JPH04348816A - Fine hole electric discharge machine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a situation in which an electrode is brought into a state to be incapable of passing through in the middle of machining and to ensure machining of a fine hole having straightness by automatically deciding whether an electrode has length enough for extension of it through a work when electric discharge of the fine hole is carried out. CONSTITUTION:A voltage pulse or a detecting voltage, being a detecting condition, is applied on an electrode 6 and a work 1 by means of an electric discharge source 7 or through contact or by means of a discharge detector 8. Electric discharge liquid pressurized and injected through the electrode 6 to the work 1 is usually lowered along a head 4 and a column 3 in a state that injection is stopped. A change in a voltage owing to discharge between the electrode 6 and the work 1 or a contact state is detected by a contact or discharge detector 8 and it is detected thereby that the lower end of the electrode 6 is lowered to the surface of the work 1. From the current working states of limit switches A-D, the approximate length of the electrode is detected by means of an electrode length detecting means 15.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a small hole machining machine used for forming a small hole as a start hole in a workpiece when performing wire cut electrical discharge machining. More specifically, a thin rod-shaped cylindrical electrode having a predetermined length is brought close to the workpiece while supplying machining fluid, and intermittent voltage pulses are applied between the two to penetrate the workpiece. This invention relates to an electric discharge machine for machining small holes.

(Prior art) In small-hole electrical discharge machining, a pipe-shaped electrode in the shape of a thin rod with a predetermined length is used, and machining fluid is jetted through the inside of the electrode into the machining part, and the spouted machining fluid is used in the machining hole. Machining is performed while flowing out machining waste together with the machining debris from the gap between the inner wall and the outer periphery of the electrode. Since the electrode wears out as machining progresses, the initial length of the electrode is longer than the thickness of the workpiece so that multiple holes can be machined, and the electrode cannot penetrate the workpiece. exchange with.

(Problem to be solved by the invention) In this small-hole electrical discharge machining, the electrode has a small diameter and therefore lacks rigidity. Therefore, the straightness of the machined hole depends on the machining fluid pressure inside the hole machined with the electrode. This is maintained by a balance between the pressure of the electric discharge during electric discharge machining, and the pressure of the electric discharge during electric discharge machining. Therefore, if the electrode wears out and becomes short during the machining of one through-hole, and the electrode cannot be penetrated anymore and the electrode is replaced, the balance state changes and cannot be kept constant, resulting in a decrease in machining accuracy. There was a point.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a small hole processing machine that can prevent deterioration in processing accuracy due to electrode consumption and replacement.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a machining depth setting means, an electrode consumption ratio setting means for an electrode attached to a machining head, and a machining depth set by these means. and a calculation means for calculating the required electrode length from the electrode consumption ratio, an electrode length detection means, and the required electrode length is detected by comparing the electrode length detected by the means with the required electrode length calculated by the calculation means. If the calculated electrode length is longer than the calculated electrode length, the transition to the target small hole electrical discharge machining is stopped, and conversely, if the calculated electrode length is shorter, the small hole electrical discharge machining is moved to the next process and the machining is continued. The invention is characterized by comprising a processing control means for starting processing.

(Function) Since the present invention has the above configuration, it is determined at the start of machining whether the length of the electrode is long enough to eliminate the need to replace it midway through, and if the length is insufficient, the fine hole is The transition to the start of electrical discharge machining is automatically stopped, and the transition to an automatic or manual electrode replacement process is started.

(Embodiment) FIG. 1 is a schematic side view showing an embodiment of a small-hole electric discharge machine according to the present invention. In FIG. 1, 1 is a workpiece placed on a processing table 2, 3 is a column, 4 is a head that is moved up and down by a Z-axis motor 5 along the column 3, and 6 is a workpiece that is held by the head 4. It is a thin rod pipe electrode. A to D are limit switches that are arranged above and below the column 3 at constant or predetermined intervals and are activated by engaging and disengaging from the head 4. This is for measuring the length by detecting the lowered position of the head 4. 7 is a processing power supply that applies intermittent voltage pulses between the electrode 6 and the workpiece 1; 8 is a contact or discharge detector that detects when the tip of the electrode 6 has reached the workpiece 1; The machining fluid is supplied to the workpiece 1 through the pipe-shaped electrode 6, but the machining fluid system is not shown.

FIG. 2 is an example of a device according to the present invention that determines whether the length of the electrode 6 measured using the limit switches A to D has a length necessary to penetrate the workpiece 1. FIG. In FIG. 2, the electrode consumption ratio δ setting means 10 and the machining depth W setting means 11 are realized by, for example, a keyboard, which is an input device of a computer, and the required electrode length Ha calculation means 12 and the comparison means 1
3 is realized by the arithmetic unit of the computer, and the display means 1
4 is also realized by a display device such as a CRT, or a lamp, etc., for displaying the contents of the computer's calculations. The electrode length detection means 15 is realized by the limit switches A to D.

The required electrode length Ha calculation means 12 calculates the required electrode length Ha from the wear ratio δ of the electrode 6 used and the machining depth W (=plate thickness) using the following formula.

Ha=W×(1+δ) (1) Comparison means 13 calculates the required electrode length Ha obtained by calculation means 12 and the limit switches A to D at the time of machining start (operation of contact or discharge detector 8). The electrode length Hb determined from the operating state is compared, and if the required electrode length is insufficient, the result is displayed on the display means 14, and the machining control means 16 controls the Z-axis motor 5 and the machining power supply 7.
If machining fluid is being supplied, the machining fluid supply is stopped, and the transition to the electrical discharge machining process is stopped.

In an apparatus in which the electrode 6 exchange is automated, the process automatically moves to an electrode automatic exchange step.

The relationship between the operations of the limit switches A to D in FIG. 1 and the length of the electrode 6, and the operation of the comparison means 13 will be explained. As shown in FIG. 1, to simplify the explanation, the intervals H between each limit switch A to D are made equal, and the interval between the lowest position limit switch D and the workpiece 1 is ΔH. guarantees the reliability of electrode length judgment. Processing power supply 7
By applying a voltage pulse or a detection voltage of the detection condition between the electrode 6 and the workpiece 1 by using the contact or discharge detector 8, the machining fluid is normally jetted under pressure to the workpiece 1 through the electrode 6. With the ejection stopped, the head 4 is lowered along the column 3, and the contact or discharge detector 8 detects voltage changes due to discharge or light contact between the electrode 6 and the workpiece 1. When it is detected that the lower end of the electrode 6 has reached the upper surface of the workpiece 1, the electrode length detection means 15 detects the approximate electrode length based on the operating states of the limit switches A to D at this time. For example, limit switches A to D
If all of the electrodes are inoperative, the length of the electrode 6 is at least H×3. For example, if H=8 cm, the length of the electrode 6 is at least (24 cm+ΔH).

For example, if the contact or discharge detector 8 is activated when the head 4 is lowered to the position shown by the two-dot chain line a in FIG. 1, the limit switches A and B will be activated at this time. The length Hb of the electrode 6 at this time is H=8cm+ΔH
The above is 16 cm+ΔH or less.

In this case, in equation (1), the machining depth W is, for example, 10
cm, and if the electrode consumption ratio is 0.5, the required electrode length Ha is 15 cm, and there is a possibility that Ha>Hb, and the electrode may not be able to penetrate during processing, so processing will be stopped. Then, replace the electrode 6 with a new one and start processing. As mentioned above, if the required electrode length is 15 cm and only the limit switch A is activated at the start of machining (when the contact or discharge detector 8 is activated), then the electrode length H
b is 16 cm + ΔH or more, and the required electrode length Ha = 15
cm or more, Ha<Hb, and the contact or electrical discharge machining process is proceeded to the next step without replacing the electrode 6, and machining is started and progressed by starting the supply of machining fluid, etc. .

The conditions for stopping processing due to the short length of the electrode 6 are as follows.

Condition (1): When only limit switch A is on,
Since the electrode length Hb is less than 24 cm+ΔH, processing is stopped if the required electrode length Ha≧24 cm.

Condition (2): When limit switches A and B are on, processing is stopped if Ha≧16 cm.

Condition (3): When limit switches A, B, and C are on, processing is stopped if Ha≧8 cm.

Condition (4): When all of the limit switches A to D are on, the process unconditionally moves to the next process and stops starting the small hole electric discharge machining.

FIG. 3 is a flowchart illustrating the above-mentioned operation.

In addition, in the case of this flowchart, the tip of the electrode 6 and the workpiece 1
The electric discharge machining power supply 7 is used to detect a predetermined proximity or contact state with the surface, and when it is detected that the electrode 6 has a length that can penetrate the workpiece 1, the machining control means 16
This shows a case in which a signal is output to start the supply of machining fluid, and the process can proceed almost directly to the electric discharge machining start process.

In the above embodiment, the lowest limit switch D
Although the height difference ΔH is set between the limit switch D and the workpiece 1, since workpieces 1 of various thicknesses are machined, this difference may also be applied when the height difference between the limit switch D and the workpiece 1 is different. By including the height difference in the value when determining the electrode length Hb, the same determination operation as above can be performed.

Furthermore, instead of using limit switches A to D, the position of the head 4 at the time of starting discharge may be determined from the output of the rotation speed detector 20 attached to the Z-axis motor 5, or from a scale. .

It goes without saying that various other changes and additions can be made to the embodiments described above without departing from the gist of the present invention.

(Effects of the Invention) According to the present invention, when performing small hole electric discharge machining, it is automatically determined whether the electrode has a length that can penetrate the workpiece, and if the electrode length is insufficient, the corresponding Since the start of machining is stopped at this position and the electrode is replaced, etc., it is possible to prevent the electrode from being unable to penetrate the workpiece during machining, and to ensure straight small hole machining. .

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing an embodiment of a small-hole electrical discharge machine according to the present invention, FIG. 2 is a block diagram showing an example of an electrode length determining device according to the present invention, and FIG. 3 is an operation of the one shown in FIG. It is a flow chart explaining. 1: Workpiece, 2: Processing table, 3: Column, 4: Head,
5: Z-axis motor, 6: Electrode, 7: Processing power supply, 8: Contact or discharge detector, 20: Rotation speed detector Patent applicant: Japax Co., Ltd. Agent, Patent attorney Katsuichi Wakata

Claims (1)

[Claims] A machining depth setting means, an electrode consumption ratio setting means, a calculation means for calculating a required electrode length from the machining depth and electrode consumption ratio set by these, and an electrode length detection means for an electrode attached to a machining head. , processing control means that compares the electrode length detected by the means with the required electrode length calculated by the calculation means and stops the start of processing when the required electrode length is longer than the detected electrode length. A small hole electrical discharge machine characterized by: