JP2002113616A - Electric discharge machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric discharge machining device capable of enhancing reproducibility of machining by enhancing reproducibility of discharge, preventing abnormal discharge, and shortening the machining time, by detecting a discharge current and controlling it. SOLUTION: This electric discharge machining device has a material to be machined 4 and a tool electrode 1 which is disposed face to face with the material to be machined 4 and is sent to it for machining, in order to machine the material to be machined 4 by a discharge current between the tool electrode 1 and the material to be machined 4, and is equipped with a variable capacitor 12 connected between the material to be machined 4 and the tool electrode 1, a power supply unit 10 connected to the variable capacitor 12 through a variable resistor 11, a discharge current detecting means 13 to detect the discharge current, and a control means to control the discharge current based on the output of the discharge current detecting means 13.

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 apparatus, and more particularly to an electric discharge machining apparatus for performing a minute electric discharge machining such as drilling of a fine hole.

[0002]

2. Description of the Related Art A conventional electric discharge machine will be described below with reference to the drawings. FIG. 6 is a configuration diagram schematically showing a generally used electric discharge machining apparatus, and FIG. 7 is an electric circuit diagram showing a configuration of a discharge circuit in the apparatus shown in FIG.

As shown in FIG. 6, this apparatus controls the movement of a machining head 2 for machining and feeding (vertically moving) a tool electrode 1, and a workpiece 4 held in an electric discharge machining fluid 3. A positioning mechanism 5 for determining the position of the workpiece 4 with respect to the electrode 1 and a control box section 6 having an NC control section have a basic configuration, and the workpiece 4 positioned with respect to the tool electrode 1 is processed. The head part 2 is lowered to bring the tool electrode 1 close to the workpiece 4, and electric discharge machining is performed on this. As shown in FIG. 7, an electric circuit for performing electric discharge machining connects a capacitor 9 between the workpiece 4 and the facing tool electrode 1, and further comprises a power supply device 7 for charging the capacitor 9 and a resistor 8. The capacitor 9 is charged by the voltage supplied from the power supply device 7, and when the machining head 2 descends and the tool electrode 1 approaches the workpiece 4,
The electric charge charged in the capacitor 9 is discharged and the workpiece 4 is subjected to electric discharge machining.

[0004]

However, such a configuration has the following problems.

That is, when processing is performed with the device configuration shown in FIGS. 6 and 7, the peak current and the discharge time during charging and discharging of the capacitor 9 are determined by the capacitance of the capacitor 9 and the resistance value of the resistor 8. However, depending on the shape of the tool electrode 1 and the shape of the workpiece 4, the resistance value and the capacitance on the actual discharge circuit change, and this causes a variation in the machining shape. When an abnormal discharge such as an arc discharge occurs, the charged energy is released, which not only deteriorates the surface condition of the workpiece 4 but also requires the tool electrode 1 and the workpiece to restart the apparatus. 4
In this case, the tool electrode 1 has been evacuated due to the short circuit detection due to the small amount of electric discharge machining. Therefore, the processing time becomes longer.

The present invention solves the above-mentioned conventional problems. By detecting and controlling the discharge current, the reproducibility of discharge is improved, and the reproducibility of machining is improved.
It is another object of the present invention to provide an electric discharge machining apparatus capable of preventing abnormal electric discharge and reducing machining time.

[0007]

SUMMARY OF THE INVENTION An electric discharge machining apparatus according to the present invention comprises a sample stage for fixing a workpiece in a machining fluid, a tool electrode facing the sample stage, and a driving mechanism for machining and feeding the tool electrode. Having an electrical discharge machining apparatus for machining a workpiece by a discharge current between the tool electrode and the workpiece,
A variable capacitor connected between the workpiece and the tool electrode; a power supply connected to the variable capacitor via a variable resistor; discharge current detection means for detecting a discharge current of the variable capacitor; And a control means for controlling the discharge current based on the output of the detection means.

According to the present invention, the discharge current is controlled, the machining reproducibility is improved, abnormal discharge is prevented, and the machining time can be reduced.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an electric circuit diagram showing a configuration of a discharge circuit in one embodiment of the electric discharge machining apparatus of the present invention, and FIG. 2 is an explanatory diagram of discharge timing in one embodiment of the electric discharge machining apparatus of the present invention. 3 is a side view of a main part showing each example of a tool electrode in an embodiment of the electric discharge machine of the present invention, FIG. 4 is an explanatory view of a data table for determining various constants of the electric discharge circuit shown in FIG. FIG. 2 is an explanatory diagram of an algorithm for determining various constants of the discharge circuit shown in FIG. It should be noted that the mechanical part of the general electric discharge machining apparatus shown in FIG. 6 can be used as the mechanical part of the electric discharge machining apparatus in the present embodiment. Will be described.

In FIG. 1, 10 is a power supply device, 11 is a variable resistor, 12 is a variable capacitor, 13 is discharge current detecting means, 14 is first calculating means, and 15 is second calculating means. Connected to form a discharge circuit.

In this discharge circuit, the variable capacitor 12 is charged by the voltage supplied from the power supply device 10, and when performing the electric discharge machining, the tool electrode 1 is processed to be brought close to the workpiece 4 so as to be variable. This discharges the electric charge charged in the capacitor 12 to cause a discharge current to flow, thereby performing a discharge machining on the workpiece 4. However, in comparison with the conventional example shown in FIG. The point is the feature.

That is, as shown in FIG. 2A, a voltage Ep is applied between the tool electrode 1 and the workpiece 4 and is accumulated in the variable capacitor 12 when the distance between the electrodes exceeds a certain value (decreases). The discharged electric charge flows out, and as shown in FIG. 2B, a discharge current ip flows, and electric discharge machining is performed. When the discharging is completed, the variable capacitor 12 is charged again with the charging time tg and discharged again. This charging and discharging occurs repeatedly at the time interval tp or more. At this time, it is known that the charging time tg and the discharging current ip are determined by the resistance value of the variable resistor 11 and the capacity of the variable capacitor 12, but it is known that the tool electrode 1 generated at the time of electric discharge machining.
The discharge current ip is affected by the impedance between the workpiece 4 and the workpiece 4, and when a minute hole is made, the machining accuracy and the machining time are affected.

FIGS. 3A and 3B show examples of processing of the workpiece 4 by the tool electrode 1. FIG. 3A shows a case where the workpiece 4 is drilled by the simple cylindrical tool electrode 1 having a diameter φD. FIG. 3B shows an example in which a plurality of (n) simple cylindrical tool electrodes 1 having a diameter φd are simultaneously drilled into a plurality of holes in a workpiece 4. The impedance between the electrode 1 and the workpiece 4 is not the same, and if machining is performed under the same discharge conditions, the machining accuracy and machining time will vary.

In the present embodiment, the discharge current ip,
The value of the variable resistor 11 is adjusted as a control means for controlling the discharge current pulse width τp and the charging time tg based on the output of the discharge current detection means 13 and the output so that each value becomes a predetermined value. It is characterized in that the first arithmetic means 14 and the second arithmetic means 15 for adjusting the value of the variable capacitor 12 are provided. When the workpiece 4 is subjected to electric discharge machining by the tool electrode 1, the machining is started simultaneously. 2B, a current waveform as shown in FIG. At this time, the resistance value of the variable resistor 11 is calculated based on the measured charging time tg and the discharge current ip according to the data table of FIG. 4A, and the capacitance of the variable capacitor 12 is calculated according to the data table of FIG. Is calculated. In this case, the algorithm for calculating the resistance value of the variable resistor 11 and the capacitance of the variable capacitor 12 is as shown in FIG. 5. The control is performed in a loop on the right side of FIG. In this calculation, the variable resistor 1 is also referred to with reference to the data table of FIG. 4 in the case of FIGS.
1 and the capacity of the variable capacitor 12 can be adjusted to set an optimum discharge current according to the material of the workpiece 4 and the shape and material of the tool electrode 1, thereby improving machining reproducibility. Also, abnormal discharge can be prevented.

As described above, according to the present embodiment, by detecting and controlling the discharge current, it is possible to process the optimum discharge current according to the material of the workpiece and the shape and material of the tool electrode. It can be set at any time, so that the reproducibility of electric discharge is improved, the reproducibility of machining is improved, and abnormal discharge can be prevented and machining time can be shortened.

[0017]

As described above, according to the present invention, it is possible to set an optimum discharge current at the time of machining without depending on the material of the workpiece and the shape and material of the tool electrode. Discharge reproducibility is improved, machining reproducibility is improved,
In addition, an advantageous effect of preventing abnormal discharge and shortening the machining time can be obtained.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing a configuration of a discharge circuit in an electric discharge machine according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a discharge timing in one embodiment of the electric discharge machining apparatus of the present invention.

FIG. 3 is a side view of a main part showing each example of a tool electrode in the embodiment of the electric discharge machine of the present invention.

FIG. 4 is an explanatory diagram of a data table for determining various constants of the discharge circuit shown in FIG.

FIG. 5 is an explanatory diagram of an algorithm for determining various constants of the discharge circuit shown in FIG.

FIG. 6 is a configuration diagram showing an outline of a commonly used electric discharge machine.

7 is an electric circuit diagram showing a configuration of a discharge circuit in the device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tool electrode 2 Machining head part 3 Electric discharge machining liquid 4 Workpiece material 5 Positioning mechanism part 6 Control box part 10 Power supply device 11 Variable resistor 12 Variable capacitor 13 Discharge current detecting means 14 First computing means 15 Second computing means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 3C059 AA01 AB01 BA11 CA01 CC02 CD01 CF01 CG02 CG04

Claims (3)

[Claims] An apparatus has a sample stage for fixing a workpiece in a machining fluid, a tool electrode facing the sample stage, and a drive mechanism for machining and feeding the tool electrode. An electric discharge machining apparatus for machining a workpiece by a discharge current, a variable capacitor connected between the workpiece and the tool electrode, and a power supply device connected to the variable capacitor via a variable resistor, An electric discharge machining apparatus comprising: discharge current detection means for detecting a discharge current of the variable capacitor; and control means for controlling the discharge current based on an output of the discharge current detection means. 2. The electric discharge machining apparatus according to claim 1, wherein the discharge current detection means detects a discharge current peak value and a discharge current pulse width. 3. The control means, based on the peak value, the pulse width and the charging time of the discharge current detected by the discharge current detection means, adjusts the variable so that the peak value and the pulse width of the discharge current become constant. 2. The electric discharge machining apparatus according to claim 1, wherein the resistance value of the resistor and the capacity of the variable capacitor are adjusted.