WO2008026323A1 - Dispositif d'usinage par décharge électrique - Google Patents

Dispositif d'usinage par décharge électrique Download PDF

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Publication number
WO2008026323A1
WO2008026323A1 PCT/JP2007/000945 JP2007000945W WO2008026323A1 WO 2008026323 A1 WO2008026323 A1 WO 2008026323A1 JP 2007000945 W JP2007000945 W JP 2007000945W WO 2008026323 A1 WO2008026323 A1 WO 2008026323A1
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WO
WIPO (PCT)
Prior art keywords
electrode
spindle
workpiece
electric discharge
gap
Prior art date
Application number
PCT/JP2007/000945
Other languages
English (en)
Japanese (ja)
Inventor
Xiaodong Yang
Masanori Kunieda
Sadao Sano
Ichiro Araie
Original Assignee
Sodick Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sodick Co., Ltd. filed Critical Sodick Co., Ltd.
Publication of WO2008026323A1 publication Critical patent/WO2008026323A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
    • B23H1/00—Electrical discharge machining, i.e. removing metal with a series of rapidly recurring electrical discharges between an electrode and a workpiece in the presence of a fluid dielectric
    • B23H1/02—Electric circuits specially adapted therefor, e.g. power supply, control, preventing short circuits or other abnormal discharges
    • B23H1/022—Electric circuits specially adapted therefor, e.g. power supply, control, preventing short circuits or other abnormal discharges for shaping the discharge pulse train

Definitions

  • the present invention relates to an electric discharge machining (EDM) apparatus for machining a workpiece by intermittently generating an electric discharge in a machining gap formed between a tool electrode and the workpiece.
  • EDM electric discharge machining
  • the present invention relates to an electric discharge machining apparatus capable of generating a discharge of very small energy in a machining gap.
  • An electric discharge is generated by applying a pulse voltage or an alternating voltage between machining gaps filled with a dielectric liquid. Along with the occurrence of electric discharge, a current / loss with a high current density flows through the machining gap for a predetermined on-time. As a result, a minute amount of workpiece material melts and is washed away by the dielectric liquid. By removing the material, an indentation called a crater is formed on the workpiece surface. By repeatedly forming such a crater, a desired shape is processed into a workpiece.
  • Non-Patent Document 1 describes electric discharge machining (micro E D M) for forming a micro-sized shape of 500 m or less on a workpiece.
  • a device that performs micro-EDM is characterized by the ability to form very small craters. The size of the crater depends on the discharge energy supplied to the machining gap. Discharge energy E is expressed by equation (1).
  • V d is the voltage between machining gaps during discharge
  • I is the peak of the current pulse
  • T is the on-time of the current pulse.
  • the voltage V d is determined by the physical properties of the tool electrode and the workpiece and is in the range of 10 V to 40 V.
  • a current I of at least 50 O mA is required. Therefore, attempts have been made to minimize on-time to form smaller craters.
  • FET field effect transistor
  • the other is an RC circuit that obtains a current pulse by releasing the charge stored in the capacitor.
  • the energy E c stored in the capacitor is the upper limit of the discharge energy E.
  • the maximum energy E c that can be stored in the capacitor with the capacitance C is expressed by equation (2).
  • the RC circuit can generate a discharge with much smaller energy than the switching circuit.
  • an RC circuit can generate a discharge with as little energy as the capacitance C of the capacitor is reduced.
  • Non-Patent Documents 2 to 4 and Patent Documents 1 and 2 describe a micro E DM that uses electrostatic induction power supply to reduce stray capacitance and stray inductance.
  • a conventional electric discharge machining method using electrostatic induction feeding will be described with reference to FIGS.
  • a first electrode including a rotatable conductive spindle 3 and a tool electrode 1 attached to the lower end of the spindle 3 is vertically supported.
  • the tool electrode 1 is positioned very close to the workpiece 2, and the size of the machining gap formed between the tool electrode 1 and the workpiece 2 is 10 m or less.
  • the spindle 3 is passed through a cylindrical power supply electrode 4 which is a second electrode.
  • the feed electrode 4 is capacitively coupled to the spindle 3.
  • the gap formed between the spindle 3 and the feeding electrode 4 has such a size that no electric discharge is generated in the gap when a voltage is applied.
  • the size of the void is approximately several hundreds larger than the processing gap; U m.
  • Patent Document 2 states that the gap needs to have a capacitance approximately 100 times that of the gap so as not to affect the capacitance of the machining gap.
  • a power supply for electrical discharge machining is connected to the feed electrode 4 and the workpiece 2.
  • V represents the voltage of the power supply and R. Represents the internal resistance of the power supply.
  • the arrows indicate the movement of electrons, and the solid arrows indicate the movement of electrons during discharge.
  • the lower end of 1 is positively charged, and the workpiece 2 facing the tool electrode 1 is negatively charged.
  • a discharge occurs in the machining gap due to this potential difference, electrons move from the workpiece 2 to the tool electrode 1 and further to the spindle 3 as shown in FIG. 5 (B).
  • the tool electrode 1 and the spindle 3 are negatively charged as shown in FIG. 5 (C).
  • Work 2 and feed electrode 4 are positively charged by the emission of electrons.
  • electric discharge occurs again in the machining gap due to this potential difference, electrons move from the tool electrode 1 and the spindle 3 to the workpiece 2 as shown in FIG. 5 (D).
  • Non-Patent Document 2 reports an experiment on electric discharge machining using electrostatic induction power feeding. As a result of the experiment, a hole having a surface roughness (R z) of 0.272 m and a depth of 6.5 m was added.
  • the experimental conditions are as follows.
  • FIG. 6 shows the voltage between the machining gaps (“gap voltage”) in the experiment.
  • the symbols (A), (B), (C), and (D) in FIG. 6 correspond to the same symbols in FIG. By repeating the cycle from (A) to (D), fine holes were machined. Discharge occurs at a minute time indicated by symbols (B) and (D) in Fig. 6.
  • the electric discharge machining apparatus of FIG. 5 generates electric discharge in the machining gap without bringing an energizing brush or the like into contact with the spindle 3. Therefore, a highly accurate micro-EDM can be realized without causing energizing brushes to cause shaft runout of spindle 3.
  • a displacement current flows between the feed electrode 4 and the spindle 3, but no conduction current flows. For this reason, stray capacitance and stray inductance do not have an undesirable effect on the discharge.
  • Discharge energy E is feed denden electrode 4 and the capacitance between the spindle 3 C and is determined by only the capacitance C 2 between the tool electrode 1 and the workpiece 2.
  • the power supply voltage V is divided as shown in Equation (3).
  • Non-Patent Document 3 discloses that the electrostatic capacitance C is changed by changing the length and inner diameter of the feeding electrode 4.
  • Non-Patent Document 1 Takahisa Masuzawa, “Outline of Micro Electrical Discharge Machining Technology” Journal of Electrical Machining Society, Vol. 35, No. 80, pp. 5-20, published on January 30, 2001
  • Non-patent document 2 Norihiro Hanada, 2 others, “Development of micro-EDM using electrostatic induction power supply”, 2005 JSPE Spring Conference Annual Lecture, 1 323-1 324, Heisei 1 Published on March 1, 2007
  • Non-Patent Document 3 Norihiro Hanada, 2 others, “Development of micro-EDM using electrostatic induction power supply”, Journal of Japan Society for Precision Engineering, Vol. 72, No. 5, 636_640, May, 1998 5 Issue
  • Non-Patent Document 4 Yasuhiko Hayasaka and 3 others, “Additional Characteristics of Micro-Electric Discharge Machining Using Electrostatic Induction Feeding”, Proc. Issued March 1, 1996
  • Patent Document 1 Japanese Patent Laid-Open No. 2000_21 8438, paragraphs [0025]-[00 28] and FIG.
  • Patent Document 2 Japanese Unexamined Patent Application Publication No. 2004 _ 1 2231 6
  • An object of the present invention is to provide an electric discharge machining apparatus capable of generating an electric discharge in a machining gap using electrostatic induction power feeding, which can generate even smaller discharge energy.
  • an electric discharge machining apparatus for machining a workpiece by generating electric discharge in a gap formed between the tool electrode (1) and the workpiece (2).
  • a power source (5) connected to the second electrode and the workpiece
  • a third electrode (8) that is formed between the spindle and a gap having a size that does not cause discharge, and is capacitively coupled to the spindle;
  • An electrical discharge machining device that processes a workpiece by generating an electric discharge in the machining gap includes a conductive spindle (3) with a tool electrode attached,
  • a power source (5) connected to the second electrode and the workpiece
  • It includes a capacitor (7) connected in parallel with the machining gap between the spindle and the workpiece.
  • FIG. 1 is a diagram showing an electric discharge machining apparatus according to the present invention.
  • FIGS. 2 (A) and 2 (2) are diagrams showing an equivalent circuit of the electric discharge machining apparatus of FIG.
  • FIG. 3 shows voltage waveforms at various parts of the electric discharge machining apparatus of FIG.
  • FIG. 4 (A) is a circuit diagram partially showing the circuit of FIG. 2
  • FIG. 4 (B) is a circuit diagram showing a modification of the circuit of FIG. 4 (A)
  • FIG. 4 (C) is a partial equivalent circuit of the electric discharge machine in Fig. 5.
  • FIG. 5 is a view showing a conventional electric discharge machining apparatus.
  • FIG. 6 is a timing chart showing the voltage between the tool electrode and the workpiece in FIG.
  • a power supply 5 for electric discharge machining is connected to a power supply electrode 4 as a second electrode and a work 2 in order to apply a voltage.
  • the feed electrode 4 is capacitively coupled to the spindle 3.
  • Work 2 is placed on a precision movable table 6.
  • Capacitor 7 is provided in parallel with the machining gap to reduce the discharge energy.
  • Capacitor 7 is connected to work 2 and third electrode 8.
  • the third electrode 8 is a ring and is capacitively coupled to the spindle 3.
  • the rotatable spindle 3 passes through the third electrode 8 together with the feeding electrode 4.
  • the third electrode 8 is not in contact with the spindle 3 and does not apply a lateral load to the spindle 3.
  • the size of the gap formed between the spindle 3 and the third electrode 8 is larger than the machining gap to the extent that no discharge is generated in the gap due to the application of voltage.
  • C is a capacitance between the feeding electrode 4 and the spindle 3
  • C 2 is a capacitance between the tool electrode 1 and the workpiece 2
  • C 3 is a capacitance between the third electrode 8 and the spindle 3
  • C 0 represents the capacitance of capacitor 7.
  • Fig. 2 (A) is an equivalent circuit of the EDM device in Fig. 1.
  • Fig. 2 (B) is an equivalent circuit of the EDM device in Fig. 1 when electric discharge is generated in the machining gap.
  • a theoretical analysis of the circuit of FIG. 2 was performed.
  • a rectangular wave voltage pulse with a period of 200 s and an amplitude of 230 V is applied with a duty ratio of 50%.
  • the machining gap resistance R was assumed to be 100 ⁇ and the gap voltage V d was 2 OV.
  • the internal resistance R 0 of the power supply was assumed to be 1 ⁇ .
  • the delay time from when voltage was applied to when discharge occurred in the machining gap was assumed to be 1/4 of one cycle, that is, 50 s.
  • C was 7.5 p F
  • C 2 was 0.06 p F
  • C 3 was 0.75 p F
  • C 0 was 20 p F.
  • the gap voltage V C2 (solid line), the voltage V C3 between the third electrode 8 and the spindle 3 (dotted line), and the voltage V acting on the capacitance C 0 co ( —Dash- dot line) was obtained by theoretical analysis.
  • V C2 When the machining gap was open, V C2 was ⁇ 1 88.26 V, V C3 was ⁇ 1 81.46 V, and V C0 was ⁇ 6.80 V.
  • V C2 When discharge was generated in the machining gap, V C2 was ⁇ 20V, V C3 was ⁇ 19.28V, and V co was ⁇ 0.72V.
  • the voltage V C2 is the capacitance C 3 and C. The pressure is divided by.
  • FIG. 4A partially shows the circuit of FIG. Table 1 shows the Figure 4 when the electrostatic capacitance C 3 is made larger from 0. 75 p F 7. to 5 p F of (A), changes in the discharge machining Nerugi. It is possible to generate a smaller discharge energy by greater than the electrostatic capacitance C 3.
  • Capacitances C 3 and C 0 are connected in series in FIG. 4A, and their combined capacitance is smaller than capacitance C 0 . Therefore, an electric discharge machining apparatus in which the capacitance C 3 is removed to generate smaller electric discharge energy is shown in FIG. 4 (B).
  • the capacitor 7 is connected in parallel to the machining gap between the spindle 3 and the workpiece 2.
  • Capacitor 7 is connected to rotating spindle 3 by an energizing brush. Alternatively, the capacitor 7 may be connected to the non-rotating spindle 3 by soldering, for example.
  • FIG. 4C shows a conventional electric discharge machining apparatus that does not include the third electrode 8 and the capacitor 7. As shown in Table 2, EDM energy was determined for each EDM in Fig. 4, and the average crater size was measured. The electric discharge machine shown in Fig. 4 (B) generates a smaller crater by generating smaller discharge energy.
  • the present invention is not limited to the disclosed form. Many modifications and variations are possible with reference to the above description.
  • the third electrode 8 can also be regarded as forming one capacitor that should replace the capacitor 7. Therefore, the capacitor 7 may be removed, and the third electrode 8 may be connected to the work 2 by a conductive wire.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

Abstract

La présente invention concerne un dispositif d'usinage par décharge électrique pour usiner une pièce (2) par la génération d'une décharge dans un espace d'usinage qui est formé entre une électrode-outil (1) et la pièce. Ce dispositif d'usinage à décharge électrique comporte une broche conductrice (3) à laquelle l'électrode-outil est fixée, une électrode d'alimentation (4) couplée de façon capacitive avec la broche et présentant un écartement dont la dimension empêche la génération d'une décharge, et une alimentation (5) couplée à l'électrode d'alimentation et à la pièce. Ce dispositif d'usinage par décharge électrique comporte en outre une troisième électrode (8) couplée de façon capacitive avec la broche et présentant un écartement dont la dimension empêche la génération d'une décharge, et un condensateur (7) couplé à la troisième électrode et à la pièce.
PCT/JP2007/000945 2006-08-31 2007-08-31 Dispositif d'usinage par décharge électrique WO2008026323A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2006-235772 2006-08-31
JP2006235772A JP5084202B2 (ja) 2006-08-31 2006-08-31 放電加工装置

Publications (1)

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WO2008026323A1 true WO2008026323A1 (fr) 2008-03-06

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* Cited by examiner, † Cited by third party
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JP2013160377A (ja) * 2012-02-08 2013-08-19 Honda Motor Co Ltd ベルト式無段変速機

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61260923A (ja) * 1985-05-15 1986-11-19 Mitsubishi Electric Corp 放電加工用電源
JPS6284918A (ja) * 1985-10-08 1987-04-18 Amada Co Ltd 放電加工装置の加工状態検出方法及びその装置
JPH01234113A (ja) * 1988-03-11 1989-09-19 Matsushita Electric Ind Co Ltd 微細放電加工装置
JPH10202432A (ja) * 1997-01-27 1998-08-04 Matsushita Electric Ind Co Ltd 微細穴放電加工方法とその装置
JP2000061732A (ja) * 1998-08-18 2000-02-29 Mitsubishi Electric Corp 放電加工装置
JP2000218438A (ja) * 1999-01-26 2000-08-08 Mitsutoyo Corp 放電加工機
JP2004122316A (ja) * 2002-10-04 2004-04-22 Mitsutoyo Corp 放電加工装置

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61260923A (ja) * 1985-05-15 1986-11-19 Mitsubishi Electric Corp 放電加工用電源
JPS6284918A (ja) * 1985-10-08 1987-04-18 Amada Co Ltd 放電加工装置の加工状態検出方法及びその装置
JPH01234113A (ja) * 1988-03-11 1989-09-19 Matsushita Electric Ind Co Ltd 微細放電加工装置
JPH10202432A (ja) * 1997-01-27 1998-08-04 Matsushita Electric Ind Co Ltd 微細穴放電加工方法とその装置
JP2000061732A (ja) * 1998-08-18 2000-02-29 Mitsubishi Electric Corp 放電加工装置
JP2000218438A (ja) * 1999-01-26 2000-08-08 Mitsutoyo Corp 放電加工機
JP2004122316A (ja) * 2002-10-04 2004-04-22 Mitsutoyo Corp 放電加工装置

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JP5084202B2 (ja) 2012-11-28
JP2008055551A (ja) 2008-03-13

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