JP2001087946A - Method of controlling supply of machining fluid for wire electric discharge machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a proper condition of supplying a working fluid to a machining part between a wire electrode and a work in a wire electric discharge machine. SOLUTION: A wire electric discharge machine 11 is configured so that a limit value is set for the revolving speed of a pump 37 supplying a working fluid to a machining part between a work 13 and a wire electrode 23 and also a limit value is set for the pressure of the working fluid supplied, and the operation of the pump 37 is controlled so that the pump revolving speed and the fluid pressure are maintained under the limit values. In case the machining start hole provided in the work 13 penetratively is positioned inside an upper 31 and a lower nozzle 33, the nozzle operation is controlled so that the machining is started after at least either of them 31 and 33 is put in relative movement to a position some apart from the work 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying a machining fluid to an electric discharge machining portion between a wire electrode stretched between nozzles and the work via a pair of nozzles arranged above and below the work. The present invention relates to a machining fluid supply control method for a wire electric discharge machine.

[0002]

2. Description of the Related Art In wire electric discharge machining, a wire is used as a machining electrode, and an intermittent spark discharge is generated by applying a pulse voltage from a machining power source between the workpiece and the wire electrode. The workpiece is machined into a thread saw type using the discharge energy. In a wire electric discharge machine which performs such wire electric discharge machining, a wire electrode is sent out from a supply reel at a constant speed, and is supplied between heads arranged above and below a work and provided with a wire guide. At the same time, the machining fluid is ejected from the upper and lower machining fluid supply nozzles to the electric discharge machining action portion between the wire electrode and the work to provide a cooling function and remove machining chips. by this,
Disconnection of the wire electrode and adhesion of machining chips in the machining gap are prevented, and a smooth and stable electric discharge machining operation is promoted. Therefore, it is necessary that the machining fluid is sufficiently and stably supplied to the electric discharge machining action portion.

[0003] By the way, the wire electrodes stretched between the heads vibrate due to the impact of spark discharge. Vibration may also occur due to a change in the supply amount of the working fluid. It is desirable that this vibration be suppressed in order to affect the processing accuracy. For that purpose, it is effective to increase the tension of the wire electrode, keep the flow rate of the processing liquid low, and shorten the distance between the heads. .

Therefore, it is desirable that the nozzle provided in the head is as close as possible to the work as long as it does not hinder the relative movement between the work and the wire electrode. When the workpiece and the nozzle are close to each other and are almost in close contact with each other, the flow path of the machining fluid supplied from the nozzle is substantially limited to the machining trajectory and the electric discharge machining action part. By keeping it constant, the flow rate of the machining fluid to the electric discharge machining action part is maintained almost constant. Further, if the pressure is kept constant, even if the machining trajectories intersect and there are a plurality of outflow paths of the machining fluid, the flow rate to the electric discharge machining action portion is kept almost constant. Therefore, it is common to provide a pressure detection device for detecting the pressure of the processing fluid at a stage preceding the nozzle for supplying the processing fluid, and to perform constant pressure control based on the detected value.

[0005]

However, since the surface of the work is not limited to a flat surface, the work and the nozzle are often separated from each other. Such a situation appears, for example, when the nozzle moves relative to the workpiece from a flat portion to a recessed portion in the workpiece shape such as a counterbore portion as compared to the surrounding portion.

When the nozzle is moved relative to the work from the flat portion to the recessed portion by the servo feed operation during the constant pressure control, the tip of the nozzle is brought close to the work surface and substantially. The state changes from the close contact state to the state in which a gap is formed between the work surface and the tip of the nozzle away from the work surface. Then, since the machining fluid leaks from between the tip of the nozzle and the surface of the workpiece, the flow path of the machining fluid is not limited to the gap of the machining trajectory and the electric discharge machining action part, and the pressure of the machining fluid ejected and supplied from the nozzle is reduced. Drops sharply. Accordingly, the rotation speed of the pump is increased to increase the pressure of the working fluid, and the flow rate of the working fluid is increased. Therefore, due to the increase in the flow rate of the processing liquid, vibration is caused in the wire electrode, and a processing defect is induced. Further, there is also a problem that the pump rotation speed may increase to a pump performance limit value and cause an alarm to be stopped.

In addition, when the nozzle is relatively moved with respect to the workpiece from the recessed portion to a flat portion higher than the recessed portion by the servo feed operation during the pump rotation speed command control, the nozzle is moved to the surface of the workpiece. The state changes again from the state separated from the work surface to the state close to the work surface. Then, since the flow path of the machining fluid supplied from the nozzle outlet is limited to the gap of the machining trajectory and the electric discharge machining action portion, the pressure of the machining fluid ejected from the nozzle and supplied increases sharply. . Along with this, the flow rate of the machining fluid in the electric discharge machining section also increases, and the delay amount of the wire electrode, that is, the amount of bending of the wire electrode toward the machining locus increases, and the machining delay increases as the distance from the nozzle increases. As a result, there is a problem that processing accuracy is greatly affected. In addition, an increase in the pressure of the working fluid exerts an excessive load on the pump, causing a problem that the pump may stop or fail.

In order to address such a problem, conventionally,
When the part to be processed includes a flat part and a concave part, a method of performing processing by adjusting the nozzle position so that the wire electrode and the work are always kept separated from each other even in the flat part of the work. Etc. have been adopted. In this method, the distance between the nozzle and the surface of the work is unnecessarily large, and the processing liquid is not sufficiently supplied to the processing portion, so that the processing speed is reduced. This can cause another problem of increased delay.

In general, instead of starting processing from the edge of the work, a processing start hole is provided in the work, and processing is started through a wire electrode through the processing start hole. In such a case, there is no groove formed by the processing locus of the wire electrode around the processing start hole, that is, the outflow path of the processing liquid. Therefore, when the diameter of the machining start hole provided in the workpiece is smaller than the diameter of the nozzle and the machining start hole is located inside the nozzle, that is, the nozzle surrounds and blocks the periphery of the machining start hole. In such a case, the working fluid injected and supplied from the upper and lower nozzles cannot flow out of the working start hole. Therefore, there is a problem that a sufficient flow of the machining fluid does not occur in the electric discharge machining action portion, the cooling is insufficient, and the wire electrode is disconnected.

In order to solve this problem, there is a method of switching electrical processing conditions such as reducing a pulse voltage applied between a wire electrode and a work at the start of processing, but the processing efficiency is remarkably deteriorated. At the same time, disconnection of the wire electrode cannot be completely prevented. in this way,
Conventionally, there are some problems in supplying a machining fluid to an electric discharge machining portion between a wire electrode and a work.

Accordingly, it is an object of the present invention to maintain the supply of the machining fluid between the wire electrode and the workpiece to the working portion of the electric discharge machining in an appropriate state, maintain a sufficient cooling action, and prevent the wire from being disconnected. It is also to reduce the influence on the processing accuracy.

[0012]

SUMMARY OF THE INVENTION In view of the above-mentioned object, the present invention provides a method for setting a limit value for one or both of an operating rotational speed of a pump and a working fluid pressure at a nozzle so as to maintain them at or below the limit value. Controls the supply of machining fluid to ensure a sufficient cooling effect regardless of changes in the surface shape of the workpiece, and also to prevent the flow rate and pressure of the machining fluid from rising more than necessary to suppress the amount of delay or vibration generated at the wire electrode. In addition, the influence on the processing accuracy is reduced. In addition, the present invention provides a method for controlling a nozzle to automatically separate from a work surface when a processing start hole provided in the work is penetrated by the nozzle and surrounding the work electrode with a wire electrode and the work electrode. In this case, a sufficient flow rate of the machining fluid is supplied to the electric discharge machining action section between the steps.

That is, according to the present invention, the machining fluid is applied to the electric discharge machining section between the work and the wire electrode stretched between the pair of nozzles via the pair of nozzles arranged above and below the work. A method for controlling a machining fluid supply of a wire electric discharge machine having a pump for supplying, wherein a pressure of the machining fluid is detected at a stage preceding the nozzle, and a delay amount of the wire electrode is maintained at a predetermined level or less. Thus, there is provided a machining fluid supply control method for an electric discharge machine in which a limit value of the pressure is determined and the operation of the pump is controlled such that the pressure is maintained at or below the limit value.

Further, according to the present invention, the machining fluid is applied to the electric discharge machining portion between the work and the wire electrode stretched between the pair of nozzles via the pair of nozzles arranged above and below the work. A machining fluid supply control method of a wire electric discharge machine having a pump to supply, wherein a limit value of a rotation speed of the pump is determined so that a vibration state of a predetermined level or less is maintained in the wire electrode, There is provided a method of controlling a supply of a machining fluid for a wire electric discharge machine, which controls the operation of the pump such that the rotation speed is maintained at or below the limit value.

Further, according to the present invention, as another embodiment, electric discharge machining between the work and a wire electrode stretched between the pair of nozzles via a pair of nozzles arranged above and below the work. A machining fluid supply control method for a wire electric discharge machine equipped with a pump for supplying a machining fluid to an action section, wherein a pressure of the machining fluid is detected at a stage preceding the nozzle, and a delay amount of the wire electrode is predetermined. A limit value of the pressure is determined so as to be maintained at or below a predetermined level, and a limit value of a rotation speed of the pump is determined such that a vibration state of a predetermined level or less is maintained in the wire electrode. And a machining fluid supply control method for a wire electric discharge machine that controls the operation of the pump such that the rotation speed is maintained at or below the limit value.

Further, according to the present invention, a machining fluid is applied to a discharge machining portion between the work and a wire electrode stretched between the pair of nozzles via a pair of nozzles arranged above and below the work. A method for controlling the supply of a machining fluid of a wire electric discharge machine, wherein the pair of nozzles is located at a first position in a vertical direction close to a surface of the work, and a machining start hole provided through the work is provided. When located inside the nozzle, at least one of the pair of nozzles is moved from the first position to the second position in the vertical direction separated from the surface of the work as compared with the first position to perform processing. Starting, after at least a part of the machining start hole comes to be located outside the nozzle, by moving the nozzle in the vertical direction and controlling the wire to return to the first position. Addition Liquid supply control method is provided.

According to the present invention, for example, when a pump rotational speed command control is performed by setting a limit value relating to the pressure of the machining fluid so that the delay amount of the wire electrode is maintained at a predetermined value or less. In the processing feed direction, the tip of the nozzle moves relatively from the spotted portion of the work to the flat portion, and the distance between the work surface and the tip of the nozzle approaches so that the machining fluid supplied from the nozzle Due to the fact that the outflow path is substantially limited to the gap of the machining path and the electric discharge machining action portion, the pressure of the machining fluid is prevented from rising and exceeding the limit value. Therefore, it is possible to prevent the pressure of the machining fluid in the electric discharge machining section from increasing, thereby increasing the delay amount of the wire electrode and affecting machining accuracy.

Further, by limiting the rotation speed of the pump so that the vibration state of the wire electrode at a predetermined level or less is maintained, for example, when constant pressure control is performed, flattening occurs along with processing feed. The nozzle tip moves relatively to the part where the workpiece shape, such as the counterbore part, is recessed compared to the surrounding part, and the distance between the workpiece surface and the nozzle tip is increased and the machining fluid supplied from the nozzle In order to compensate for a pressure drop caused by a transition from a state in which the outflow path is only the gap of the machining path and the electric discharge machining action part to a state in which the outflow path can flow out from the gap between the work surface and the nozzle, the rotation speed of the pump is increased. As a result, the flow rate of the processing liquid supplied from the nozzle is increased, thereby causing an effect of preventing the wire electrode from vibrating and causing a processing defect.

Further, when the pair of nozzles is at the first position in the vertical direction close to the workpiece and the processing start hole penetrating through the workpiece is located inside the nozzle, at least one of the pair of nozzles is turned off. The machining fluid supplied to the electric discharge machining portion between the wire electrode and the workpiece by starting the machining by moving the workpiece from the first position to the second vertical position separated from the surface of the workpiece in comparison with the first location. Is prevented from being trapped in the machining start hole, a sufficient supply of machining fluid to the electric discharge machining portion is ensured, a sufficient cooling action is ensured, and disconnection of the wire electrode is suppressed. And
At least a part of the processing start hole is located outside the nozzle, and after a path through which the processing liquid flows out from the processing start hole is secured, the nozzle is moved vertically to return to the first position. By doing so, normal processing is performed.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the main components of a wire electric discharge machine that implements the machining fluid supply control method of the present invention. First, an overall configuration will be outlined with reference to FIG. The wire electric discharge machine 11 includes an upper head 15 and a lower head 17 arranged above and below the workpiece 13, respectively.
A wire electrode 23 supplied from a wire electrode supply reel 19 via a guide roller 21 is stretched between the upper head 15 and the lower head 17, and runs in a vertical direction. The work 13 and the wire electrode 23 are electrically connected to a processing power supply 25. When a pulse voltage is applied between the work 13 and the wire electrode 23, a spark is applied to a minute processing gap therebetween. Electric discharge occurs, and electric discharge machining is performed on the work 13 by the energy of the spark discharge.

The work 13 is supported by a work support (not shown) which can be fed and moved in a two-dimensional plane. The operation of the work 13 is controlled by a numerical controller 27 to move the work support to the upper and lower heads 15 and 17. The two-dimensional relative movement with respect to the upper and lower heads 15, 17, and thus with respect to the wire electrode 23, is possible by the moving device 29 for relatively moving. Further, the numerical controller 27 can move the upper and lower heads 15, 17 in the vertical direction (Z-axis direction) by the moving device 29. Thus, the workpiece 13 is desirably moved relative to the wire electrode 23 in a two-dimensional plane by the workpiece support using the machining start hole or the edge of the workpiece formed in the workpiece 13 as a starting point of the electrical discharge machining. Two-dimensional wire electric discharge machining is performed. It goes without saying that the wire electrode 23 may be moved with respect to the work 13.

The upper head 15 and the lower head 17 are provided with nozzles 31 and 33, respectively, for supplying a processing liquid. The central portions of the nozzles 31 and 33 are extended so that the wire electrode 23 extends therethrough. It is configured. The working fluid pumped by a pump 37 having a variable rotation speed is supplied from the working fluid tank 35 to the nozzles 31 and 33,
The liquid is supplied as a jet from the nozzles 31 and 33 to the electric discharge machining portion between the workpiece 13 and the wire electrode 23.

Normally, the tips of the nozzles 31 and 33 are arranged close to the surface of the work 13 within a range that does not hinder the relative displacement between the work 13 and the wire electrode 23. The configuration is such that the jet flow is sufficiently supplied to the gap of the processing locus, and the leakage of the working fluid from the gap between the tips of the nozzles 31 and 33 and the surface of the work 13 is suppressed as much as possible. However, when the surface of the work 13 is not flat, the gap between the nozzles 31 and 33 and the surface of the work 13 can be set apart.

A pressure detecting means such as a pressure sensor 39 is provided on the supply path of the machining fluid from the pump 37 to the nozzles 31 and 33, and constantly detects the pressure of the machining fluid supplied to the nozzles 31 and 33. , Monitoring. Pressure sensor 39
Is amplified by the amplifier 41 and fed back to the pump control device 43. The pump control device 43 determines the pump rotation speed based on the feedback pressure, outputs a pump drive signal corresponding to the pump rotation speed to the AC-driven pump 37 via the inverter 45, and controls the rotation speed. I do. These controls can be realized using a known microprocessor, for example.

Generally, when the surface of the work 13 and the tips of the nozzles 31 and 33 are brought close to each other, the nozzle 3
A constant pressure control is used to control the pump rotation speed so as to keep the pressure of the machining fluid injected from the nozzles 1 and 33 constant. When the surface of the work 13 is separated from the tips of the nozzles 31 and 33, the pump is used. Pump rotation speed command control for specifying the rotation speed is used. However, the present invention is not limited to this. For example, when the surface of the work 13 and the tips of the nozzles 31 and 33 are brought close to each other, the rotation speed command control may be used. In addition, the pump 37 is used as a direct index using the flow rate of the machining fluid injected from the nozzles 31 and 33.
It is also possible to control the rotation speed of. In this case, a flow rate detecting means such as a flow meter or a current meter is used instead of the pressure sensor 39.

In this manner, the machining fluid is ejected from the upper nozzle 31 and the lower nozzle 33 to the electric discharge machining portion between the work 13 and the wire electrode 23 to provide a cooling function, and
Removal of processing waste. This prevents disconnection of the wire electrode 23 and adhesion of machining debris in the machining gap, and promotes a smooth and stable electric discharge machining operation. Preferably, the work 13 is completely immersed in a processing tank (not shown) filled with a processing liquid. This makes it possible to eliminate the risk of air discharge.

In the machining fluid supply control method for the wire electric discharge machine 11 according to the present invention, the pump control device 43 further sets a limit value of the pump rotation speed or a limit value of the pressure. The pump rotation speed limit value is determined so that the vibration state of the wire electrode 23 at a predetermined level or less is maintained. Further, the pressure limit value is determined by the wire electrode 2
The delay amount of No. 3, that is, the amount of deflection toward the machining trajectory is determined so as to be maintained at or below a predetermined level. Preferably, both the pump rotation speed limit value and the pressure limit value are set in the pump control device 43.

As another embodiment, in the method for controlling the supply of the machining fluid of the wire electric discharge machine 11 according to the present invention, the nozzles 31 and 33 arranged above and below the work 13 are located in close proximity to the work 13 in close contact with the work 13 and As shown in FIG. 2, the flow rate of the working fluid flowing out of the machining start hole 47 is such that the machining start hole 47 provided through the work 13 is located inside the nozzles 31 and 33. When the cooling is insufficient and the wire electrode 23 is disconnected, the numerical controller 27 moves the at least one of the upper nozzle 31 and the lower nozzle 33 to a position separated from the work 13 to some extent to start the processing. The operation of the nozzles 31 and 33 is controlled by the moving device 29. Nozzles 31, 33
The moving distance in the Z-axis direction for moving the distance from the surface of the work 13 is set and stored in the numerical controller 27 in advance.

Further, as shown in FIG. 3, after at least a part of the machining start hole 47 is located outside the nozzles 31 and 33, the nozzles 31 and 33 are
The workpiece 13 and the nozzle 3
Nozzles 31, 3 within a range that does not hinder the relative movement of 1, 33
The numerical controller 27 controls the operation of the nozzles 31 and 33 via the moving device 29 so that the tip of the nozzle 3 returns to the close position almost in contact with the surface of the work 13.

The above control is performed by the processing start hole 47 and the nozzle 3
Irrespective of the size of 1, 33, it may be performed always at the start of electric discharge machining. Further, the same control may be applied when electric discharge machining is started from the edge of the work 13 instead of from the machining start hole 47. Further, in the above control, at least one of the upper and lower heads 15 and 17 provided with the nozzles 31 and 33 is
The upper head 15 may be moved in the axial direction, and the upper head 15 may be raised in the Z-axis direction to advance the processing, and after at least a part of the processing start hole 47 is positioned outside the nozzles 31 and 33, The upper head 15 may be lowered toward the work 13. Further, the lower head 17 is lowered in the Z-axis direction to advance the processing, and after at least a part of the processing start hole 47 is located outside the nozzles 31 and 33, the lower head 17 is moved toward the work 13. 17 may be raised.
Similarly, it goes without saying that the upper and lower heads 15 and 17 may be simultaneously separated and approached from the work 13.

The lead block 51 (see FIGS. 2 and 3), which is a run-up section required for stabilizing discharge prior to machining of the machining shape block 49 for machining the work 13 into a desired shape, is performed. , Usually the machining start hole 47
Since the distance is set to be sufficiently long compared with the diameter of the nozzles 31 and 33, the nozzles 31 and 3 are preferably used.
3 designates the terminal end 53 of the lead block 51 as a position to approach the work 13 again and approach the surface of the work 13. More preferably, as the wire electrode 23 advances along the lead block 51, the nozzles 31 and 33 gradually approach the surface of the work 13, and the leading ends of the nozzles 31 and 33 at the end 53 of the lead block 51. It is made to approach the surface of the work 13.

Next, the flow of the machining fluid supply control in each of the above embodiments of the present invention will be described in detail below with reference to the flowcharts shown in FIGS. FIG. 4 is a flowchart when the pump rotation speed limit value is provided and the pressure constant control is performed, and FIG. 5 is a flowchart when the pressure rotation value is provided and the pump rotation speed command control is performed. FIG. 6 shows that the diameter of the processing start hole 47 provided in the work 13 is
FIG. 9 is a flowchart of control performed to raise the distal ends of the nozzles 31 and 33 by a predetermined distance in a direction in which the tips of the nozzles 31 and 33 are separated from the surface of the work 13 when the nozzles 31 and 33 are located inside the nozzles 31 and 33.

First, with reference to FIG. 4, a description will be given of control when constant pressure control is performed with a pump rotation speed limit value provided. As described above, the pump rotation speed limit value _RL is determined such that the vibration of the wire electrode 23 is maintained at a predetermined level or less. In detail, the pump rotation speed limit value _RL is set to a value at which the vibration generated in the wire electrode 23 by the injected machining fluid causes the machining instability or machining failure caused by the oscillation to reach the upper limit of the allowable range. Defined as rotational speed.

First, the pressure command value commanded under the processing conditions is read into the storage section of the pump control device 43 (step 10).
1). Next, a pump rotation speed initial setting command value for discharging the preset and stored minimum flow rate is read from the storage unit of the pump control device 43 and output to the pump 37 (step 103). Here, the pressure versus rotation speed characteristic curve of the pump 37 when the flow rate is 0 is stored and stored in the storage unit of the pump control device 43 in advance, and the pump rotation speed initial value according to the input and set pressure command value is stored. The setting command value may be automatically set with reference to this characteristic curve.

Next, the pressure sensor 39 detects whether the pump 37
Of the working fluid in the piping to the nozzles 31 and 33
The pressure value is detected (step 105), and this is controlled by the pump.
Feedback to the device 43, the pump control device 43
The difference between the pressure command value and the actual pressure value, that is, the pressure difference E
_rIs obtained (step 107). Next, this pressure difference E
_rTo obtain a new pump rotation speed command value R according to
Step 109). Next, the determined pump rotational speed command value R
Is the pump rotation speed limit value R determined from the processing performance _LLess than
It is determined whether the value is a small value (step 11).
1) If the judgment result is yes, the calculated pump rotation speed
Is output to the pump 37 (step 1).
13). If no, the pump rotation speed limit value R_LTo
Output to pump 37 as pump rotation speed command value R
(Step 115).

In this way, the supply of the working fluid to the nozzles 31 and 33 by the pump 37 is continued, and if the working is not completed (step 117), the pressure in the piping is detected again by the pressure sensor 39, and The detected value is fed back to the pump control device 43 and the same control flow as described above is repeated until the machining is completed. By controlling the operation of the pump 37 by providing the pump rotation speed limit value _RL in this manner, for example, the tip portions of the nozzles 31 and 33 are arranged almost in close contact with the surface of the work 13 as shown in FIG. When performing the constant pressure control, the lower nozzle 33 moves from the flat portion 55 to the recessed portion 57 by relative movement with respect to the work 13, and the surface of the work 13 and the lower nozzle 33 are separated from each other, and the working fluid is Leaks and the pressure drops. As a result, when the pump rotation speed is increased to compensate for this pressure drop, the pump rotation speed limit value is set so that the vibration generated in the wire electrode 23 is maintained at a certain level or less. By setting, it is possible to suppress the occurrence of vibration and to prevent processing defects and processing instability.

Next, with reference to FIG. 5, a description will be given of the control when the pump rotational speed command control is performed with the pressure limit value provided. As described above, the pressure limit value P _L is determined by the wire electrode 2
3 is determined such that the delay amount is maintained at or below a predetermined level. Specifically, the pressure limit value P _L
7 is defined as the pressure of the working fluid when the processing accuracy reaches the upper limit of the allowable range due to the influence of the delay amount of the wire electrode 23 within the allowable range.

First, the rotational speed command value instructed under the processing conditions is read into the storage section of the pump control device 43 (step 119). Next, the pump rotation speed command value R is output to the pump 37 (step 121). Next, the pressure sensor 39 detects the pressure value _Pn of the working fluid in the piping from the pump 37 to the nozzles 31 and 33 (step 123). Next, the detected pressure value _Pn becomes the pressure limit value P
It is determined whether or not the value is smaller than _L (step 125). If the determination result is yes, the process is continued. In the case of No, a value obtained by subtracting a predetermined value α from the rotation speed command value R set in step 119 is newly set as the rotation speed command value R (step 1).
29).

In this way, if the processing has not been completed (step 127), the processing liquid nozzle 3
Supply to the pump rotation speed command value R
There is continuously output to the pump 37, again, the pressure of the working fluid in the pipe line is detected by the pressure sensor 39, determines the detected pressure value P _n of whether it is smaller than the pressure limit P _L Is performed, and the same control flow as described above is repeated until the machining is completed.

As described above, the operation of the pump 37 is controlled by providing the pressure limit value P _L which affects the processing performance.
For example, as shown in FIG. 8, when the tip of the upper nozzle 15 is arranged away from the surface of the work 13 and the pump rotation speed command control is performed, the upper nozzle 15 is recessed relative to the work 13. Is moved relative to the flat portion 55 raised from the upper nozzle
By setting the pressure limit value such that the pressure rises in a state in which the wire electrode 23 is almost in contact with the wire electrode 3 and the amount of delay generated in the wire electrode 23 is maintained at a certain level or less,
It is possible to suppress the amount of delay and to prevent the occurrence of poor processing accuracy or defective processing.

Finally, referring to FIG. 6, when the diameter of the machining start hole 47 formed in the work 13 is smaller than the nozzles 31 and 33 and located inside the nozzles 31 and 33, the tip of the upper nozzle 31 Control when the operation of the upper head 15 is controlled so as to raise the portion by a predetermined distance so as to separate the portion from the surface of the work 13 in the Z-axis direction will be described.

Here, the jet flow of the machining liquid is sufficiently supplied to the gap of the machining trajectory without obstructing the relative displacement between the workpiece 13 and the wire electrode 23, and the tip of the nozzles 31, 33 and the workpiece 13 are Liquid leakage from the gap with the surface as much as possible,
In order to suppress, the tip of the nozzles 31 and 33
3 is close to the surface. The end 53 of the lead block 51 is set as a position where at least a part of the processing start hole 47 is located outside the nozzles 31 and 33.

First, when wire electric discharge machining is started, the length of the lead block 51 is read from an input from an operator or from a program (step 131). Next, the diameter of the processing start hole 47 provided in the work 13 is
It is determined whether or not it is smaller than 33 (step 1).
33). In the case of Yes, the set value of the Z-axis rise amount for the upper head 15 set and stored in advance in the storage unit of the numerical control device 27 is read (step 135), and for example, as shown in FIG. With respect to the relative movement along the lead block 51 of the upper head 15 provided with the workpiece 13 along the lead block 51, the processing proceeds from the processing start position 47 which is the starting end of the lead block 51 to the position of the end 53 of the lead block 51, and The numerical controller 27 controls the movement in the Z-axis direction so that the tip of the nozzle 31 provided on the workpiece 15 gradually shifts from a state in which the distal end of the nozzle 31 is separated from the surface of the work 13 by a certain distance to a state in which the end approaches the surface of the work 13. The generated read block interpolation data is generated (step 137). Further, the numerical controller 27 raises the upper head 15 in the Z-axis direction by the Z-axis raising amount read in step 135 in order to separate the upper head 15 from the work 13 via the moving device 29 (step 139).

In the case of No at step 133, the work 13 of the upper head 15 provided with the nozzle 31
With respect to the relative movement along the lead block 51 with respect to the lead block 51, the lead block interpolation data including only the components related to the X axis and the Y axis perpendicular to the Z axis from the start end (the processing start hole 47) to the end end 53 of the lead block 51 is converted into a numerical controller 2
7 is created (step 141).

Next, machining of the lead block 51 is started, and electric discharge machining is performed while the upper head 15 is relatively moved with respect to the work 13 based on the lead block interpolation data created in step 137 or 141. (Step 143), end 53 of read block 51
The processing of the lead block 51 is completed by the
The tips of the nozzles 31 and 33 provided on the nozzles 5 and 17 are brought into a state of approaching the work 13 (step 145). Next, the processing of the processing shape block 49 is started (step 147).

When the diameter of the processing start hole 47 provided in the work 13 is smaller than the nozzles 31 and 33 and located inside the nozzles 31 and 33, the nozzles 31 and 33
The head 1 is moved up by a predetermined distance so that the tip of the head 13 is separated from the surface of the work 13 in the Z-axis direction.
By controlling the operations of 5 and 17, the machining fluid supplied between the wire electrode 23 and the work 13 is confined inside the machining start hole 47, so that the flow of the machining fluid does not occur. It is possible to prevent an inadequate cooling action from being obtained, thereby preventing the wire electrode 23 from being disconnected. Further, after at least a part of the processing start hole 47 is located outside the nozzles 31 and 33 as in the terminal end 53 of the lead block 51, the work 13 and the nozzles 31 and 33 are again moved along the Z axis. By approaching in the direction, the leakage of the machining fluid from the gap between the tips of the nozzles 31 and 33 and the surface of the work 13 is suppressed as much as possible, and a sufficient amount of machining fluid is stably supplied to the electric discharge machining portion. So that

In the flowchart shown in FIG. 6, it is described that only the upper head 15 can be moved up and down in the direction away from the work 13 with respect to the Z axis. Only 17 or both the upper and lower heads 15 and 17 may be simultaneously moved with respect to the work 13 with respect to the Z axis. When the lower head 17 is moved with respect to the work 13, the lower head 17 is first lowered in the Z-axis direction so as to be separated from the work 13, and the lower head 17 is moved toward the terminal end 53 of the lead block 51. It is only necessary to gradually increase toward 13. When both the upper and lower heads 15 and 17 are relatively moved with respect to the work 13, the above operations of the upper head 15 and the lower head 17 may be performed simultaneously.

Further, the heads 15 and 17 are relatively moved from the machining start hole 47 which is the starting end of the lead block 51 toward the end 53 of the lead block 51, and the heads 15 and 17 are not gradually approached to the work 13 in the Z-axis direction. The nozzles 31 and 33 are moved in a direction perpendicular to the Z axis while maintaining a state where the nozzles 31 and 33 are separated from the work 13 by a fixed distance from the start end (the processing start hole 47) to the end end 53 of the block 51. You may make it approach the work 13 at a stretch. Furthermore, finally, the nozzle 31,
The end 53 of the lead block 51 is selected as the position where the work 33 and the work 13 are brought close to each other.
The workpiece 13 and the nozzles 31 and 33 can be made to approach each other at an arbitrary position after being positioned outside the area.

It is needless to say that the machining fluid supply control method shown in FIGS. 4, 5 and 6 can be executed simultaneously in combination with any of the methods.

[0050]

As described above, according to the present invention,
A pump rotation speed limit value is provided so that the pump rotation speed does not rise above a certain value.When performing constant pressure control, the tip of the nozzle may come into contact with the work surface due to the recessed part provided on the work surface. The pump is moved relatively from the close state to the separated state, and when the pressure drops due to the separation between the nozzle and the work surface and the working fluid leaking out of the gap, the pump rotation speed increases due to the pressure feedback signal. The pump rotation speed limit value is set so that the vibration generated in the wire electrode is maintained at a certain level or less, so that it is possible to suppress the occurrence of vibration and prevent machining defects and machining instability. .

Further, since the pressure limit value is provided so that the pressure does not rise above a certain value, when the pump rotation speed command control is performed, the tip of the nozzle is brought into contact with the work surface by a recessed portion provided on the work surface. The pressure is limited so that the amount of delay generated in the wire electrode is kept below a certain level even when the pressure of the machining fluid rises due to the nozzle being almost in close contact with the transition from the separated state to the close state. By setting the value, it is possible to suppress the amount of delay of the wire electrode and to prevent the occurrence of poor processing accuracy or defective processing.

As a result, even if the shape of the surface of the workpiece changes, it is not necessary to switch the control method of the operation of the pump for supplying the processing liquid, and the processing can be performed appropriately and stably while performing the processing with only a single control method. The supply of the working fluid can be achieved, so that the working efficiency is improved and the working accuracy is improved. Further, when the diameter of the processing start hole provided in the work is smaller than the nozzle and located inside the nozzle, the tip of the nozzle is moved by a predetermined distance to separate from the work surface in the Z-axis direction. Therefore, the supply of the machining fluid to the electric discharge machining action portion is properly maintained, and a sufficient cooling action can be obtained, and it is possible to avoid the disconnection of the wire electrode.

[Brief description of the drawings]

FIG. 1 is a schematic structural view showing main components of a wire electric discharge machine for implementing a machining fluid supply control method of the present invention.

FIG. 2 is a diagram showing a state in which a processing start hole provided in a work is located inside a nozzle.

FIG. 3 is a diagram showing a state where a part of a processing start hole provided in a work is located outside a nozzle.

FIG. 4 is a flowchart of a working fluid supply method of the present invention in which a pump rotation speed limit value for performing constant pressure control is provided.

FIG. 5 is a flowchart of a working fluid supply method of the present invention in which a pressure limit value is set when performing pump rotation speed command control.

FIG. 6 is a diagram showing a process in which when the diameter of a processing start hole provided in a workpiece is smaller than the nozzle and located inside the nozzle, control is performed such that the tip of the nozzle is moved by a predetermined distance in a direction away from the surface of the workpiece. It is a flowchart of the working fluid supply method of the present invention as described above.

FIG. 7 is a diagram illustrating a situation in which the tip of the nozzle shifts from a state close to the work to a state separated from the work.

FIG. 8 is a diagram illustrating a situation where the tip of the nozzle shifts from a state in which the nozzle is separated from the work to a state in which the tip approaches the work.

FIG. 9 is a diagram showing a state in which a head and a nozzle separated from a workpiece gradually approach the workpiece as the processing proceeds.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Wire electric discharge machine 13 ... Work 15 ... Upper head 17 ... Lower head 23 ... Wire electrode 31 ... Nozzle 33 ... Nozzle 37 ... Pump 43 ... Pump control device 47 ... Processing start hole

Claims (4)

[Claims] 1. A pump for supplying a machining fluid to an electric discharge machining portion between a work and a wire electrode stretched between the pair of nozzles via a pair of nozzles arranged above and below the work. A machining fluid supply control method of a wire electric discharge machine, wherein the pressure of the machining fluid is detected at a stage preceding the nozzle, and the pressure of the pressure is controlled so that a delay amount of the wire electrode is maintained at a predetermined level or less. A machining fluid supply control method for a wire electric discharge machine, wherein a limit value is determined, and an operation of the pump is controlled so that the pressure is maintained at or below the limit value. 2. A pump for supplying a machining fluid to an electric discharge machining portion between a wire electrode stretched between the pair of nozzles and a workpiece through a pair of nozzles disposed above and below the workpiece. A machining fluid supply control method for a wire electric discharge machine, wherein a limit value of a rotation speed of the pump is determined so that a vibration state of a predetermined level or less is maintained in the wire electrode, and the rotation speed is limited to the rotation speed. A method for controlling the supply of a machining fluid for a wire electric discharge machine, wherein the operation of the pump is controlled so as to be maintained at or below a value. 3. A pump for supplying a machining fluid to an electric discharge machining section between the work and a wire electrode stretched between the pair of nozzles via a pair of nozzles arranged above and below the work. A machining fluid supply control method of a wire electric discharge machine, wherein the pressure of the machining fluid is detected at a stage preceding the nozzle, and the pressure of the pressure is controlled so that a delay amount of the wire electrode is maintained at a predetermined level or less. A limit value is determined, and a limit value of a rotation speed of the pump is determined so that a vibration state of a predetermined level or less is maintained in the wire electrode, and the pressure and the rotation speed are each maintained at the limit value or less. And controlling the operation of the pump so that the machining fluid is supplied to the wire electric discharge machine. 4. An electric discharge machine which supplies a machining fluid to an electric discharge working portion between a wire electrode stretched between said pair of nozzles and said work via a pair of nozzles arranged above and below the work. A method of controlling a working fluid supply, wherein the pair of nozzles are located at a first vertical position close to a surface of the work, and a working start hole provided through the work is located inside the nozzle. Sometimes, at least one of the pair of nozzles is moved from the first position to the second position in a vertical direction separated from the surface of the work as compared with the first position to start processing, and the processing start hole is started. A machining fluid for a wire electric discharge machine, characterized in that after at least a part of the nozzle is positioned outside the nozzle, the nozzle is moved vertically so as to return to the first position. Supply control Law.