JP2007021632A - Electrochemical machining method and device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical machining method capable of improving machining accuracy. <P>SOLUTION: A cylindrical electrode 20 is fixed to an electrode mounting part 18 first. Next, the electrode 20 is connected to a cathode of a machining power source 40, and a workpiece 26 is connected to anode of the machining power source 40. An XY-axis motor 23, and a Z-axis motor 15 are respectively driven to move an XY table 22 and a Z-axis mechanism part 16. The electrode 20 and the workpiece 26 are opposedly disposed at a predetermined gap, and an electrolysis solution is supplied to the gap between the electrode 20 and the workpiece 26 by driving a pump 32. Aqueous solution of 0.5 wt.% sodium nitrate is used as the supplied electrolysis solution. Low voltage pulse having a voltage of 15 V and a pulse width of 1 μs is applied with 500 KHz cycle in such a state that the electrolysis solution is filled in the gap, and a high voltage pulse having a voltage of 75 V and a pulse width of 10 μs is applied with 1 KHz cycle to perform the electrochemical machining of the workpiece 26. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrolytic processing method and an electrolytic processing apparatus.

In an electrolytic solution such as sodium chloride (NaCl) or sodium nitrate (NaNO ₃ ), a voltage of about 5 to 20 V is applied between the electrode (−electrode) and the workpiece (+ electrode) to pass a current, and the workpiece is caused by an electrochemical reaction. There is known an electrolytic processing method for performing processing by eluting a metal (see, for example, Patent Document 1). In the electrolytic processing, the workpiece is processed into a shape obtained by transferring the electrode shape, and it is possible to perform a complicated shape that is difficult to be processed by cutting or the like. Further, the electrolytic processing method has features such as high productivity because it can increase current according to the electrode area, no generation of residual stress due to processing, and low surface roughness.
JP 09-285117 A

  However, the electrolytic processing method is difficult to perform fine processing due to poor processing accuracy, such as large shape distortion at the edge portion. Machining accuracy can be slightly improved by pulsing the applied voltage or applying a reverse pulse, but this is not sufficient. Therefore, improvement of processing accuracy has been desired.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electrolytic processing method and an electrolytic processing apparatus capable of improving processing accuracy.

  In the electrolytic processing method according to the present invention, a voltage pulse is periodically applied to the workpiece and the electrode in a state where the electrolytic solution is filled between the workpiece and the electrode, and the defect formed on the workpiece. An electrolytic machining method for machining a workpiece by applying a high voltage pulse higher than the above voltage pulse in a cycle different from the cycle of the voltage pulse, which breaks the working film, and the concentration of the electrolyte is only the voltage pulse It is characterized in that the electrolytic processing speed of the workpiece is adjusted to be substantially zero when the pressure is applied.

  Further, an electrolytic processing apparatus according to the present invention is an electrolytic processing apparatus used for carrying out the electrolytic processing method, wherein an electrolytic solution supply means for supplying an electrolytic solution between the workpiece and the electrode, the workpiece and the electrode A power source that periodically applies a high voltage pulse higher than the above voltage pulse, which breaks the passive film formed on the workpiece, at a cycle different from the cycle of the voltage pulse. It is characterized by providing.

  According to the electrolytic processing method or the electrolytic processing apparatus according to the present invention, the electrolytic processing of the workpiece covered with the passive film when the concentration of the electrolytic solution is applied with only the voltage pulse, that is, when the high voltage pulse is not applied. Is adjusted to a concentration that does not progress almost at all, so in places where the passive film is broken by the intermittently applied high voltage pulse, the electrochemical machining by the voltage pulse proceeds, but in places where the passive film is not broken. Since the workpiece is protected by the passive film, the electrolytic machining hardly proceeds. Therefore, highly accurate electrolytic processing becomes possible.

  In the electrolytic processing method according to the present invention, the period of the high voltage pulse is preferably longer than the period of the voltage pulse.

  In this case, the high voltage pulse is mainly used for removing the passive film, and the low voltage pulse mainly determines the progress of the electrolytic processing. Therefore, it is possible to improve the processing accuracy of electrolytic processing.

  According to the present invention, when only the voltage pulse is applied, the voltage pulse is applied to the work piece and the electrode in a state where the electrolytic solution whose concentration is adjusted to be substantially zero is filled. Since the high voltage pulse that is periodically applied and the high voltage pulse that breaks the passive film formed on the workpiece is applied with a period different from the voltage pulse, the machining accuracy of the electrolytic machining can be improved.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the figure, the same reference numerals are used for the same or corresponding parts.

  First, the configuration of the electrolytic processing apparatus 1 according to the present embodiment will be described with reference to FIGS. FIG. 1 is a diagram showing an overall configuration of the electrolytic processing apparatus 1. FIG. 2 is a diagram showing a schematic configuration of a machining power source 40 used in the electrolytic machining apparatus 1.

  The electrolytic processing apparatus 1 includes a base 12 that is placed on a floor or the like, and a support portion 14 that stands vertically on the base 12. A Z-axis mechanism portion 16 that is moved up and down by a Z-axis motor 15 is provided on a side portion of the support portion 14, and an electrode attachment portion 18 is fixed to the Z-axis mechanism portion 16. An electrode 20 is attached to the lower portion of the electrode attachment portion 18 so as to be rotatable about an axis.

  An XY axis motor 23 is disposed on the base 12, and an XY table 22 is disposed on the XY axis motor 23 and is movable in two orthogonal directions on a horizontal plane. The XY table 22 is driven by an XY axis motor 23. On the upper surface of the XY table 22, a processing tank 24 to which a work (workpiece) 26 is fixed is disposed. The XY axis motor 23 and the Z axis motor 15 are controlled by an electronic control device (not shown). The XY table 22 is driven by the XY axis motor 23 and moved in the horizontal direction, whereby the workpiece 26 is positioned with respect to the electrode 20. Further, the gap between the electrode 20 and the workpiece 26 is adjusted by the Z-axis mechanism 16 being driven by the Z-axis motor 15 and moved in the vertical direction.

  The tank 30 stores an electrolytic solution made of an aqueous solution such as sodium nitrate or sodium chloride. The electrolytic solution in the tank 30 is supplied to the processing tank 24 by a pump 32 provided in the circulation path 31, and the workpiece 26 and the electrode 20 are immersed in the electrolytic solution stored in the processing tank. During the electrolytic processing, the electrolytic solution stored in the processing tank 24 is circulated through the circulation path 31 by the pump 32, and sludge and the like are removed by the filter 34 during the circulation.

  Here, the concentration of the electrolytic solution used in the conventional electrolytic processing is usually about 10 to 30% by weight, but in this embodiment, about 1% to 0.04% by weight, and more preferably about 0.5%. An electrolyte solution having a concentration of about% by weight is used. Here, FIG. 4 shows a relationship among the concentration (or specific resistance) of the electrolytic solution, the voltage pulse, and the machining speed. The horizontal axis in FIG. 4 is the concentration (% by weight) of the electrolytic solution (or specific resistance (Ωm)), and the vertical axis is the processing speed (μm / s).

  As indicated by ● (applied voltage 15 V) or ▲ (applied voltage 5 V) in FIG. 4, when only the voltage pulse is applied, the processing speed decreases as the concentration of the electrolyte decreases, and the concentration is about 1 weight. In the region of about% to 0.04% by weight, the electrolytic processing hardly proceeds due to the passive film formed on the surface of the workpiece 26. However, when a high voltage pulse, which will be described later, is applied in addition to the voltage pulse, the machining speed increases and electrolytic machining proceeds as indicated by ◯ or Δ in FIG.

  The electrolytic processing apparatus 1 includes a processing power source 40. The electrode 20 is connected to the negative pole of the machining power source 40, and the workpiece 26 is connected to the positive pole of the machining power source 40. The machining power supply 40 applies a voltage pulse of about 5 to 15 V, for example, between the electrode 20 and the workpiece 26 at a predetermined cycle (for example, about 500 KHz), and has a higher voltage (for example, about 75 to 100 V) than the voltage pulse. The high voltage pulse is applied with a period (for example, about 20 Hz to 1 KHz) longer than the voltage pulse (to be clearly distinguished from the high voltage pulse, hereinafter referred to as “low voltage pulse”).

  As shown in FIG. 2, the machining power supply 40 is configured by connecting in parallel a low voltage pulse circuit 41 that generates a low voltage pulse and a high voltage pulse circuit 42 that generates a high voltage pulse. Therefore, by appropriately controlling ON / OFF of each voltage pulse, the low voltage pulse generated by the low voltage pulse circuit 41 and the high voltage pulse circuit 42 are generated as schematically shown in FIG. The high voltage pulse is superimposed and applied between the electrode 20 and the workpiece 26. FIG. 3 schematically shows an output waveform of the machining power source 40, that is, a pulse waveform applied between the electrode 20 and the workpiece 26.

  Returning to FIG. 2, in more detail, the low voltage pulse circuit 41 includes a low voltage pulse circuit protection diode 43 whose anode terminal is connected to the electrode 20, and a low voltage pulse circuit whose negative electrode is connected to the cathode terminal of the diode 43. The voltage source 44 and the drain terminal are connected to the + terminal of the low voltage source 44 and the source terminal is connected to the work 26. The first power MOSFET 45 that performs a switching operation and the gate terminal of the first power MOSFET 45 are connected to the first terminal. A first pulse generator 46 for generating a signal for switching the power MOSFET 45 is included.

  On the other hand, the high voltage pulse circuit 42 has a high voltage source 47 whose negative electrode is connected to the electrode 20, a current limiting resistor 48 whose one end is connected to the positive electrode of the high voltage source 47, and a current limiting resistor 48 whose drain terminal is connected. And a source terminal connected to the work 26, a second power MOSFET 49 for performing a switching operation, and a second power MOSFET 49 connected to the gate terminal of the second power MOSFET 49 for generating a signal for switching the second power MOSFET 49. It has a pulse generator 50 and the like.

  Next, the operation of the electrolytic processing apparatus 1 and the electrolytic processing method will be described by taking the case of performing hole processing as an example. First, the cylindrical electrode 20 is fixed to the electrode mounting portion 18. Next, the electrode 20 is connected to the negative pole of the machining power source 40, and the workpiece 26 is connected to the positive pole of the machining power source 40. Subsequently, the XY-axis motor 23 and the Z-axis motor 15 are driven to move the XY table 22 and the Z-axis mechanism unit 16, and the electrode 20 and the workpiece 26 are separated by a predetermined gap (for example, 0.1 mm to 0.7 mm). ) To face each other.

  The pump 32 is driven to supply the electrolytic solution to the gap between the electrode 20 and the work 26. As the electrolytic solution to be supplied, for example, a 0.5 wt% aqueous sodium nitrate solution is used. Then, with the electrolyte filled between the gaps, for example, a low voltage pulse with a voltage of 15 V and a pulse width of 1 μs is applied with a cycle of 500 KHz, and a high voltage pulse with a voltage of 75 V and a pulse width of 10 μs is applied with a cycle of 1 KHz, for example. Electrolytic machining of the workpiece 26 is performed.

  During the electrolytic machining, the Z-axis motor 15 is driven to move the electrode 20 downward so that the machining current is constant. In addition, the electrolytic solution stored in the tank 30 is pumped to the processing portion by the pump 32, and the electrolytic solution in the processing tank 24 is collected in the tank 30 through the filter 34.

  According to the present embodiment, the concentration of the electrolytic solution is adjusted to a concentration at which only the low voltage pulse is applied, that is, when the high voltage pulse is not applied, the electrolytic processing of the workpiece 26 covered with the passive film hardly proceeds. Therefore, although the electromachining by the low voltage pulse proceeds at the location where the passive film is broken by the intermittently applied high voltage pulse, the work 26 is the passive film at the location where the passive film is not broken. Since it is protected, the electrolytic processing hardly proceeds. Therefore, highly accurate electrolytic processing becomes possible.

  Further, according to the present embodiment, the low voltage pulse is applied between the electrode 20 and the work 26 at a predetermined cycle (for example, about 500 KHz), and the high voltage pulse is longer than the low voltage pulse (for example, , About 20 Hz to 1 KHz). Therefore, the high voltage pulse is mainly used for removing the passive film, and the low voltage pulse mainly determines the progress of the electrolytic processing. As a result, it is possible to improve the processing accuracy of electrolytic processing.

  Further, depending on the application conditions (pulse width, voltage value, etc.) of the high voltage pulse, discharge may occur between the gap between the electrode 20 and the workpiece 26. However, in this embodiment, electrolytic processing is performed even under conditions where no discharge occurs. The discharge is not necessarily required. According to the present embodiment, since the discharge between the gaps is suppressed by increasing the pulse period of the high voltage pulse or shortening the pulse width of the high voltage pulse, the consumption of the electrode 20 is suppressed or eliminated. Is possible.

  In the conventional electrolytic machining, it was necessary to send a high-speed jet of an electrolyte solution of 6 to 60 m / second between the gaps during the electrolytic machining. Therefore, when performing deep processing, it is necessary to provide a large number of injection holes in the electrode. When it was difficult to provide an injection hole in the electrode, the processing depth was limited. However, according to the present embodiment, since it is not necessary to send a high-speed jet of the electrolyte between the gaps during electrolytic processing, deep holes can be processed without providing injection holes in the electrodes. More specifically, the processing limit depth of the conventional electrolytic processing is about 1.8 mm, but in the present embodiment, a processing depth of about 3.5 mm was obtained.

  As mentioned above, although the invention made by the present inventors has been specifically described based on the embodiment, the present invention is not limited to the above embodiment. For example, the machining power source 40 only needs to be able to apply a low voltage pulse and a high voltage pulse between the electrode 20 and the workpiece 26, and the circuit configuration is not limited to this embodiment.

  Needless to say, the types of the electrolytic solution and the workpiece 26 are not limited to the above embodiment. Furthermore, the above-described electrolyte concentration, applied voltage of low voltage pulse and high voltage pulse, pulse width, period, and the like are not limited to the present embodiment, but the type of electrolyte, the material of the workpiece 26, the required processing accuracy and requirements. It is preferable to set appropriately according to the processing speed or the like.

  Next, the content of the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
Using a tungsten electrode having a diameter of 0.35 mm, a SUS plate (SUS304) was drilled. A 0.5 wt% sodium nitrate solution was used as the electrolyte. At this concentration, the electrolytic processing hardly proceeds due to the passive film formed on the surface of the SUS plate.

  Drilling a hole with a depth of about 0.5 mm by applying a low voltage pulse of 15 V (ON: OFF = 1 μs: 1 μs) and applying a high voltage pulse of about 75 V, a maximum current of 30 A and a pulse width of 10 μs every 1 ms. Went. The processed cross-sectional shape of the present example is shown in FIG.

(Comparative Example 1)
In Comparative Example 1, electrolytic processing was performed without applying a high voltage pulse to Example 1. Further, when no high voltage pulse was applied, electrolytic processing did not proceed at an electrolyte solution concentration of 0.5% by weight, so a sodium nitrate solution having a concentration of 5% by weight was used. Other conditions were the same as in Example 1. The processed cross-sectional shape of Comparative Example 1 is shown in FIG.

  The processed cross-sectional shape of Example 1 shown in FIG. 5 is significantly smaller than the processed cross-sectional shape of Comparative Example 1 shown in FIG. . Thus, the improvement of processing accuracy was confirmed.

  As a secondary effect, the processed surface of Comparative Example 1 is black, but the processed surface of Example 1 has a metallic luster. The reason why the metallic gloss surface was obtained is that the current density was increased by applying the high voltage pulse.

(Comparative Example 2)
In Comparative Example 2, electrolytic processing was performed in the same manner as in Example 1 except that a sodium nitrate solution having a concentration of 5% by weight was used. The processing accuracy of Comparative Example 2 was almost the same as that of Comparative Example 1.

  From Example 1, Comparative Example 1 and Comparative Example 2, in order to improve the processing accuracy, the concentration of the electrolytic solution is set to such an extent that the electrolytic processing hardly proceeds when the high voltage pulse is not applied, and the high voltage pulse It was confirmed that the application of is important.

(Example 2)
In Example 2, electrolytic processing was performed in the same manner as in Example 1 except that the application interval of the high voltage pulse was changed from every 1 ms to every 50 ms. The processed cross-sectional shape of Example 2 is shown in FIG. When a high voltage pulse is applied, a discharge is generated between the gap between the electrode 20 and the workpiece 26 and the electrode 20 is consumed. The electrode consumption rate in Example 1 was 2.5%. Because of this electrode consumption, in Example 1, the corner of the bottom surface of the processed hole is slightly rounded. In Example 2, when the application interval of the high voltage pulse was changed from every 1 ms to every 50 ms, the electrode consumption was reduced to 1% or less, and the shape of the corner of the bottom of the processed hole became sharp. According to Example 2, it was confirmed that electrode consumption can be suppressed and processing accuracy can be further improved. The processing speed hardly decreased.

(Example 3)
When the pulse width of the high voltage pulse is 6 μs or less, no discharge is generated between the gap between the electrode 20 and the workpiece 26. In Example 3, the electrolytic processing was performed in a state where the pulse width of the high voltage pulse was 4 μs and no discharge was observed. Other conditions were the same as in Example 1. The processed cross-sectional shape of Example 3 is shown in FIG. As shown in FIG. 8, it was confirmed that processing was possible regardless of the presence or absence of electric discharge. The reason for this is that when a high-voltage pulse is applied, the passive film of the workpiece 26 is broken even if no discharge occurs, the electrolytic current density on the surface increases, bubbles are generated, and the passive film and the anode product are removed. It is thought to do. According to Example 3, it was confirmed that highly accurate electrolytic processing can be performed without consuming the electrode 20 at all.

It is a figure which shows the whole structure of the electrolytic processing apparatus which concerns on embodiment. It is a figure which shows schematic structure of the power supply used for the electrolytic processing apparatus which concerns on embodiment. It is a schematic diagram which shows the waveform of the voltage pulse applied between an electrode and a workpiece | work. It is a figure which shows the relationship between the density | concentration of electrolyte solution, and a processing speed. It is a figure which shows the process cross-sectional shape of Example 1. FIG. It is a figure which shows the process cross-sectional shape of the comparative example 1. It is a figure which shows the process cross-sectional shape of Example 2. FIG. It is a figure which shows the process cross-sectional shape of Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrolytic processing apparatus, 12 ... Base, 14 ... Support part, 15 ... Z-axis motor, 16 ... Z-axis mechanism part, 18 ... Electrode attaching part, 20 ... Electrode, 22 ... XY table, 23 ... XY motor, 24 ... Processing tank, 26 ... work, 30 ... tank, 31 ... circulation path, 32 ... pump, 34 ... filter, 40 ... processing power supply, 41 ... low voltage pulse circuit, 42 ... high voltage pulse circuit.

Claims (3)

Periodically applying a voltage pulse to the workpiece and the electrode in a state where an electrolyte is filled between the workpiece and the electrode, and breaking the passive film formed on the workpiece, An electrochemical machining method for machining the workpiece by applying a high voltage pulse having a voltage higher than the voltage pulse at a cycle different from the cycle of the voltage pulse,
The electrolytic processing method is characterized in that the concentration of the electrolytic solution is adjusted so that the electrolytic processing speed of the workpiece becomes substantially zero when only the voltage pulse is applied.   The electrolytic processing method according to claim 1, wherein a period of the high voltage pulse is longer than a period of the voltage pulse. In the electrolytic processing apparatus used for implementation of the electrolytic processing method according to claim 1 or 2,
An electrolyte supply means for supplying an electrolyte between the workpiece and the electrode;
A voltage pulse is periodically applied to the workpiece and the electrode, and a high-voltage pulse higher than the voltage pulse that breaks the passive film formed on the workpiece is a period of the voltage pulse. And a power supply that applies at different periods.

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