JPH071244A - Wire cut electric discharge machine - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a wire cut electric discharge machining apparatus capable of preventing wire electrode breakage and machining shape accuracy deterioration due to an increase in plate thickness of a workpiece and deterioration of machining scrap removal effect. [Structure] The wire-cut electric discharge machine 1 has a wire electrode 3
Wire drive device 7 for moving the workpiece, feed motors 9 and 11 for feeding the workpiece 5, a machining feed speed detection circuit 15, an ECU
(Electronic control device) 23 and the like are provided. A signal from the tacho generators 31, 33 indicating the number of rotations of the feed motors 9, 11 is inputted to the machining feed speed detection circuit 15, and the machining feed speed detection circuit 15 inputs the actual machining feed speed to the ECU 23. In the ECU 23, the machining feed speed is read a predetermined number of times and averaged, and then the value of the traveling speed of the wire electrode 3 is inversely calculated or determined in accordance with the increase or decrease of the average speed. , The wire drive device 7 is controlled to change the traveling speed of the wire electrode 3 to the calculated value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire-cut electric discharge machine for machining a work piece by applying a voltage between a wire electrode and the work piece to generate an electric discharge.

[0002]

2. Description of the Related Art Conventionally, in a wire-cut electric discharge machining apparatus of this type, a machining gap is formed between a wire electrode traveling at a constant speed in the linear direction and a workpiece, and the machining gap has a predetermined cycle. A voltage is applied to repeatedly generate an electric discharge, and the workpiece is horizontally moved by a feed motor or the like to feed the workpiece, thereby processing the workpiece into a desired shape.

As a method of controlling the machining feed rate, a method of controlling the distance between the machining gaps to be kept constant is adopted. For example, discharge is started after applying a voltage to the machining gaps. The method of controlling the distance of the machining gap so as to match the no-load time with a preset time is used.

The wire electrode is wound and run at a constant speed preset according to various processing conditions by a wire electrode driving device equipped with a winding motor and the like.

[0005]

However, the above-mentioned conventional wire-cut electric discharge machine has the following problems. That is, when the plate thickness of the workpiece changes during processing and becomes thicker, the increase in the thickness causes
The portion of the wire electrode that receives the discharge faces the workpiece for a longer time, and the number of discharges that portion receives increases, so that the consumption of the wire electrode partially increases. Therefore, there arises a problem that the wire electrode is broken or the accuracy of the processed shape is deteriorated.

Further, for example, when the machining shape is complicatedly bent or the plate thickness of the workpiece is increased, it becomes difficult to remove the machining waste from the machining gap, whereby the machining waste and the wire electrode are separated. During this period, an undesired arc discharge occurs and the wire electrode is broken.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to prevent disconnection of a wire electrode and deterioration of accuracy of a machined shape due to an increase in a plate thickness of a workpiece and a deterioration of a removal effect of machining scraps. An object of the present invention is to provide a wire cut electric discharge machine that can be used.

[0008]

In order to achieve this object, a wire-cut electric discharge machining apparatus according to the present invention comprises a wire electrode which travels in a linear direction by a wire driving device M1 and a work piece which is the other electrode. A voltage is applied between the wire electrode and the work piece to discharge it by controlling the feed rate to keep the distance between the wire electrode and the work piece substantially constant. Processing feed speed detecting means for detecting the processing feed speed, and processing feed speed detecting means M2
And a wire driving device control means M3 for controlling the wire driving device M1 so as to decrease or increase the traveling speed of the wire electrode, contrary to the change of the processing feeding speed, according to the increase or the decrease of the processing feeding speed detected by. Is equipped with.

[0009]

In the present invention having the above-described structure, the wire driving device M1 applies a voltage at a predetermined cycle between the wire electrode traveling in the linear direction and the work piece which is the other electrode, and at the same time, discharges. The machining feed rate is controlled so that the distance of the machining gap between the wire electrode and the workpiece is kept substantially constant, and the workpiece is cut into a desired shape.

At the time of this machining, the machining feed speed detecting means M2 detects the machining feed speed, and according to the detected increase or decrease of the machining feed speed, the wire driving device control means M3 causes the wire driving device M1. Control
The traveling speed of the wire electrode is decreased or increased contrary to the change in the machining feed speed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The wire-cut electric discharge machining apparatus 1 of the embodiment shown in FIG. 2 applies a voltage at a predetermined cycle between the wire electrode 3 and the workpiece 5 to generate an electric discharge, thereby forming the workpiece 5 into a desired shape. A wire drive device 7 for moving the wire electrode 3 in a linear direction, feed motors 9 and 11 for feeding the workpiece 5 and a motor drive circuit 13, and a feed speed detection circuit for detecting feed speed. 15, a machining power supply 17 and a switching element 18 for generating a discharge, a discharge detection circuit 19 and a no-load time counting circuit 21 for controlling the machining feed rate, an ECU (electronic control unit) 23 for controlling the operation of the entire device, and the like. I have it.

Here, the wire electrode 3 includes a pulley 25,
It is stretched by 27 and faces the workpiece 5 with a machining gap G in between. During processing of the workpiece 5, the wire electrode 3 is equipped with a motor 7a for winding the wire drive device 7
While being wound by, the vehicle travels in the line direction (arrow Z direction).

The feed motors 9 and 11 respectively move the work piece 5 in the X-axis direction or the Y-axis direction which are orthogonal to each other to feed the work piece 5 in the horizontal direction. It is controlled by the ECU 23 via the circuit 13. Further, the feed motors 9 and 11 are provided with tacho generators 31 and 33 for detecting the number of rotations, respectively, which are connected to the machining feed speed detection circuit 15.

The machining power source 17 for generating an electric discharge has its positive electrode connected to the workpiece 5 and further grounded. On the other hand, the negative electrode of the processing power supply 17 is connected to the wire electrode 3 via the switching element 18 and the power supply 35, and a voltage is applied between the wire electrode 3 and the workpiece 5 at a predetermined cycle. , Generate a discharge. Further, the discharge detection circuit 19 for detecting the occurrence of discharge and the no-load time counting circuit 21 for counting the no-load time described later are connected between the switching element 18 and the power supply 35, and the machining gap G The machining feed rate is controlled to keep the distance constant.

The ECU 23 includes a well-known CPU 35 and ROM
37, RAM 39, input / output port 41 and bus line 4
The wire drive device 7, the motor drive circuit 13, the machining feed rate detection circuit 15 and the like are connected to the input / output port 41. ROM 37 and RAM
A program for controlling various operations of the apparatus and various data such as processing conditions are stored in 39. In addition, the ECU 2
A keyboard 45 for inputting the programs and data described above is connected to the keyboard 3.

Next, the above-mentioned wire-cut electric discharge machine 1
The control operation of the machining feed rate in the above will be described. In the processing apparatus 1 of the present embodiment, the time from the application of voltage to the processing gap G to the start of discharge (no-load time T).
Is counted by the no-load time counting circuit 21, and the count value T is output to the ECU 23. Then, the ECU 23 controls the motor drive circuit 13 and, by extension, the feed motors 9 and 11 so that the no-load time T coincides with a preset time Tc, and the machining feed speed is maintained so as to keep the distance of the machining gap G substantially constant. Adjust.

That is, since the no-load time T becomes longer in proportion to the distance of the machining gap G, the machining speed decreases due to the increase in the plate thickness of the workpiece 5 and the deterioration of the effect of removing machining scraps. When the distance is shortened, the no-load time T is shortened. Therefore, the machining feed speed is slowed down so as to match the set time Tc, and the distance of the machining gap is kept constant. On the contrary, when the plate thickness is relatively thin and the machining speed is fast, the distance of the machining gap becomes long. Therefore, the machining feed speed is increased to keep the distance constant.

Next, the control operation of the traveling speed of the wire electrode 3 will be described in detail. In this embodiment, a signal from the tacho generators 31 and 33 indicating the number of rotations of the feed motors 9 and 11 (that is, a signal indicating the machining feed speed in the X-axis or Y-axis direction) is input to the machining feed speed detection circuit 15. From this machining feed rate detection circuit 15, the actual machining feed rate F
A signal indicating (vector sum of machining feed rates in the X-axis and Y-axis directions) is input to the ECU 23.

Then, the ECU 23 reads the machining feed speed F in a constant cycle, integrates it a predetermined number of times, averages it, and then increases or decreases the speed (average machining feed speed Fa) of the wire electrode 3. The traveling speed is calculated and determined so as to be decreased or increased, and the wire driving device 7 is controlled to change the actual traveling speed of the wire electrode 3 to the calculated value.

Here, the above-mentioned operation will be specifically described with reference to the flow chart of FIG. First, prior to the processing of the workpiece 5, in step 1 (hereinafter step is abbreviated as S), the sampling time T of the processing feed speed is set in advance.
s and the total number N of samplings are set.

Next, when the machining is started, in S2, the values of the sum Fp of the machining feed speed and the sum n of the number of samplings are once reset, and the counting of the sampling time is started.
Next, in S3, it is determined whether or not the sampling time Ts set in S1 has elapsed. If it has not elapsed, the process returns to S3 again, but if it has elapsed, the process advances to S4.

At S4, the machining feed rate detection circuit 1
The machining feed speed F output from 5 is read into the ECU 23 and added to the sum Fp of the machining feed speeds (that is,
Fp = Fp + F), and 1 is added to the sum n of sampling times (that is, n = n + 1). Next, in S5, it is determined whether or not the sum n of the sampling times is equal to the value N set in S1. If they are not equal, the process returns to S3, but if they are equal, the process proceeds to S6.

Then, in S6, the Fp added by repeating the above S3 to S5 is divided by N to calculate the average machining feed speed Fa (= Fp / N). Next, in S7, the wire electrode traveling speed Ws is calculated as follows according to the average machining speed Fa obtained in S6. That is, the ROM 37 or the RAM 39 of the ECU 23 stores data indicating the correlation between the average machining feed speed Fa and the wire electrode traveling speed Ws, as shown in the graph of FIG. 4, for example. The electrode traveling speed Ws is calculated. Therefore, for example, as shown in FIG. 4, when the average machining feed speed decreases from Fa0 to Fa1 due to an increase in the plate thickness of the workpiece 5, the calculated value of the wire electrode traveling speed increases from Ws0 to Ws1.

Next, in S8, the wire driving device 7 is controlled according to the wire electrode traveling speed Ws obtained in S7 to change the actual traveling speed of the wire electrode 3 to Ws. That is, in the example of FIG. 4 described above, the traveling speed is W
Increase from s0 to Ws1. Then, the procedure proceeds to S9, where it is determined whether or not the traveling of the wire electrode 3 is to be terminated. , S3-S
The operation of 8 is repeated to control the wire electrode traveling speed Ws. On the other hand, when it is determined in S9 that the traveling of the wire electrode is to be ended (that is, the processing is stopped), the processing is ended once.

As described in detail above, in the wire-cut electric discharge machine 1 of this embodiment, the average machining feed rate Fa
The wire drive device 7 can be controlled so as to decrease or increase the traveling speed of the wire electrode 3 contrary to the change of Fa according to the increase or decrease of

Therefore, when the plate thickness of the work piece 5 is increased or the removal effect of the machining waste is deteriorated during machining, and the machining feed rate is reduced, the wire electrode 3 is changed according to the degree of the reduction of the machining feed rate. It is possible to increase the traveling speed of the wire electrode 3, prevent the wire electrode 3 from being broken, and improve the processing accuracy.

Although the embodiments have been described above, the present invention is not limited to the above embodiments and can be implemented in various modes. For example, in the embodiment, the wire electrode traveling speed is linearly changed with respect to the machining feed speed as shown in FIG. 4, but the changing method is not limited to this, and the wire electrode traveling speed is changed in a curve or in a stepwise manner. You can also let it.

The section for controlling the wire electrode traveling speed may be limited. That is, instead of infinitely increasing or decreasing the wire electrode traveling speed, an upper limit value or a lower limit value may be set and the traveling speed may be controlled so as not to exceed these set values. Further, in the machining feed, the wire electrode 3 can be moved in the horizontal direction without moving the workpiece 5.

In addition, the processing feed speed can be detected by various methods other than the above-mentioned embodiment. For example, the processing feed speed can be detected by using the internal data of the ECU 23 for controlling the feed speed of the feed motors 9 and 11. You can also do it.

[0030]

As described in detail above, in the wire-cut electric discharge machining apparatus of the present invention, the machining feed speed is detected by the machining feed speed detecting means, and the wire driving device is operated according to the detected increase or decrease of the speed. By controlling the wire driving device by the control means, it is possible to decrease or increase the traveling speed of the wire electrode contrary to the change in the machining feed speed.

Therefore, even when the plate thickness of the work piece becomes thick or the effect of removing the processing waste deteriorates during the processing, the wire electrode traveling speed is increased to prevent the wire electrode from breaking and the processed shape. It has a remarkable effect that the accuracy of can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a basic configuration of the present invention.

FIG. 2 is a block diagram of a wire cut electric discharge machine according to an embodiment.

FIG. 3 is a flowchart showing an operation of the wire cut electric discharge machine according to the embodiment.

FIG. 4 is a graph showing a relationship between an average machining feed speed and a wire electrode traveling speed in the example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wire-cut electric discharge machining device 3 ... Wire electrode 5 ... Workpiece 7 ... Wire drive device 13 ... Motor drive circuit 15 ... Machining feed speed detection circuit 17 ... Machining power supply 19 ... Discharge detection circuit 21 ... No-load time counting circuit 23 ... ECU
(Electronic control unit) G ... Machining gap

Claims (1)

[Claims] 1. A wire driving device applies a voltage at a predetermined cycle between a wire electrode traveling in a line direction and a workpiece, which is the other electrode, to discharge the wire electrode and the workpiece. In a wire-cut electric discharge machining apparatus for machining the workpiece by controlling the machining feed speed so as to keep the distance of the machining gap between the machining gaps substantially constant, machining feed speed detecting means for detecting the machining feed speed, The wire driving device is controlled so as to decrease or increase the traveling speed of the wire electrode, contrary to the change in the machining feed speed, in response to the increase or decrease in the machining feed speed detected by the machining feed speed detection means. A wire-cut electric discharge machine comprising: a wire driving device control means.