JPS624527A - Electric discharge machine for machining fine hole - Google Patents

Abstract

PURPOSE:To obtain a machine, which enables a fine hole to be electric discharge machined, with no necessity for using an expensive high pressure pump, by providing a machining fluid passage, vertically penetrating through a rotary main spindle mounting an electrode, while a rotary main spindle vibrating means and a machining fluid pressure increasing means. CONSTITUTION:Machining fluid is allowed to flow into a fluid reservoir chamber 14 via a pressure pump 21 from a tank 20, here pressure fluid is allowed to flow into an upper chamber 13a via a four way type guide valve 16, and a cylinder case 13, being lifted, contains a sufficient amount of the fluid. While the four way type guide valve 16 is switched by a dog 17a and a limit switch 18a, and a machine, switching the pressure fluid to change its flow into the bottom chamber 13b and lowering the cylinder case 13, finely displaces a main spindle 3 upward. In this way, the machine, pressurizing the machining fluid in the fluid reservoir chamber 14 to be jetted from a fluid passage 5 to a fine hole H, performs machining. When the machining fluid can not be supplied because of very small size of the fine hole, the machine, using no sealing die 8 and switching the four way type guide valve 16 to be operated at a high speed by a control device 19, performs machining by actuating the main spindle 3, that is, an electrode bar to be vertically oscillated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electric discharge machining device, and in particular, an electric discharge machining device for fine hole machining that is effective when machining a fine hole with a diameter of about 1 mm in a metal workpiece. Regarding.

[Prior art]

Electrical discharge machining has traditionally been used to process fine holes in metal materials, particularly in hard metal workpieces. A method is adopted in which machining progresses at high speed while feeding electrical discharge machining fluid. However, when the pore diameter becomes 0.5 mm or less, it is necessary to supply high-pressure processing fluid of several tens of atmospheres in order to maintain a high progress rate, and such high-pressure processing fluid is generated by a pump. requires a high-pressure pump that is not commensurate with the scale of the electrical discharge machining equipment. In addition, in the case of pores with a diameter of 0.1 mm or less, where it is impossible to supply machining fluid using a hollow electrode, it is recommended to apply upward and downward vibrations to the electrode during electrical discharge machining to improve machining progress. It has long been known to be effective.

[Problems to be solved]

Therefore, when machining small holes by electrical discharge machining, it is possible to supply high-pressure machining fluid without using a high-pressure generation pump, and for ultra-fine holes with a diameter of 0.1 mm or less, it is possible to apply vertical and downward vibrations to the electrode. There is a need for electrical discharge machining equipment that has a comprehensive built-in mechanism that can excite.

An object of the present invention is to provide an electric discharge machining apparatus for fine hole machining that achieves the mechanisms necessary for such comprehensive fine hole machining with a structure as simple as possible.

[Means of solution and action]

In order to achieve the above-mentioned object of the invention, the present invention provides an electric discharge machining apparatus for fine hole machining, in which an electric discharge machining liquid passage is provided which penetrates from the upper end to the lower end of a motor-driven rotating main shaft on which an electrode rod for fine hole machining is attached. The lower end is formed into an electrode rod attachment part, and the rotating main shaft is supported by an elastically held rotating bearing, and a piston formed approximately in the center of the rotating main shaft is attached to the upper part.
Mounted in a cylinder box that can move downward above the piston.

A rotary shaft excitation means configured to alternately supply working fluid to the lower chamber, and an upper end of the rotary main shaft facing a liquid reservoir chamber formed in the upper part of the cylinder box to perform upward and downward strokes of the cylinder box. There is provided an electric discharge machining apparatus for small hole machining, characterized in that a pressure increasing means is provided for supplying electric discharge machining fluid under increased pressure to the electric discharge machining fluid passage of the rotating main shaft according to the excitation means and the pressure increasing means. The electric discharge machining fluid whose pressure is increased by the cooperation of the means is supplied, and the vibrating means is used alone to apply an excitation force to the fine-hole electrode, thereby carrying out electric discharge machining of the ultra-fine hole.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

The figure is a cross-sectional mechanical diagram showing an embodiment of the basic configuration of an electrical discharge machining apparatus for fine hole machining according to the present invention. In the same figure, a bearing base 1 is formed in a part of the Z-axis moving part of the electrical discharge machining apparatus, that is, a movable part that gives longitudinal feed to the discharge electrode with respect to the workpiece W to be machined. A main shaft 3 is rotatably held by a thrust bearing 2. Further, the thrust bearing 2 is supported by springs 4 disposed above and below within the bearing base 1 so that it can be slightly displaced upward and downward, and therefore the main shaft 3 is also supported by the thrust bearing 2.
At the same time, slight displacement with respect to the bearing base l is possible. The main shaft 3 has a through hole 5 for a liquid passage extending through the main shaft 3 from the upper end to the lower end approximately at the center thereof, and a gripping portion 7 for gripping an electrode rod 6 for forming fine holes at the lower end. This grip part 7
has a sealing die 8 and a presser foot 9, and the presser foot 9 is detachably attached to the lower end of the main shaft 3 by, for example, screw engagement, and presses the sealing die 8 upward and guides the electrode rod 6. It is provided as a member having a hole and also performing a supporting and guiding function. Note that the sealing die 8 may be replaced by an oil seal member or a rubber bag. Note that the above-mentioned gripping part 7 is used when the electrode rod 6 itself is a hollow electrode rod and the electric discharge machining fluid (described later) flows down inside, but in order to form an ultra-fine hole, a solid small-diameter electrode rod is used. Needless to say, when gripping, the gripping part is replaced with a collet chuck type gripping part, for example.

Now, the main shaft 3 has a gear 10, and this gear 10 is configured to engage with a pinion 11 and receive a rotational drive from a drive morph 12, thereby exerting a rotational action on the electrode rod 6 for fine hole machining. This makes it possible to promote machining in the electrical discharge machining action with the workpiece W and to homogenize the machined surface. Further, the main shaft 3 has a piston 1 fitted in a cylinder box 13.
5 is formed, and defines an upper chamber 13a and a lower chamber 13b which are airtightly partitioned in the cylinder box 13, and the upper chamber 13a
When pressure fluid is supplied to the lower chamber 13b side, the cylinder box 13 moves upward and the main shaft 3 receives pressure from the upper surface of the piston 15, causing a slight downward displacement, and when pressure fluid is supplied to the lower chamber 13b side. As the cylinder box 13 moves downward, pressure is applied to the lower surface of the piston 15, so that the main shaft 3 is slightly displaced upward. That is, the cylinder box 13 itself is movable upward and downward, and is configured to move smoothly and stably by a guide means (not shown). Pressure fluid is supplied to the upper chamber 13a and lower chamber 13b of the cylinder box 13 by alternately supplying the pressure fluid to the upper chamber 13a and the lower chamber 13b from a fluid source (not shown) via the four-way guide valve 16. The pressure fluid is preferably pressurized air or pressure oil, and pressure oil is particularly desirable. The flow path switching of the four-way guide valve 16 is performed using a cylinder box 1 that can be moved upwardly and downwardly.
A limit switch 18 in which dogs 17a and 17b attached to the upper and lower ends of 3 are provided at preselected positions.
a, 18b and other suitable position detectors such as proximity switches, etc., and the configuration is achieved by the control device 19 sending a switching control signal to the four-way guide valve 16 in accordance with the signal of the displacement end detector that is emitted. It has become.

On the other hand, the upper end of the main shaft 3 is structured to face a liquid reservoir chamber 14 formed above the cylinder box 13 described above, and a pressure pump 21 and a check valve 2 are connected to the liquid reservoir chamber 14 from an electrical discharge machining fluid tank 20.
2, machining fluid pressurized to a desired pressure value is supplied. This machining liquid flows into the passage 5 of the main shaft 3, and furthermore, if the electrode rod 6 is a hollow electrode, it is ejected into the small hole H to be machined into the workpiece W through the electrode rod 6. Note that electrical discharge machining power is supplied to the main spindle 3 through an electrode 23 between it and the workpiece W to be machined.

The operation of the electric discharge machining apparatus for fine hole machining of the present invention having the above-described configuration will be described below.

First, a case where the electrode rod 6 is a hollow electrode rod and a pore having a diameter of about 1.0 mm is formed will be described.

When the main spindle 3 descends together with the bearing base 1 until it approaches the workpiece W to prepare for the start of fine hole machining, electrical discharge machining power is supplied via the electrode 23, and at the same time the main spindle 3 is moved at a predetermined speed by the motor 12. Rotationally driven. Further, the machining fluid, which has been raised to a certain pressure in advance, is sent from the electrical discharge machining fluid tank 20 to the fluid storage chamber 14 via the pressure pump 21 via the check valve 22 . At this time, pressure fluid is first supplied to the upper chamber 13a via the four-way guide valve 16, and since the cylinder box 13 is moved upward, a sufficient amount of machining fluid is supplied to the liquid reservoir chamber 14. When the dog 17a operates the limit switch 18a in accordance with the upward movement of the cylinder box 13, the control device 19 sends a switching signal to the four-way guide valve 16 in response to the signal from the limit switch 18a. This switching signal causes the four-way guide valve 16 to
When the pressure fluid is switched, the pressure fluid returns from the upper chamber 13a and is again supplied to the lower chamber 13b. As a result, the cylinder box 13 moves downward. At this time, the main shaft 3 is slightly displaced upward. In this way, the volume of the liquid reservoir chamber 14 to which the machining fluid is supplied decreases, so the pressure of the machining fluid is increased, and the pressurized machining fluid flows into the fluid passage 5 of the main shaft 3. That is, a pressure increasing means is formed between the liquid reservoir chamber 14 and the upper end of the main shaft 3, which performs the two functions of sucking in the machining fluid and increasing the pressure according to the upward and downward displacement of the cylinder box 13.

By imparting a pressure increasing effect to the electrical discharge machining fluid in this way, the pressurizing capacity of the pressure pump 21 provided near the electrical discharge machining fluid tank 20 is reduced, making it unnecessary to use an expensive high-pressure pump. This eliminates the problem. The pressurized machining fluid that has passed through the liquid passage 4 of the spindle 3 is ejected into the pores H of the workpiece W to be machined, and performs conventionally well-known functions such as promoting electric discharge, cooling the electrode, and removing machining waste, thereby promoting high-speed machining. Needless to say.

When the cylinder box 13 moves downward and the dog 17b operates the limit switch 18b, the control device 19 again sends a switching signal to the four-way guide valve 16 in accordance with the signal from the limit switch 18b, causing the four-way guide valve 16 to perform a switching action. . Therefore, pressure fluid is supplied to the upper chamber 13a of the cylinder box 13, and pressure fluid is returned from the lower chamber 13b. As a result, the cylinder box 13 moves upward again, and the electrical discharge machining fluid is supplied to the fluid storage chamber 14. During this process, the ejection of the pressurized machining fluid is stopped, but at this time, it is preferable that the supply of electrical discharge machining power is also interrupted using an appropriate interrupting means, such as an automatic opening/closing relay, and the machining is stopped.

During the above process, the main shaft 3 is displaced in the opposite direction to the cylinder box 13 as a reaction between the upward and downward displacements of the cylinder box 13, but since the thrust bearing 2 is elastically held by the spring 4, the main shaft 3 No abnormal reaction force acts on .

In this way, electric discharge machining using the hollow electrode rod 6 for machining small holes is properly performed under the supply of high-pressure machining fluid.

Next, if the diameter of the pore is extremely small and it is not possible to perform electrical discharge machining by supplying machining fluid, the electrical discharge machining apparatus of the present invention can perform micro-hole machining using vibration. Explain the point.

First, in order to attach the solid electrode rod 6 for fine hole machining to the lower end of the main shaft 3, the gripping part 7 is replaced with a gripping part such as the collet chuck type mentioned above, the electrode rod 6 is attached, and the hollow As in the case of the electrode rod, it is lowered to a processing position close to the workpiece W to be processed. That is, the sealing die 8 is not used.

In this state, start supplying electrical discharge machining power and also
The rotation of the four-way guide valve 16 is the same as in the previous example of operation.Next, the four-way guide valve 16 is switched alternately to both the upper chamber 13a and the lower chamber 13b of the cylinder box 13 at high speed by the control device 19. Pressure fluid is supplied by

As a result, the cylinder box 13 vibrates upward and downward. At this time, since the thrust bearing 2 of the main shaft 3 is elastically held against the bearing base 1 by the spring 4, an excitation force is applied to the main shaft 3. That is, vibration is applied to the solid electrode rod 6 via the main shaft 3. In this way, the electric discharge machining action using the vibration of the pore H is performed.

Note that when performing fine hole machining using this vibration, it is necessary to use pressure oil as the pressure fluid supplied to the cylinder box 13, and pressurized air is not suitable for applying high-speed vibrations. Moreover, if hydraulic pressure is used, it can be applied to fine hole machining using either a solid or hollow electrode rod 6.

As is clear from the above description, according to the present invention, when performing micro-hole electrical discharge machining on a metal workpiece using an electrode rod, the vibration method is also utilized for micro-hole machining by supplying high-pressure machining fluid. An electric discharge machining device that can also handle extremely small-diameter hole machining can be realized with a mechanically relatively simple configuration, and the use of an expensive high-pressure pump can also be avoided.

[Brief explanation of the drawing]

The figure is a cross-sectional mechanical diagram showing a configuration example of an electric discharge machining apparatus for electric discharge machining according to the present invention. 2... Thrust bearing, 3... Main shaft, 4... Spring, 5... Through hole, 6... Electrode rod,
7... Gripping part, 13... Cylinder box, 14
...liquid reservoir chamber, 15...piston, 16...
Four-way guide valve, 17a, 17b...dog, 18a,
18b... Limit switch, 19... Control device,
20... Electric discharge machining fluid tank, 21... Pressure pump, 22... Check valve.

Claims (1)

[Scope of Claims] 1. In an electric discharge machining device for fine hole machining, an electric discharge machining liquid passage is formed in a motor-driven rotating main shaft to which an electrode rod for fine hole machining is attached, penetrating from the upper end to the lower end. is made into the electrode rod mounting part, and the rotating main shaft is supported by an elastically held rotating bearing, and a piston formed approximately in the center of the rotating main shaft is installed in a cylinder box that can move upwardly and downwardly. a rotary shaft excitation means configured to alternately supply working fluid to both the upper and lower chambers; and a rotary shaft vibrating means arranged above the cylinder box such that the upper end of the rotary main shaft faces a liquid reservoir chamber formed in the upper part of the cylinder box; An electrical discharge machining apparatus for small hole machining, comprising a pressure increasing means for supplying electrical discharge machining fluid under increased pressure to the electrical discharge machining fluid passage of the rotating main shaft in accordance with a downward stroke. 2. The electric discharge machining apparatus for small hole machining according to claim 1, wherein the rotary shaft vibration means is equipped with a hydraulic oil supply mechanism that is switched by a four-way valve. 3. The pore according to claim 1 or 2, wherein the liquid reservoir chamber is configured to be supplied with the machining fluid from a supply source of the electric discharge machining fluid via a check valve. Electric discharge machining equipment for machining. 4. The fine hole according to any one of claims 1 to 3, wherein the elastically held rotary bearing is incorporated in a bearing box that allows feeding and access to the workpiece. Electric discharge machining equipment for machining. 5. The fine hole machining according to claim 2, wherein the upper and lower stroke ends of the cylinder box of the rotating shaft excitation means are detected by a limit switch, and the four-way valve is switched based on the detection signal. electrical discharge machining equipment.