JPH04171122A - Breakdown detecting device of processing liquid suction pump for electric discharge machine - Google Patents

Abstract

PURPOSE:To improve the accuracy of breakdown detection for a processing liquid suction pump, by calculating differences in operation time between reciprocal suction strokes of the suction pump from time values detected with a time measuring means and providing a breakdown decision means deciding that the pump is broken when the difference exceeds a specified value. CONSTITUTION:A time measuring means 36 is provided to obtain switching time intervals between respective operations detected with a switch detecting means 32. Differences in operation time between reciprocal suction strokes of a suction pump 21 are calculated in an arithmetical section 38 from time values detected with the time measuring means 36, and when the difference exceeds a specified value it is decided that abnormalities such as a diaphragm breakdown or the like are generated in the pump 21, then alarm signals to drive a specified alarm circuit are outputted from a control section 35 through an interface.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement in the machining fluid treatment system of an electrical discharge machine, and particularly to an electrical discharge machining section that performs electrical discharge machining of a workpiece using a full-form machining electrode in a machining fluid tank. An air-operated machining fluid suction pump that sucks machining debris, gas, etc. generated due to discharge from the machining tank together with the machining fluid. In a machining fluid treatment system equipped with an air-operated machining fluid suction pump, the chamber wall of which is formed by a diaphragm that pulsates according to the supply of pressurized air, damage to the machining fluid suction pump is detected and necessary actions such as stopping electrical discharge machining are performed. The present invention relates to a damage detection device for a machining fluid suction pump of an electrical discharge machine that enables control processing to be performed.

[Prior art]

In electric discharge machines, especially die-sinking electric discharge machines, machining of the workpiece into a desired shape is progressed by generating electric discharge accompanied by heat generation between the general electric discharge machining electrode and the workpiece. The workpiece is always processed inside a machining tank containing a cooled machining fluid. The machining fluid also functions to remove machining debris removed from the workpiece by electrical discharge machining from the workpiece surface. For this reason, the machining fluid always circulates through a certain circulation system between the machining fluid supply tank and the machining tank where electrical discharge machining is performed, and when it returns to the machining fluid supply tank, it undergoes the necessary machining fluid treatment such as removing machining debris. It is configured so that after performing this process, it is sent out to the supply system again. Generally, a machining fluid treatment system that circulates and processes machining fluid supplies the machining fluid from the machining fluid supply tank to the machining tank using an electric pump, and collects the machining fluid that overflows from the machining fluid tank into the machining fluid supply tank. In recent years, the electric discharge machining method, which uses large discharge energy to increase the machining speed and perform rough machining, has been used, and the generation of machining debris and gas from the discharge heat has increased. As a processing method, a machining fluid suction pump circuit is used that connects a machining fluid flow path to the electrical discharge machining electrode and a suction pump, and sucks and collects machining debris and generated gas flowing out from the machining section while being mixed with the machining fluid. provided. (For example, JP-A No. 6
3-221929). As this suction pump, pumps of various operating types are applicable, but an aired pump whose working medium is compressed air compressed by a compressor may be used.

This aired pump is provided outside the machining tank, and sucks machining fluid mixed with machining debris and generated gas from the electrical discharge machining section through a piping path. The sucked machining fluid is subjected to processing to separate machining debris by a machining debris separator at the downstream stage of the suction pump's delivery port, and is returned to the machining fluid supply tank from the fluid discharge port at the bottom of the device via the reflux pipe. On the other hand, the processed waste is sent to the upper part of the apparatus by a screw-type feed mechanism provided in the processed waste separation device, and is collected from the processed waste outlet into a suitable processed waste collection box. In addition, various treatment methods have already been proposed, such as absorbing the generated gas into a processing fluid or releasing it into the atmosphere after deodorizing treatment.

[Problem to be solved by the invention]

However, conventionally, in the machining fluid suction pump circuit in the electrical discharge machine described above, the diaphragm that forms the machining fluid suction chamber in the aired pump for sucking machining fluid breaks during repeated use, and the operation starts from the damaged part. If there is a failure in which the pressurized air medium leaks, or if the switching valve installed in the circuit for the pressure air that is the working medium fails or stops, or if there is a failure in the pressure air supply source and the working air is Even if the pressure drops and the prescribed suction pump action is no longer carried out, an advanced configuration has been developed to quickly detect this and send some kind of alarm signal to the control system of the electrical discharge machine. As a result, there was a problem in which machining fluid mixed with machining debris, gas, etc. was recovered from the electrical discharge machining section while the operator was not monitoring.
There were problems to be solved, such as the possibility of machining defects. In order to solve these problems, the applicant has already provided a damage detection device for a machining fluid suction pump circuit in view of the above-mentioned problems in electric discharge machines, thereby further improving the machining performance of electric discharge machines. We are proposing to change the

That is, in the machining fluid recovery pump circuit of an electrical discharge machine that uses an air pump as a suction pump, there is a pressure detector that detects the occurrence of a pressure reduction in the discharge path of pressurized air, which is the working medium of the suction pump, and a detection system of the same detector. and a control device that sends a stop control signal for electrical discharge machining in response to the signal,
Considering that if the machining fluid suction pump circuit is damaged, the pressure of the working medium air will decrease, so this system detects the decrease in pressure and feeds back the detection multiplier to the electric discharge machine side. It is.

However, the damage detection device for the machining fluid suction pump circuit described above monitors the pressure change of the pressurized air and indirectly detects the occurrence of damage to the machining fluid suction pump from the state of the pressure change. Since the pressure in the air path fluctuates each time the operation is switched, the accuracy of damage detection is slow and there are problems such as easy malfunction. It is an object of the present invention to develop and provide a damage detection device for a machining fluid suction pump that can further improve the electrical discharge machining performance of an electrical discharge machine by determining the damage.

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

[Means to solve the problem]

The present invention provides a pressurized air-operated machining fluid suction pump used in a machining fluid treatment system of an electric discharge machine, which has a pair of machining fluid suction chambers, and these chambers alternately suck the machining fluid according to the alternate supply of pressurized air. Focusing on the pump's operation, we detected the operation time of each suction operation in the compartment as a clock value, and found the difference in operation time from the difference in the clock values.When the pump is operating normally, the difference value is approximately zero. Nevertheless, if pump damage occurs, the difference value becomes large, so pump damage is detected by determining the difference between the counted values.

That is, according to the present invention, the machining fluid mixed with generated gas and machining debris from the electrical discharge machining section in the electrical discharge machining tank is repeatedly sucked by the alternate suction operation of a pair of machining fluid suction chambers that operate according to the supply of pressurized air. A damage detection device for detecting damage to an air-operated machining liquid suction pump, which is provided in a pressure air path of the suction pump, and configured to provide a pressure air supply corresponding to the alternate suction operation of a pair of machining liquid suction chambers of the suction pump. a pressure detector for detecting a pressure change; a switching detection means for detecting a switching point between alternate suction operations of the suction pump from an output signal of the pressure detector; and a timer for determining the time intervals between the switching operations, and a timer for calculating the difference between the operation times of the alternate suction operations of the suction pump from the timer value detected by the timer. a damage determination means that determines that the pump is damaged when the value is exceeded;
The present invention provides a damage detection device for a machining fluid suction pump of an electrical discharge machine.

Hereinafter, the present invention will be explained in more detail based on embodiments shown in the accompanying drawings.

〔Example〕

Fig. 1 is a mechanical diagram showing the structure 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 an output waveform of a pressure sensor depending on whether the machining fluid suction pump is normal or damaged. FIG. 3 is a flowchart explaining the damage detection function of the pressurized air-operated machining fluid suction pump. FIG. 4 shows an example of the structure of the pressurized air-operated machining fluid suction pump. FIG.

First, referring to the configuration of the electrical discharge machining section of the electrical discharge machine shown in FIG. A workpiece 3 (hereinafter simply referred to as the work) is fixed on the workpiece mounting base 2 with a suitable mounting means, and the processing electrode 6 is attached to the electrode mounting head 4 via the electrode mounting plate 5. is attached by an appropriate method such as screw engagement, and is configured to face the workpiece 3 and to be fed by the electrode mounting rod 4 toward the workpiece 3.

Further, as is well known, both the workpiece 3 and the electrode 6 are supplied with pulsed power from an electric discharge machining power source (not shown) through electrical wiring, and the machining is performed through the gap between the workpiece 3 and the electrode 6. The workpiece 3 is subjected to electrical discharge machining due to the electrical discharge phenomenon. In other words, the workpiece 3 is
The excess portion is removed as machining waste, and the desired machining shape is formed on the workpiece 3. At this time, the electrode mounting head 4 moves the electrode 6 closer to the workpiece 3 in the direction of the feed axis via a motor-driven feed screw mechanism, and performs a feed operation to move it away from the workpiece 3 as necessary, thereby performing the electrical discharge process. It is well known that the function is to perform continuous operations. The workpiece mounting base 2 and the electrode mounting head 4 are configured to be movable relative to each other in the X1 and Y-axis directions perpendicular to the feed axis direction, and the above-mentioned relative three axes are moved by four processing machines (not shown). A supported structure is provided for directional movement.

Now, a machining fluid 9 is stored in the machining tank 1, and the workpiece 3 and the electrode 6 on the workpiece mount 2 are immersed in the machining fluid 9 to perform electrical discharge machining. There is. The machining liquid 9 in the machining bath 1 cools the electrode 6 and the workpiece 3, which become hot due to discharge heat, and also functions to remove machining debris from the surface of the workpiece 3. The machining fluid 9 is in the machining fluid tank 1.
2 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 pipe line 15 through a suitable machining fluid cooling device. The machining fluid overflowing from the machining tank 1 is collected into the machining fluid tank 12 via appropriate piping (path shown). In addition, when performing rough machining with large electrical discharge energy, the amount of machining debris and generated gas flowing out from the machining area increases, so machining fluid flow passages 16 and 17 are provided in the machining electrode 6 and the electrode mounting plate 5. The machining fluid 9 is sucked together with machining waste and generated gas by the suction action of an air-operated machining fluid suction pump 21 operated by a pressurized air source 20, and is returned to the machining fluid tank 12 via the reflux pipe 18. , performs post-processing such as cooling treatment and removal of processing waste and generated gas. In other words, the machining fluid supply circuit, overflow circuit, machining fluid suction, and recirculation circuit described above constitute a machining fluid treatment system, so that electrical discharge machining is always performed using fresh, cooled machining fluid 9.

Now, according to the present embodiment, the machining fluid suction and circulation circuit is configured such that the machining fluid suction pump is connected to the region where the electrical discharge machining electrode 6 and the workpiece 3 face each other to perform electrical discharge machining, that is, from the electrical discharge machining section. A piping system is formed in which the generated gas and machining waste are sucked by the suction action of 21 and collected together with the machining fluid 9 through the reflux pipe 18. A suction pump 21 is provided. Since the air-operated machining liquid suction pump 21 is a pump that uses pressurized air supplied from the pressurized air source 20 as a working medium,
It has a built-in pair of diaphragm chambers (described below) that are driven by pressurized air, and expands and contracts a pair of machining liquid suction chambers provided in contact with the diaphragm chambers in response to the expansion and contraction of the diaphragm chambers due to vibrational displacement of the diaphragm. , and has a structure that performs a suction action on machining fluid by contracting it. The air-operated machining liquid suction pump 21 sends contaminants such as the machining liquid 9, generated gas, and machining waste from the machining tank 1 sucked from the inlet 21a of the suction pump 21 through the return pipe line 18 to the outlet 21b. The flow is returned to the machining liquid tank 12 via the delivery pipe 18', and the delivery pipe is equipped with a well-known processing waste separation device, in which the processing waste and the processing liquid are separated by magnetic force or Separated by centrifugal force. The processing waste is collected from the processing waste separator into a suitable processing waste collection box, and 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 (exhaust path in this example) of the pressure air that is the working medium of the machining liquid suction pump 21. In other words, the air-operated machining liquid suction pump 21 constantly detects the pressure value of pressurized air that alternately operates a pair of air chambers, which will be described later, each having a diaphragm chamber wall.

Referring now to FIG. 4, a detailed example of the construction of a commercially available pressurized air operated machining liquid suction pump is shown.

Pressure air, which is the working medium of the pressurized air-operated machining fluid suction pump 21, is sent out from the pressure air source 20 (Fig. 1) through a supply pipe, and is connected to an air supply pipe switching valve (not shown) for appropriate operation control. The machining fluid is supplied into the machining fluid suction pump 21 via the machining fluid suction pump 21. As shown in the figure, inside this machining liquid suction pump 21, air flows from an air supply port 40 through a switching valve chamber 48 equipped with a well-known spool valve, etc., into a pair of left and right machining chambers 42 and 44 having equal volumes. Pressure air is supplied alternately.

Therefore, the action of this pressurized air forms the chamber walls of the two left and right machining liquid suction chambers 52 and 54 whose volume is variable, and the sliding shaft 6
50 two diaphragms connected at both ends 62.6
4 is pulsatingly displaced.

As a result, since the volumes of the machining fluid suction chambers 52 and 540, which are variable volume and have approximately the same chamber volume, are alternately changed, the electrical discharge machining fluid is sucked from the machining fluid suction port 21a, and the assembly of the ball valves 66a and 66b is By alternately opening and closing the valves of the set 68a and 68b, the variable volume chamber 5
2.54 alternately, and the machining fluid is discharged from the machining fluid discharge port 21b to the recovery pipe 18°. FIG. 4 shows that the machining fluid suction chamber 52 on the right side is sucked into the ball valve 66 due to the expansion of the chamber volume.
The liquid is maintained by opening the valve a 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 flows through the opening of the ball valve 68b and the ball valve 6.
6b is in a state of discharging by closing the valve.

Further, the pressurized air alternately supplied to the diaphragm air chambers 42 and 44 via the switching valve chamber 48 is discharged from the other chamber while being supplied to one chamber, and the machining fluid is discharged from the air exhaust port 46. is exhausted to the external pipe line of the suction pump 21,
For example, in a configuration that is open to the atmosphere.

Referring again to FIG. 1, in accordance with the present invention, the pump 2
1, changes in the pressure value of the pressurized air are constantly monitored by the pressure sensor 30 (FIG. 1). The illustrated example in FIG. 1 shows an embodiment in which the pressure value of exhausted pressurized air is monitored. At this time, in many cases, both of the diaphragms 62 and 64 are not damaged at the same time, and one of the diaphragms 62 and 64 is damaged first. Furthermore, if one of the diaphragms 62 or 64 is damaged, the pressure air leaks into the machining fluid flow path from the damaged diaphragm side, so the pressure change in the air chamber 42 or 44 that has the damaged diaphragm will be slow. As a result, the pressure pulsation period becomes longer. That is, an abnormality such as diaphragm damage occurring in the machining fluid suction pump 21 appears in the pressure value of the operating pressure air of the machining fluid suction pump 21. FIG. 2 shows a detected waveform when this pressure air is detected by the pressure sensor 30. That is, FIG. 2(a) is a waveform diagram of the pressure air output by the pressure sensor 30 when the machining liquid suction pump 21 is in a normal state.
By having an output characteristic that becomes 0 below the same threshold value, it becomes a rectangular wave as shown in the figure. Note that the output waveform in FIG. 2(A) shows that the machining fluid suction pump 21 is used for processing a pair of machining fluids as one of the air chambers 42 and 44 expands and contracts in response to switching of the air supply path switching valve. Liquid suction chamber 52
．． 54 alternately perform suction operation, one chamber 52 or 5
4 expands and sucks in the machining fluid (process step), and the process of discharging the sucked machining fluid from the same chamber (step ■) (during the same time, the machining fluid suction chamber on the opposite side On the other hand, the two processes of discharging the electrical discharge machining fluid and then suctioning it are defined as one cycle T1, and within that one cycle T, the pressure change of the pressurized air due to expansion and -contraction is generated by two rectangular waves 1 and II.
This shows how it appears.

When an abnormality occurs in the machining fluid suction pump 21 due to damage to one of the diaphragms, pressurized air is pumped into the machining fluid suction chamber 2 or 54 (see Fig. 4) on the side where the abnormality occurs. Due to the leakage, the time of the expansion process becomes longer, and therefore the time of one cycle becomes longer, and the cycle changes to T. In other words, as shown in FIG. 2(b), a difference occurs between the periods of the two rectangular waves within one period T2.

The present invention focuses on changes in the pressure waveform of pressurized air detected by the pressure sensor 30 described above, and calculates one period T1 in the output waveform of the pressure sensor 30. 2 from the two square waves in T2
This is detected by a switching detection means 32 that detects switching between two processes. This switching detection means 32 can be formed, for example, by a well-known T-type flip-flop, and by inverting the output at the rise of the rectangular wave shown in FIGS. , shows two output states, before and after reversal, thus making it possible to detect the switching of the two processes, respectively.

That is, two reversible, alternate outputs of the switching detection means 32 are sent to a control device 33 comprising a CPU such as a microcomputer. In the control device 33, the two outputs of the switching detection means 32 are alternately connected to the interface 3.
4 to the control unit 35, and at this time, the control unit 3
5, the counting unit 36 counts the output duration time for each of the two outputs. Here, the counting section 36 is a counter function section that counts reference clock pulses. Counting part 36
The digital count values related to the time widths of the two processes counted by the controller 35 are stored in the first memory 37a and the second
The memo IJ37b is stored separately. The control unit 35 stores count data regarding the above two output values in both memos.
Once stored in 137a and 37b, the counting unit 36 is reset to immediately count the time width of the next process.

On the other hand, the digital count values stored in both the first and second memories 37a and 37b are sent to the arithmetic unit 38, and a calculation is performed to find the difference between the two digital count values.

In this calculation result, if the absolute value of the difference value is approximately zero, it is determined that the machining fluid suction pump 21 detected by the pressure sensor 30 is operating normally. On the other hand,
If the absolute value of the above difference value is a large value, it is determined that the machining fluid suction pump 21 is experiencing an abnormality due to diaphragm damage, etc., and the control unit 35 controls the interface 34
It sends out an alarm signal that drives a predetermined alarm circuit via the alarm.

Of course, since the control device 33 repeats the above-mentioned counting, memorization, calculation, and discrimination regarding the pressure detection force input one after another from the switching detection means 32, the processing fluid suction pump 21
When damage occurs, it is possible to immediately detect the damage and send out an alarm signal. FIG. 3 shows the control unit 35, counting unit 36, and first and second memories 37a of the control device 33 described above.

37b1 is a flowchart illustrating a process of detecting damage to the machining liquid suction pump 21 performed by the calculation unit 38. FIG.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in an electric discharge machine, when the machining liquid suction pump that sucks and collects the electric discharge machining liquid from the electric discharge machining section to the machining liquid recovery tank is damaged, the pump The operating characteristics of the pump, in particular, the time width of each of the four pulsations due to expansion and contraction of the diaphragm are directly extracted via the pressure detection value of the pump operating pressure air, and the difference in time width is calculated and determined. Since damage is detected, the accuracy of damage detection of the machining fluid suction pump is improved, and therefore, repair processing such as generating an alarm signal and temporarily stopping the electrical discharge machining operation of the electrical discharge machine can be performed quickly. Therefore, it is possible to prevent processing defects due to insufficient suction action.

[Brief explanation of the drawing]

Fig. 1 is a mechanical diagram showing the structure 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 an output waveform of a pressure sensor depending on whether the machining fluid suction pump is normal or damaged. FIG. 3 is a flowchart explaining the damage detection function of the pressurized air-operated machining fluid suction pump, and FIG. 4 shows an example of the structure of the pressurized air-operated machining fluid suction pump. A sectional view shown. 1... Processing tank, 3... Workpiece, 6... Processing electrode,
9... Electric discharge machining fluid, 21... Pressure air operated machining fluid suction pump, 30... Pressure sensor, 32... Switching detection means, 33... Control device, 35... Control part, 3.6--counting part, 37a, 37b--first and second memory, 38--calculating part. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. Machining fluid mixed with gas and machining debris generated from the electrical discharge machining section in the electrical discharge machining tank is repeatedly sucked by a pair of machining fluid suction chambers operated in accordance with the supply of pressurized air. In a damage detection device for detecting damage to an air-operated machining fluid suction pump, the system includes a pressure air passage provided in a pressure air path of the suction pump and corresponding to an alternate suction operation of a pair of machining fluid suction chambers of the suction pump. a pressure detector for detecting a change in pressure; a switching detection means for detecting a switching point between alternate suction operations of the suction pump from an output signal of the pressure detector; a timer for determining the time interval between each switching operation, and a timer for calculating the difference between the operation times of the alternating suction operations of the suction pump from the timer value detected by the timer and the timer, and the difference value being set to a predetermined value. What is claimed is: 1. A damage detection device for a machining fluid suction pump of an electrical discharge machine, characterized in that the device comprises damage determination means for determining that the pump is damaged when the value exceeds the value of . 2. Damage detection of a machining fluid suction pump of an electrical discharge machine according to claim 1, further comprising an alarm means for generating an alarm signal indicating occurrence of damage when the damage determination means detects damage to the machining fluid suction pump. Device.