Electrical discharge machine

Abstract

The present invention provides an electric discharge machine capable of reducing splashing and overflowing of liquid flowing from a drain. An electric discharge machine (10) of one embodiment has a liquid tank (52) that stores liquid, a drain valve (54) that opens and closes a drain (62) for draining the liquid stored in the liquid tank (52), an actuator (56) that drives the drain valve (54), a water level sensor (58) that detects the water level of the liquid stored in the liquid tank (52), and a control unit (60) that controls the actuator (56) in such a manner that the amount of opening of the drain valve (54) increases as the water level detected by the water level sensor (58) decreases.

Description

TECHNICAL FIELD

[0001] The present application relates to an electro-discharge machine that processes a processing target by discharging generated by applying a voltage between electrodes of the processing target and the electrodes. BACKGROUND

[0002] In Japanese Patent Application Publication No. 2000-210818, a wire electro-discharge machine is disclosed that has an opening and closing door provided by an actuator driving an opening and closing drain of a processing tank. The wire electro-discharge machine detects the liquid level of the processing liquid in the processing tank at the time of stopping the processing tank by a liquid level detecting sensor, and calculates the discharge time corresponding to the detected height. SUMMARY

[0003] However, in the case of the wire electro-discharge machine of Japanese Patent Application Publication No. 2000-210818, if the opening and closing door is fully opened at the time of discharge, although the time until the liquid in the processing tank disappears (discharge time) becomes short, there is a concern that the liquid flowing out from the drain splashes and overflows.

[0004] Therefore, an object of the present application is to provide an electro-discharge machine that can reduce the splashing and overflowing of the liquid flowing out from the drain.

[0005] The electro-discharge machine according to the present application has a liquid tank that stores a liquid, a drain valve that opens and closes a drain for discharging the liquid stored in the liquid tank, and an actuator that drives the drain valve, and further has a water level sensor that detects the water level of the liquid stored in the liquid tank, and a control section that controls the actuator in such a manner that the opening amount of the drain valve becomes larger as the water level detected by the water level sensor becomes lower.

[0006] According to the present application, the variation in the amount of liquid flowing out from the drain per unit time can be suppressed, as a result of which the elongation of the drain time can be suppressed, and the splashing and overflowing of the liquid flowing out from the drain can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a diagram showing the configuration of the electro-discharge machine.

[0008] Figure 2 is a diagram showing the configuration of the drain mechanism of the electro-discharge machine.

[0009] Figure 3 is a relational graph showing the relationship between the water level and the opening amount. DETAILED DESCRIPTION

[0010] The present application will be described in detail below with reference to preferred embodiments, with reference to the accompanying drawings.

[0011] [Embodiment]

[0012] Figure 1 A schematic diagram of the discharge machining apparatus 10 according to the embodiment is shown. Figure 1 The X direction, the Y direction, and the Z direction in which the axes of the discharge machining apparatus 10 extend are shown. In addition, the X direction and the Y direction are orthogonal to each other in a plane, and the Z direction is orthogonal to the X direction and the Y direction, respectively. In addition, the -Z direction is the direction in which the force of gravity acts (the direction of gravity).

[0013] The discharge machining apparatus 10 performs machining on a machining target by discharge generated by applying a voltage between electrodes of the machining target. The machining target is also referred to as a workpiece or a work. The discharge machining apparatus 10 includes a machining apparatus main body 12, a machining liquid processing device 14, and a control device 16 that controls the machining apparatus main body 12 and the machining liquid processing device 14.

[0014] The machining apparatus main body 12 includes a machining tank 17 and an electrode 18. The machining tank 17 stores a liquid for immersing the machining target. The electrode 18 is used to machine the machining target. A worktable that holds the machining target is provided inside the machining tank 17. The electrode 18 is provided so as to be relatively movable with respect to the worktable. In a state in which the machining target and the electrode 18 are immersed in the liquid stored in the machining tank 17, a voltage is applied between the electrodes of the electrode 18 and the machining target, and the machining target is machined by discharge generated between the electrodes. Sludge is generated at the time of machining.

[0015] The machining liquid processing device 14 supplies a liquid (machining liquid) used in machining of the machining target to the machining tank 17. For example, deionized water or the like can be used as the machining liquid. The machining liquid processing device 14 can also recover the machining liquid discharged from the machining tank 17. In a case in which the machining liquid processing device 14 recovers the machining liquid discharged from the machining tank 17, sludge contained in the recovered machining liquid can be removed, the quality of the recovered machining liquid can be adjusted, and the like, and the machining liquid from which the sludge has been removed and whose quality has been adjusted can be returned to the machining tank 17.

[0016] In addition, the electrode 18 of the machining apparatus main body 12 can be a wire electrode or a shaped electrode used for die sinking. Figure 1 A machining apparatus main body 12 in which the electrode 18 is a wire electrode is shown. In a case in which the electrode 18 is a wire electrode, the machining apparatus main body 12 includes a supply system 20 and a recovery system 22. The supply system 20 supplies the electrode 18 to the machining target. The recovery system 22 recovers the electrode 18 that has passed through the machining target.

[0017] The supply system 20 has a bobbin 24 on which the unused electrode 18 is wound, a torque motor 26 that applies a torque to the bobbin 24, a brake shoe 28 that applies a brake force generated by friction to the electrode 18, a brake motor 30 that applies a brake torque to the brake shoe 28, a tension detection section 32 that detects the magnitude of the tension of the electrode 18, and an upper die guide 34 that guides the electrode 18 above the machining target object.

[0018] The recovery system 22 has a lower die guide 36 that guides the electrode 18 below the machining target object, pinch rollers 38 and a feed roller 40 that can hold the electrode 18, a torque motor 42 that applies a torque to the feed roller 40, and a recovery tank 44 that recovers the electrode 18 after being conveyed by the pinch rollers 38 and the feed roller 40.

[0019] A support section 34a that supports the electrode 18 is provided to the upper die guide 34, and a support section 36a that supports the electrode 18 is provided to the lower die guide 36. In addition, a guide roller 36b that changes the orientation of the electrode 18 and guides it to the pinch rollers 38 and the feed roller 40 is provided to the lower die guide 36.

[0020] During machining, the upper die guide 34 and the lower die guide 36 are disposed within the groove of the machining tank 17 and are immersed in the machining liquid accumulated in the machining tank 17. In addition, at least the upper die guide 34 among the upper die guide 34 and the lower die guide 36 can also eject clean machining liquid that does not contain sludge toward the electrode 18 and the electrode-to-machining-target-object gap. In the case where clean machining liquid is ejected toward the electrode 18 and the electrode-to-machining-target-object gap, the gap is filled with clean liquid suitable for machining, and the decrease in machining accuracy caused by sludge generated by machining can be reduced.

[0021] Figure 2 A diagram showing the configuration of a drainage mechanism 50 of the electro-discharge machine 10. The drainage mechanism 50 is a mechanism that drains the liquid accumulated in a liquid tank 52. The liquid tank 52 can also be the machining tank 17. In addition, in the case where the machining liquid is recovered by the machining liquid treatment device 14, the liquid tank 52 can also be a sewage tank or a clean water tank provided to the machining liquid treatment device 14. In addition, the sewage tank is a tank that accumulates machining liquid containing sludge (sewage), and the clean water tank is a tank that accumulates machining liquid after passing through a filter that removes sludge (clean water) from the sewage tank.

[0022] The drainage mechanism 50 is provided with a drain valve 54, an actuator 56, a water level sensor 58, and a control section 60.

[0023] The drain valve 54 is a valve that opens and closes a drain port 62 for draining the liquid accumulated in the liquid tank 52. The drain port 62 can be provided to the liquid tank 52 or to a communication section 64 that communicates with the liquid tank 52. Figure 2The drain port 62 is provided in the communication portion 64 in this embodiment. The drain valve 54 is arranged so as to cover the drain port 62 provided in the bottom wall 64W of the communication portion 64.

[0024] The configuration of the communication portion 64 is not particularly limited. Figure 2 The communication portion 64 is configured in a box shape, and protrudes outward from the side wall 52W of the sump 52. The capacity and height of the communication portion 64 are smaller than those of the sump 52. The inner bottom surface of the communication portion 64 is at the same level as the inner bottom surface of the sump 52.

[0025] The actuator 56 drives the drain valve 54. The actuator 56 drives the drain valve 54 so as to change the opening amount of the drain valve 54 with respect to the drain port 62. In addition, in the case where the drain valve 54 closes the drain port 62, the opening amount of the drain valve 54 is zero. In the case where the opening amount of the drain valve 54 is greater than zero, the liquid accumulated in the sump 52 flows out from the drain port 62 through the communication portion 64, and falls to the water receiving portion of the drain passage 66 due to gravity. The drain passage 66 supplies the liquid that has fallen to the water receiving portion of the drain passage 66 to, for example, the processing liquid treatment device 14.

[0026] The actuator 56 can be pneumatic, electric, hydraulic, or solenoid. In this embodiment, the actuator 56 is electric, and has a servo motor 56A. The servo motor 56A rotates and changes the opening amount of the drain valve 54 in accordance with the control of the control portion 60. That is, the servo motor 56A rotates in the positive direction (or the negative direction) to drive the drain valve 54 in the direction away from the drain port 62 (in the direction opposite to the direction of gravity), and increases the opening amount of the drain valve 54. In addition, the servo motor 56A rotates in the negative direction (or the positive direction) to drive the drain valve 54 in the direction close to the drain port 62 (in the direction of gravity), and decreases the opening amount of the drain valve 54.

[0027] The water level sensor 58 detects the water level of the processing liquid accumulated in the sump 52, and outputs a signal indicating the water level. The water level sensor 58 can be contact type or non-contact type. The contact type water level sensor 58 can be, for example, float type, capacitance type, electrode type, pressure type, differential pressure type, or the like. The non-contact type water level sensor 58 can be, for example, electric wave type, ultrasonic wave type, or the like.

[0028] Further, the float type is configured to convert the rotation angle of a pulley connected to a float disposed on the liquid surface via an electric wire into an electric level. The capacitance type is configured to convert the change in capacitance between a probe and the groove wall of a container into an electric level. The electrode type is configured to convert the change in resistance between electrodes of a length corresponding to each liquid level into an electric level. The pressure type is configured to convert the deformation of a diaphragm caused by the liquid level into an electric level. The differential pressure type is configured to convert the change in pressure difference between the hydraulic pressure and the pressure inside the container into an electric level. The electric wave type is configured to emit a microwave whose frequency is changed, measure the frequency difference between the received signal reflected from the liquid surface and the transmission signal emitted at that time, and convert it into an electric level. The ultrasonic wave type is configured to measure the time until the ultrasonic wave emitted in a pulse shape is reflected from the measurement object and convert it into an electric level.

[0029] The control section 60 controls the actuator 56, which is provided to the control device 16. The control section 60 changes the opening amount of the drain valve 54 by controlling the actuator 56 at the time of machining stop when the machining of the machining object is stopped. In the present embodiment, the control section 60 can finely change the opening amount of the drain valve 54 by controlling the servo motor 56A of the actuator 56.

[0030] However, the higher the water level of the liquid accumulated in the sump 52 at the time of machining stop, the greater the water pressure of the liquid, and the outflow amount of the liquid from the drain port 62 per unit time increases. Therefore, if the opening amount of the drain valve 54 is fully open from the initial stage of drainage, splashing and overflowing of the liquid falling from the drain port 62 to the water receiving portion of the drain passage 66 easily occur at the initial stage of drainage. In addition, if the opening amount of the drain valve 54 is constant in a relatively small state from the initial stage of drainage, the drainage time easily becomes long.

[0031] Therefore, the control section 60 controls the actuator 56 in such a manner that the lower the water level detected by the water level sensor 58, the greater the opening amount of the drain valve 54 with respect to the drain port 62. Thereby, the change in the outflow amount of the liquid from the drain port 62 per unit time can be suppressed, as a result of which the elongation of the drainage time can be suppressed, and splashing and overflowing of the liquid from the drain port 62 can be reduced.

[0032] In the present embodiment, the control section 60 is configured by a computer including a processor, a storage section 60A. The storage section 60A stores correspondence information corresponding the water level to the opening amount of the drain valve 54.

[0033] Figure 3The relationship graph shows that the relationship between the water level and the opening amount is a linear straight line waveform Wl, the relationship is a convex curve waveform W2 that is non-linear and convex, and the relationship is a concave curve waveform W3 that is non-linear and concave. The straight line waveform Wl, the convex curve waveform W2, and the concave curve waveform W3 all have a relationship in which the lower the water level, the greater the opening amount.

[0034] The storage section 60A stores a relationship formula or a work sheet that represents the relationship of at least one of the straight line waveform Wl, the convex curve waveform W2, and the concave curve waveform W3 as the corresponding information. The work sheet includes a plurality of water levels and opening amounts corresponding to the plurality of water levels.

[0035] In the case where the relationship formula is stored in the storage section 60A, the control section 60 calculates the opening amount corresponding to the water level detected by the water level sensor 58 using the relationship formula stored in the storage section 60A, and controls the actuator 56 so as to reach the calculated opening amount. Thus, compared to the case where the work sheet is stored in the storage section 60A, the amount of the corresponding information stored in the storage section 60A can be reduced.

[0036] In the case where the work sheet is stored in the storage section 60A, the control section 60 acquires the opening amount corresponding to the water level detected by the water level sensor 58 using the work sheet, and controls the actuator 56 so as to reach the acquired opening amount. Thus, the actuator 56 can be controlled without performing the calculation of the opening amount, and as a result, the load on the control section 60 can be reduced.

[0037] In addition, in the case where a plurality of relationship formulas or work sheets are stored as the corresponding information, the control section 60 can control the actuator 56 based on the corresponding information selected from among the plurality of corresponding information according to the operation of the operator or the like. Thus, even if the model of the electro-discharge machine 10 is different, or the liquid tank 52 is replaced with a liquid tank having a different shape, size, or the like, so that the type of the liquid tank 52 changes, the lengthening of the drain time can be suppressed, and at the same time, the splashing or overflowing of the liquid flowing out from the drain port 62 can be reduced.

[0038] In addition, the control section 60 can control the actuator 56 so that the flow rate of the liquid discharged from the drain port 62 is constant. For example, the control section 60 controls the actuator 56 based on the corresponding information that represents the relationship between the water level and the opening amount of the liquid discharged from the drain port 62 so that the flow rate is constant. In addition, in the case where a flow rate sensor is provided on the drain port 62, the control section 60 can perform feedback control on the actuator 56 so that the flow rate detected by the flow rate sensor reaches a target value. By controlling the actuator 56 so that the flow rate of the liquid discharged from the drain port 62 is constant, the control section 60 can suppress the variation in the amount of the liquid flowing out from the drain port 62 per unit time.

[0039] [Modifications]

[0040] The above-described embodiments can also be modified as follows.

[0041] For example, the control section 60 can also switch the drive power output to the actuator 56 in accordance with the level of the signal output from the water level sensor 58, to control the actuator 56 in a manner in which the opening amount of the drain valve 54 is greater the lower the water level. In this way, the actuator 56 can be controlled without performing data computation.

[0042] [Invention derived from the embodiments]

[0043] The present application is a discharge machining device (10) having a liquid tank (52) that stores a liquid, a drain valve (54) that opens and closes a drain port (62) for draining the liquid stored in the liquid tank (52), and an actuator (56) that drives the drain valve (54). The discharge machining device (10) also has a water level sensor (58) that detects the water level of the liquid stored in the liquid tank (52), and a control section (60) that controls the actuator (56) in a manner in which the opening amount of the drain valve (54) is greater the lower the water level detected by the water level sensor (58). Thus, the variation in the amount of the liquid that flows out of the drain port (62) per unit time can be suppressed, which results in the suppression of the elongation of the drain time, and the reduction of the splashing and overflowing of the liquid that flows out of the drain port (62).

[0044] The discharge machining device (10) has a storage section (60A) that stores correspondence information that associates the water level with the opening amount, and the control section (60) controls the actuator (56) in a manner in which the opening amount corresponding to the water level detected by the water level sensor (58) is reached. Thus, even if there is a design change of the liquid tank (52) or the like, the mechanical system does not need to be changed, and the actuator (56) can be controlled by merely changing the correspondence information, which makes it easy to cope with the design change of the liquid tank (52) or the like.

[0045] The correspondence information can also be a work table that includes a plurality of water levels and the opening amounts corresponding to the plurality of water levels, respectively. Thus, the actuator (56) can be controlled without performing the computation of the opening amount, which results in the reduction of the load on the control section (60).

[0046] The storage section (60A) stores a plurality of correspondence information, and the control section (60) controls the actuator based on the correspondence information selected from the plurality of correspondence information. Thus, even if the type of the liquid tank (52) changes, the elongation of the drain time can be suppressed, and the splashing and overflowing of the liquid that flows out of the drain port (62) can be reduced.

[0047] The control section (60) can also control the actuator (56) in a manner in which the flow rate of the liquid that is drained from the drain port (62) is constant. Thus, the variation in the amount of the liquid that flows out of the drain port (62) per unit time can be suppressed.

[0048] The liquid tank (52) can also be a processing tank (17) that stores a liquid used for immersion processing of the processing target. Thus, the liquid containing sludge generated by processing can be discharged.

[0049] The actuator (56) can also include a servo motor (56A). Thus, the opening amount of the drain valve (54) can be finely changed.

[0050] Symbol Explanation

[0051] 10: electrical discharge machine, 17: processing tank, 52: liquid tank, 54: drain valve, 56: actuator, 56A: servo motor, 58: water level sensor, 60: control section, 60A: storage section, 62: drain.

Claims

1. An electric discharge machine having: a tank (52) that stores a liquid; a drain valve (54) that opens and closes a drain port (62) for draining the liquid stored in the tank; and an actuator (56) that drives the drain valve, characterized by further comprising: a water level sensor (58) that detects a water level of the liquid stored in the tank; and a control section (60) that controls the actuator in such a manner that the more the water level detected by the water level sensor is lower, the more the opening amount of the drain valve is increased.

2. The electric discharge machine according to claim 1, characterized in that: there is a storage section (60A) that stores correspondence information that causes the water level and the opening amount to correspond to each other, and the control section controls the actuator in such a manner that the opening amount corresponding to the water level detected by the water level sensor is reached.

3. The electric discharge machine according to claim 2, characterized in that: the correspondence information is a work table that includes a plurality of the water levels and the opening amounts corresponding to the plurality of the water levels, respectively.

4. The electric discharge machine according to claim 2 or 3, characterized in that: the storage section stores a plurality of the correspondence information, and the control section controls the actuator based on the correspondence information selected from among the plurality of the correspondence information.

5. The electric discharge machine according to any one of claims 1 to 4, characterized in that: the control section controls the actuator in such a manner that the flow rate of the liquid drained from the drain port is constant.

6. The electric discharge machine according to any one of claims 1 to 5, characterized in that: the tank is a processing tank (17) that stores the liquid used for immersion processing of a processing target.

7. The electric discharge machine according to any one of claims 1 to 6, characterized in that: the actuator includes a servo motor (56A). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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