applicability of this method to automated production of very fine spindles.View full abstractDownload PDF (2083K) -
Thermal Fatigue Characteristics on the Annealed SKD61 Sample after EDMYoshitsugu MUKOYAMA, Masahiko HIHARA1991 Volume 24 Issue 48 Pages 24-34
Published: March 20, 1991
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSThe electric discharge machining (EDM) are effective processes for making various dies. The apparatus for EDM with high qualities and many functions have been developed recently, and it becomes possible to use them through a series of die making process. The residual solidify melt layer fomed by EDM markedly affects the life of hot die. Thermal fatigue characteristics of samples prepared by making use of EDM have been evaluated using thermal fatigue test, residual stress measurement and scanning electron microscopy. The main results are as follows; (1) The residual stress in the surface layer after EDM was tensile stress, however, it became compression stress after thermal fatigue test more than about 100 cycle. (2) The depth, width and multiplication of cracks increased in proportion to fatigue cycle.View full abstractDownload PDF (2570K) -
Kimihiro WAKABAYASHI, Akio ONISHI, Takahisa MASUZAWA1991 Volume 24 Issue 48 Pages 35-44
Published: March 20, 1991
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSHigh quality micro electric discharge machining (Micro EDM) was achieved by so called Quality Engineering. Micro EDM has been known as an excellent microhole machining method, but repeatability in accuracy was not good enough in case of multi-hole machining. In this report, the influence of machining parameters was investigated by Quality Engineering, and the main factors that influence the repeatability were found out.View full abstractDownload PDF (772K) -
Micro-finishing by High-Frequency AC SourceTakuji MAGARA, Tsuyoshi YATOMI, Kazuhiko KOBAYASHI1991 Volume 24 Issue 48 Pages 45-64
Published: March 20, 1991
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSSubstantive efforts have been directed to improving the performance of EDM over the last twenty yeays and new applications of EDM are being made at an increasing rate. The industrial application of Wire-EDM have been expanding rapidly and offering many new applications. As an example, there in an increasing industrial demand for micro-finishing of less than 1μm Rmax surface roughness by Wire-EDMs to replace conventional jig-grinding operations and polishing processes. This paper describes a detailed research investigation on the use of a high-frequency AC power source for achieving submicron surface roughness based on theoretical analysis and experimental methods.
The current pulse duration of high-frequency AC power source can be extremely short in comparison with the DC power source and allows a submicron machined surface. Reducing the current energy, a high-gloss micro-finished surface of less than 0.2μm Rmax has been achieved.View full abstractDownload PDF (6936K)
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