JP6164611B2 - Electrolytic machining method, tool electrode for electrolytic machining, and electrolytic machining apparatus - Google Patents

Description

  The present invention relates to an electrolytic machining method, a tool electrode for electrolytic machining, and an electrolytic machining apparatus.

There is known an electrolytic processing apparatus that performs electrolytic processing while injecting an electrolytic solution between a conductive workpiece and an electrode.
[Prior art documents]
[Patent Literature]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2007-069328

  The conventional electrolytic processing apparatus immerses the workpiece in the electrolyte over a wide range, so that the processing proceeds even in a region other than the region to be processed, and the reduction in processing accuracy is inevitable.

  The electrolytic machining method according to the first aspect of the present invention includes an approaching step in which the tool electrode approaches the workpiece, the inside of the tool electrode, the tip of the tool electrode and the surface of the workpiece, and the inside of the tool electrode in this order. A circulation step of circulating the electrolytic solution; and an energization step of passing a current between the tool electrode and the workpiece via the electrolytic solution.

  The tool electrode for electrolytic processing according to the second aspect of the present invention includes a first inner through-hole that causes the electrolytic solution to flow and be discharged from the tip portion, and a second inner through-hole that sucks and circulates the electrolytic solution from the tip portion. With.

  An electrolytic processing apparatus according to a third aspect of the present invention is an electrolytic processing apparatus to which the above-described tool electrode is attached, and includes a suction pump connected to the second internal hole for sucking and circulating the electrolytic solution. Prepare.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is a conceptual diagram which shows notionally the electric discharge machine which concerns on this embodiment. It is sectional drawing of the tool electrode with which an electric discharge machine is mounted | worn, and the workpiece which is a process target. It is sectional drawing of a tool electrode and a workpiece | work which shows each step of drilling. It is a figure which shows the relationship between the distance between electrodes during a hole process, and a suction pressure. It is a figure which shows the relationship between a feed amount and a side surface gap. It is a control flowchart of hole processing. It is a conceptual diagram explaining the application to plane processing. It is a figure which shows the variation of application control.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a conceptual diagram conceptually showing an electrolytic processing apparatus 10 according to the present embodiment. The electrolytic processing apparatus 10 is an apparatus that is equipped with a tool electrode 100 and performs hole processing on a workpiece 200 to be processed by electrolytic processing. As shown in the figure, the direction away from the workpiece 200 along the central axis of the tool electrode 100 is the z-axis plus direction. One direction orthogonal to the z axis is defined as the x axis, and the direction orthogonal to both the z axis and the x axis is defined as the y axis. In the following several figures, the coordinate axes are displayed so that the orientation of each figure can be understood with reference to the coordinate axes of FIG.

  The electrolytic processing apparatus 10 includes a stage 300 on which the workpiece 200 is placed, a holder 400 that holds the tool electrode 100 so as to be movable back and forth in the z-axis direction, a pump 500 that sucks the electrolytic solution 550, and the tool electrode 100 through the electrolytic solution. A power supply 600 for passing an electric current between the workpieces 200 and a control unit 700 for controlling the entire electrolytic processing apparatus 10 are mainly provided. The control unit 700 includes a CPU 710 and an operation panel 720. The CPU 710 executes processing control in accordance with the processing procedure, processing conditions, and the like input via the operation panel 720. The operation panel 720 is a display device including an input unit such as a touch panel, and accepts input from an operator and displays menu items, processing progress, and the like.

  The tool electrode 100 is a metal tool electrode including a supply port 120 for supplying the electrolytic solution 550 and a recovery port 130 for collecting the electrolytic solution 550, as will be described in detail later. The electrolytic solution 550 is discharged from the tip portion 110 which is an end surface facing the planned machining position 210 of the workpiece 200 toward the planned machining position 210 and is collected again from the distal end portion 110. The tool electrode 100 is replaceably mounted on the holder 400. Specifically, it is fixed to the holder 400 by a clamp.

  The holder 400 is pivotally supported by a support column 410 fixed along the z-axis direction, and moves up and down the support column 410 by a driving force of a drive unit 420 provided integrally with the holder 400. Therefore, the tool electrode 100 advances and retreats with respect to the workpiece 200 as the holder 400 moves up and down. In particular, during drilling, the drive unit 420 is controlled by the CPU 710, and the tool electrode 100 is sent stepwise in the direction of arrow 490 (z-axis minus direction). In addition, the drive part 420 is comprised by the motor containing the gear mechanism which meshes | engages with the support | pillar 410, for example.

  The stage 300 is a mounting table on which the workpiece 200 is fixed by the chuck 310. The chuck 310 is movable in the xy plane direction, and a planned machining position 210 set on the surface of the workpiece 200 can be disposed immediately below the tip portion 110 of the tool electrode 100.

  The pump 500 is a suction pump that sucks the electrolytic solution 550 through a recovery tube 562 connected to the recovery port 130. The collected electrolytic solution 550 is sent to the filtering device 580 to filter impurities. Then, the filtered electrolyte 550 is sent to the tank 520 and stored through the reflux tube 563 connected to the filtering device 580.

  The pump 500 has, for example, a gauge pressure with a maximum suction pressure of −53 kPa and a maximum suction amount of about 0.6 L / min. Further, the pump 500 includes a pressure gauge 510, and the pressure gauge 510 outputs a suction pressure of the electrolytic solution 550. During processing, the CPU 710 receives the output of the pressure gauge 510 and monitors the suction pressure of the electrolytic solution 550.

  The tank 520 is a container that stores the electrolytic solution 550. One end of a supply tube 561 is connected to the tank 520, and the other end of the supply tube 561 is connected to the supply port 120. The supply tube 561 is connected to the tank 520 and the supply port 120 so as to be filled with the electrolytic solution 550 even when the electrolytic processing apparatus 10 is stopped.

  Thus, the circulation path of the electrolytic solution 550 is as follows: tank 520 → supply tube 561 → tool electrode 100 (supply port 120 → tip portion 110 → recovery port 130) → recovery tube 562 → pump 500 → filter device 580 → reflux tube 563. → established as (tank 520). Here, the pump 500 for circulating the electrolytic solution 550 is provided as a suction pump connected to the recovery port 130 of the tool electrode 100 as described above. In the present embodiment, the electrolytic solution 550 is pushed out to the supply port 120. The pump for delivery is not connected. The mechanism by which the electrolytic solution 550 circulates through the tip portion 110 of the tool electrode 100 will be described later with reference to other drawings. In the present embodiment, the collected electrolytic solution 550 is filtered and returned to the tank 520. However, if the tank 520 can store an amount of the electrolytic solution 550 necessary for processing, the electrolytic solution 550 is stored in the tank. The configuration of returning to 520 is not necessary.

  The power supply 600 applies a positive voltage to the workpiece 200 via the power line 610 and keeps the tool electrode 100 at the ground potential via the ground line 620. The power line 610 may be directly connected to the workpiece 200 or may be connected to the workpiece 200 via the chuck 310 or the like. Similarly, the ground line 620 may be directly connected to the tool electrode 100 or may be connected to the tool electrode 100 via the holder 400 or the like.

  The power supply 600 is turned on / off and the amount of power supply is controlled by a control signal from the CPU 710. The CPU 710 controls energization of the power supply 600 in a constant current mode in which, for example, the value of the pulse current during processing is constant. For example, the pulse current is set such that the high-level current value is 15 A, the low-level current value is 0 A, the pulse width is 5 msec, and the pulse period is 50 msec.

  FIG. 2 is a cross-sectional view of the tool electrode 100 mounted on the electrolytic processing apparatus 10 and the workpiece 200 to be processed. The tool electrode 100 according to the present embodiment has a double cylindrical structure, and its body is held by a holder 400.

  More specifically, the two cylinders of the outer cylinder 140 and the inner cylinder 150 are concentrically fitted with the z-axis direction as the central axis. The inner diameter of the upper part of the outer cylinder 140 and the outer diameter of the upper part of the inner cylinder 150 are substantially equal and are fitted to each other. The outer cylinder 140 is formed to have a larger inner diameter than the upper part up to the tip part 110 except for the upper part. An O-ring 160 is fitted in a boundary portion on the lower end side of the upper part, and the outer cylinder 140 and the inner cylinder 150 are fixed to each other.

  For example, the outer diameter of the outer cylinder 140 is 10 mm, and the inner diameter other than the upper part is 8 mm. Similarly, the outer diameter of the inner cylinder 150 is 5 mm, and the inner diameter is 3 mm. In the figure, the ratio is different from this ratio from the viewpoint of explanation.

  By adopting the double cylindrical structure in this way, the first inner through hole 121 that is a space between the inner surface of the outer cylinder 140 and the outer surface of the inner cylinder 150, and the space on the central axis side from the inner surface of the inner cylinder 150. The second inner through hole 131 is formed. The first inner through hole 121 communicates with the supply port 120 through which the electrolytic solution 550 is introduced above the tool electrode 100. The second inner hole 131 communicates with the recovery port 130 that discharges the electrolytic solution 550 at the upper end of the tool electrode 100.

  The first inner through hole 121 is opened on the distal end 110 side, and the opening functions as a discharge port 171 that discharges the electrolytic solution 550 to the planned processing position 210. The second inner through-hole 131 is also opened on the distal end portion 110 side, and the opening functions as a suction port 172 that sucks the electrolyte solution 550. In such a structure, the discharge port 171 of the first inner through hole 121 is provided on the peripheral side at the distal end portion 110 than the suction port 172 of the second inner through hole 131.

  As shown in the drawing, the distal end portion 110 includes an outer cylinder distal end portion 141 that is a distal end portion of the outer cylinder 140 and an inner cylinder distal end portion 151 that is a distal end portion of the inner cylinder 150. The outer cylinder tip 141 has a taper that tapers so that the inner diameter gradually increases toward the tip. The inner cylinder front end 151 is formed as a flange extending in the direction of the outer cylinder 140. The collar portion is a flat surface on the surface of the workpiece 200 that faces the planned machining position 210, but has a taper that gradually becomes thinner toward the outer cylinder 140. In this embodiment, the outer diameter of the collar is 9 mm. Due to the taper of the outer cylinder tip 141 and the taper of the inner cylinder tip 151, the discharge port 171 becomes an opening narrower than the flow path cross section of the first inner through hole 121, and has a slightly peripheral edge in the vertical direction. Inclined in the direction.

By forming the inner cylinder front end portion 151 as such a wide flange portion, the inner cylinder front end portion 151 functions as an effective electrode for flowing a current between the planned processing position 210. Therefore, if at least the inner cylinder 150 is a conductor, even if the outer cylinder 140 is an insulator, drilling can be performed. Various conductors can be adopted for the inner cylinder 150 according to the material of the workpiece 200. For example, when the workpiece 200 is stainless steel, brass can be used. In the present embodiment, the workpiece 200 is SUS304, which is stainless steel, and the outer cylinder 140 and the inner cylinder 150 are described using brass. Further, the electrolytic solution 550 is appropriately selected according to the material of the tool electrode 100 and the workpiece 200. For example, in the present embodiment, a 10% by weight solution of NaNO ₃ is used.

The outer cylinder tip 141 protrudes toward the workpiece 200 with respect to the inner cylinder tip 151. In the electrolytic machining, the tool electrode 100 and the workpiece 200 are not brought into contact with each other. At the time of processing, let c be the clearance of the outer cylinder tip 141 with respect to the surface of the workpiece 200. Further, the distance between electrodes is the distance between the inner cylindrical tip 151 and the surface of the workpiece 200 and g _w. Then, the projecting amount against the inner cylindrical tip 151 of the barrel tip portion _141, a _g w -c. In the present embodiment, the protruding amount is 50 μm.

  In such a cross-sectional structure, a flow path in a state where the tip portion 110 is sufficiently close to the surface of the workpiece 200 and the electrolytic solution 550 is sucked and circulated by the pump 500 will be described.

  The electrolytic solution 550 is introduced from the supply port 120 to the first inner through hole 121, passes through the first inner through hole 121, and reaches the discharge port 171. Then, the electrolytic solution 550 is discharged from the discharge port 171 by the suction force of the pump 500. Since the suction pressure acts from the suction port 172 side which is the central axis direction, and the outer cylinder tip 141 protrudes toward the surface side of the workpiece 200 and hardly leaks to the outside, almost the entire amount of the electrolyte 550 is It flows toward the suction port 172. That is, the electrolytic solution 550 moves to the suction port 172 so as to fill an inter-electrode space formed between the inner cylinder front end portion 151 and the surface of the workpiece 200. The electrolytic solution 550 taken into the tool electrode 100 again from the suction port 172 passes through the second inner through hole 131, reaches the recovery port 130, and is discharged to the outside.

  Further, the mechanism by which the electrolytic solution 550 circulates through the tip 110 of the tool electrode 100 will be described in detail with reference to FIG. FIG. 3 is a cross-sectional view of the tool electrode 100 and the workpiece 200 showing each stage of drilling.

  FIG. 3A is a diagram illustrating a state in which the tip portion 110 of the tool electrode 100 is gradually approaching the surface of the workpiece 200. At this stage, since the tip portion 110 is largely separated from the surface of the workpiece 200, only the air is taken in from the suction port 172 even if the pump 500 sucks, and therefore the electrolyte 550 is contained in the second inner portion. It is not led to the through hole 131. On the other hand, the first inner through hole 121 connected to the tank 520 is filled with the electrolytic solution 550. Here, as described above, the discharge port 171 is narrower than the cross section of the flow path of the first internal hole 121, and the supply port 120 is not connected to a pump for delivery. The surface tension at 171 stays in the first inner through hole 121 and does not drop from the discharge port 171. In the present embodiment, the electrolytic solution 550 is retained in the first inner through hole by surface tension, but the configuration in which the electrolytic solution 550 does not drop is not limited thereto. For example, a valve that opens and closes due to a pressure difference can be provided near the discharge port 171 to prevent dripping. Further, by adjusting the height of the supply port 120 and the height of the liquid level of the tank 520, dripping can be prevented by the pressure difference of the discharge port 171.

  FIG. 3B is a diagram illustrating a state in which the tip portion 110 of the tool electrode 100 has sufficiently approached the surface of the workpiece 200 and the electrolytic solution 550 has started to circulate. This is substantially the same as the state of the tip portion of FIG. When the tip 110 is gradually brought closer to the surface of the workpiece 200, the cross-sectional area of the flow path, which is the space between the inner cylinder tip 151 and the surface of the workpiece 200, is narrowed and taken in from the suction port 172. The air flow rate increases. Then, the pressure in the interelectrode space decreases due to the Benchery effect. When the pressure difference between the inter-electrode space and the first inner through hole 121 exceeds the threshold value, the electrolyte solution 550 that has remained in the first inner through hole until then blows out from the discharge port 171 and fills the inter-electrode space, and the suction port 172. It flows toward. Then, it is sucked up from the suction port 172 by the suction pressure and goes back through the second inner hole 131. In this way, circulation of the electrolytic solution 550 is started. If the distance between the tip portion 110 and the surface of the workpiece 200 is less than a certain distance, the circulation is continued.

Since the discharge port 171 is provided on the peripheral side of the suction port 172, the electrolytic solution 550 flows toward the central axis of the tool electrode 100. Therefore, it is possible to significantly reduce the leakage of the electrolyte solution 550 to the outside of the tip portion 110 rather than flowing toward the peripheral direction. That is, the electrolytic solution 550 can be circulated only in the processing region. Moreover, than the flow path cross-sectional g _w of interpolar space, since the small clearance c of the outer tube distal end portion 141 to the surface of the workpiece 200, while preventing leakage of the electrolytic solution 550, circulation of the electrolyte 550 It is also possible to reduce the inflow of air.

  After the circulation of the electrolytic solution 550 is started, energization by the power source 600 is started. When energization is started, the electrolytic reaction proceeds, and a hole corresponding to the shape of the tip 110 is gradually formed. When the hole grows, the inter-electrode distance gw increases, so that the tool electrode 100 is fed stepwise in the direction of the arrow (z-axis minus direction) as the hole grows.

  In the present embodiment, a delivery pump is not connected to the supply port 120, but a delivery pump that operates in cooperation with the pump 500 may be interposed in the supply tube 561. As described above, the Benchery effect occurs when the pressure difference between the interpolar space and the first inner hole 121 exceeds a threshold value. However, the delivery pump is actuated to temporarily turn the pressure in the first inner hole 121 temporarily. By increasing the efficiency, the blowing out of the electrolyte 550 can be promoted. By adopting such a configuration, the venturi effect can be effectively produced even for an electrolytic solution having a high viscosity, an electrolytic solution in which particulate matter is mixed, and the like.

FIG. 3C is a diagram illustrating a state in which the drilling has progressed to the machining depth f. In the present embodiment, since the electrolytic solution 550 can be supplied in a limited manner to the target processing region, the processing proceeds so that the tip shape of the tool electrode 100 is transferred as a substantially hole shape as illustrated. . That is, it is possible to realize highly accurate processing without progressing in a region other than the target processing region. In other words, the side gap g _s that is the distance between the side surface of the tool electrode 100 and the inner surface of the hole formed by processing can be reduced.

  Here, the difference with the processing method by the conventional electrolytic processing apparatus is demonstrated. A conventional electrolytic processing apparatus is configured such that at least a tool electrode tip is immersed in an electrolytic solution and approached to the workpiece with respect to a workpiece submerged in an electrolytic solution that fills an electrolytic bath, and a current is passed between the workpiece and the tool electrode. Was flowing. When such a configuration is adopted, a current path is also generated in the electrolyte solution between the tool electrode and a region other than the workpiece target region (the region facing the tip of the tool electrode). Machining has progressed in areas other than the machining target area. That is, the presence of the electrolytic solution outside the processing region causes a drift current to be generated, leading to a decrease in processing accuracy. In addition, in such a configuration, a large electrolytic bath is required, which consumes a large amount of electrolytic solution and is not preferable from the viewpoint of environmental pollution.

  In addition, according to another conventional electrolytic processing apparatus, the generated solution is removed by directly injecting the electrolytic solution onto the workpiece, thereby improving the processing speed. However, since the electrolytic solution is not supplied only to the target processing region, the processing accuracy is only slightly improved, and a large amount of electrolytic solution is still consumed.

  For example, when mirror machining is performed instead of drilling, only the area facing the tip of the tool electrode is not the target machining area, and the electrolyte may flow out in the plane direction. Even if it is the structure which injects from the center axis | shaft of an electrode, there are few problems on processing accuracy. However, in order to realize drilling with high accuracy, it is important that the electrolytic solution is distributed only in the target processing region, in other words, the region other than the target processing region is not immersed in the electrolytic solution. From this point of view, the electrolytic processing machine is required to discharge the electrolytic solution to the target processing area and to reliably recover the liquid without leaking from the target processing area. The electrolytic processing apparatus 10 according to the present embodiment has an advantage that the processing accuracy is excellent by satisfying these requirements, and processing can be performed with a small amount of electrolytic solution.

  Next, the relationship between the distance between the electrodes and the suction pressure during drilling will be described. FIG. 4 is a diagram showing the relationship between the distance between the electrodes and the suction pressure during drilling. In the figure, the horizontal axis represents the distance (μm) between the inner cylinder tip 151 and the surface of the workpiece 200, and the vertical axis represents the suction pressure (kPa) indicated by the pressure gauge 510. Each curve represents the relationship of the suction pressure with respect to the distance between the poles for each feed amount indicating how much the tip portion 110 is fed in the direction of the machining hole with respect to the surface of the workpiece 200, as shown in the legend.

  As is apparent from the figure, once the processing has progressed, the relationship between the distance between the electrodes and the suction pressure is approximately the same regardless of the amount of feed. In particular, when the feed amount exceeds 300 μm, the degree of coincidence is high. In the region where the distance between the electrodes is less than about 100 μm, the amount of change in the suction pressure with respect to the change in the distance between the electrodes is large as a whole. In particular, it can be said that this tendency is strong when the feed amount exceeds 300 μm.

  From this experimental result, it can be seen that the distance between the electrodes can be estimated by monitoring the suction pressure. Therefore, in the present embodiment, the electrolytic processing apparatus 10 repeats the operation of feeding the tool electrode 100 by a certain amount when the suction pressure of the pressure gauge 510 monitored by the CPU 710 exceeds a predetermined threshold value, so that the processing hole of the target depth is obtained. Form. The threshold value of the suction pressure is set to, for example, −12 kPa corresponding to about 100 μm, which is a boundary value between a region where the amount of change in suction pressure with respect to a change in the interelectrode distance is large and a region where the suction pressure is small. Further, the feed amount may be an amount smaller than the distance between the electrodes, but is 10 μm here in consideration of the safety width.

  Immediately after the tool electrode 100 is sent, the distance between the electrodes is about 90 μm, so that the suction pressure is temporarily reduced. Then, after a while, the processing proceeds and the distance between the electrodes opens again, and the suction pressure becomes larger than −12 kPa. Then, the tool electrode 100 is fed again by 10 μm. Such an operation is repeated until the hole depth f reaches the target value.

  In the conventional electrolytic processing apparatus, it is difficult to measure the distance between the electrodes. In many cases, the feed amount of the tool electrode per unit time is determined based on an empirical rule. However, since the feed control is not based on the actual distance between the poles, the processing speed is uneven or the processing shape is not stable. However, as in this embodiment, the control for monitoring the suction pressure having a correlation with the distance between the electrodes and sending the tool electrode is so-called feedback control. According to such control, the optimum machining speed and stable The processed shape can be obtained. Even in the case where the delivery pump is supplementarily provided as in the above-described application example, if the delivery pump is stopped at the stage of monitoring the suction pressure, the feedback control can be executed similarly. . In addition, according to the present embodiment, the electrolyte solution 550 is circulated at the tip portion 110 of the tool electrode 100. However, the present invention is not limited to such a configuration. For example, the tool electrode tip is immersed in the electrolyte solution in the electrolyte bath and processed. Even in this apparatus, the feedback control based on the estimation of the distance between the electrodes can be similarly performed by monitoring the pressure of the electrolyte sucked from the tip of the tool electrode.

  Next, the relationship between the feed amount of the tool electrode 100 and the side gap will be described. FIG. 5 is a diagram showing the relationship between the feed amount and the side gap. The horizontal axis represents the feed amount (μm) of the tool electrode 100, and the vertical axis represents the side gap (μm).

  As shown in the drawing, it has been clarified through experiments that if the tool electrode is fed at least 300 μm or more, then the machining does not proceed on the side of the tool electrode. In the case of this experimental data, the side gap is stable at about 220 μm, which is a very small value compared to the side gap by the conventional electrolytic processing apparatus.

  In the case of a machining apparatus that immerses the workpiece and the tool electrode in the electrolytic solution, the electrolytic solution also penetrates into the side gap, so that current also flows in the lateral direction, and machining in the lateral direction proceeds as the feed amount increases. As a result, the inner surface of the hole has a truncated cone shape with the tip end side as the apex side. However, the inner surface of the hole processed by the electrolytic processing apparatus 10 according to the present embodiment has a stable side gap with the tool electrode at a constant value, that is, a predetermined cylindrical surface is realized. Therefore, according to the electrolytic processing apparatus 10 in the present embodiment, it is possible to realize highly accurate processing not only two-dimensionally but also three-dimensionally.

  Next, control of the CPU 710 will be described. FIG. 6 is a control flow diagram of drilling. The flow starts when the tool electrode 100 is mounted on the holder 400 and the electrolytic processing apparatus 10 is activated.

  In step S101, the CPU 710 starts the pump 500 and starts suction. At this time, it is a stage of Fig.3 (a) and air is inhaled through the 2nd internal through-hole 131. FIG.

  In step S102, the CPU 710 drives the drive unit 420 to gradually bring the tool electrode 100 closer to the workpiece 200. In step S103, the CPU 710 receives the output value of the pressure gauge 510 and determines whether or not the circulation of the electrolyte 550 is started by determining whether or not the output value is included in the pressure range at the time of circulation of the electrolyte 550. Judge whether or not. The mechanism by which the electrolytic solution 550 starts to circulate when the tip 110 of the tool electrode 100 approaches the planned machining position 210 of the workpiece 200 is as described with reference to FIG. If it is determined that the circulation of the electrolytic solution 550 has not yet started, the process returns to step S102.

  If it is determined that the circulation of the electrolytic solution 550 has started, the CPU 710 causes the power source 600 to start energization between the tool electrode 100 and the workpiece 200 in step S104. In the workpiece 200, the electrolytic reaction starts from this point and the generation of holes proceeds.

CPU710, by continuously receive the output value _{P t} of the pressure gauge 510 monitors the suction pressure during drilling. In step S105, the CPU 710 determines whether or not the output value P _t as the suction pressure has exceeded a predetermined threshold value P ₀ (−12 kPa in the example described with reference to FIG. 4). If it is determined that it has not exceeded, step S105 is periodically repeated.

If it is determined that it has been exceeded, the CPU 710 integrates the feed amounts of the tool electrode 100 up to that time to determine whether or not the target depth has been reached in step S106. If it is determined that the target depth has not been reached, the process proceeds to step S107, and the tool electrode 100 is sent by a distance D ₀ (10 μm in the example described with reference to FIG. 4) that is a predetermined distance. Then, the process returns to step S105. By repeating Step S105 to Step S107, the machining hole becomes deep. As described above, the CPU 710 and the drive unit 420 function as an adjustment unit that adjusts the distance between the tool electrode 100 and the workpiece 200.

  If it is determined in step S106 that the target depth has been reached, the process proceeds to step S108, and the CPU 710 stops energization by the power source 600. In step S109, the driving unit 420 is driven to retract the tool electrode 100 from the workpiece 200. Then, since the circulation of the electrolytic solution 550 is automatically stopped in the retreating process, the suction of the pump 500 is stopped in step S110, and the series of hole processing is finished.

  Although the hole processing has been described above, the electrolytic processing apparatus can be applied to processing other than hole processing. FIG. 7 is a conceptual diagram illustrating an application to planar processing.

As shown in FIG. 7A, a case where an N-shaped recess is formed on the surface of the workpiece 220 will be described. The electrolytic processing apparatus includes a drive unit that moves the tool electrode 100 in the xy plane direction, and sweeps the tool electrode 100 several times along the N shape according to the target depth. At this time, as shown in FIG. 7 (b), the machining depth s to proceed in a single sweep, keep smaller than inter-electrode distance g _w. If s <g _w , the tool electrode 100 can be moved in the direction of the arrow, so that the depth can be gradually increased by repeating the sweep, and the N-shaped concave portion of the target depth is formed on the workpiece. 220 can be formed on the surface.

  Next, variations of the applied voltage will be described. In each of the above-described examples, pulse application control for applying a positive potential to the workpiece while maintaining the tool electrode at the ground potential is performed. However, the application control is not limited to this.

  It is known that if the pulse application control is performed, the machining accuracy is improved. However, if the workpiece potential is repeatedly turned on and off between 0 and + V volts, it will be instantaneous due to overshoot at the fall of the pulse. Negative potential. In the pulse application control, ON and OFF are repeated many times in a short time, so that the accumulated time for the negative potential is increased, resulting in melting of the tool electrode. That is, when pulse application control is performed with reference to 0 volts, the tool may be consumed. Until now, in order to avoid the consumption of the tool electrode, direct current application control has been performed instead of pulse application control.

Variations of application control in this embodiment will be described. FIG. 8 is a diagram showing variations of application control. The CPU 710 can be controlled to give a positive potential offset voltage by slightly raising the reference voltage of the workpiece. That is, by applying an offset voltage to the workpiece with respect to the grounded tool electrode, the potential of the workpiece during machining is not lowered to 0 V or less. The pulse voltage is set to a higher voltage with this offset voltage as a reference. In this case, as shown in the drawing, the high level voltage is V _HI , the low level voltage (offset voltage) is V _LO, and a fixed stop time is provided for each X _p pulse. In this case, a low level voltage is also applied to the stop time. Specifically, when setting the V _HI to about 10V, V _LO is that may be, for example, about 2V in the range of about 30% from 10% of V _HI was found experimentally. In this way, if the offset voltage is provided on the same polarity side, the possibility that the potential is inverted at the fall of the pulse is reduced, and thus the consumption of the tool electrode can be avoided.

  Further, if the tool electrode is vibrated during a certain stop time, impurities adhering to the tool electrode can be removed or the electrolytic solution can be stirred. Specifically, when the piezoelectric element attached to the tool electrode is controlled by the CPU 710, the tool electrode can be vibrated in synchronization with the stop time.

  In the present embodiment described above, the double-cylindrical tool electrode 100 has been described. However, the tool electrode structure is not limited to a combination of two cylinders. The first inner hole and the second inner hole may be formed in the metal rod by drilling. In this case, it is preferable that the discharge port of the first inner through hole is provided on the peripheral side at the tip portion than the suction port of the second inner through hole. Further, the tool electrode is not limited to a cylindrical shape, and various shapes can be adopted. For example, if a square pole-shaped tool electrode is used, a square hole can be formed in a workpiece instead of a round hole.

  In addition, according to the tool electrode 100 in the present embodiment, the electrolytic solution can be circulated only in the target machining area, so that unlike the conventional electrolytic machining apparatus, it can be easily applied to three-dimensional machining. . For example, if the holder that holds the tool electrode has a moving mechanism that allows the tip of the tool electrode to approach a fixed workpiece from various directions different from the vertical direction, such as a robot hand The processing progress direction is not limited to the vertical direction. That is, the electrolytic processing apparatus provided with such a moving mechanism can process a workpiece three-dimensionally.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

DESCRIPTION OF SYMBOLS 10 Electrolytic processing apparatus, 100 Tool electrode, 110 Tip part, 120 Supply port, 121 1st internal through-hole, 130 Recovery port, 131 2nd internal through-hole, 140 Outer cylinder, 141 Outer cylinder tip, 150 Inner cylinder, 151 Inner cylinder tip, 160 O-ring, 171 discharge port, 172 suction port, 200 workpiece, 210 planned processing position, 220 workpiece, 300 stage, 310 chuck, 400 holder, 410 strut, 420 drive unit, 490 arrow, 500 Pump, 510 pressure gauge, 520 tank, 561 supply tube, 562 recovery tube, 563 reflux tube, 580 filtration device, 600 power supply, 610 power line, 620 ground line, 700 control unit, 710 CPU, 720 operation panel

Claims (12)

An approach process for bringing the tool electrode closer to the workpiece;
A circulation step of circulating the electrolyte using only suction force in the order of the inside of the tool electrode, the tip of the tool electrode and the surface of the workpiece, and the inside of the tool electrode;
An energization step of passing a current between the tool electrode and the workpiece via the electrolytic solution ;
A feeding step of feeding the tool electrode to the workpiece side based on a change in pressure for sucking the electrolytic solution .   The electrolytic processing method according to claim 1, wherein in the circulation step, the electrolytic solution is caused to flow from a peripheral side to a central side at the tip portion.   In the circulation step, the electrolysis is performed using a Benchery effect generated by a cross section of a flow path formed between the tip of the tool electrode and the surface of the workpiece being smaller than a cross section of another flow path. The electrolytic processing method according to claim 1 or 2, wherein the liquid is circulated.   The electrolytic processing method according to claim 3, wherein in the circulation step, the electrolytic solution remains inside the tool electrode until the electrolytic solution is circulated by the Benchery effect. A tool electrode for electrolytic processing comprising a first inner through-hole through which an electrolytic solution is circulated and discharged from the tip portion, and a second inner through-hole through which the electrolytic solution is sucked and circulated from the tip portion ;
A suction pump connected to the second inner through hole for circulating the electrolyte using only suction force;
A pressure detector for detecting the pressure of the suction pump;
A drive unit for sending the tool electrode to the workpiece side based on a change in pressure for sucking the electrolytic solution;
An electrolytic processing apparatus comprising: 6. The electrolytic processing apparatus according to claim 5 , wherein the discharge port of the first inner through hole is provided closer to the peripheral side at the tip than the suction port of the second inner through hole. The electrolytic processing apparatus according to claim 6 , wherein a peripheral edge side of the distal end portion protrudes toward a workpiece from an inner peripheral side of the discharge port. The tool electrode is
An inner cylinder forming the second inner through hole ;
The electrolytic processing apparatus according to claim 5, further comprising: an outer cylinder that is inserted through the inner cylinder and forms the first inner through hole between the inner cylinder and the inner cylinder. The electrolytic processing apparatus according to claim 8, wherein an inner cylinder distal end portion of the inner cylinder, which is a part of the distal end portion, has a flange portion extending in an outer cylinder direction. The electrolytic processing apparatus according to any one of claims 5 to 9, further comprising a moving mechanism that allows the tool electrode to approach the workpiece from a direction different from a vertical direction. 11. The electrolytic processing apparatus according to claim 5, further comprising a control unit that performs pulse application control to apply a high level voltage based on a positive low level voltage to the workpiece. The electrolytic processing apparatus according to claim 11, wherein the low level voltage is a voltage that is 10% or more and lower than 30% of the high level voltage.

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