JPS5993238A - Electric discharge machining device - Google Patents

Abstract

PURPOSE:To decrease the consumption ratio of an electrode so as to enable the all night unmanned operation of electric discharge machining to be performed, by controlling temperature regulating fluid of the electrode through at least either one the fluid temperature or the flow rate so that temperature of the electrode is controlled to a level decreasing the consumption ratio of the electrode. CONSTITUTION:A controller 9, in which temperature of an electrode 1 is indirectly measured from a difference of temperatures between temperature detectors 8, 8', provided in a fluid outlet pipe part 5a from the electrode 1 and its inlet pipe part 5b, and from a signal of the flow rate or the like of fluid, drives a pump 13 and a motor 14a or controls the working condition of a heater 11 and/or a cooler 14 while changes the flow rate of the fluid in accordance with said measurement of temperature of the electrode, thus maintaining the temperature of the electrode at about, for instance, 40 deg.C minimizing consumption ratio of the electrode. In such way, water system machining fluid, which causes the consumption ratio of the electrode to be largely different by temperature, can be used, and all night numanned operation of electric discharge machining can be performed, further a machining speed can be also increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric discharge machining apparatus that improves the electrode consumption ratio or the machining accuracy, and is particularly suitable when a water-based electric discharge machining fluid is used.

In the field of drilling and die-sinking using rod-shaped or contracted electrodes in the field of electrical discharge machining, hydrocarbon oil-based machining fluids such as kerosene (white kerosene) and transformer oil are commonly used. On the other hand, in the field of so-called wire-cut electrical discharge machining that uses wire electrodes, water,
In particular, pure water-based products have come into regular use.

In the former case, kerosene is used because it is useful for preventing rust in the machine, but in general, the machining speed is slow, but the surface roughness is small and the dimensional accuracy is high. Various machining performances are generally superior to others over the entire machining condition range, from the machining condition range to the rough machining range where the machined surface is rough but the machining speed is fast, and it is proportional to the set machining conditions. It is relatively cheap and easy to obtain, has a relatively long life, and does not cause any particular pollution problems during processing or after-treatment such as disposal, or is relatively easy to dispose of. However, the biggest drawback of hydrocarbon oil-based machining fluids such as kerosene and transformer oil is that they are flammable, and are not suitable for electrical discharge machining. Electrical machining, such as the , electric discharge, electrostatic discharge, etc. are continuously generated and maintained during machining.On the other hand, such electric processing equipment does not require an operator to be constantly attached to the machine during operation. Since it is a type of automatic processing, the processing fluid used is kerosene with various additives added to raise the ignition temperature. Those where the device is attached to each individual machine for the above electrical processing equipment\
There is still a risk of ignition and fire, and for this reason, even though the machine is an automatic processing machine as described above, it is difficult to operate unattended or overnight. The latter processing liquid water has no danger of fire or the like, is extremely inexpensive even if various additives such as rust preventive agents are required, is easy to recycle and dispose of, and is not a hydrocarbon. It has various advantages over hydrocarbon oil-based machining fluids, such as not causing damage to human skin like oils, and in terms of machining performance, for example, the duration of the voltage pulse is a fraction of the time. 10
In the so-called finishing machining condition range where the machined surface roughness is around 10 μm or less and the machined surface roughness is about several 10 μm Rmax or less, it can be fully compared to hydrocarbon oil-based machining fluids. When the machining conditions are close to machining, there are disadvantages such as the machining speed drops dramatically, machining becomes difficult, and electrode consumption increases, making it impossible to perform machining with low electrode consumption. For this reason, the above-mentioned machining liquid water is only used in wire-cut electrical discharge machining (usually numerically controlled) where the machining conditions are limited to the so-called finishing machining condition range that allows electrode wear. In some wire-cut electric discharge machining, the workpiece is machined while being immersed in the machining fluid, but usually the machining process is performed in the upper part of the machining tank or machining fluid in the open atmosphere. If hydrocarbon oil is used as the machining fluid, there is a risk of immediate ignition from the machining part, making machining virtually impossible. It is thought that it is used because it has the advantages and conditions of using water as a machining fluid. and,
Since wire-cut electrical discharge machining using water as the machining fluid has become popular in recent years, water or water, which poses no danger of fire or the like, is also used in the field of electrical discharge machines for drilling and die-sinking. There is a strong desire for the development and appearance of electrical discharge machining (usually referred to as water machining) using a machining fluid mainly composed of Like machines, they are numerically controlled and therefore highly automated, and as they become more expensive, they become even more powerful.

However, for example, in the case where so-called pure water with a resistance of 5 x 103Ω or more is used as the machining fluid (of course, it also includes those to which rust preventives, etc. of around a numerical coefficient or less are added), the machining voltage pulse (or discharge current) <Pulse) width (τ0n or τ0) is approximately 30 to 5
Approximately 0 μs, approximately 30 to 50 μs Rma for machined surface roughness
When the machining conditions are around or above x, that is, the medium machining conditions or higher, the electrode machining area becomes
As it becomes larger like 0C4, the gap resistance during machining becomes lower, so for example, the no-load voltage of the voltage pulse (τOn) may be made exceptionally large, or the discharge current < pulse (τ
0) Emission 1 Exceptionally special machining conditions such as when the electrophoresis amplitude (IP) is made particularly large, i.e. the conventional normal voltage pulse (τ.n) or discharge pulse (τ0),
If it is still necessary, change the body dwell time (τo) between voltage pulses (τon)
ff), or to the extent that they can be modified to a relatively easily possible degree, it is currently impossible to put it into practical use due to the sudden decrease in processing speed and increase in electrode consumption as described above.

By the way, the temperature of the machining fluid in electrical discharge machining is usually around 20 to 25 degrees above the working room temperature. A device and a temperature control device are provided, but in this case as well, the machining fluid is kept at the same temperature, that is, at room temperature, which is about the above-mentioned room temperature, and the temperature of the electrode is also brought to a temperature close to that of the machining fluid due to the cooling effect of the machining fluid. If high-speed rough machining is continued under high load for a long time unless the machining fluid is particularly cooled, the machining fluid in the machining tank may rise to around 50-60°C or more. It may be possible, but it is highly unlikely that high temperature conditions will continue to be processed.

As described above, in conventional electric discharge machining using kerosene or the like as a machining fluid, the machining fluid is either simply cooled to around room temperature or temperature control is not performed. (In the present invention, the electrode temperature, workpiece temperature, or machining fluid temperature refers to a temperature that is several degrees or more higher than the average temperature of the electrode and workpiece, i.e.,
The temperature slightly inside the machining gap exposed surface (machining surface) of the electrode and workpiece, and therefore the temperature of the machining fluid in the processing tank where the electrode or workpiece is installed and where machining is performed, is also about 10~ It refers to a temperature as high as 20° or less. ), we conducted an experiment to determine the electrode consumption ratio under the commonly used discharge pulse conditions of low electrode consumption (for example, the voltage pulse width is approximately 3
It has been found that the electrode temperature at which the electrode consumption ratio is the lowest and/or the optimum temperature of the workpiece vary greatly depending on the electrode material and the composition of the processing fluid in the 0-500 μs)
It was also found that the electrode consumption ratio differed greatly depending on the electrode temperature. The table below shows that when the workpiece is iron and the electrode is copper, graphite, or brass, the machining fluid should be pure water and a surfactant such as silicone oil, alkyl, allyl, or ether should be added to about 1 part. Water containing a numerical coefficient (cloud point approximately 45)
The figure shows the electrode temperature of the large hole at which the electrode consumption ratio is optimal when the temperature is set to (°C).

In addition, in Figure 1, the electrode is copper, the workpiece is iron, and the machining polarity is
The processing liquid used was a mixture of pure water with 1% nonionic polyether-modified silicone oil as a surfactant and 1% spindle oil as a hydrocarbon oil, and the electrode temperature was easily adjusted. An electrical discharge machining method in which the machining gap is machined without being immersed in the machining fluid, which allows control changes to be made and machining can be performed at high electrode temperatures. In an electric machining method in which machining is performed by electric discharge generated by applying intermittent voltage pulses while leaving a pause time between micro-machining intervals in which machining fluid is interposed, A machining method in which machining is performed while continuously or intermittently injecting machining liquid into the machining gap while at least the machining gap is formed and held in the air outside the stored machining liquid. The width of the machining voltage pulse is approximately 120μs, the amplitude of the discharge current is approximately 15A, the width of the voltage pulse is approximately 40μs.
It is variable in front and back, and the amount of machining fluid jetted to the machining interval,
The electrode wear ratio ( Based on these excellent experimental results, the present invention provides an electric discharge machining apparatus equipped with a means for controlling electrode temperature such that the electrode consumption ratio is reduced.

The present invention will be explained below with reference to the embodiments shown in FIGS. 2 to 5. In Fig. 2, 1 has a temperature regulating liquid (
an electrode having a passage 1a through which water (water, etc.) flows; 2 is a workpiece; 3
2 is a mechanical tank containing a workpiece 2, and the tank 3 is filled with a machining liquid 4 made of water containing the above-mentioned surface activator so that it is filled between the electrode 1 and the workpiece 2. It is a container. In this case, since the electrode temperature can be controlled and set as desired, it is different from the processing method for obtaining the processing characteristics shown in FIG. 1 described above, and is a conventional processing method of immersion in a processing liquid. 5 is a circulation path for circulating a temperature regulating liquid to the electrode 1; 6 is a liquid temperature control device provided in the circulation path; 7
8.8' is a liquid circulation pump provided in the circulation path, 8.8' is a liquid temperature sensor provided in the outlet pipe 5a and inlet pipe 5b of the liquid from the electrode 1, and 9 is a liquid circulation pump provided in the electrode 1. This is a control device that commands and controls the electrode temperature of the electrode 1 so that the electrode consumption ratio is small by controlling the temperature or flow rate of the liquid. The liquid temperature control device 6 includes a liquid storage tank 10, a heater 11 that heats the liquid in the storage tank 10, a liquid circulation path 12 for the storage tank 10,
The cooling device includes a pump 13 and a cooler 14 including a motor 14a. The control device 9 indirectly determines the electrode temperature of the electrode 1 from, for example, the difference between the temperature detected by the temperature detector 8 and the temperature detected by the temperature detector 8', and a signal that takes into account the flow rate or flow rate of the liquid. According to the results, the pump 13 and motor 4a are driven, or the operating conditions of the heater 1 and/or cooler 4 are controlled, and the liquid flow rate by the pump 7 is changed to maintain the electrode temperature at a predetermined temperature. Control as follows. As a means for changing the liquid flow rate, there is also a method of providing a flow rate control valve on the discharge side of the pump 7 and adjusting the opening degree of the valve.

By performing such electrode temperature control, it is possible to maintain the electrode temperature of the electrode 1 at a temperature at which the electrode consumption ratio is small (for example, around 40°C in the example shown in Fig. 1). It is possible to obtain an electrode wear ratio close to that obtained when kerosene oil is used as a machining fluid, making it possible to put water-based machining fluids to practical use.

Note that depending on the target temperature of the electrode 1, the liquid temperature control device 6 may include only the heater 1 or only a cooling device including the cooler 4, and instead of heating the entire liquid in the storage tank 10, It may be configured such that only the liquid pumped up from 10 to be supplied to the electrode 1 and the circulation path 5 is supplied while being heated to a predetermined temperature using a heater or the like.

In FIG. 3, the electrode temperature of the electrode 1' is controlled, and the temperature of the machining fluid 4 is also controlled to ensure that the electrode temperature is more accurately and reliably controlled than in the embodiment shown in FIG. This allows it to be maintained at a predetermined value. The structure of the device for controlling the temperature of the working fluid 4 is shown in FIG. 2 and is the same as that of the device for controlling the temperature of the electrode 1. That is,
A circulation path 15 including a machining tank 3, a machining fluid storage tank 20 and a machining fluid circulation pump 17 provided in the middle of the circulation path 15, and a temperature detector 18 that detects the temperature of the machining fluid in the machining fluid tank 3.
, a heater 21 that heats the machining fluid in the machining fluid storage tank 20, a cooler 24 that includes a circulation path 22 that leads the machining fluid in the storage tank 20 to the outside and circulates it, a pump 23, and a motor 24a.
Then, the heater 21 or the pump 23' and the motor are set so that the machining fluid temperature detected by the temperature detector 18 is a predetermined temperature lower than the electrode temperature at which the electrode consumption ratio of the electrode 1' is the lowest. 24a to control the machining fluid temperature or a control device 19 that changes the circulating flow rate by the pump 17. Note that the electrode 1' in this example is solid, and there is a The annular hollow body 16 provides a passage 1a' through which the temperature regulating liquid flows around the electrode 1', and the control of the pump 7 and the liquid temperature control device 6 controls the outlet temperature of the passage 1a'. This is done based on the temperature detected by the detector 8.

If the temperature of the machining fluid is also controlled in this way, the temperature of the machined part of the electrode, which is important for reducing the electrode wear rate, can be maintained under good control, thereby reducing the stain and extreme wear rate. In addition, when controlling the temperature of the machining fluid, it is also possible to provide a heater or a cooling coil for coolant flow in the machining tank 3 to perform temperature control.

Further, when a machining fluid supply hole is provided in the electrode 1' or the workpiece 2 to supply machining fluid to the machining gap, the temperature-controlled machining fluid can be used to control the electrode temperature.

In the embodiment shown in FIG. 3, the circulation path 1 for the machining fluid 4
5 and 20 parts of the processing liquid storage tank, there is a filtration device to remove processing waste from the added liquid, deionization to keep the properties of the processing liquid 4 constant, and various processing liquids used such as addition of organic substances and surfactants. It is clear that the regeneration, adjustment means, etc. corresponding to the above are omitted. , FIG. 4 shows another embodiment of the present invention, in which the temperature of the workpiece 2 is indirectly controlled by heat conduction by controlling the temperature of the processing table 25 on which the workpiece 2 is set. In this embodiment, the temperature of the electrode or the like can be controlled as appropriate, such as to a slightly lower temperature.
A circulation path 29 having a liquid storage tank 27 and a pump 28 is formed in the hole 26; Cooler 3 including pump 32 and motor 33a
3, and a temperature sensor 3 provided at the entrance and exit of the hole 26.
The temperature of the table 25 is kept at a predetermined temperature by controlling the pump 28, the heater 30, and the cooler motor 33a by the control device 35 in accordance with the temperature detected by 4.34'. With this configuration, the temperature of the table 25 is set to a predetermined temperature (the electrode temperature at which the electrode consumption ratio is small, or a slightly higher temperature), and the workpiece temperature is lower than the electrode temperature. ), the temperature of the workpiece 2 can also be controlled by heat conduction, and the electrode temperature can be maintained more stably than when only the temperature of the electrode 1 is controlled. The electrode 1'' in this embodiment is formed by forming a thin metal plate into a predetermined shape, and a pipe 3 forming a liquid passage is provided on the back surface of the electrode 1''.
A low melting point alloy 37 such as solder, which is embedded in 6 and molded into a shape that matches the shape of the back surface, is adhered to the supporting frame 39 through powder or granular material with excellent thermal conductivity or thermally conductive paint 38 . This is advantageous when a plurality of electrodes are used, since the electrode 1'' can be detached from the low melting point alloy 37 if the electrode 1'' wears out. Drawing 5th
The figure is a partial view of an embodiment of the present invention with some changes made to the structure, in which a so-called heat nob 40 made of a high thermal conductor is provided between the electrode 1'' and the temperature regulating liquid to control the liquid. 2nd~
As in the embodiment shown in Figure 4, there is no need to supply and distribute the supply to integral parts such as the inside of the electrodes 1.1' and 1'' and the contact parts, giving flexibility in the configuration. ″ is an electrode formed from stain electrode material by cutting, press molding, electroforming, etc. and reinforced with lining if necessary, and is attached to the electrode mounting plate 42 of the electrode spindle 41 and is attached to the heat pipe 40. The normal heat-absorbing end 40a of the electrode 1'' is brought into close contact with the inner surface of the electrode 1'', and in the illustrated embodiment, one end is covered with a filler 43 such as a low-melting point alloy, corresponding to the sharp portion 1b where the temperature of the electrode t' cannot be avoided. However, in order to maintain and control the required parts of the electrode t' at the electrode temperature, it is sufficient to arrange a predetermined number of them in parallel. Heat dissipation fins 4 as needed.
0c and placed in the circulation path 44 of the temperature regulating liquid supplied from the liquid temperature control device 6), the temperature of the heat absorption end 40a of the heat nozzle 40 can be changed to the heat radiation end 4.
0b is a shearing force that can be cooled to maintain a temperature close to the same, and even if the electrode 1'' is in the form of a thin plate such as an electroformed shell, the electrode temperature can be controlled and maintained at a predetermined temperature. Note that the processing fluid used in the present invention is not limited to water-based fluids, but as can be seen from FIG.
It is most effective in reducing the electrode consumption ratio when used in water-based products. The aqueous processing fluid has a weight percentage of 0.
．． 1 to 10% water-soluble silicone oil or alkyl,
A nonionic surfactant having a relatively low clouding point, preferably around 100°C or less, such as allyl or ether, dissolved in pure water, and a hydrocarbon oil of 0.1
It is effective to add and mix one or both of ~5% or fine particles of metals, alloys, carbon, etc. with a diameter of about 1 to 3 μm or less, or 0.5 to 5 cm, and the processing mode is as follows:
In addition to the conventional machining method in which machining is performed while the machining gap is immersed in the machining liquid 4 as illustrated and explained in FIGS. 2 to 4 above,
As explained above as an experimental example in which the characteristic curve shown in FIG. Controls the supply of machining fluid, the discharge pulse, or the temporal generation of the discharge pulse, etc., so as to maintain a state in which the machining fluid decomposes, burns, vaporizes, etc. and is released from the machining gap to the outside. It is even more useful when applied to a processing method according to the embodiment.

In addition, in the case of the conventional electric machining method using a hydrocarbon oil system such as kerosene, which was explained in detail earlier, and in the case of electric machining under so-called finishing electrical discharge machining conditions using pure water as the machining fluid, There are cases where the electrode temperature at which the electrode wear is lower is lower than that of the conventional one under processing conditions where the electrode wear is lower or the processing accuracy is better, or the processing speed is increased compared to the conventional one. It is also useful when applied to processing.

As described above, according to the present invention, it is possible to control the electrode temperature to the temperature at which the electrode consumption ratio is the lowest. Therefore, when the present invention is applied to electrical machining equipment that uses a water-based machining fluid whose electrode consumption ratio varies greatly depending on the temperature, it is possible to significantly reduce the electrode consumption ratio. It can be used as something that can withstand

Therefore, according to the present invention, for example, electric discharge machining using a numerical control method can be operated unattended all night, and the machining mode is changed so that the electrode is not immersed in the machining fluid, that is, the electrode and the workpiece are immersed in the air. It is also possible to obtain an unprecedented machining speed by maintaining the machining fluid and scattering the decomposed products and machining debris around the machining fluid along with sparks by jetting the machining fluid.

[Brief explanation of the drawing]

FIG. 1 is a correlation diagram of the electrode consumption ratio with respect to the electrode source degree when an aqueous machining fluid is used, and FIGS. 2 to 9 are block diagrams showing embodiments of the present invention. 1, 1', 1//, IJ//...electrode, la,
la'... passage, 2... workpiece, 4... machining fluid,
5...Circulation path, 6...Liquid temperature control device, 7...Pump, 8.8'...Temperature detector, 9...Control device patent applicant Inoue Japax Laboratory Co., Ltd. Agent
Young Patent Attorney 1) Katsu −

Claims (1)

[Claims] 1. Machining by electric discharge generated by applying a voltage pulse with a workpiece set on a processing table and a machining fluid interposed between the workpiece and an electrode. An electric discharge machining apparatus for performing the above-mentioned electrical discharge machining includes: an electrode device in which the electrode is mounted and a passage for a temperature regulating liquid of the electrode is provided; a circulation path for the temperature regulating liquid including the passage; The temperature of the electrode is maintained at a predetermined level by controlling at least one of the temperature and flow rate of the liquid supplied to the passage, a liquid circulation pump, a temperature control device for heating or cooling the liquid, and a temperature control device for heating or cooling the liquid. An electrical discharge machining device characterized by comprising a control device that controls the value so that the value is constant. 2. The electric discharge machining apparatus according to claim 1, further comprising a machining fluid temperature control device that controls the temperature of the machining fluid to a predetermined value. 3. The electric discharge machining apparatus according to claim 1, further comprising a table temperature control device for controlling the temperature of the machining table to a predetermined value. 4. The electrode device has a heat conductor interposed such that one end is in contact with the electrode and the other end is in contact with the liquid in the passageway. The electric discharge machining apparatus according to any one of Item 3.