JP5466255B2 - Electric discharge control method for fine hole electric discharge machine and power supply device for fine hole electric discharge machining - Google Patents

Description

  The present invention relates to a discharge control method for a fine hole electric discharge machine and a power supply device for fine hole electric discharge machining.

  Since the fine hole electric discharge machining apparatus uses water as a machining fluid, there is a problem that the workpiece is oxidized and corroded by electrolytic action and the surface of the workpiece is discolored (see FIG. 9). Further, according to the narrow hole electric discharge machining apparatus described in Patent Document 1, the average voltage in the machining gap is reduced by changing the pulse width of the positive polarity according to the state of the machining gap consisting of the workpiece and the electrode. Thus, means for weakening the electrolytic action have been proposed.

  On the other hand, assuming that the electrolytic action can be suppressed more effectively than the voltage pulse applying means described in Patent Document 1, an average voltage in the machining gap is reduced to 0 by alternately applying positive and negative polarity pulse voltages to the machining gap. There are a thin hole electric discharge machining device and a power supply device for electric discharge machining (for example, FIG. 4).

Power supply 101 for electrical discharge machining of small hole electric discharge machining apparatus 100 shown in FIG. 4 includes a positive pulse power supply 102 to output voltage is E _1, a negative pulse power supply 103 output voltage is E _2, the positive electrode side of the positive pulse power supply 102, Yes positive pulse current limiting resistor R ₁ and the positive pulse blocking diode elements D ₁ and switching element T _R1 is connected in series, similarly, the power supply and the negative pulse A negative pulse current limiting resistor R ₂ , a negative pulse backflow prevention diode element D ₂ , and a switching element TR ₂ are connected in series to the positive electrode side 103.

The output side of the switching element _{T R1} is Yes connected via wires 104 and 105 to the workpiece 106, the negative electrode side of the positive pulse power supply 102 is connected to the electrode 109 through an electric wire 107, 108 . Further, the output side of the switching element _{T R2} is Yes connected to the electrode 109 through an electric wire 107, the negative electrode side of the negative pulse power supply 103 is connected via a wire 104, 105 on the workpiece 106 is there.

Incidentally, the negative electrode side and the output side of the switching element T _R2 of the positive pulse power supply 102 is connected by wire 107, the negative side of the output side and the negative pulse power supply 103 of the switching element T _R1 is connected by wire 104 Yes. Further, a discharge energy discharging capacitor 110 having a capacitance C is provided between the electric wires 105 and 108. Further, the power supply apparatus 101 is provided with machining pulse generation means 111 that generates the machining pulse timing by controlling the switching elements T _R1 and T _R2 .

ここに、Ｔ１は任意の時間。 The purpose of the conventional discharge machining power supply apparatus is to control the average voltage V _W of the machining gap so that the 0 volts. That is,

Here, T1 is an arbitrary time.

In the above power supply apparatus 101, assuming that the capacitor 110 is not provided, for convenience, E ₁ = E ₂ and R ₁ = R _{2 are set} , and the positive pulse ON time t _PP and the negative pulse time OFF time t _NP Are equal (t _PP = t _NP ), the interelectrode voltage between the workpiece 106 and the electrode 109 is V _W (t), and the average voltage is V _W , as shown in the time chart of FIG. The average voltage V _W when the pulse voltage and the negative pulse voltage are applied alternately is expressed by the following equation (2).

  In the case of small-hole electrical discharge machining equipment, the purpose of the positive pulse is to generate dielectric breakdown between the electrodes and excavate the workpiece with the discharge current energy, and the purpose of the negative pulse is to connect between the poles generated by the positive pulse. By canceling out the positive voltage component, the average voltage between the electrodes is stabilized at 0 volts to suppress the electrolytic action.

A capacitor 110 is inserted between the electric wires 105 and 108 of the power supply device 101. Then, the electrostatic capacitance C of the capacitor 110 is for sufficiently larger than that of the machining gap clearance, inter-electrode voltage V _W can be regarded as the voltage across the capacitor 110.

Now, in the power supply device 101, an output voltage E ₁ of the positive pulse power supply 102, a charge capacitance is stored in the capacitor 110 in the RC circuit composed of a capacitor 110 and a positive pulse current limiting resistor R ₁ of C If Q is set, the following differential equation holds.
(Equation 3)
R ₁ (dQ / dt) + Q / C = E ₁ (3)
Here, t is time.

When the differential equation (3) is solved with t = 0 and Q = 0 as initial conditions, the following equation (4) is obtained.
(Equation 4)
Q = CE ₁ (1-e− ^{t / CR1} ) (4)

From V _W = Q / C, the interelectrode voltage V _W is
(Equation 5)
V _W = E ₁ (1-e− ^{t / CR1} ) (5)
Here, the time constant τ is CR ₁ and E ₁ is the final value at t-> ∞. The time of t = τ, is _{V W} = 0.632E _1.

Further, the current i _C flowing into the capacitor 110 can be obtained by differentiating the equation (4) with respect to time t.
(Equation 6)
i _C = (E ₁ / R ₁ ) e ^{−t / CR} ₁ (6)
Is required.

FIG. 6 is a graph of the interelectrode voltage V _W (Formula 5) and the current i _C flowing into the capacitor (Formula 6) when the switching element TR ₁ is turned on from OFF at time t = 0. From this graph, the rise delay of the inter-electrode voltage V _W due to the step response in the RC circuit is seen to occur. About Similarly power supply for a negative pulse can also describe up delay of the inter-electrode voltage V _W.

In equation (5), since the time constant τ = CR ₁ , when the pulse current limiting resistor R ₁ or R ₂ increases, the time constant τ increases and the rise of the interelectrode voltage V _W increases. I understand that. Accordingly, the rise delay as shown in FIG. 7 in the waveform V _W of inter-electrode voltage shown in FIG. 5 occurs. FIG. 7 shows the relationship between the change in the current i _C flowing into the capacitor 110 and the inter-electrode voltage V _W when the inter-electrode gap is in a no-load state.

JP 2005-177939 A

  In the power supply device 101 for electric discharge machining of the fine hole electric discharge machining apparatus 100 shown in FIG. 4, a positive pulse voltage and a negative pulse voltage are alternately applied to both ends of the discharge energy discharging capacitor. This is inefficient from the standpoint of power supply. That is, the power supply works even when the gap between the electrodes is in a no-load state.

  When the capacitor is repeatedly charged and discharged, the rise of the interelectrode voltage is delayed within the positive pulse time and the negative pulse time, so that the dischargeable time within the pulse time is shortened and the discharge efficiency is deteriorated. Further, if the positive pulse time and the negative pulse time are set near the rise delay time of the interelectrode voltage, the no-load voltage does not reach the voltage necessary for dielectric breakdown, so that the machining does not proceed without discharging.

For the positive pulse current limiting resistor R ₁ and the negative pulse current limiting resistor R _2, it is practical to set different resistance values according to the purpose of processing. Therefore, as shown in FIG. since the rise delay time of the machining gap voltage during the negative pulse switching from the pulse, the rise delay time of the inter-electrode voltage at the positive pulse switching from the negative pulses different, positive or negative without being average voltage V _W of the machining gap is 0 volt It becomes impossible to suppress the electrolytic action by biasing to either.

すなわち、極間の平均電圧Ｖ_Ｗが正に偏ってしまうことがわかる。なお、ここで、Ｖ_Ｗ＝０にすべく、tpp＜tnpとすると加工速度が遅くなる。 FIG. 8 shows that when the positive pulse current limiting resistor R ₁ is generally smaller than the negative pulse current limiting resistor R ₂ (R ₁ <R ₂ ), the positive interelectrode voltage V _W is The time constant τ ₁ of the pulse is smaller than the time constant τ ₂ of the pulse of the negative interelectrode voltage V _W (τ ₁ <τ ₂ ). Here, when tpp = tnp, the interelectrode voltage (no load voltage) mean value _{V W} of the V _W is expressed by the following equation (7).

That is, it can be seen that the average voltage V _W between the poles will be biased positive. Here, if tpp <tnp so that V _W = 0, the machining speed becomes slow.

  The present invention has been made in order to solve the above-described problems. An object of the present invention is to avoid unnecessary charging / discharging of a discharge energy discharging capacitor in a power supply device for electric discharge machining, and It is an object to provide an efficient power supply device for fine hole electric discharge machining in which the average voltage of the no-load voltage is almost 0 volts.

  It is another object of the present invention to provide a fine hole electric discharge machining method and a fine hole electric discharge machining power supply device in which the rise of the interelectrode voltage during charging / discharging of the discharge energy discharging capacitor is small and the discharge efficiency is high within the pulse time. .

  It is another object of the present invention to provide a power supply device for small hole electric discharge machining in which the workpiece is not oxidized and corroded by electrolytic action and the surface of the workpiece is not discolored.

  As a means for solving the above-mentioned problems, the thin hole electric discharge machining power supply device according to claim 1 is a pulse control circuit for alternately applying a positive or negative pulse voltage between the electrodes between the machining electrode and the workpiece. A first voltage applying means for applying a positive pulse voltage between the electrodes to increase the potential of the workpiece with respect to the machining electrode; and Second voltage application means for applying a negative pulse voltage for lowering the potential of the workpiece between the electrodes is provided, and a first diode is provided on the output side of the first voltage application means and the second voltage application means. A charging circuit in which an element and a capacitor element are connected in series is provided, and a discharging circuit in which a second diode element and a switching element are connected in series is provided, and the discharging circuit is connected in parallel to the first diode element. With the gist Is shall.

  The thin hole electric discharge machining power supply device according to claim 2 is the thin hole electric discharge machining power supply device according to claim 1, wherein the first diode element of the charging circuit includes the positive pulse voltage between the electrodes. The second diode element connected in series with the switching element of the discharge circuit has a discharge current due to the charge accumulated in the capacitor from the workpiece. The gist of the invention is that it is arranged in the direction of flow toward the electrode.

  The thin hole electric discharge machining power supply device according to claim 3 is the thin hole electric discharge machining power supply device according to claim 2, wherein the positive pulse voltage is applied between the electrodes in the switching element of the discharge circuit. The gist is to provide a pulse control means which is conductive during a period and is non-conductive during a period when the negative pulse voltage is applied between the electrodes.

  The fine hole electric discharge machining power supply device according to claim 4 is the fine hole electric discharge machining power supply device according to claim 3, wherein the pulse control is performed so that an average voltage of the no-load voltage between the electrodes becomes 0 volt. The gist is to suppress the electrolytic action on the surface of the workpiece by controlling the means.

  The electric discharge control method for a fine hole electric discharge machine according to claim 5 is for electric discharge machining provided with a pulse control circuit for alternately applying a positive or negative pulse voltage between the electrode for machining and the workpiece. In the power supply device, a first voltage applying unit that applies a positive pulse voltage between the electrodes to increase the potential of the workpiece with respect to the processing electrode; and a potential of the workpiece with respect to the electrode. Second voltage applying means for applying a negative pulse voltage to be lowered between the electrodes is provided, and a first diode element and a capacitor element are provided on the output side of the first voltage applying means and the second voltage applying means. A charging circuit connected in series is provided, and a discharge circuit in which a second diode element and a switching element are connected in series is connected in parallel to the first diode element. Gap The gist is to shape the voltage waveform between the electrodes into a voltage waveform close to a rectangular wave by conducting during the applied period and non-conducting during the period when the negative pulse voltage is applied between the electrodes. To do.

  The discharge control method for the fine hole electric discharge machine according to claim 6 is the electric discharge control method for the fine hole electric discharge machine according to claim 5, wherein the first diode element of the charging circuit is disposed between the electrodes. The second diode element connected in series with the switching element of the discharge circuit has a discharge current due to the charge accumulated in the capacitor when the positive pulse voltage is applied. The gist of the present invention is that the material is arranged in a flow direction from the workpiece toward the electrode.

  The discharge control method for the fine hole electric discharge machine according to claim 7 is the electric discharge control method for the fine hole electric discharge machine according to claim 6, wherein the average voltage of the no-load voltage between the electrodes is 0 volt. The gist is to suppress the electrolytic action on the surface of the workpiece by controlling the thickness of the workpiece.

According to the thin hole electric discharge machining power supply device of the present invention, the charging action from the electric discharge machining power source to the discharge energy discharging capacitor is only when a positive pulse is applied. Charging action does not occur every time. Further, when a negative pulse is applied, charging of the capacitor is stopped by the diode element (D ₃ ) in the charging circuit. Therefore, inefficient work for each cycle from the standpoint of the power source to the capacitor is released.

  Moreover, the rise delay of the interelectrode voltage in the no-load state occurs only when the charging action for the discharge energy discharging capacitor when the positive pulse is applied, and the capacitor is fully charged and negative. The rise delay of the inter-electrode voltage during pulse application is shorter than that of the prior art, and a voltage waveform close to a rectangular wave can be obtained. This is an effect of waveform shaping, and the dischargeable time within the pulse time becomes longer, and the discharge efficiency is improved. In addition, since the positive pulse time reaches a dischargeable voltage and can be discharged, it contributes to short pulse machining with reduced roughness of the machined surface.

  Also, due to the effect of waveform shaping, the rise delay time of the interpolar voltage when switching from positive to negative pulse when the gap is unloaded is equal to that from negative to positive pulse, so both positive and negative pulses By making the widths equal, the average voltage between the electrodes can be controlled to 0 volts, so that the electrolytic action between the electrodes can be suppressed and discoloration of the workpiece surface can be prevented.

Further, a switching element (T _R3 ) that suppresses the discharge current from the capacitor is disposed between the discharge energy discharging capacitor and the gap between the electrodes, and this switching element (T _R3 ) is used when a positive pulse is applied. Since it is turned on and turned off when a negative pulse is applied, positive discharge energy is prevented from being released as machining energy from the capacitor when a negative pulse is applied, and machining can be controlled by switching between positive and negative pulses. Can contribute to the stabilization of

The circuit diagram which shows the pulse control circuit in the power supply apparatus for thin hole electrical discharge machining of this invention, and the power supply apparatus for electrical discharge machining. The timing chart of the process pulse in the power supply apparatus for thin hole electrical discharge machining of this invention. The graph which contrasted the voltage waveform between electrodes in the power supply device for fine hole electrical discharge machining of this invention, and the current waveform of the capacitor | condenser for discharge energy discharge | emission. The circuit diagram which shows the pulse control circuit and the power supply apparatus for electrical discharge machining in the conventional power supply apparatus for fine hole electrical discharge machining. The time chart at the time of controlling so that the average voltage between poles may be set to 0 volt | bolt in the conventional power supply apparatus for electric discharge machining which applies a positive and negative polarity pulse voltage alternately. Graph showing current i _C relationship flowing the step response in the RC circuit to the inter-electrode voltage V _W and the capacitor. Graph interpolar gap showed the charging current change and inter-electrode voltage (charging voltage) of the i _C V _W Noto relation to the capacitor when the unloaded condition. In conventional small hole electric discharge machining power supply apparatus including an RC circuit, when the positive pulse current limiting resistor R ₁ is smaller than the negative pulse current limiting resistor _{R 2 (R 1 <R 2} ), an average gap voltage V _The figure which showed a mode that _W was biased positively. The figure which showed the discoloration state of the process surface resulting from the electrolysis at the time of using the conventional power supply apparatus for fine hole electric discharge machining which cannot control the average voltage between electrodes to be 0 volt.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit diagram of a pulse control circuit and a power supply apparatus for electric discharge machining in a thin hole electric discharge machining power supply apparatus of the present invention.

Referring to FIG. 1, a power supply device 3 for electric discharge machining of the narrow hole electric discharge machining apparatus 1 includes a positive pulse power supply 5 which is a first voltage applying means having an output voltage E ₁ , and an output voltage of E _2. A negative pulse power source 7 as a second voltage application means, and the positive pulse power source 5 includes a positive pulse current limiting resistor R ₁ , a positive pulse backflow prevention diode element D _1, and a switching element ( for example, EFT) T _R1 is Aru from the positive electrode side of the positive pulse power supply 5 are connected in series in this order.

Similarly, the negative pulse power supply 7 whose output voltage is E ₂ includes a negative pulse current limiting resistor R ₂ , a negative pulse backflow prevention diode element D _2, and a switching element TR ₂ on the positive side of the negative pulse power supply 7. Are connected in series.

The output side of the switching element T _R1 serves to connect the workpiece 13 of the small hole electric discharge machining apparatus 1 through an electric wire 9, 11, the negative electrode side of the negative pulse power supply 7 through the wires 9 Connected.

On the other hand, the output side of the switching element _TR2 is connected to the negative electrode side of the positive pulse power source 5 through the electric wire 15 and faces the workpiece 13 through the electric wire 17 with a discharge gap. It is connected to the processing electrode 19.

  The positive pulse power source 5 serving as the first voltage applying means described above applies a positive pulse voltage that raises the potential of the workpiece 13 with respect to the electrode 19 between the electrode of the workpiece 13 and the electrode 19. The negative pulse power supply 7 as the second voltage applying means applies a negative pulse voltage between the electrodes to lower the potential of the workpiece 13 with respect to the electrode 19.

Between the branch point A of the electric wire 11 connected to the output side of the switching element T _R1 and the branch point B of the electric wire 17 connected to the output side of the switching element T _R2 , the first diode element D ₃ and a capacitor element 21 having a capacitance C are connected in series. In addition, the discharge circuit and a second diode element D ₄ and the switching element T _R3 formed by the series connection are provided in parallel to the first diode element D _3. The branch point A and the branch point B are provided in the vicinity of the electrode 19 and the workpiece 13.

The polarity of the diode element D ₃ in the charging circuit, is provided toward a direction of accumulating the electric charge to the capacitor 21 upon application of the positive pulse voltage. Further, the diode element D ₄ and the switching element T _R3, the discharge current due to electric charges accumulated in the capacitor is connected in series in the direction of flow toward the electrode 19 from the workpiece 13.

The switching element T _R3 of the discharge circuit described above is turned on while the positive pulse voltage is applied between the electrodes, and is turned off when the negative pulse voltage is applied between the electrodes. It is controlled by the pulse control means 23. The pulse control means 23 is connected to the switching element T _{R3 through a} signal line S1, and is connected to the switching elements T _R1 and T _R2 through signal lines S2 and S3.

Referring to FIG. 2, the relationship between the pulses output by the pulse control means 23 to the switching elements T _R1 , T _R2, and T _R3 and the interelectrode voltage V _W is set to ON, OFF with the time axis t as the horizontal axis. The state is shown on the vertical axis.

In the above-mentioned switching element _{T R1} and the switching element _{T R3} is ON, when the switching element _{T R2} is OFF, the (negative switching _{T R2} is OFF positive switching _{T R1} and capacitor switching _{T R3} is ON in FIG. 2) a positive pulse A positive pulse voltage for increasing the potential of the workpiece 13 is applied across the electrode 19 from the power source 5 for electric power.

Further, the switching element _{T R1} and the switching element _{T R3} is OFF, when the switching element _{T R2} is in the ON state, when the (negative switching _{T R2} is ON positive switching _{T R1} and capacitor switching _{T R3} is OFF in Fig. 2) A negative pulse voltage that lowers the potential of the workpiece 13 is applied to the electrode 19 from the negative pulse power source 7 between the electrodes.

In the pulse control by the pulse control means 23 described above, the ON / OFF timing of the capacitor discharge switching element _TR3 is controlled to be synchronized with the positive pulse switching element _TR1 . The positive pulse ON time t _PP and the negative pulse time OFF time t _NP are made equal.

As shown in FIG. 2, the rise delay time (t ₊ ) of the inter-electrode voltage V _{W when} the capacitor is fully charged and the rise delay time (t ₋ ) when applying a negative pulse are much higher than those of the prior art. The voltage waveform is reduced and a rectangular wave is obtained. Thus, approximately equal the area of the area and a negative pulse waveform of a positive pulse waveform of the machining gap voltage V _W, it is possible to the average voltage V _W of the machining gap to approximately 0 volts.

  FIG. 3 is a diagram showing the difference between the inter-electrode voltage waveform and the current waveform of the discharge energy discharging capacitor in comparison with the conventional one in order to easily understand the effect of the power supply device for narrow hole electric discharge machining of the present invention. It is.

Referring to FIG. 3, the charging action of the electric discharge machining power supply in the technique of the present invention to the capacitor for discharge energy release is only when a positive pulse is applied by the effect of the diode D _3, the machining gap is in the unloaded condition It can be seen that the charging action does not occur every pulse.

Also, when the discharge positive after charging has not been generated, the charging of the capacitor is not performed, at the time of negative pulse applied charging of the capacitor by a diode element D ₃ in the charging circuit is restrained. Therefore, it is understood that inefficient work for each cycle from the standpoint of the power source to the capacitor is released.

DESCRIPTION OF SYMBOLS 1 Thin hole electric discharge machining apparatus 3 Power supply apparatus 5 Power supply for positive pulses 7 Power supply for negative pulses 9, 11, 15, 17 Electric wire 13 Workpiece material 19 Electrode 21 Capacitor element D ₁ Reverse current prevention diode element for ₁ positive pulse D _{2 For} negative pulse blocking diode element D ₃ first diode element D ₄ second diode element R ₁ positive pulse current limiting resistor R ₂ negative pulse current limiting resistor S1, S2, S3 signal line _{T R1,} T R2, T _R3 switching element

Claims (7)

In an electric discharge machining power supply device having a pulse control circuit for alternately applying a positive or negative pulse voltage between the electrodes between the machining electrode and the workpiece, the potential of the workpiece relative to the machining electrode A first voltage applying means for applying a positive pulse voltage between the electrodes, and a second voltage application for applying a negative pulse voltage between the electrodes to lower the potential of the workpiece relative to the electrodes. And a charging circuit in which a first diode element and a capacitor element are connected in series are provided on the output side of the first voltage applying means and the second voltage applying means, and the second diode element and switching are provided. A thin hole electric discharge machining power supply device comprising: a discharge circuit connected in series to an element; and the discharge circuit connected in parallel to the first diode element. 2. The power supply device for fine hole electric discharge machining according to claim 1, wherein the first diode element of the charging circuit is arranged in a direction in which electric charge is accumulated in the capacitor when the positive pulse voltage is applied between the electrodes. The second diode element connected in series to the switching element of the discharge circuit is arranged in a direction in which a discharge current due to the electric charge accumulated in the capacitor flows from the workpiece toward the electrode. Power supply device for fine hole electrical discharge machining. 3. The power supply device for fine hole electric discharge machining according to claim 2, wherein the switching element of the discharge circuit is conductive during a period in which the positive pulse voltage is applied between the electrodes, and the negative pulse voltage is applied between the electrodes. A fine hole electric discharge machining power supply device, characterized in that a pulse control means for discontinuity is provided during a period of time. 4. The thin hole electric discharge machining power supply device according to claim 3, wherein the pulsed control means is controlled so that the average voltage of the no-load voltage between the electrodes becomes 0 volts, thereby suppressing the electrolytic action on the workpiece surface. A power supply device for fine hole electric discharge machining. In an electric discharge machining power supply device having a pulse control circuit for alternately applying a positive or negative pulse voltage between the electrodes between the machining electrode and the workpiece, the potential of the workpiece relative to the machining electrode A first voltage applying means for applying a positive pulse voltage between the electrodes, and a second voltage application for applying a negative pulse voltage between the electrodes to lower the potential of the workpiece relative to the electrodes. And a charging circuit in which a first diode element and a capacitor element are connected in series are provided on the output side of the first voltage applying means and the second voltage applying means, and the second diode element and switching are provided. A discharge circuit connected in series with an element is connected in parallel to the first diode element, the switching element of the discharge circuit is conductive during a period in which the positive pulse voltage is applied between the electrodes, and the negative pulse voltage is Period is applied between Kikyoku is by non-conductive, the discharge control method of the small hole electric discharge machine, characterized by shaping the voltage waveform between the poles to the rectangular wave voltage close waveform. 6. The discharge control method for a fine hole electric discharge machine according to claim 5, wherein the first diode element of the charging circuit is arranged in a direction in which electric charge is accumulated in the capacitor when the positive pulse voltage is applied between the electrodes. The second diode element connected in series with the switching element of the discharge circuit is arranged in a direction in which a discharge current due to the electric charge accumulated in the capacitor flows from the workpiece toward the electrode. A discharge control method for a fine hole electric discharge machine. 7. The discharge control method for a fine hole electric discharge machine according to claim 6, wherein the electrolytic action on the surface of the work piece is suppressed by controlling the average voltage of the no-load voltage between the electrodes to be 0 volt. A discharge control method for a fine hole electric discharge machine.

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