JPH04283022A - Detecting device for electric discharge machining penetration - Google Patents

Abstract

PURPOSE:To provide an electric discharge machining penetration detecting device which can correctly detect whether a fine hole penetrates a workpiece or not in a fine hole electric discharge machine to machine a fine hole on the workpiece by using an electrode. CONSTITUTION:In an electric discharge machining penetration detecting device 30, a contact 31 is arranged below the lower face 62 of a part where a fine hole 61 is machined on a workpiece 6, and is opposite to the lower end 15 of an electrode 3. A machining penetration detecting circuit 56 having the contact 31 and a resistor 51 is assembled into a machining circuit 50 formed of the electrode 3 and the workpiece 6. At the time when the lower end 15 of the electrode 3 having penetrated the workpiece 6 comes into contact with the contact 31, the machining penetration detecting circuit 56 is closed to send a machining penetration detecting signal.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a small-hole electrical discharge machine that processes a fine hole in a workpiece by lowering a vertically movable electrode and generating electric discharge energy between the electrode and the workpiece. The present invention relates to an electric discharge machining penetration detection device that detects the penetration of a fine hole into a workpiece.

0002

[Prior Art] Generally, a wire electrical discharge machine has a diameter of 0.03
A thin wire of ~0.3 mm is used as an electrode, and while the wire electrode is running under tension, an electrical discharge is caused between the workpiece and the wire electrode, and the workpiece is machined using the discharge energy. be. By using a wire electrical discharge machine, it is possible to machine tough materials and superhard materials that are difficult to machine, and it is also possible to easily process two-dimensional contour shapes and taper processes.

By the way, in order to perform wire electrical discharge machining on a workpiece using a wire electrical discharge machine, it is first necessary to form a start hole in the workpiece to be machined, into which a wire is inserted. As a device for machining a start hole, a small-hole electric discharge machine or a wire electric discharge machine with a start hole machining device is conventionally known. It is also widely known that the small-hole electric discharge machine is used for machining parts with high hardness. For example, there is a small-hole electric discharge machine disclosed in Japanese Patent Application No. 14917/1999 filed by the present applicant.

[0004] The fine-hole electrical discharge machine is shown in FIGS. 9, 10, and 1.
1, an electrode holding device is attached to the tip of the rotating main shaft, the pipe electrode 3 is held in the electrode holding device, and a discharge is caused between the pipe electrode 3 and the workpiece 6 to form a pore in the workpiece 6. 61. When electrical discharge machining a small hole 61 in a workpiece 6 using a small-hole electrical discharge machine, the workpiece 6 is fixed on a table 10 with a clamp 9, the slide rod 4 is lowered relative to the head 1, and the slide rod 4 is The guide holder 11 attached to the lower end is set close to the workpiece 6.

This guide holder 11 is, for example, shown in FIG.
As shown in FIG.
Guide case 14 and guide case 1 attached via
The electrode guide member 17 is disposed within the guide case 14 and is spaced apart by a guide collar 20 to fix the pair of electrode guides 12 and 13 to the guide case 14. The electrode 3 is
It passes through the electrode guides 12 and 13 of the guide holder 11 and is installed facing the workpiece 6.

[0006] In order to make a hole penetrating the workpiece 6 using a small-hole electrical discharge machine, under average machining conditions, the workpiece 6 must be
It is generally said that about twice the length of the electrode is consumed compared to the plate thickness. That is, in order to penetrate a pore into a workpiece with a thickness of 10 mm, the electrode will be consumed by about 20 mm. Therefore, it can be determined whether a pore has penetrated the workpiece based on the length of the electrode consumed. but,
The length of the electrode required for the pores to actually penetrate differs depending on whether the electrode is new or used. That is, when the electrode is used, the surface of the electrode is rough, so that the length of the electrode required to penetrate the pore becomes longer. Therefore, conventionally, the feed rate for the electrode was set to be about 2.5 times the thickness of the plate. That is, when the plate thickness was 10 mm, when the electrode was fed out by an amount of 25 mm, it was considered that the workpiece was pierced by a pore.

[0007]

[Problem to be Solved by the Invention] However, in conventional small-hole electrical discharge machines, it is assumed that a pore has been formed in the workpiece based on the length of the sent-out electrode. It is not possible to accurately detect whether this is the case. For this reason, it is necessary to set the length of the electrode to be sent out to be somewhat larger than the amount of electrode feeding necessary for penetrating the pore, and some waste in the amount of electrode consumption cannot be avoided. In addition, the feed rate of the electrode must be reset each time depending on the processing conditions, which has been an obstacle to automating the machine. For this reason, there has been a problem of how to accurately detect whether or not a pore has penetrated a workpiece.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems, and to accurately detect whether or not a hole has penetrated when drilling a hole in a workpiece in a small hole electrical discharge machine. An object of the present invention is to provide an electric discharge machining penetration detection device that can improve machining efficiency and avoid unnecessary consumption of electrodes.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention is constructed as follows. That is,
This invention provides a small-hole electrical discharge machine for machining a pore in a workpiece by lowering a vertically movable electrode and using discharge energy generated between the electrode and the set workpiece.
a contact held in an electrically insulated state with respect to the workpiece and disposed below the lower end of the pore to be machined in the workpiece;
The present invention also relates to an electrical discharge machining penetration detection device, comprising: a detection device that generates a machining penetration detection signal when the electrode penetrates the workpiece and the lower end of the electrode comes into contact with the contact.

Further, in this electric discharge machining penetration detection device, the detection device includes an electric discharge machining penetration detection circuit having the contactor and a resistor incorporated in a machining circuit for machining a hole in the workpiece with the electrode. A machining penetration detection signal is generated by detecting the voltage generated between the resistors.

Alternatively, in this electric discharge machining penetration detection device, the detection device includes the contactor and a current transformer incorporated in a machining circuit for machining small holes in the workpiece with the electrode. A machining penetration detection signal is generated by detecting the current detected by the current transformer of the circuit.

[0012] Furthermore, in this electric discharge machining penetration detection device, a jet nozzle is provided for injecting machining fluid toward the lower surface of the workpiece at a portion where a small hole is to be machined in the workpiece.

[0013]

[Operation] Since the present invention is constructed as described above, it operates as follows. In other words, this electrical discharge machining penetration detection device can machine a pore in a workpiece using the discharge energy generated by electrical discharge between the electrode and the workpiece. Since the electrode penetrates the workpiece and the lower end of the electrode comes into contact with the contact, a current flows through the electric discharge machining penetration detection circuit and a voltage is generated across the resistor. Therefore, by detecting this voltage or this current as a detection signal, it is possible to accurately detect that the pore has penetrated the workpiece.

[0014] Furthermore, if even a small hole is created in the workpiece using this electric discharge machining penetration detection device, the machining fluid supplied between the workpiece and the electrode will flow out from the hole during machining. do. Therefore, the machining fluid is not completely supplied between the electrodes and the workpiece, and machining of the workpiece tends to become unstable. However, this electrical discharge machining penetration detection device is provided with a jet nozzle that injects machining fluid toward the lower surface of the workpiece. A sufficient amount of machining liquid is supplied between the poles and the electrode, and stable machining can be continued until the pores are completely penetrated. Therefore, the jet nozzle can perform an extremely important function in accurately detecting whether or not the pore has penetrated.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the electrical discharge machining penetration detection device according to the present invention will be described with reference to the drawings. FIG. 1 is a front view showing a small-hole electrical discharge machine equipped with an electric discharge machining penetration detection device according to the present invention, FIG. 2 is an enlarged front view of the electric discharge machining penetration detection device of FIG. 1, and FIG. Side view and Figure 4 are Figure 2
FIG. 2 is an enlarged side view of the electrical discharge machining penetration detection device of FIG. In addition, this small-hole electrical discharge machine is shown in Figs. 9, 10, and 1.
Compared to the conventional small-hole electrical discharge machine shown in 1, the structure is the same except that the electrical discharge machining penetration detection device 30 is placed directly below the pipe electrode 3, so the same parts are given the same reference numerals. However, duplicate explanations will be omitted.

Particularly, as shown in FIGS. 2 and 4, the electric discharge machining penetration detection device 30 is configured such that the pipe electrode 3, which is an electrode extending in the vertical direction, penetrates the workpiece 6 and the lower surface 62 of the workpiece 6.
It has a contact 31 with which the tip 15 of the pipe electrode 3 comes into contact when the tip 15 of the pipe electrode 3 protrudes from the pipe electrode 3, and a holder 33 that holds the contact 31 via an insulating member 32. The holder 33 is fixed to the side surface of the column 25 of the machine body. A jet pipe 34 is attached to the side surface of the holder 33, and the machining fluid is jetted from a jet nozzle 35 provided at the tip of the jet pipe 34. For this reason, it is preferable that the contactor 31 be made of copper material, which has excellent rust prevention and conductivity. The contactor 31 is composed of a disk 311 and a threaded rod 312 protruding downward from the center of the disk 311, and the threaded rod 312 of the contactor 31 is inserted into a through hole 321 formed in the insulating member 32 and tightened with a nut 36. Accordingly, the contact 31 is fixed to the insulating member 32. Further, the insulating member 32 is fixed to the holder 33 by a set screw 38. Therefore, the contactor 31 is supported in an insulated manner with respect to the workpiece 6. contact 31
A line 37 electrically conductive to is connected to a control device (not shown).

Furthermore, a holder 33 that holds the insulating member 32 is provided.
A jet nozzle 35 is arranged. This jet nozzle 35 is connected to the lower surface 62 of the part of the workpiece 6 where the pore 61 is to be machined.
This is to inject machining fluid towards. That is, electrode 3
When the hole 61 penetrates the lower surface 62 of the workpiece 6 even slightly, the machining fluid supplied to the electrode 3 tends to flow out from the hole 61 and machining becomes unstable.
By discharging machining fluid from the bottom surface 62 of the workpiece 6,
Stable processing continues and complete pores 61 can be formed. That is, in this electrical discharge machining penetration detection device 30, if even a small hole 61 is formed in the workpiece 6, the hole 6
1, the machining fluid supplied between the workpiece 6 and the pipe electrode 3 flows out. Therefore, the machining fluid is not completely supplied between the workpiece 6 and the pipe electrode 3, and machining of the workpiece 6 tends to become unstable. However, this electric discharge machining penetration detection device is provided with a jet nozzle 35 that injects machining fluid toward the lower surface 62 of the workpiece 6, so the machining fluid is injected from the jet nozzle 35 toward the lower surface 62 of the workpiece 6. As a result, a sufficient amount of machining fluid is supplied between the workpiece 6 and the pipe electrode 3, and stable machining can be continued until the pore 61 is completely penetrated without being exposed to air. Therefore, the jet nozzle 35 plays an extremely important function in accurately detecting whether or not the pore 61 has penetrated.

FIG. 6 is an explanatory diagram showing an embodiment of the machining penetration detection circuit in this electric discharge machining penetration detection device, showing a state before or during machining to penetrate a fine hole in a workpiece. As shown in the figure, a machining penetration detection circuit 56 in this electric discharge machining penetration detection apparatus is connected to a machining circuit 50 that derives a power supply voltage from a transistor circuit power supply, as an example. The processing circuit 50 includes a workpiece 6 and a pipe electrode 3.
A machining voltage is applied between the electrodes and a discharge is generated between the two to generate discharge energy.A transistor 52 for switching the discharge current, a power source 53 of the power supply device, a pipe electrode 3 and a workpiece 6 are connected by a line 55. The pipe electrode 3 and the workpiece 6 are connected to each other to form a gap between the pipe electrodes 3 and the workpiece 6. This machining penetration detection circuit 56 is constructed by connecting the line 37 connected to the contactor 31 in parallel to the machining circuit 50. In other words, the variable resistor 51 built into the line 37, the contactor 31, Transistor 52, power supply 53
It can be said that this is an electric circuit in which the pipe electrodes 3 and 3 are connected in series, and the tip 15 of the pipe electrode 3 and the contact 31 can be connected and disconnected.

This machining penetration detection circuit 56 detects that the tip 15 of the pipe electrode 3 and the contact 31 are not in contact with each other before or during machining the workpiece 6, and the electric circuit is open. When the pore 61 penetrates through the pipe electrode 3 and the tip 15 of the pipe electrode 3 comes into contact with the contact 31, the electric circuit is closed and a current flows in the circuit. That is, the pipe electrode 3
The tip 15 and the contact 31 function as a switch. A pore 61 formed in the workpiece 6 that is smaller than the outer diameter of the pipe electrode 3
Since the inner diameter of the pipe electrode 3 is made larger by the discharge gap, the pipe electrode 3 is not in contact with the workpiece 6, and a voltage is generated across the variable resistor 51 incorporated in the electric circuit. This voltage value is sent to the control device as a detection signal to perform necessary controls such as stopping the feeding of the pipe electrode 3.

Another embodiment of this electric discharge machining penetration detection device can be constructed as shown in FIG. FIG. 7 is an explanatory diagram showing another embodiment of the machining penetration detection circuit showing a machining completion state in which a fine hole is penetrated through the workpiece. In the machining penetration detection circuit 56 of this embodiment, a current transformer 54 is incorporated in the machining penetration detection circuit 56 in FIG. It is also possible to construct an electric circuit in which the current value is detected by the current flow device 54 and the current value is used as a detection signal.

FIG. 5 is a diagram of the electrical discharge machining penetration detection device 30 viewed from directly above. As shown in FIG. 5, the center axis of the pipe electrode 3 and the center axis of the contactor 31 are arranged coaxially. ,
A workpiece 6 is set on a table 10 by a clamp 9 so as to cross the central axis. The table 10 holding the workpiece 6 is configured to move in two directions (X-axis direction and Y-axis direction), and the pipe electrode 3 is placed within the movement range of the workpiece 6 (the range shown by the two-dot chain line). The workpiece 6 is set so that the central axis is aligned. The workpiece 6 fixed within this movement range can be subjected to electrical discharge machining at any location.

Another embodiment of the electrical discharge machining penetration detection device according to the present invention can be constructed as shown in FIG. In this embodiment, the contactor 40 supports a lever 41 rotatably about a pivot point 42, one end of the lever 41 is arranged directly below the electrode 3, and the other end of the lever 41 is connected to a limit switch or a mercury switch. 43 are arranged. When the tip 15 of the electrode 3 pushes down one end of the lever 41,
The lever 41 rotates and the other end of the lever 41 becomes the switch 43.
It is designed to close. Note that the lever 41 is arranged so that the slight movement of the electrode 3 is magnified at the other end of the lever 41.
is supported, so the tip 15 of the electrode 3 touches the lever 41.
contact is immediately and reliably detected. Also,
In this embodiment, it is preferable that the switches be placed outside the machine and waterproofed.

[0023]

The electric discharge machining penetration detection device according to the present invention is constructed as described above, and therefore has the following effects. With conventional micro-hole electrical discharge machines, it is assumed that a pore has penetrated the workpiece when the moving distance of the sent-out electrode, that is, the descending electrode, has reached a predetermined distance. However, if the electric discharge machining penetration detection device according to the present invention is used, a machining penetration detection signal will be generated when the electrode penetrates the workpiece and contacts the contact. Since it is configured to emit light, it is now possible to accurately detect that a pore has penetrated a workpiece. For this reason, with conventional small-hole electrical discharge machines, each time the workpiece is replaced or the machining conditions are changed, the electrode feed amount must be set according to the thickness of the part of the workpiece to be machined. However, if the electric discharge machining penetration detection device of the present invention is used, such setting work is completely unnecessary, and the detection of the machining penetration state in the process of machining a fine hole in a workpiece using a fine-hole electric discharge machine can be completely performed. can be automated, greatly improving processing efficiency.

Further, this electrical discharge machining penetration detection device utilizes a power supply device of a machining circuit that applies a voltage between the poles of a workpiece and an electrode, and uses the power supply device as a machining penetration detection device consisting of a contact and the electrode. The device itself can be incorporated into a circuit, detect the connection/disconnection state between the contactor and the electrode, and extract the detection signal as voltage or current, and does not require a separate power source for detection. The electrical discharge machining penetration detection device can be manufactured simply and at low cost.

Furthermore, in this electric discharge machining penetration detection device, a jet nozzle is provided that sprays the machining fluid toward the lower surface of the workpiece at the portion where the fine hole is to be machined in the workpiece.
The electrode can reliably perform the fine hole machining of the workpiece to the end, and the electrical discharge machining penetration detection device can also reliably detect the machining penetration state.

Furthermore, this electrical discharge machining penetration detection device has the advantage that it operates reliably because it is constructed of a switch consisting of an electrode and a contact, and does not use an electrical contact that is sensitive to machining fluid.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a small-hole electrical discharge machine equipped with an electrical discharge machining penetration detection device according to the present invention.

FIG. 2 is an enlarged front view showing an embodiment of the electrical discharge machining penetration detection device according to the present invention.

FIG. 3 is a side view of a small-hole electrical discharge machine equipped with the electrical discharge machining penetration detection device of FIG. 1;

FIG. 4 is an enlarged view of the electrical discharge machining penetration detection device of FIG. 3;

FIG. 5 is a plan view of the electrical discharge machining penetration detection device according to the present invention.

FIG. 6 is an explanatory diagram of an embodiment of the machining penetration detection circuit in the electrical discharge machining penetration detection device, showing a state before or during machining to penetrate a fine hole in a workpiece.

FIG. 7 is an explanatory diagram of another embodiment of the machining penetration detection circuit in the electric discharge machining penetration detection device, showing a machining completion state in which a fine hole is penetrated through the workpiece.

FIG. 8 is a front view showing another embodiment of the electric discharge machining penetration detection device according to the present invention.

FIG. 9 is a front view showing an example of a conventional small-hole electrical discharge machine.

FIG. 10 is a side view of FIG. 9;

11 is a cross-sectional view showing an example of a guide holder of the small-hole electric discharge machine shown in FIG. 9. FIG.

[Explanation of symbols]

3 Pipe electrode 6 Workpiece 30 Electric discharge machining penetration detection device 31 Contactor 32 Insulating member 35 Jet nozzle 40 Contact 50 Processing circuit 51 Variable resistor 53 Power supply 54 Current transformer 56 Machining penetration detection circuit 61 Pore 62 Bottom surface of workpiece

Claims (4)

[Claims] 1. A fine-hole electric discharge machine that processes a fine hole in a workpiece by lowering a vertically movable electrode and using discharge energy generated between the electrode and a set workpiece, wherein the fine hole is machined in the workpiece. a contact that is electrically insulated from the workpiece and placed below the lower end of the pore to be machined into the workpiece; and the electrode penetrates the workpiece so that the lower end of the electrode comes into contact with the contactor. An electrical discharge machining penetration detection device comprising: a detection device that issues a machining penetration detection signal when 2. The detection device detects a voltage generated between the resistors of an electric discharge machining penetration detection circuit including the contact and a resistor, which is incorporated into a machining circuit for machining small holes in the workpiece with the electrode. The electrical discharge machining penetration detection device according to claim 1, wherein the electrical discharge machining penetration detection device generates a machining penetration detection signal upon detection. 3. The detection device detects with the current transformer of an electric discharge machining penetration detection circuit having the contact and a current transformer incorporated in a processing circuit for processing the workpiece with the electrode. 2. The electrical discharge machining penetration detection device according to claim 1, wherein the electrical discharge machining penetration detection device generates a machining penetration detection signal by detecting a current flowing through the electrical discharge machining. 4. The electrical discharge machining penetration detection device according to claim 1, further comprising a jet nozzle that injects machining fluid toward the lower surface of the workpiece at a portion where a pore is to be machined in the workpiece.