JP2969027B2 - EDM method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining method, and more particularly to an electric discharge machining method capable of performing stable electric discharge machining even when there is a portion where a gap between an electrode and a work is narrow in swing machining.

[0002]

2. Description of the Related Art At the time of die-sinking electric discharge machining, a concave portion having a predetermined shape is formed in a workpiece while a machining electrode is swung with respect to a workpiece to be processed, or the inner surface of a hole is subjected to electric discharge machining in a predetermined shape. In the so-called rocking type electric discharge machining, machining having a shape similar to the electrode shape can be performed by using an electrode having a desired machining shape. Details of such a swing type electric discharge machining method are disclosed in Japanese Patent Publication No. 55-16773.
As the orbital path (oscillation pattern) of the oscillating motion,
A simple pattern such as a square pattern or a circular pattern is used.

In this type of oscillating electric discharge machining method, the oscillating speed at the time of oscillating the electrode affects the amount of electric discharge machining of the workpiece. By utilizing this fact, the swing speed of the electrode is controlled to be low when it is desired to increase the processing amount of the work, and is controlled to be high when the processing amount is small.

[0004] An example of a method of controlling the swing speed is disclosed in Japanese Patent Application Laid-Open No. 2-212026 filed by the present applicant.
In this control method, the remaining machining allowance to be machined is obtained from the current electrode position and the final electrode position after machining specified by the NC program. When the machining allowance is small, control for increasing the swing speed is performed.

On the other hand, there has been proposed a technique in which a gap length between an electrode and a work is used instead of a remaining machining allowance as a criterion for determining a swing speed. If the gap length is used as a criterion for determining the swing speed, the actual required amount of machining can be monitored in real time, so that more accurate electric discharge machining can be performed. The gap length can be represented by the voltage between the electrodes applied between the electrode and the workpiece during discharge.

[0006]

As described above, in the conventional swing type electric discharge machining, the gap length (inter-electrode voltage) between the electrode and the work is detected in order to perform high-precision machining. Control is performed such that the swing speed is low when the gap length is small and high when the gap is wide. By the way, there has been proposed a technique of processing while mixing chips such as semiconductors, fine powder of a resistor, and processing chips into a processing liquid interposed between an electrode and a workpiece (Japanese Patent Laid-Open No. 3-2513).
No. 22 and JP-A-3-277421). According to this technique, at the time of electrical discharge machining, the distance between the electrode and the workpiece can be increased, the floating capacity between the electrodes can be reduced, and a stable machining operation can be secured. At this time, the electrode is moved up and down with respect to the workpiece, and the amount of chips interposed between the electrodes is adjusted by pumping (jumping), processing of a machining liquid jet or suction, thereby enabling stable electric discharge machining.

However, the conventional electric discharge machining method for determining the swing speed based on the gap length while interposing a chip has the following problems. That is, in the above-described electric discharge machining method, the swing speed in the region where the gap is small becomes low, and the amount of chips generated accompanying the electric discharge machining increases. As a result, a large number of chips are interposed between the narrow gaps, causing an abnormal discharge to cause the machining operation to become unstable, thereby causing a problem that a stain-like machining mark remains on the workpiece.

An object of the present invention is to provide an electric discharge machining method which enables stable and highly accurate machining even when there is a portion where a gap between an electrode and a work is narrow in swing machining.

[0009]

In order to solve the above-mentioned problems, an electric discharge machining method according to the present invention is directed to an electric discharge machining method in which an electrode is oscillated around a workpiece according to a predetermined oscillating locus. The gap length information between the electrode and the work is detected at the time of circling according to the swing trajectory of the electrode, a narrow gap region where the gap length is equal to or smaller than a predetermined threshold is obtained and stored in the memory, and at the time of the next circling. The position of the current electrode is detected, and when it is confirmed that the detected position is in the narrow gap area stored in the memory, the process of increasing the jump amount of the electrode, the jump period of the electrode A process for shortening, a process for jetting a working fluid supplied between the electrode and the work, a process for sucking the working fluid between the electrode and the work, and a process for increasing the speed of the circling of the electrode At least one processing performed, configured to facilitate the discharge from between the electrodes of the chip and the work generated by electric discharge machining of the. here,
The gap length information is detected based on a voltage between the electrodes and the workpiece.

[0010]

According to the present invention, in the narrow gap region where the gap between the electrode and the work is equal to or less than a predetermined value based on the above-described structure, the amount of the chip interposed between the electrode and the work is promoted by promoting the discharge of the chip. The occurrence of abnormal electric discharge caused by excessive amount of electric discharge is suppressed, and high-precision electric discharge machining is enabled.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an apparatus configuration diagram for realizing an embodiment of the electric discharge machining method according to the present invention. NC unit 1
The feed screws 6X, 6Y and 6Z corresponding to the respective motors are driven via the feed motors 5X, 5Y and 5Z in the X, Y and Z directions by drive signals from the motor drive unit 101 controlled by the motor control unit 102. You. By driving the feed screws 6X, 6Y and 6Z, the electrode 7 is moved in the X, Y and Z directions. The movement of the electrode 7 includes the movement along the swing pattern. A voltage is applied between the electrode 7 and the work 8 from the machining power supply 2 to control discharge.
In addition, the voltage between the electrodes 7 and the work 8 is detected by the work voltage detector 3 and sent to the I / O controller 103 of the NC unit 1.

A machining fluid is supplied from a machining fluid tank 13 by a pump 12 through a jet line to a gap between an electrode 7 and a work 8 via a solenoid valve 10, and penetrates through the electrode 7 by the action of the pump 11. Through the hole 7A, the working fluid is returned to the working fluid tank 13 through the suction line via the solenoid valve 9. Based on a signal from the I / O control unit 103 of the NC unit 1, the solenoid valve control unit 4 controls opening and closing of the solenoid valve 9 in the suction pipe and the solenoid valve 10 in the jet pipe.

The NC unit 1 includes the motor drive unit 10
1. In addition to the motor control unit 102 and the I / O control unit 103,
Operation control unit 104 for controlling various processing conditions, operations, etc., N
A CPU 105 that performs overall control of the electric discharge machining operation based on the C program, and a memory unit 106 that stores gap data described later are provided, and are connected via a bus BUS.

The CPU 105 specifies the moving position and the moving mode of the electrode 7 (moving during the machining process, the above-mentioned swinging motion, etc.), and through the motor control unit 102 and the motor driving unit 101, the motors 5X, 5Y and 5Z. And I
The machining power supply 2 is controlled via the / O control unit 103 to supply a voltage required for discharge between the electrode 7 and the work 8, and the solenoid valves 9 and 10 are controlled to be opened and closed via the solenoid valve control unit 4 for machining. Adjust the liquid supply.

In this embodiment, the gap between the electrode 7 and the work 8 is detected by monitoring the voltage between the electrodes obtained by the voltage between electrodes 3 in this embodiment. This gap voltage is supplied to the CPU 105 via the I / O control unit 103.
As a result, the following control is executed. That is, as described above, the gap voltage corresponding to the narrow gap interval at which the amount of chips interposed between the electrode 7 and the work 8 becomes large and unstable discharge occurs is set in advance as a threshold value by experiments or the like, and In some cases, the region of the swing locus where the gap voltage detected by the gap voltage detection unit 3 is smaller than the threshold is stored in the memory unit 10.
6 is stored. At the time of the next swing orbit, the memory 1
In a narrow gap region where the voltage between contacts becomes equal to or less than the threshold value based on the information stored in 06, the chip discharge process is promoted in order to prevent the increase in the chip amount. The chip discharge processing can be promoted by processing such as increasing the jump amount of the electrode 7, shortening the jump cycle, using a jet flow of a processing liquid, suction processing, or increasing the swing speed.

For example, in the (square) oscillating pattern, when gap length data (corresponding to the gap voltage) is obtained as shown in FIG. , R2, and R3, the information of these regions R1, R2, and R3 is stored in the memory unit 106. At the time of the next circuit, when the electrode position is in the regions R1, R2, and R3, at least one of the above processes is performed in order to promote chip ejection.

The memory section 106 is composed of a memory 106A and a memory 106B. The memory 106A stores narrow gap area information detected based on the voltage between contacts in one round. At the next round, the memory 106A
Is stored in the memory 106B.
Is forwarded to At the time of the next circuit, when the electrode exists in the narrow gap region R1, R2, or R3 obtained in the certain circuit stored in the memory 106B, the above-described chip ejection processing is promoted, and at the time of the next circuit, The gap (inter-pole) voltage that is sequentially detected is monitored, and a region that is equal to or smaller than the threshold is newly stored in the memory 106A.
By repeating such a round, unstable electric discharge machining due to an excessive number of chips is finally prevented, and highly accurate electric discharge machining becomes possible.

FIG. 3 is a flowchart showing the processing procedure of the above embodiment. First, after the initial setting process (step S1), machining is started (step S2), and position management control as shown in FIG. 4 is performed (step S3). In the position management control, a gap voltage is detected (step S31), and the detected gap voltage is compared with a reference value (step S3).
2). If the gap voltage is smaller than the reference value, it is determined whether the gap voltage is a state change from a state larger than the reference value to a smaller state (step S33). If the gap voltage is larger than the reference value, Then, it is determined whether or not the inter-electrode voltage is a state change from a state smaller than the reference value to a state larger than the reference value (step S35). Steps S33 and S35
If "NO", the process returns to step S31, and if "YES", the position information is stored in the memory (steps S34 and S36). Next, step S
Based on the position information stored in S34 and S36, a narrow gap length region in which the gap voltage is smaller than the reference value is determined, and the region is set (step S37). Next, based on the circulation flag, the current circulation is odd-numbered (“0”) or even-numbered (“0”).
1 ") (step S38), and if" 1 ", the area data is written to the" 0 "table (step S39); if" 0 ", the area data is written to the" 1 "table.

Subsequently, it is determined whether or not there is a chip processing area (step S4). If "yes", a chip ejection control process as shown in FIG. 5 is executed (step S5). If "none", the lap is updated as it is (step S6). In the chip ejection control in step S5, first, the electrode position is read (step S51), and the electrode position is compared with the area (step S52). As a result of the comparison, if the discharge processing is necessary, the above-described discharge promotion processing is performed (step S53), and if not, the value related to the discharge processing is returned to the normal value (step S54).

After the tip discharge control, it is determined whether or not the circulation has been updated (step S6).
The circulation flag is inverted (step S7), and the area data table on the side where the circulation is completed is cleared (step S8).
In step S6, when it is determined that the rotation has not been updated and after the processing in step S8, it is determined whether or not the processing has been completed.
Returning to the processing of step 3, if not completed, the processing is terminated.

[0021]

As described above, according to the electric discharge machining method of the present invention, chip ejection is promoted in a narrow gap region where the gap between the electrode and the work is smaller than a predetermined value. In addition, it is possible to suppress the occurrence of abnormal discharge due to an excessive amount of chips interposed between the electrode and the work, to prevent formation of a spot-like portion on a workpiece, and to perform highly accurate electrical discharge machining.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of an apparatus for realizing an electric discharge machining method according to the present invention.

FIG. 2 is a diagram illustrating a narrow gap region detected at the time of swing rotation in an embodiment of the present invention.

FIG. 3 is a flowchart illustrating a procedure of an electric discharge machining process according to the embodiment of the present invention.

FIG. 4 is a flowchart illustrating a procedure of a position management control process in the embodiment of FIG. 3;

FIG. 5 is a flowchart illustrating a procedure of a chip discharging process in the embodiment of FIG. 3;

[Explanation of symbols]

 Reference Signs List 1 NC unit 2 Machining power supply 3 Inter-electrode voltage detecting unit 4 Solenoid valve control unit 5X, 5Y, 5Z motor 6X, 6Y, 6Z Feed screw 7 Electrode 8 Work 9, 10 Solenoid valve 11, 12 Pump 13 Machining fluid tank 101 Motor drive Unit 102 Motor control unit 103 I / O control unit 104 Operation control unit 105 CPU 106 Memory unit 106A, 106B Memory

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B23H 1/02 B23H 7/26 B23H 7/28 B23H 7/32

Claims (2)

(57) [Claims] 1. An electric discharge machining method in which an electrode is oscillated around a workpiece according to a predetermined oscillating locus to perform electric discharge machining, wherein information on a gap length between the electrode and the workpiece is detected at the time of circling along the oscillating locus of the electrode. Then, a narrow gap region where the gap length is equal to or less than a predetermined threshold is obtained and stored in the memory, and the current position of the electrode is detected at the next round, and the detected position is stored in the memory. When it is confirmed that it is in a narrow gap region, a process of increasing the jump amount of the electrode, a process of shortening the jump period of the electrode, a process of jetting a machining fluid supplied between the electrode and the workpiece, the electrodes and processing for sucking the working fluid in the inter-working, performed cormorants <br/> Chi least one processing of processing to speed up the rate of swing orbit of the electrode, to generate the electrical discharge machining
Discharge machining method characterized in that to promote the discharge from between the electrode and workpiece chips that. 2. The electric discharge machining method according to claim 1, wherein the gap length information is detected based on a voltage between the electrodes and a workpiece.