JPH0698538B2 - Damage detection device for machining fluid suction pump of electric discharge machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a machining liquid treatment system of an electric discharge machine, and more particularly, to an electric discharge machining section for performing electric discharge machining of a work by a forming electrode in a machining liquid tank. From the machining tank, which sucks machining dust, gas, etc., generated by the discharge from the machining tank together with the machining fluid, in particular, has a pair of machining fluid suction chambers,
The wall of each machining fluid suction chamber pulsates according to the supply of pressurized air. The machining fluid suction pump in the machining fluid processing system equipped with an air-operated machining fluid suction pump formed by a diaphragm detects damage to the machining fluid suction pump and stops electrical discharge machining. The present invention relates to a damage detection device for a machining fluid suction pump of an electric discharge machine that can perform required control processing such as.

[Prior art]

In the electric discharge machine, especially in the die-sinking electric discharge machine, the electric discharge machining electrode progresses the machining into the desired shape by causing the electric discharge with heat generation between the total shape electric discharge electrode and the workpiece. The work is always performed inside the processing tank in which the cooled processing liquid is stored. The machining fluid also has a function of removing machining chips removed from the work by electric discharge machining from the surface of the work. For this reason, the machining fluid always circulates between the machining fluid supply tank and the machining tank where electrical discharge machining is performed via a certain circulation system, and when returning to the machining fluid supply tank, the required machining fluid treatment such as removal of machining chips is performed. After that, it is again sent to the supply system. Generally, a machining fluid processing system that circulates and processes the machining fluid is supplied from a machining fluid supply tank to a machining tank by an electric pump, and the machining fluid overflowing from the machining tank is collected in the machining fluid supply tank. , The electric discharge machining method that increases the machining speed with large electric discharge energy to perform rough machining has come to be performed, and the generation of machining scraps and gas generated by discharge heat from the machining part has increased. As a method to do so, a machining fluid flow passage is provided in the electric discharge machining electrode and is connected to a suction pump, and a machining fluid suction pump circuit is provided that sucks and collects machining debris and generated gas spouting from the machining section while mixing with the machining fluid. To be (For example,
63-221929). And, as this suction pump, various operating type pumps can be applied,
An air pump that uses compressed air compressed by a compressor as a working medium may be used. This aird pump is provided outside the machining tank and sucks the machining liquid in which machining chips and generated gas are mixed from the electric discharge machining section through a pipe line. The suctioned machining fluid is subjected to a process of separating the machining waste by a machining waste separation device after the outlet of the suction pump, and is returned from the liquid discharge port at the lower part of the device to the machining fluid supply tank via the reflux pipe. On the other hand, the processing waste is sent to the upper part of the apparatus by a screw type feeding mechanism provided in the processing waste separating device, and is processed to be collected in an appropriate processing waste collection box from the processing waste outlet. In addition, various treatment methods have been already proposed, such as absorbing the generated gas into the working fluid or opening it to the atmosphere after the deodorizing treatment.

[Problems to be Solved by the Invention]

However, conventionally, in the machining fluid suction pump circuit in the above-mentioned electric discharge machine, the diaphragm forming the machining fluid suction chamber in the aird pump for suctioning the machining fluid is damaged during repeated use, and the working medium is damaged from the damaged portion. If there is a failure that the pressure air leaks, or if the switching valve provided in the pressure air circuit, which is the working medium, fails or stops, the pressure air supply source also fails and the pressure of the working air Even if the specified suction pump action is no longer achieved, etc., it is necessary to quickly detect it and send an alarm signal to the control system of the electric discharge machine before providing an advanced configuration. There is a problem that has not been reached, and as a result, due to the collection failure of machining liquid such as machining scraps and gas from the electric discharge machining part while the operator's monitoring was interrupted,
There was a problem to be solved such as sometimes causing processing defects. In order to solve such a problem, the present applicant has already provided a damage detection device for a machining fluid suction pump circuit in view of the above-mentioned problems in the electric discharge machine to further improve the machining performance of the electric discharge machine. I am proposing to turn it into.

That is, in a machining fluid recovery pump circuit of an electric discharge machine that uses an air pump as a suction pump, a pressure detector that detects occurrence of pressure reduction in a discharge path of pressure air that is a working medium of the suction pump, and the detector. And a control device that sends a stop control signal for electric discharge machining in response to the detection signal of
In the case where the machining fluid suction pump circuit is damaged, the pressure air of the working medium causes a pressure decrease, so that the decrease in the pressure is detected and the detection signal is fed back to the electric discharge machine side. is there.

However, the above-mentioned damage detection device for the working fluid suction pump circuit monitors the pressure change of the pressure air and indirectly detects the occurrence of damage to the working fluid suction pump from the state of change in the pressure. Since the pressure in the air path fluctuates each time the operation is switched, the damage detection accuracy is slow, and there are drawbacks such as easy malfunctions.Therefore, damage to the machining fluid suction pump can be detected more directly or An object of the present invention is to develop and provide a damage detection device for a machining fluid suction pump that can further improve the electric discharge machining performance of an electric discharge machine by making a distinction.

Therefore, an object of the present invention is to provide a damage detection device for a machining fluid suction pump of an electric discharge machine that can solve such problems.

[Means for Solving the Problems]

According to the present invention, a pressure air-operated machining fluid suction pump used in a machining fluid treatment system of an electric discharge machine has a pair of machining fluid suction chambers, and both chambers are alternately sucked according to alternate supply of pressure air. Focusing on the operation, each operation time of the suction operation of both chambers is detected as a time value, the difference value of the operation time is found from the difference between the time values, and the difference value is almost zero during normal operation of the pump. Nevertheless, when a pump breakage occurs, the difference value becomes large. Therefore, the pump breakage is detected by determining the difference between the count values.

That is, according to the present invention, the machining fluid mixed with the generated gas and the machining scraps from the electric discharge machining section in the electric discharge machining tank is repeatedly sucked by the alternate suction operation of the pair of machining fluid suction chambers operated according to the supply of the pressure air. In a damage detection device for detecting damage to an air-actuated working fluid suction pump, a pressure air corresponding to alternate suction operation of a pair of working fluid suction chambers of the suction pump is provided in a pressure air path of the suction pump. A pressure detector that detects a pressure change, a switching detection unit that detects a switching time point of the alternate suction operation of the suction pump from an output signal of the pressure detector, and a switching detection unit that detects the switching time. The time difference between the operation time of the alternate suction operation of the suction pump is calculated from the time measuring means for obtaining the time interval between the switching of each operation, and the time measured value detected by the time measuring means. Further, there is provided a damage detection device for a machining fluid suction pump of an electric discharge machine, which is provided with a damage determination means for determining that the pump is damaged when the difference value exceeds a predetermined value.

Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the accompanying drawings.

〔Example〕

FIG. 1 is a mechanical diagram showing the configuration of a damage detection device for a machining fluid suction pump of an electric discharge machine according to the present invention, and FIG. 2 shows the output waveform of a pressure sensor depending on whether the machining fluid suction pump is normal or damaged. FIG. 3 is a waveform diagram for explaining an example of a situation where the pressure air actuated working fluid absorption pump is broken. FIG. 4 is an example of a structure of the pressure air actuated working fluid suction pump. It is sectional drawing shown.

First, referring to the structure of the electric discharge machine part of the electric discharge machine shown in FIG. 1, the electric discharge machine includes a machining tank 1 in which an electric discharge machining liquid 9 is stored and provided at the bottom. The workpiece 3 (hereinafter, simply,
It is called work. ) Is fixed by an appropriate attachment means, while the machining electrode 6 is attached to the electrode attachment head 4 via the electrode attachment plate 5 by an appropriate method such as screw engagement, and faces the work 3 and works 3 The electrode mounting head 4 is configured to receive a feeding operation toward the.
Further, as is well known, both the work 3 and the electrode 6 are supplied with a pulse power from an electric discharge machining power source (not shown) by electric wiring, and an electric discharge is generated through a machining gap between the work 3 and the electrode 6. Due to the phenomenon, the electric discharge machining is applied to the work 3. That is, according to the shape of the shaping electrode 6, the work 3
Is removed as machining waste, and a desired machining shape is machined and formed on the work 3. At this time, the electrode mounting head 4 carries out a feeding operation of bringing the electrode 6 closer to the work 3 in the feed axis direction through a feed screw mechanism driven by a motor, and separating it as necessary to perform the above electric discharge machining. It is well known that the action of continuously performing the above is performed. The workpiece mounting base 2 and the electrode mounting head 4 are configured to be relatively movable also in the X and Y axis directions orthogonal to the feed axis direction, and the above-mentioned relative movement is made by a processing machine body not shown. A structure supported so as to be movable in three axial directions is provided.

Now, the machining liquid 9 is stored in the machining tank 1, and the work 3 and the electrode 6 on the workpiece mount 2 are immersed in the machining liquid 9 to perform the electric discharge machining. There is. The machining liquid 9 in the machining tank 1 cools the electrode 6 and the work 3 which are heated to a high temperature by electric discharge heat, and acts to remove machining chips from the surface of the work 3. Working fluid 9 is working fluid tank 12
Is pumped up by a machining fluid supply pump 14 driven by a motor 13, and is supplied to the machining tank 1 through a supply pipeline 15 through an appropriate machining fluid cooling device. The working fluid overflowing from the working tank 1 is collected in the working fluid tank 12 through an appropriate pipe (not shown). Further, when rough machining is performed with a large amount of discharge energy, especially the amount of machining chips and generated gas spouting from the machining section is large, so machining fluid flow passages 16 and 17 are provided in the machining electrode 6 and the electrode mounting plate 5, By the suction action of the air-operated machining fluid absorption pump 21 which is operated by the pressurized air source 20, the machining fluid 9 is sucked together with the machining chips and the generated gas, and the reflux conduit 18 is provided.
It is returned to the working liquid tank 12 via the through hole, and post-processes such as a cooling process and a removal process of processing dust and generated gas are performed. In other words, the machining fluid supply circuit, the overflow circuit, the machining fluid suction, and the reflux circuit described above constitute a machining fluid processing system, and the electric discharge machining is always performed by the fresh machining fluid 9 which is cooled.

Now, according to the present embodiment, in the machining fluid suction / reflux circuit, a machining fluid suction pump is provided from a region portion where the electric discharge machining electrode 6 and the work 3 face each other to perform electric discharge machining, that is, from the electric discharge machining section. A piping system for suctioning by the suction action of 21 and collecting the generated gas and machining waste together with the machining fluid 9 through the reflux pipeline 18 is formed, and the air-operated machining fluid described above is provided downstream of the reflux pipeline 18. A suction pump 21 is provided. The air-operated machining liquid suction pump 21 is a pump that uses the pressure air supplied from the pressurized air source 20 as the working medium, and therefore incorporates a pair of diaphragm chambers, which will be described later, driven by the pressure air, and the diaphragm membrane. According to the expansion and contraction of the diaphragm chamber due to the dynamic displacement, the pair of machining liquid suction chambers provided in contact with the diaphragm chamber are expanded and contracted to suck the machining liquid. An air-operated machining fluid suction pump
Reference numeral 21 denotes a processing liquid 9 from the processing tank 1, which is sucked from an inlet 21a of a suction pump 21 via a reflux pipe 18, a generated gas, a contaminant such as processing waste, is processed from a delivery port 21b through a delivery pipe 18 '. Liquid tank 12
However, a known processing waste separation device is provided in the delivery pipe line, and the processing waste and the processing liquid are separated by a magnetic force or centrifugal force in the processing waste separation device. Then, the processing waste is collected from the processing waste separating device into an appropriate processing waste collection box, while the processing liquid from which the processing waste has been separated is returned to the processing liquid supply tank 12.

Here, according to the present invention, the pressure sensor 30 is provided in the path of the pressure air that is the working medium of the machining liquid suction pump 21 (the exhaust path in this example). That is, in the air-operated machining liquid suction pump 21, the pressure value of the pressure air that alternately operates a pair of air chambers having a diaphragm chamber wall, which will be described later, is constantly detected.

Referring now to FIG. 4, there is shown a detailed example of the structure of a commercially available pressure air actuated working fluid suction pump.

Now, the pressure air, which is the working medium of the pressure air actuation type working fluid suction pump 21, is sent out from the pressure air source 20 (FIG. 1) through the supply pipe line, and the air supply line switching valve (illustration for controlling) is appropriately operated. Is supplied to the inside of the working fluid suction pump 21 via In this machining fluid suction pump 21, as shown in the figure,
From the air supply port 40, through a switching valve chamber 48 equipped with a well-known spool valve, etc., air chambers 42, 44 having a pair of left and right equal volumes.
Pressure air is alternately supplied inside. Therefore, due to the action of this pressure air, the left and right volumetric variable machining fluid suction chambers 52,
The two diaphragms 62, 64 forming the chamber wall of 54 and connected to both ends of the sliding shaft 65 are pulsatingly displaced. As a result, the chamber volumes of the volume-variable machining fluid suction chambers 52 and 54, which also have substantially the same chamber volume, are alternately changed, so that the electrical discharge machining fluid is sucked from the machining fluid suction port 21a, and the ball valves 66a and 66b are operated. By alternately opening and closing the valve of the group and the group of 68a, 68b, the variable volume chambers 52, 54 are alternately passed and the machining fluid is collected from the machining fluid discharge port 21b. Discharge to ′. FIG. 4 shows that the machining fluid suction chamber 52 on the right side is expanded by the expansion of the chamber volume.
The machining liquid is in a state of holding the liquid by opening the ball valve 66a and closing the ball valve 68a. On the other hand, in the machining fluid suction chamber 54 on the left side, due to the contraction of the chamber volume, the retained machining fluid opens the ball valve 68b,
The ball valve 66b is in the state of discharging by closing the valve.

Further, through the switching valve chamber 48, the diaphragm air chamber 4
The pressure air alternately supplied to 2, 44 is discharged from the other chamber while being supplied to one chamber, and is discharged from the air exhaust port 46 to the external conduit of the machining liquid suction pump 21, for example,
It is open to the atmosphere.

Referring again to FIG. 1, according to the present invention, the pressure of the pressure air is measured by the pressure sensor 30 (FIG. 1) during the process of exhausting to the external conduit or the process of supplying the pressure air source 20 into the pump 21. The change in value is constantly monitored. The illustrated example of FIG. 1 shows an embodiment in which the pressure value of the exhausted pressure air is monitored. At this time, in most cases, the diaphragms 62 and 64 are not damaged at the same time, and one diaphragm 62 or 64 is damaged first.
If one of the diaphragms 62 or 64 is damaged,
Pressure air leaks into the machining fluid flow path on the damaged diaphragm side, so an air chamber with a damaged diaphragm
The pressure change at 42 or 44 becomes slow and the pressure pulsation cycle becomes long. That is, an abnormal occurrence such as a diaphragm breakage in the machining fluid suction pump 21 appears in the pressure value of the working pressure air of the machining fluid suction pump 21. FIG. 2 shows a detection waveform when this pressure air is detected by the pressure sensor 30. That is, FIG. 2 (a) shows the machining fluid suction pump 21.
Is a waveform diagram of pressure air output by the pressure sensor 30 in a normal state, and has an output characteristic of 1 when the pressure sensor 30 exceeds a set constant pressure threshold value and 0 when the pressure sensor 30 is equal to or lower than the threshold value. It becomes the illustrated rectangular wave. The output waveform of FIG. 2 (a) shows a pair of machining as the machining liquid suction pump 21 expands and contracts one of the air chambers 42, 44 in response to the switching of the air supply path switching valve. When the liquid suction chambers 52 and 54 alternately perform suction operation, one chamber
Process in which 52 or 54 expands and sucks the working liquid (process I)
And the process of discharging the suctioned machining fluid from the same chamber (process
II) and the time of executing (during the same time, in the machining liquid suction chamber on the opposite side, conversely, discharge of the electric discharge machining liquid and then suction is performed) are defined as one cycle T ₁ and one cycle T ₁ Swelling in,
The change in pressure of the compressed air due to contraction is two rectangular waves I, II
It shows how it appears.

When an abnormality occurs due to damage to one of the diaphragms in the machining fluid suction pump 21, pressure air leaks toward the machining fluid suction chamber in the machining fluid suction chamber 52 or 54 (see FIG. 4) on the abnormality occurrence side. As a result, the expansion process takes a long time, and therefore one cycle takes a long time, and the cycle becomes T ₂
Changes to. That is, as shown in FIG. 2B, one cycle
There is a difference in the period of the two rectangular waves within T ₂ .

The present invention focuses on the change in the pressure waveform of the pressure air detected by the pressure sensor 30 described above, and cuts two steps from two rectangular waves in one cycle T ₁ and T ₂ in the output waveform of the pressure sensor 30. The change detection means 32 for detecting the change detects the change. This switching detecting means 32 can be formed by, for example, a well-known T-type flip-rop, and by inverting the output at the rising edge of the rectangular wave shown in FIGS. , Before reversal, after reversal 2
Two output states are shown, thus making it possible to detect the switching between the two steps respectively.

That is, the two alternating outputs of the inversion of the switching detection means 32 are sent to the control device 33 composed of a CPU such as a microcomputer. In the control device 33, switching detection means
Two outputs of 32 are alternately input to the control unit 35 via the interface 34. At this time, the control unit 35 counts the output duration time by the counting unit 36 for each of the two outputs. Here, the counting unit 36 is a counter function unit that counts the reference clock pulse. The digital count value related to the time width of the two steps counted by the counting section 36 is separately stored in the first memory 37a and the second memory 37b via the control section 35. When the count data relating to the above two output values is stored in both memories 37a and 37b, the control unit 35 resets the counting unit 36 and immediately causes the time width of the next process to be counted.

On the other hand, the digital count values stored in the first and second memories 37a and 37b are sent to the arithmetic unit 38 to perform a calculation for obtaining the difference value between the digital count values. If the absolute value of the difference value is substantially zero in this calculation result, it is determined that the working fluid suction pump 21 detected by the pressure sensor 30 is operating normally. On the other hand, when the absolute value of the above difference value is large, it is determined that the machining fluid suction pump 21 is abnormal due to diaphragm damage or the like, and the control unit 35 causes a predetermined alarm via the interface 34. It sends an alarm signal that drives the circuit.

Of course, the control device 33 repeats the above counting, storage, calculation, and determination regarding the pressure detection force input one after another from the switching detection means 32, so when the machining fluid suction pump 21 is damaged. Immediately, damage can be detected and an alarm signal can be sent. FIG. 3 shows the control device 33 described above.
6 is a flowchart for explaining a damage detection process of the machining fluid suction pump 21 performed by the control unit 35, the counting unit 36, the first and second memories 37a and 37b, and the arithmetic unit 38 of FIG.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, in an electric discharge machine, when a machining liquid suction pump that sucks and collects the electric discharge machining liquid from the electric discharge machining unit to the machining liquid collection tank is damaged, the pump is used. Of the operating characteristics of the pump, in particular, each time width of pulsation pulsation due to expansion and contraction of the diaphragm is directly taken out through the pressure detection value of the pressure air for pump operation, and the pump is damaged by the direct method of calculating and determining the difference of the time width. Since it detects the damage, the accuracy of the damage detection of the machining fluid suction pump is improved, and therefore, the alarm signal is generated to quickly perform the repair processing such as temporarily stopping the electric discharge machining operation of the electric discharge machine. Therefore, it is possible to prevent processing defects due to insufficient suction action.

[Brief description of drawings]

FIG. 1 is a mechanical diagram showing the configuration of a damage detection device for a machining fluid suction pump of an electric discharge machine according to the present invention, and FIG. 2 shows the output waveform of a pressure sensor depending on whether the machining fluid suction pump is normal or damaged. FIG. 3 is a waveform diagram for explaining an example of a situation where the pressure air actuated working fluid suction pump is broken. FIG. 4 is an example of a structure of the pressure air actuated working fluid suction pump. Sectional drawing to show. 1 ... Machining tank, 3 ... Work, 6 ... Machining electrode, 9 ...
Electric discharge machining fluid, 21 ... Pressure air actuated machining fluid suction pump, 30 ... Pressure sensor, 32 ... Switching detection means, 33 ...
... control device, 35 ... control unit, 36 ... counting unit, 37a, 37b ...
… First and second memories, 38 …… Calculator.

Claims (2)

[Claims] 1. Air for repeatedly sucking a machining fluid mixed with a gas and machining waste generated from an electric discharge machining section in an electric discharge machining tank by alternate suction operations of a pair of machining fluid suction chambers operating in accordance with the supply of pressure air. A breakage detecting device for detecting breakage of an operating type working fluid suction pump, wherein a pressure change of pressure air provided in a pressure air path of the suction pump and corresponding to alternate suction operation of a pair of working fluid suction chambers of the suction pump. A pressure detector for detecting, a switching detection means for detecting a switching time point of the alternate suction operation of the suction pump from an output signal of the pressure detector, and each detected by the switching detection means. The time difference between the operation time of the alternate suction operation of the suction pump is calculated from the time measuring means for obtaining the time interval for switching the operation and the time measured value detected by the time measuring means. And damage discriminating means for discriminating a pump failure when the difference value exceeds a predetermined value, breakage detection device of the working fluid suction pump discharge machine, characterized in that it is configured by including. 2. A machining fluid suction pump for an electric discharge machine according to claim 1, further comprising alarm means for generating an alarm signal of occurrence of damage when the damage determination means detects damage of the machining fluid suction pump. Damage detection device.