JPH04261713A - Work liquid feed control device of wire electric discharging machine - Google Patents

Abstract

PURPOSE:To precisely set various working conditions interfaced with a work shape, by controlling the feed of a work liquid from upper and lower nozzles so as to prevent the disconnection of a wire electrode strenuously, while suppressing the level reduction of the electric discharging efficiency caused on the feed of the work liquid, also executing the control of the top and bottom separately and independently. CONSTITUTION:The pressure of the work liquid fed from the upper and lower nozzles 12a, 14a of the upper head 12 and lower head 14 of a wire electric discharging machine is respectively set at the specified value, the upper and lower pressures of the work liquid are respectively detected close to the above- mentioned upper and lower nozzles of the fed work liquid, and the discharging outputs of work liquid feeding pumps 20, 21 are adjusted independently respectively, so that the detected pressure follows up to the specified pressure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machining fluid supply control device for a wire electrical discharge machine.

0002

2. Description of the Related Art In general, a wire electrical discharge machine runs a wire electrode along a wire electrode feeding path defined between upper and lower heads having a wire guide and a machining fluid supply nozzle. A workpiece is attached to a workpiece table that is arranged and can be freely moved in two-dimensional directions, and a discharge action is applied via a gap between the wire electrode and the workpiece starting from an initial hole formed in the workpiece or the end face of the workpiece. The electric discharge machining action is caused to proceed along a desired trajectory path from the starting point position according to the relative displacement between the workpiece to be machined and the wire electrode.

At this time, machining fluid with a high fluid pressure of several kg/cm2 is ejected from the upper and lower machining fluid supply nozzles to the electrical discharge machining area between the wire electrode and the workpiece to provide a cooling effect. By removing machining debris, wire electrode breakage and machining path clogging are prevented, and electrical discharge machining progresses smoothly and stably.

0004

[Problems to be Solved by the Invention] However, the tip of the machining fluid supply nozzle that supplies machining fluid to the electrical discharge machining section is formed as a circular fluid spout with a constant diameter, and it The machining fluid at the tip of the machining fluid supply nozzle is set close to the machining fluid supply nozzle, and the machining fluid at the tip of the machining fluid supply nozzle always concentrates and supplies the spouted machining fluid to the electrical discharge machining action area. Machining conditions such as a machining locus that has already been machined appearing within the area of the diameter of the spout, or the tip of the machining fluid supply nozzle protruding from the edge of the workpiece, or furthermore, for some reason, the machining fluid supply nozzle and the workpiece may If an inconvenient machining condition occurs, such as fluid leaking from a part that is in close contact with the work surface to a part other than the electrical discharge machining area,
The amount of machining fluid spouted from the machining fluid supply nozzle onto the machining trajectory currently in progress decreases, and as a result, unstable machining begins due to lack of fluid in the electrical discharge machining area, which ultimately causes damage to the wire electrode. There is a problem in that heating, wire breakage, etc. occur, leading to interruption of the electrical discharge machining operation.

Conventionally, when the above-mentioned unstable machining occurs,
The conventional method was to detect a change in the value of the electrical discharge machining current, and at that time reduce the electrical discharge power from the electrical discharge machining power supply to prevent wire electrode breakage as much as possible at the expense of machining speed. , the reduction in machining speed has the disadvantageous result of reducing the machining efficiency of the electrical discharge machine.

Furthermore, when the nozzle and the workpiece are close together, the valve is generally opened, and when the nozzle and the workpiece are far apart, the valve is closed for adjustment. Depending on the shape of a workpiece, vertical imbalance may occur, so in order to efficiently perform electrical discharge machining, valves must be installed in the upper and lower supply pipes, and the valves must be adjusted by the operator visually and audibly. There was the inconvenience of not being able to do so.

The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to prevent a decrease in the efficiency of electrical discharge machining due to the supply of machining fluid, and to The supply of machining fluid to the wire electrical discharge machine is controlled to prevent electrode breakage as much as possible, and by independently performing the supply and control for the upper and lower parts, it is possible to set and program various machining conditions that suit the shape of the workpiece. The aim is to provide a device that automates the process.

[0008]

[Means for Solving the Problems] In order to achieve the above object, a machining fluid supply control device for a wire electrical discharge machine according to the present invention supplies machining fluid from a machining fluid tank to the upper and lower portions of an electrical discharge machining section.
In a machining fluid supply device for a wire electric discharge machine that ejects fluid from two opposing nozzles, an upper nozzle supply path leading from the machining fluid tank to the upper nozzle and a lower nozzle supply path leading to the lower nozzle are provided, and the upper and lower nozzles are supplied. Each path includes a liquid feeding means consisting of a pump with a variable discharge amount, a pressure detection means provided near the nozzle to detect the pressure of the machining fluid, and a pressure detection means for detecting the pressure of the machining fluid so that the detected pressure follows the commanded pressure value. The pump controller is connected to a pump control means for controlling the discharge amount of the pump.

[0009]

[Operation] According to the above-described machining fluid supply control device for a wire electric discharge machine of the present invention, each supply pressure of machining fluid at the front stage of the upper and lower machining fluid supply nozzles is controlled so as to follow each command supply pressure. A sufficient amount of machining fluid is constantly supplied to the electrical discharge machining section of the wire electrical discharge machine from each pump forming a machining fluid supply source through the upper and lower nozzles. Therefore, the electric discharge machining action is stabilized while maintaining the vertical balance, and the occurrence of disconnection of the wire electrode can be prevented as much as possible. As a result, the electrical discharge machining efficiency can also be maintained at a relatively high level.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a schematic mechanical diagram showing the basic configuration of a device that uses a pressure sensor to control machining fluid supply in a wire electrical discharge machine according to the present invention, and FIGS. 2 and 3 show a wire FIG. 4 is a plan view illustrating the leakage phenomenon of machining fluid that occurs during the process of performing electrical discharge machining with the electrode; FIG. 4 is a graph diagram showing the relationship between pressure and frequency of an AC-driven pump for supplying machining fluid; FIG. 2 is a schematic mechanical diagram showing the basic configuration of another embodiment using a flow rate sensor.

Referring first to FIG. 1, the wire electric discharge machine is equipped with an upper head 12 and a lower head 14, and a running path having a guide roller is run between the upper and lower heads 12 and 14 from a wire electrode supply reel. The wire electrode 16 supplied via the wire electrode 16 is configured to run in the vertical direction. Between the upper and lower heads 12 and 14 is placed a workpiece W that is fixed and mounted on a worktable (not shown) that can be fed and displaced in a two-dimensional plane. Electric discharge machining is performed using the wire electrode 16 using the formed initial hole (small hole) or the edge of the workpiece as a starting point for electric discharge machining.

Both the wire electrode 16 and the workpiece W are connected to an electric discharge machining power source (not shown), and when they face each other through a small gap, an electric discharge occurs between the gaps, and the energy of this electric discharge causes the workpiece W to The wire electrode 16 is electrically connected to the electrical discharge machining power source via the electrical feeder in the vicinity of the electrical discharge machining area, and the workpiece W is electrically discharged.
is also connected to the electrical discharge machining power supply via a suitable conduction circuit. Then, during the electrical discharge machining process, the workpiece W to be machined is subjected to feed control in a two-dimensional plane together with the worktable, so that the electrical discharge machining progresses along a desired trajectory, and a product having a desired shape is produced from the workpiece W to be machined. It is ready to be processed.

The upper and lower heads 12 and 14 are provided with nozzles 12a and 14a for supplying machining fluid, and the machining fluid supplied to the machining fluid supply nozzles 12a is supplied to a cleaning fluid tank 18.
A is pumped up by a pump 20, supplied via piping lines 22a and 22b before and after the pump 20, and supplied from above to the electrical discharge machining section as a jet stream from a machining fluid nozzle 12a.

Further, the machining fluid supplied to the machining fluid supply nozzle 14a is pumped up from the cleaning fluid tank 18a by a pump 21, and is passed through piping lines 23a and 23b before and after the pump 21.
The machining fluid nozzle 14a is supplied as a jet stream from below to the electrical discharge machining section. Upper and lower head 12
, 14 machining fluid supply nozzles 12a, 14a are formed as circular machining fluid spouting parts, and the center part is connected to the wire electrode 1.
6 passes through the processing liquid supply nozzle 1.
The tips of 2a and 14a are usually set as close to the surface of the workpiece W as possible without interfering with the relative displacement between the workpiece W, the wire electrode 16, and the machining from the nozzle. The structure is such that a sufficient amount of liquid jet is supplied to the gap in the machining trajectory, and liquid leakage from the gap between the nozzle tip and the workpiece surface is suppressed as much as possible.

A function is provided to control the machining fluid supply action by the pumps 20 and 21 so that a stable amount of machining fluid is always supplied to the electrical discharge machining action area between the workpiece and the electrode. The machining fluid pumped up by the pumps 20 and 21 from the cleaning fluid tank 18a is ejected under pressure to the electrical discharge machining action section.

Next, the machining fluid that has completed the predetermined machining fluid action such as cooling and removing machining powder is collected in the recovery section 2 of the wire electric discharge machine.
4 is recovered and returned to the recovery liquid tank 18b of the machining liquid tank 18 via the recovery piping 25, from where it is pumped to the pump 2.
6. A circulation system is constructed in which the cleaning liquid is sent to the cleaning liquid tank 18a through the filter 28 and reused.

Furthermore, both tanks are communicated through a regulating pipe 29 so that the liquid overflowing from the cleaning liquid tank 18a is returned little by little to the recovery liquid tank 18b. In this case, conventionally, the flow rate of the pump that pumps up the cleaning liquid and supplies it to the nozzle causes contamination due to backflow from the recovery tank 18b to the cleaning liquid tank 18a, or the cleaning liquid exceeds the level of the adjustment pipe 29 and flows from the cleaning liquid tank 18a. There was some control in adjusting the action of both pumps to prevent overflow, but still.
Control to stabilize the electric discharge machining operation by strictly controlling the supply of machining fluid to the electric discharge machining operation section of a wire electric discharge machine has not been performed.

Now, referring to FIGS. 2 and 3,
The relationship between the workpiece W and the tip of the machining fluid supply nozzle 12a or 14a is illustrated. In FIG. 2, the wire electrode 16 that passes through the center of the nozzle along the machining trajectory A of the workpiece W is currently continuing the electrical discharge machining action, and the machining trajectory B that has already been machined is also approaching the machining trajectory A. The figure shows that it is formed.

In such an electrical discharge machining process, the machining fluid ejected under pressure from the machining fluid supply nozzles 12a and 14a is mainly supplied to the machining trajectory A as a jet stream, but there are other machining fluids within the diameter of the nozzle tip. Since there is a flow path according to the trajectory B, the machining fluid also flows to the same trajectory B side. Therefore, even if the upper and lower nozzles 12a and 14a are in close contact with the surface of the workpiece W, the supply of machining liquid to the machining trajectory A that is currently being continued becomes insufficient, such as insufficient cooling, removal of machining powder, etc. The electrical discharge machining operation becomes unstable due to situations such as improper operation. If such an unstable machining state continues, the wire electrode 16 will immediately break, and the electrical discharge machining operation will be interrupted.

Furthermore, as shown in FIG. 3, when the machining trajectory C is close to the edge of the workpiece, the machining fluid supply nozzle 1
Parts of the tips of 2a and 14a protrude from the edge of the workpiece, and as a result, the supply of machining fluid cannot be concentrated on the machining trajectory C, resulting in the same problem as described above. Therefore, the present invention aims to solve this problem. Now, referring to FIG. 1 again, in this embodiment, in order to control the amount of machining fluid ejected from the machining fluid supply nozzles 12a and 14a, the fluid pressure at the position upstream of the jet ports of both nozzles 12a and 14a is adjusted. A mechanism is configured to control the discharge supply amount by the machining fluid supply pumps 20 and 21 in order to perform follow-up control to the optimum command pressure value.

That is, pressure sensors 30 and 31 are provided to detect the machining fluid pressure in the machining fluid piping lines 22b and 23b, and the machining fluid pressure detected by the pressure sensors 30 and 31 is converted into an electrical signal. The pressure command value input units 36 and 37 are fed back via feedback control circuits 34 and 35 having amplifiers 32 and 33, respectively. The pressure command value input units 36 and 37 create a command signal according to the difference between the pressure command value and the detected value and send it to the control units 40 and 41 of the pump drive circuits 38 and 39. At this time, the control units 40 and 41 convert the command signal into a pump drive signal, which is converted into an AC drive signal by the inverters 42 and 43 to control the pumping action of the AC drive type machining fluid supply pumps 20 and 21. The liquid pressure in the piping paths 22b and 23b is controlled by adjusting the amount of liquid discharged.

Now, when performing the machining fluid supply control described above in a wire electric discharge machine, the machining fluid supply pump 20
It is necessary to harmonize the pumping actions of the filter 21 and the filtration pump 26 that pumps up the recovered processing fluid from the tank 18b and sends it to the filter 28. That is, the action of the recovered liquid pump 26 is to detect the level of the clean machining liquid in the clean liquid tank 18a and operate the filtration pump 26 in accordance with the drop in the water level, but it also supplies clean machining liquid. If the pumps 20 and 21 are maintained in a large amount to supply a sufficient amount of machining fluid to the electrical discharge machining action section described above, the amount of recovered fluid will inevitably increase and overflow will occur in the recovery tank 18b.
There is a possibility that the contaminated recovery liquid may enter the cleaning liquid through the adjustment pipe 29.

Therefore, the discharge operation of the machining fluid supply pumps 20 and 21 is controlled by the command pressure input sections 36 and 3 described above.
7 and the pump drive circuits 38 and 39, the characteristic data of the pressure and pump drive frequency in the piping lines 22b and 23b is obtained in advance for the rated discharge capacity of the same pumps 20 and 21, and is processed on the recovery liquid tank 18b side. It is necessary to control so that the machining fluid is not supplied from the pumps 20 and 21 in excess of the maximum pump discharge amount to prevent overflow of the fluid.

[0024] This can be controlled using, for example, a well-known microprocessor, and a control method in that case will be briefly explained with reference to the pressure versus frequency characteristic curve of the pump shown as an example in FIG. Referring to the pressure versus frequency characteristic curve of the pump shown in the graph of Figure 4, the vertical axis is the pressure value (
Kg/cm2), and the horizontal axis shows the pump drive frequency. The same graph shows the discharge flow rate Q of the pumps 20 and 21.
The characteristic curves are shown for both O [l/min] and the limit discharge flow rate Q=L [l/min] at which no tank overflow occurs. Of course, the discharge capacities of the pumps 20 and 21 are selected in advance to be capable of outputting a larger discharge flow rate in terms of rating.

The machining fluid supply pumps 20 and 21 must supply machining fluid at a discharge flow rate Q between O and L. Here, a machining fluid piping path 2 leading from the machining fluid supply pumps 20 and 21 to the nozzles 12a and 14a.
If the pressure values in 2b and 23b are controlled based on the target value and the detected value while maintaining the above-mentioned control conditions, the machining fluid will not overflow in either the cleaning fluid tank 18a or the recovery fluid tank 18b. The machining fluid supply control of the wire electric discharge machine according to the present invention can be carried out smoothly.

FIG. 5 shows an example in which flow rate sensors 30' and 31' are used in place of the pressure sensors 30 and 31, and the same parts as in FIG. In this example, the values detected by the flow rate sensors 30' and 31' are converted into pressure values through the calculation circuits of the flow rate/pressure converters 34' and 35', based on the known quantitative relationship that the pressure decreases as the flow rate increases. This shows that the same control as described above can be performed. In any case, the present invention controls the detected pressure to follow the command pressure. It is also possible to combine the above two embodiments and apply a flow rate sensor to one and a pressure sensor to the other.

[0027]

According to the present invention, during electrical discharge machining in a wire electrical discharge machine, the upper and lower pressure values of the machining fluid from the upper and lower machining fluid spouting nozzles to the electrical discharge machining action section are set respectively according to command values, and the above-mentioned The actual upper and lower pressure values of the machining fluid are constantly detected near the machining fluid spout ports of the upper and lower machining fluid jetting nozzles, and the detected pressures are routed from the machining fluid supply source to the upper and lower nozzles so that they follow the command pressure. Since the discharge output of the pumps installed in each machining fluid supply path is adjusted independently, the machining fluid is always stably supplied to the electrical discharge machining area in the necessary and sufficient amount, and therefore the wire electrode and workpiece are In the electrical discharge machining section where the upper and lower workpieces face each other, even if the shapes of the upper and lower workpieces are different, the cooling effect and the removal of machining debris by the upper and lower machining fluids are stably performed, and therefore, the electrical discharge machining is not interrupted due to wire electrode breakage. This will be prevented as much as possible, and as a result, electrical discharge machining efficiency can be maintained at a high level. Furthermore, it is possible to programmably set various machining conditions according to the shape of the workpiece without using switching valves or adjustment valves, allowing fine automatic control.
It can be unmanned and automated.

[Brief explanation of the drawing]

FIG. 1 is a schematic mechanical diagram showing the basic configuration of an apparatus that implements a machining fluid supply control method for a wire electric discharge machine according to the present invention using a pressure sensor.

FIG. 2 is a plan view illustrating a leakage phenomenon of machining fluid that occurs during the process of performing electrical discharge machining on a workpiece using a wire electrode.

FIG. 3 is a plan view illustrating a leakage phenomenon of machining fluid that occurs during the process of performing electrical discharge machining on a workpiece using a wire electrode.

FIG. 4 is a graph showing the relationship between pressure and frequency of an AC-driven pump for supplying machining fluid.

FIG. 5 is a schematic mechanical diagram showing the basic configuration of an apparatus that implements the method of the present invention using a flow rate sensor.

[Explanation of symbols]

12a, 14a Machining fluid jet nozzle 16
Wire electrodes 20, 21 Pumps 22a, 22b, 23a, 23b Machining fluid supply lines 30, 31 Parameter (pressure) detection means 30
', 31' Parameter (flow rate) detection means 36, 37
Input part (pressure) 36', 37' Input part (flow rate) 38, 39 Pump drive circuit

Claims (1)

[Claims] 1. A machining fluid supply device for a wire electrical discharge machine in which machining fluid in a machining fluid tank is ejected from two opposing nozzles above and below an electrical discharge machining section, wherein an upper nozzle supplies the machining fluid from the machining fluid tank to the upper nozzle. and a lower nozzle supply path leading to the lower nozzle, and each of the upper and lower nozzle supply paths includes a liquid feeding means consisting of a variable discharge amount pump, and is provided near the nozzle to detect the pressure of the machining fluid. A wire electric discharge machine characterized in that a pressure detection means is connected to a pump control means for controlling the discharge amount of the pump so that the pressure of the detected machining fluid follows a commanded pressure value. machining fluid supply control device.