JPH0457455B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, machining is performed by the electric discharge generated by applying intermittent voltage pulses between the machining electrode and the electrode workpiece, with machining liquid jetted in the discharge gap between the electrode and the electrode workpiece, which are opposed to each other. This relates to the improvement of electric discharge machining equipment, especially electric discharge hole machining equipment that processes small and deep holes. The object of the present invention is to provide an electric discharge pore machining device that can perform machining at a much higher speed and in a shorter time than the method and device of the present invention. Machining of small holes with a large shape ratio L (depth) / Dφ (hole diameter) around 1 mmφ or less by electrical discharge machining is
For example, it is widely used in a wide variety of applications, such as drawing dies, diesel engine fuel injection nozzles, overhead wire nozzles, and wire cut electrical discharge machining workpiece holes. One (for example, Yoshihiro Iizuka "Pore machining by electrical discharge machining" Electric discharge machining technology Vol. 4. No. 1)
(1961)), but a pipe-shaped material such as a copper pipe or a syringe needle is used as an electrode, and the machining fluid is jetted (or sucked) from the electrode side.Also, a pilot hole with a smaller diameter is inserted into the electrode workpiece. Since machining is difficult, it is almost impossible to use jets or suction from the lower hole on the workpiece side. (edited by the Technical Research Group, "Electro-discharge Machining Technology Handbook," p. 323, Nikkan Kogyo Shimbun, December 20, 1960), it is a difficult process that requires various ingenuity depending on the situation. There is no doubt that processing time is always a problem because it takes too much time compared to the scale of the process. Therefore, the present invention overcomes the above-mentioned difficulties in fine hole machining, and provides electric discharge fine hole machining that allows fine hole carving or hole drilling to be performed at an extremely high speed and without requiring various techniques. This is proposed for the purpose of proposing a device. Therefore, the machining fluid in this type of electrical discharge machining is used to maintain insulation in the discharge gap, generate and extinguish the discharge, cool the electrode, workpiece, and gap, and reduce the explosive force in the discharge gap. It is necessary to maintain the generation of kerosene and to discharge machining debris and gas from the discharge gap.In the area of drilling and engraving, mineral oil-based oils, mainly so-called kerosene (white For wire cutting electric discharge machining, water or an aqueous substance containing water as the main component is used, and for electric discharge cutting machining, water glass or water glass containing an inorganic electrolyte is usually used. Electrolytic solutions such as water ^have traditionally been used, but recently, water (purified water ^{, surfactant} As the above-mentioned wire-cut electric discharge machines that use water-based machining fluids whose main component is water have become popular, handling in the fields of drilling and die-sinking has also increased. From the viewpoints of environmental hygiene, disaster prevention, etc., there is a need for a processing machine that uses the above-mentioned water-based liquid as a processing liquid. For this reason, various proposals have been made regarding water-based machining fluids, such as the
Other than Publication No. 16480, related to the setting of pulsed power supply and power supply conditions for machining (for example, 2 Kimoto et al. "Study of low consumption electric discharge machining with underwater electrodes": Journal of the Society of Electrical Machining Engineers,
Vol.1-No.2.P43-50, etc.), but it has not yet appeared as a general-purpose practical machine. On the other hand, there are various methods for supplying machining fluid in the above-mentioned drilling and die-sinking type electrical discharge machines, such as jet flow, suction, reciprocating movement of electrodes, or a combination of these. The hydraulic pressure of the machining fluid newly supplied to the discharge gap for removal and renewal of the machining fluid is usually around several kg/cm ² or less at most (for example, the pressure of the machining fluid newly supplied to the discharge gap for removal and renewal of the machining fluid, etc. 362 pages, “Theory and Technology of Electrical Discharge Machining”, edited by the Kansai Branch of the Japan Society of Electrical Machining Engineers, No. 131
~132 pages, Yokendo Co., Ltd., November 15, 1971)
This was in good contrast to the high-pressure machining fluid jet method used in electrolytic die engraving in the field of electrical machining technology. However, according to research on high-speed electrical discharge machining, especially "Improvement of machining speed in electrical discharge machining using high-speed liquid flow" (Suda Soto, Electrical Machining Society Vol. 4, No. 7, pages 1 to 10),
Processing fluid contains 2g/conductor powder (#400 graphite)
This is a water-based machining fluid made from contaminated tap water, and the machining power source is a no-load voltage of 43V, which is full-wave rectification of single-layer commercial AC.
The average machining current is 130 to 400 A (current density approximately 10 to 32 A/cm ² ), and the machining feed of the electrode is manual, which is special, but the discharge gap flow velocity of the machining fluid is approximately 5. ~20m/sec (approx. 5~25/sec)
min), and later, ``Prototype production of a high-speed electrical discharge machining machine'' with automatic electrode feed without mixing the above-mentioned conductor powder (2 people outside Suda, academic lecture preprint of the 1972 Japan Society of Precision Machinery Spring Conference, No. 357~ (p. 358), such high-speed rough machining is used for fine hole machining where the electrode diameter is around 1 mmφ or less, and when the shape ratio L/D is around 10 or more. It is not yet clear whether it can be applied to fine hole processing. In addition, the dimensions and shape of the electrode, the size of the discharge gap, and the flow rate of the machining fluid described in these documents,
According to the flow rate, the fluid pressure at the inlet of the discharge gap of the machining fluid (tap water x 10 ³ Ωcm order) sent by the pump is lower than 10 Kg/cm ² , and the pump pressure is approximately
Estimated to be 10Kg/ ^cm2 . Furthermore, as a method of high-speed electrical discharge machining, electrolytic discharge machining methods that perform electrical discharge machining at the same time are being researched. It is described in the academic lecture preprint, pp. 437-438, "High-speed drilling of steel by electrolytic discharge machining," 1972 Japan Society of Precision Machinery Spring Conference academic lecture preprint, pp. 415-416, and approximately 10 mm/min. High-speed machining of 40mm/min to 40mm/min is performed using a machining fluid supply means with a high pressure of approximately 10Kg/ ^cm2 , but the machining fluid is approximately
With 20% salt water, the power source is approximately half-wave rectified commercial alternating current.
At a voltage of 50 V, the current density is approximately 300-800 A/cm ² , and it is not yet clear whether such a high-speed rough machining method can be applied to fine machining. Therefore, as a result of various experiments and researches, the present inventors have arrived at the present invention.
In electrical discharge machining for small holes of about 10 or more, water is used as the machining fluid, particularly preferably water-based machining fluid whose main component is water and has a resistivity on the order of 10 ⁴ Ωcm, and voltage pulses are applied intermittently as the machining power source. The electrode or the workpiece is fed according to the progress of machining using a pulsed power source applied at a constant rate, and the water-based machining fluid is processed at a high pressure of at least 20 Kg/cm ² , preferably 25 Kg/cm ² or more. The machined surface roughness is 20μmRmax or less, preferably 10μmRmax when the jet is supplied into the gap.
In the following description, electrical discharge machining is performed at a machining feed rate of at least about 5 mm/min or higher, preferably 10 mm/min or higher. In this embodiment, the diameter of the electrode is 1 mmφ or less, preferably 0.5 to 0.6 mmφ, and a pipe is used as the electrode, and water-based machining fluid is supplied and jetted from the pipe passage into the machining gap. thing,
Making the pressure of the machining fluid higher than 40Kg/cm ² , or preferably 50Kg/cm ² or more, or increasing the pressure of the machining fluid continuously or in stages according to the depth of the machined hole as the machining progresses. In other words, the height (lM) of the remaining convex portion of the workpiece corresponding to the inner diameter of the electrode is the machining depth (lH) of the machining hole.
lM/lH≒1/3 or less, preferably lM/lH≒
The temperature of the machining fluid must be maintained at a predetermined constant level to ensure stable machining. The machining fluid is heated to a predetermined value and maintained at a predetermined temperature, the viscosity of the machining fluid is reduced by heating, and a predetermined amount of water-based machining fluid is supplied to the machining gap, and water-based machining in which a jet stream intervenes in the machining gap. In addition to ensuring the flow rate of the liquid, the flow rate must also be at least 15 to 20 m/sec, preferably at least 20 to 30 m/sec, and gas is generated from the machining fluid during processing (in the case of water-based machining fluids, Workpiece (Fe) 1
330 cm ³ of gas is generated), and if the amount of gas generated (Qg) is 1, the amount of machining fluid supplied to the machining gap (Qe) is 2, that is, Qg: Qe≒
When the machining electrode is a long electrode of 400 to 500 mm or more, for example, supplying a water-based machining fluid at a ratio of 1:2 (in normal electrical discharge machining conditions). In order to prevent the loss of machining fluid supply fluid pressure, a water-based machining fluid is supplied and jetted from between a tube body coaxially surrounding the electrode and configured to feed the electrode in the axial direction, and from a passage in the electrode tube. Although the method of jetting machining fluid into the machining gap is called a forward flow method in electrolytic machining, there are other embodiments in which the jet of machining fluid is used as a reverse flow method, which is also used in electrolytic machining. Furthermore, as an improvement of the present invention, it is also useful to perform electric discharge machining under the jet of high-pressure machining fluid while applying ultrasonic vibration to the electrode or the workpiece, in order to improve machining performance. In this case, the frequency of the ultrasonic wave is the usual 20 to 30 KHz, preferably about 50 KHz or more and on the order of about 100 KHz;
In special cases, the ultrasonic wave should be on the MHz order of about 1 to 10 MHz, and the energy imparted by the ultrasonic wave should be set to zero or small when the machining condition is normal, and increased as the machining condition deteriorates. , the above-mentioned ultrasonic waves are applied from the holding side axis and end of the electrode via a horn, etc., and the electrode is placed at a predetermined fixed position spaced apart from the top surface of the workpiece in order to protect the holding part of the electrode. A guide for guiding the electrode in the axial direction in contact with the guide is provided, and the guide is preferably configured to apply the ultrasonic vibration in a direction perpendicular to the axial direction of the electrode. The supply device is equipped with a plunger type or other high-pressure pump that corresponds to the desired machining fluid pressure, and if necessary, a pressure increase device is installed, and the machining fluid supply system is provided with an accumulator to prevent fluctuations in fluid pressure. In addition, when machining is performed using an electrode with a machining fluid flow path formed in the electrode, a coaxial machining residual protrusion (usually called a navel or the like) corresponding to the machining fluid flow path is formed in the machining hole of the workpiece. As the process progresses, if the protrusions remain for a certain length of time, they may collapse or bend.
Otherwise, machining becomes unstable or even impossible due to breakage, etc., so machining conditions such as the diameter of the machining fluid flow path and electrical machining conditions such as voltage pulses are required to prevent the protrusion from becoming longer than a certain degree depending on its diameter. Alternatively, it is necessary to further set the machining feed (drilling or electrode feed) speed. The present invention will be explained below with reference to drawings and examples. FIG. 1 is a side view of an embodiment schematically showing the processing section of the processing apparatus of the present invention, and 1 is an example in which the outer diameter is 0.5 mm.
A processing electrode made of a copper pipe with an inner diameter of approximately 0.275 mmφ and a length of approximately 400 mm, one end of which is supported by a chuck portion 4 provided at the tip of a vibration amplifying horn 3 of an ultrasonic electrostrictive vibrator 2. attached.
An axial cavity 3a is hollowed out inside the horn 3, and as shown in FIG. With one end inserted up to 3a, it is tightened and fixed by a chuck nut 4a, and the outer peripheral surface of the inserted cylindrical electrode and the inner wall surface of the cavity 3a are watertightly sealed by an O-ring packing 3b. In this way, the seal member 3
By providing b, the machining fluid can be supplied smoothly and stably at a high pressure of 20 kg/cm ² or more. The cavity 3a serves as a passage for supplying machining fluid to the electrode 1, and the other end is connected to a flexible pressure-resistant pipe (not shown) connected to a high-pressure machining fluid discharge port of a machining fluid supply device described later. A machining fluid supply lamp 5 is opened at the side of the horn 3. Reference numeral 6 denotes an electrode head that holds the electrode section, and is supported by a column (not shown) set up on the bed so that it can move up and down and be fixed. The servo feed device 7 includes a servo feed device 7 that provides vertical feed. In this embodiment, the ultrasonic vibration horn 3, the chuck portion 4, and the electrode head 6 constitute a processing head. Reference numeral 8 denotes a base provided on the bed so as to face the head 6, on which a cross table 10 having servo feed mechanisms 9x and 9y for x and y axes is placed.
A workpiece 11 is fixed on top of the workpiece 1 with a fixture 12. Reference numeral 13 denotes a fixed guide on the tip side of the electrode 1 as shown in FIGS. 2B and C, which is fixed to the base 8 by an L-shaped arm 13a and maintains the positional accuracy of the tip on the processing side of the electrode 1. Since a machining liquid of at least 20 kg/cm ² is flowing in the machining gap at the tip of the electrode 1, it is important to fix the guide at a position closer to the surface of the workpiece 11. be. In addition, 2a in Fig. 1 is an exemplary ultrasonic power source of, for example, 20 to 30 KHz, and 14 is a machining power source that generates intermittent voltage pulses. Approximately 30μs or less, typically 5μs
Because it is the so-called semi-finishing to finishing machining conditions before and after,
A so-called inter-electrode capacitor of about 1 to 0.1 μF or less is often connected between the electrode 1 and the workpiece 11. Further, 15 is a numerical control device for positioning, for example, and includes a servo feed mechanism 9 such as a pulse motor, an encoder, and a DC motor with a tachometer generator.
Drive control of x and 9y. FIGS. 2B and 2C are front views and longitudinal sectional views of an embodiment of the guide 13, in which an inner cylinder 1 is inserted into an outer cylinder 13b.
3c are coaxially inserted, and the inner cylinder 13c has three or more bolts 13d provided at intervals in the axial direction of the outer cylinder 13b, each of which moves back and forth centripetally by screws. The axial center is held adjustable by the inner cylinder 13c, and three small cylinders 1 are provided at respective positions spaced apart in the axial direction within the inner cylinder 13c.
3e are inserted so that their respective centers form an equilateral triangle, and the electrode 1 is slidably guided into the gap formed by the three cylinders 13e. Therefore, even if the electrode 1 is cylindrical and a high-pressure machining fluid of 20 kg/cm ² or more is jetted from the tip into the machining gap, the position of the tip of the electrode 1 will not deviate greatly or vibrate. , it becomes possible to machine straight, narrow holes. Further, FIG. 3 shows that a machining fluid, that is, a water-diameter machining fluid whose main component is water, is supplied to the electrode 1 via the plug 5, and the machining fluid is supplied to the discharge machining gap between the electrode 1 and the workpiece 11. This is a block diagram of an embodiment of the apparatus for supplying machining fluid, particularly the circulating supply of machining fluid, which is a part of the apparatus of the present invention that produces a pressurized jet of machining fluid. Recovery tank 16b
The machining fluid in the recovery tank 16b is divided into a cleaning fluid tank 16a and a cleaning fluid tank 16a.
The cleaning liquid is sent to the cleaning liquid tank 16a through a precision filter by the pump 17 and stored therein. The conductivity of the stored machining fluid is detected by the electrical conductivity detector 19, and when the conductivity increases and the specific resistance becomes smaller than 10 ⁴ Ωcm, for example, the pump 20 is driven. The processing fluid is pumped up, brought into contact with the ion exchange resin 21, and returned to control the conductivity so as to have a predetermined specific resistance on the order of 10 ⁴ Ωcm. Reference numeral 22 denotes a temperature control device for the machining fluid in the clean tank 16a having a temperature detector 23, which cools or heats the machining fluid to maintain it at a predetermined approximately constant value. The viscosity of water-based machining fluid decreases as the temperature rises, making it possible to supply more than the desired amount of machining fluid to the machining gap with a lower supply pressure, increasing the flow rate, but as the temperature rises, the electrical conductivity of water-based machining fluid decreases. If the water-based machining fluid increases and the temperature decreases, the above will be reversed.Also, if the water-based machining fluid is supplied at high pressure against the flow resistance, the machining fluid temperature will generally decrease, although it depends on the structure and model of the pressure supply pump used. is on the rise, and the machining fluid is heated even in the discharge machining gap, so the temperature control device 22 takes these things into consideration, and also changes the electrode, workpiece material,
In consideration of the combination, processing purpose, or processing conditions, select one that can control heating or cooling, or use one that can control both heating and cooling. Reference numeral 24 is a plunger type high pressure machining fluid supply pump, which directly pumps up and supplies the clean machining fluid, or a precision filter 25 as shown in the figure.
A supply pump 26 for pumping the machining fluid to the pump 24 via the pump 24 is provided as necessary. By adopting a plunger type high pressure pump as the machining fluid supply pump, machining fluid can be pumped under high pressure conditions of 20 kg/cm ² or more. can be efficiently and stably supplied. 27 is a check valve, 28 is a high-pressure liquid retaining tank provided as necessary, 29 is a high-pressure accumulator, 30 is a relief valve provided in the clean tank return path, and further includes a plug 5 and a pump 24 discharge port or a high-pressure liquid retaining tank. The retaining tanks 28 are connected by pressure-resistant piping, whereby a high-pressure aqueous machining fluid is stably supplied via the plug 5, and is jetted into the discharge machining gap at a desired flow rate. In the case of the machining fluid supply device configured in this illustrated embodiment, the pressure of the supplied machining fluid is determined by the pressure adjustment setting of the relief valve 30. Note that 31 is a pressure gauge, and a flow meter is provided if necessary. The electrical discharge pore machining apparatus of the present invention has a machining fluid supply device capable of stably supplying machining fluid at high pressure as shown in FIG. 3, and a machining fluid supply device as shown in FIG. , and others, but in FIG. 1, the processing electrode 1
The configuration and related devices for applying ultrasonic vibrations to the device are not essential to the specific invention of the present invention. That is, the characteristic structural requirements of the electric discharge pore machining apparatus of the specific invention of the present invention are that the shape ratio L/D of the machining electrode is at least about 5 or more, usually L/D≒10.
A chuck part is provided that can hold one end of the thin rod-shaped electrode with a diameter of about 1 mm or less at the front and back sides and a diameter of about 1 mm or less against the processing head. In order to perform stable machining with no change in machining performance, use a water-based machining fluid containing additives, preferably with a specific resistance of 10 ⁴ Ω at approximately constant temperature.
Processing using a plunger-type high-pressure pump that is used as a machining fluid controlled to the cm order and capable of supplying the water-based machining fluid at a high pressure of at least 20 Kg/cm ² , preferably 25 Kg/cm ² or more. A fluid supply device is provided, and a pressure-resistant pipe is provided that connects the high-pressure machining fluid discharge port of the machining fluid supply device to the electrical discharge machining gap, and the electrical discharge machining is performed by supplying intermittent voltage pulses to the machining gap. This is what we do. This will be explained below using examples. Cu with outer diameter 0.3mmφ, inner diameter 0.15mmφ, length 150mm
Using electrodes, stainless steel SUS−
304, 2mm thickness is used as a workpiece and perforated. The processing pulse power supply has a voltage pulse width (τon) of 6μs,
Pause width between voltage pulses (τoff) 2μs, no-load voltage of voltage pulses (Vo) 100V, amplitude of discharge current (Ip)
10A, but with a 0.1μF capacitor connected in the gap,
Machining is performed at an average machining current (IM) of approximately 2A. The machining fluid is water with a specific resistance of approximately 3.5×10 ⁴ Ωcm, and the fluid temperature is approximately 24
℃, the supply pressure (Kg/cm ² ) of the machining fluid was varied, and the machining speed (speed at which the machining hole was excavated by the electrode (mm/min) was measured. Figure 4 plots the hydraulic pressure of the machining fluid on the horizontal axis and the machining speed on the vertical axis on a common logarithmic scale. Correspondingly, the flow rate (cc/min) of the machining fluid with respect to the supply fluid pressure is plotted on a logarithmic scale on the vertical axis and is shown as curve C, and the flow rate of the machining fluid in the machining gap (m/s , calculated estimated values) are plotted on a logarithmic scale on the vertical axis, and are shown as curve D. The machining speed of curve A varies depending on the machining conditions, except that the supply pressure and flow rate (therefore, the flow rate) of the machining fluid vary. is the above-mentioned constant value, and can be said to depend only on the variables of the machining fluid.According to the A curve, the machining speed rapidly rises when the fluid pressure exceeds 10 kg/ ^cm2 . , the characteristic is that it decreases after reaching the maximum at about 60 to 80 Kg/ ^cm2 , and the maximum machining speed reaches an average of about 28 mm/min.In this case, the liquid pressure is about 70 to 80 Kg/cm2. If you exceed cm ² ,
It is still not clear why the machining speed actually decreases, but as will be explained later, this may be because the energy density of electrical discharge machining in the machining gap is insufficient relative to the flow rate and velocity of the machining fluid, or because the energy density is insufficient due to the energy density being supplied. It is thought that this is because the machining fluid flow rate and flow velocity are insufficient to increase the energy density of electrical discharge machining. That is, in the above case, the machining voltage pulse τon, τoff or
Increasing the discharge energy density by changing or removing one or more values of Ip, or even the value of the capacitor, usually increases the saturation characteristic of the machining speed curve A when increasing the average machining current (IM). moves to the high pressure side of the machining fluid, increasing the maximum machining speed, but there seems to be a limit to the energy density of electrical discharge machining during machining gap increase, and even if IM is further increased, the machining fluid Even if the pressure is increased, the machining speed tends to decrease, as in curve A, because the machining gap increases into an arc state. However, when the machining fluid is heated to about 60°C, the viscosity of the machining fluid decreases, and the flow rate and flow rate of the machining fluid increase at the same supply fluid pressure, resulting in curves C and D.
However, from the point where they both move upward on the graph in Figure 4, the liquid pressure at which the machining speed is saturated moves to the higher pressure side, and at that time, τon = 6μs, τoff = 2μs, Ip = 16A, capacitor 0.1μF, The average machining current is approximately 4A, which is approximately
At a hydraulic pressure of 100Kg/cm ² , the processing speed reached approximately 40mm/min. Note that the average machining current becomes less than 2A when the liquid pressure is around 10 kg/cm ² or less, and the machining speed decreases significantly ^. The speed tends to be approximately proportional to the hydraulic pressure, reaching approximately 2.5A at maximum machining speed when the hydraulic pressure is approximately 70 kg/cm ² . In the above case, the machined surface roughness of the side surface of the machined hole is approximately 5μmRmax
Front and back, processing enlargement allowance is approximately 0.025mm on one side.
A 0.35mmφ hole is machined to prevent electrode wear (E/W×
100%) is almost proportional to the above-mentioned average machining current value, and is around 100 to 120%, but it has a fairly large influence on whether the machining is stable and smooth. Also, if we consider the shape ratio L/D above, in the case of the above experimental example, L/D≒7, but according to various experiments, the above machining speed is 1 at the start of machining. As a result, the machining speed decreases to 0.5 to 0.6 times up to a machining depth with a shape ratio of approximately 7 to 8, but even in the region of machining depths where the shape ratio is 10 or more, the desired machining fluid is supplied with high pressure. As long as the flow rate was maintained, the processing speed did not seem to decrease below 0.5 times. The desired flow rate of the machining fluid is approximately 330 to 350 cm ³ of gas generated from the machining fluid per 1 g of processed material (this value depends only on the machining fluid used). , electrode, material of workpiece,
It is a nearly constant value that has almost no relation to the combination, electrical processing conditions, etc. ), this is the flow rate that eliminates this generated gas from the machining gap, maintains a stable discharge state, and enables high-speed machining, and the machining fluid supply when the machining speed is fastest and efficient machining is being performed. According to the results of actual measurement, the processed amount was 1g.
The amount of machining fluid supplied per unit is about 660 to 700 cm ³ (flow rate is a little over 15 cm ³ /min), and it is necessary to supply the machining fluid about twice as much (in volume) as the amount of gas generated. In this way, in order to eliminate the gas generated in the machining gap during machining and perform efficient machining, it is necessary to supply approximately twice the amount of machining fluid to the machining gap as the amount of gas generated. The amount of gas generated varies depending on the type of machining fluid; when processing 1 g of iron, water-based machining fluid generates approximately 330 c.c. of gas, whereas when kerosene is used as the machining fluid, approximately 330 c.c. of gas is generated. ,
Approximately 1000 c.c. of gas is generated. Therefore, if a water-based machining fluid is used, the required amount of machining fluid to be supplied to the machining gap is 1/3 of the amount when using kerosene as the machining fluid, so a sufficient amount of machining fluid can be supplied to the machining gap. This makes it possible to perform high-speed machining. Also, in terms of the cooling effect on the processed parts, water has a larger heat capacity than kerosene and has a higher cooling effect on the processed parts.
If an aqueous machining fluid is used, the machining area can be sufficiently cooled with a smaller supply amount than when kerosene is used as the machining fluid, and high-speed machining can be performed with high energy density. In this way, water-based machining fluids are not only superior in terms of environmental hygiene and disaster prevention, but also pose problems when attempting to perform high-speed machining in machining forms where it is difficult for machining fluid to be supplied to the machining gap. This is advantageous in terms of the amount of gas generated and the cooling effect, and the present invention uses an aqueous machining fluid as the machining fluid and supplies this machining fluid at a discharge pressure of 20 kg/cm ² or more. This enables high-speed processing of small and deep holes, such as boring and drilling holes, which were previously difficult. Also, when processing with a large shape ratio (L/D),
If the remaining machining protrusion of the machining electrode 1 corresponding to the machining liquid spout grows long and thin, the electrode and the workpiece will be short-circuited through the protrusion, making it impossible to perform stable machining. It is necessary to select processing conditions such as the inner diameter of the processing electrode, the electrical conductivity (clearance) of the processing fluid, and the voltage of the processing voltage pulse or superimposed high voltage so that the protrusion does not grow beyond a certain level. Assuming that the conductivity and voltage conditions are constant depending on the device used, selection of the inner diameter of the cylindrical processing electrode is important. Furthermore, if the protrusions grow, they will also obstruct the supply of machining fluid, so their growth must be prevented as long as the process involves fine-pore machining. Therefore, under the machining conditions described above, the machining electrode has an outer diameter of 0.3 mmφ and an inner diameter of approximately 0.15 mmφ.
Also, the inner diameter is around 0.3 mmφ for the outer diameter of 0.5 mmφ, and in any case, the maximum depth of the machined hole (l; the depth from the surface of the workpiece to the deepest part of the machined hole) and the height of the top of the protrusion. It is necessary to select such a ratio that l'/l is approximately 1/5 or less. In Fig. 4 above, curve B drawn corresponding to curve A is the case where ultrasonic vibration with a frequency of 28 KHz and an output of about 20 W is applied to the processing electrode 1 in the case of the processing characteristics of curve A described above. This is a characteristic curve related to machining speed, which is almost similar to curve A, but by applying such ultrasonic vibration, the machining speed can be increased from about twice to several times or more. The effect of applying ultrasonic vibration is more pronounced as the machining fluid supply pressure approaches the region of conventional machining conditions where machining performance is low, and in some regions machining speed reaches 5 to 10 times, The hydraulic pressure of the machining fluid is higher, for example curve A
In the region of maximum machining speed and B, it decreases to about twice as much, indicating that the dependence on the pressure, flow rate, and flow rate of the machining fluid is high. Incidentally, the application of ultrasonic vibration is extremely effective as described above, but as shown in FIGS. If the electrode 1 is configured to be supported and fixed, while one or more pores are being processed using one electrode, the electrode 1 may become fatigued at the fixed part of the chuck part 4, resulting in a breakage accident. This often occurs. Therefore, in order to prevent such accidents, it is conceivable to reduce the energy of the ultrasonic vibrations applied to the minimum necessary level, but even so, repeated use will inevitably lead to the above-mentioned breakage accident, and for this reason, the above-mentioned Control is performed to increase and strengthen the energy of ultrasonic vibrations, which is set to the minimum necessary level, less than that, or zero, and is applied only when machining problems such as deterioration of machining conditions occur. Since the effect of vibration cannot be enjoyed all the time, the meaning of providing an ultrasonic vibrator and its excitation power source is diminished, and the equipment usage efficiency is also reduced, so it must be avoided. According to various experiments conducted by the present inventor, ultrasonic vibrations are applied to the electrode 1 on the electrode holding chuck side of the guide 13 or on the workpiece 11.
If you do this with the vibrator in contact with the electrode at an angle, for example 90°, with respect to one axis of the electrode,
It was found that there were almost no accidents such as breakage of the electrode 1 in the chuck portion 4, and that the effects of applying ultrasonic vibration as described above could be fully enjoyed in small hole electrical discharge machining. To explain this with reference to the drawings below, in FIG.
A contact tip 3a is welded to the end of the vibrator horn 3 and fixed by an appropriate means such as tightening, and provided on the tip of the vibrator horn 3 to the electrode 1 guided by the guide 13.
It is designed to touch lightly. An example of the structure of this abutting part is as shown in FIGS. 6A and B. In the case of FIG. 3b, and in the case of figure B, the electrode 1 is engaged from a direction perpendicular to the axial direction with a circular V groove 3b formed on the outer peripheral surface of the horn 3 in a direction perpendicular to the axial direction. In either case, the electrode 1 is subjected to vibration several times until its axial length becomes short due to electrode wear at the end of machining, and it becomes necessary to replace it. During use, there was almost no breakage in the holding chuck portion, and on the other hand, the effect on electric discharge machining by applying ultrasonic vibration was almost the same as in the case shown in FIG. 1 above. In this case, there is no major change in the dimensional accuracy of machining and the machining expansion allowance (clearance), and the configuration may be such that vibration is applied from a direction having an angle other than the right angle to the electrode axis, or the guide 13 In some cases, the guide 13 may be configured to vibrate closer to the holding chuck. According to this configuration, the cylindrical electrode with a circular cross section can be used even when machining is performed while rotating the electrode 1 around the axis in order to promote discharge of machining fluid and machining waste and to maintain a perfect circle of the machining hole. , it is not necessary to rotate the vibrator as in the case of FIG. 1, which is useful. Here, the following table shows examples in which various materials and thicknesses of the workpiece were used under the above-mentioned processing conditions. The machining fluid is an aqueous machining fluid with a specific resistance of approximately 3.5×10 ⁴ Ωcm, and its supply pressure is constant at approximately 50 Kg/cm ² .
Or the ultrasonic vibration is 28KHz, 20W, and the processing speed is an average value.

[Table] The frequency of the applied ultrasonic vibration is still unclear, but it appears that in normal cases, the desired application effect can be obtained in the normal frequency range of about 30 KHz or less. However, the material of the electrode (for example, in addition to the above-mentioned Cu, Cu-Zn alloy, W,
It seems that there are various factors such as the dimensions such as the inner and outer diameters of the electrode, the overall length, the length of the upper and lower parts of the guide, the machining fluid jet speed and the average machining current density, etc. The frequency of the applied ultrasonic vibration is approximately 50 KHz or more and on the order of 100 KHz,
and frequencies of the MHz order from 1 to 10 MHz, e.g.
Even 1.6MHz, 5W was more effective than 28KHz, 10W in some cases. Instead of being generated and applied by the so-called electrostrictive and magnetostrictive oscillators as described above, this ultrasonic vibration may be applied by changing either the current or the magnetic field, and depending on the processing conditions for the electrode. is several 100KHz
Vibration can be imparted to the electrode from a place where an intermittent discharge current flows, for example, by working on the electrode in a direction perpendicular to the axial direction or in an alternating magnetic field. As described above, according to the electrical discharge micro-hole machining apparatus of the present invention, electrical discharge machining of micro-deep holes with a shape ratio of L/D≒5 to 10 or more with a diameter of around 1 mm or less, which was conventionally considered difficult to process, can be performed at high speed and efficiency. This is a useful invention. It goes without saying that the present invention can be modified in various ways without departing from the spirit of the present invention as set forth in the claims.

[Brief explanation of drawings]

FIG. 1 is a side view of an embodiment schematically showing the machining section of the electrical discharge pore machining apparatus of the present invention, FIG. 2A is a sectional view of the electrode chuck section, and FIGS. 2, B and C
are a front view and a side sectional view of an embodiment of the electrode guide;
The figure is a configuration diagram of an embodiment of the machining fluid supply device which is a part of the apparatus of the present invention, Figure 4 is a characteristic curve diagram showing an example of machining performance by the processing apparatus of the present invention, and Figure 5 is an electrode guide and vibration diagram. FIGS. 6A and 6B are side views of a portion showing a modified embodiment of the applying means, and FIGS. 6A and 6B are front views showing the configuration of a modified example of a portion that applies vibration to an electrode. 1... Electrode, 3... Ultrasonic vibration horn, 7...
Feeding device, 11... Workpiece, 13... Electrode guide, 14... Power source for machining, 5... Machining fluid supply plug, 16... Machining fluid storage tank, 22... Temperature control device, 24... High Pressure processing fluid supply pump, 29
...Akiyumureta.

Claims (1)

[Claims] 1. During electrical discharge machining, which is formed by facing an electrode and a workpiece, intermittent voltage pulses are applied between the two with a jet of machining fluid interposed between the two. When machining is performed by electric discharge, and the electric discharge machining is performed by relatively applying a feed according to the progress of machining or a feed at a predetermined speed between the two, the shape ratio L/D
(However, L: depth of the processed hole, D: diameter of the processed hole) is a cylindrical electrode having a diameter and length to process a pore of at least 5, and one end of the cylindrical electrode is placed inside the processing head. a chuck part that is held while being inserted into a machining fluid supply passage formed in the machining fluid supply passage, and a seal that provides a watertight seal between an inner wall surface of the machining fluid supply passage and an outer peripheral surface of one end of the inserted cylindrical electrode; a member, a fixed guide for positioning and guiding the cylindrical electrode that is processed and fed in the axial direction at a position close to the workpiece on the other end side of the cylindrical electrode, and a machining fluid supply device that stores and supplies a water-based machining fluid. The machining fluid supply device has a plunger-type high pressure pump capable of setting a discharge pressure to 20 kg/cm ² or more, and the high pressure machining fluid discharge port of the machining fluid supply device is connected to the machining fluid supply passage. An electrical discharge pore machining device comprising pressure-resistant piping connected to an opening. 2. The electric discharge pore machining apparatus according to claim 1, wherein the cylindrical electrode is a rotating electrode that is rotated around an axis. 3. The electrical discharge pore machining device according to claim 1, wherein the machining fluid supplied by the machining fluid supply device has both or one of temperature and specific resistance controlled.