JP4334310B2 - EDM machine - Google Patents

Description

In the present invention, a pulse voltage is applied between a workpiece and a machining electrode in a state where a minute machining gap between the workpiece and the machining electrode is filled with a machining fluid, so that the workpiece is highly accurate. those concerning the electric discharge machining equipment for performing machining.

  In general, machining conditions in the electric discharge machining apparatus are determined in consideration of physical properties such as volume resistivity and viscosity of a new machining fluid. However, the machining fluid used in electrical discharge machining equipment undergoes thermal degradation and oxidative degradation due to the discharge energy, and generates decomposition products, fatty acids, fatty acid metal salts, etc. Since the characteristics deteriorate, the initially set machining characteristics cannot be obtained.

  Therefore, conventionally, a processing liquid is monitored, and the monitoring result is fed back to processing conditions to obtain desired processing characteristics (for example, Patent Document 1), a method for selecting a processing liquid (for example, Patent Document 2), processing A method for inspecting the quality of the liquid (for example, Patent Document 3) has been proposed.

  That is, Patent Document 1 discloses a method for detecting the volume resistivity of a machining fluid and increasing the output DC voltage of a DC voltage source when detecting that the volume resistivity of the machining fluid has decreased by a predetermined value or more. .

  In Patent Document 2, sulfur-containing hydrocarbons obtained by reacting sulfur with hydrocarbons, sulfur-containing fats and oils obtained by reacting sulfur with fats or oils for the purpose of improving the processing speed of the oil-based electric discharge machining fluid, A method for selecting an oil-based electric discharge machining fluid containing 1 to 20% by weight of at least one alkyl polysulfide is disclosed.

  Moreover, in patent document 3, the electrode for a test | inspection which formed two electrodes at a predetermined distance apart, and was formed integrally, connected one pole of a pulse power supply device to a 3rd electrode via an electric wire, and the other Each of the two branches is connected to the two electrodes via two branch energization wires with the poles passing through the wires, repeatedly supplying intermittent voltage pulses from a power supply device to generate repeated discharge. It is discriminated and detected from which of the two electrodes the discharge has occurred from the value of the current flowing through each of the energization wires, and the discharge generating electrode is changed from one electrode to the other or vice versa. A method is disclosed in which the ratio of the number of occurrences to the total number of discharge occurrences (discharge point dispersion ratio) is determined, and the quality of the inspected machining fluid is determined based on the ratio value.

  For example, in Patent Documents 4 and 5, the discharge pulse state during machining is monitored to determine whether machining is good or bad, the machining power supply is controlled so that a good machining state is obtained, and the stable machining state is deviated. In this case, an electrical discharge machining apparatus having an adaptive control function for returning from the avoidance operation to the return operation when the avoidance operation is performed by taking measures to lower the machining efficiency and recovering to a good state is disclosed.

JP-A-8-174337 Japanese Patent Laid-Open No. 5-138440 Japanese Patent Laid-Open No. 10-15737 Japanese Patent Laid-Open No. 2-212041 Japanese Patent Laid-Open No. 5-116030

  However, in the technique described in Patent Document 1, the discharge current increases when the volume resistivity decreases. Therefore, when the output current voltage is increased, the discharge current further increases, and the work surface quality after processing and surface roughness are reduced. Cause deterioration. When the volume resistivity is lowered, the insulation is not fully recovered, so that a concentrated discharge occurs, and a spot (black dot) or the like is generated on the workpiece. Further, increasing the output current voltage does not improve the concentrated discharge. As a result, there is a problem that the processing characteristics are not improved.

  In addition, in the technique described in Patent Document 2, even if a sulfur compound is added, the physical properties of the processing liquid vary greatly depending on the type and physical properties of the base oil and other components. Therefore, if the base oil is different, the intended processing characteristics can be obtained. I can't. In general, if the machining speed is too high, the finished surface roughness decreases. However, the technique described in Patent Document 2 does not take this point into consideration, so that the machining characteristics considering the finished surface roughness cannot be obtained. There is a problem.

  Further, in the technique described in Patent Document 3, even if there is no decrease in the discharge point dispersion rate, the current density may increase due to the decrease in volume resistivity due to the aging deterioration of the processing liquid, and the processing characteristics may be deteriorated. There is a problem that judgment occurs.

  The present invention has been made in view of the above, and an object thereof is to obtain an electric discharge machining apparatus capable of obtaining desired machining characteristics regardless of the type and degree of deterioration of the machining fluid.

  Another object of the present invention is to provide an electric discharge machining apparatus capable of determining the replacement timing of the machining fluid even when the machining fluid is not deteriorated without the discharge point dispersion.

In order to solve the above-described problems and achieve the above-described object, the present invention provides a work gap between a workpiece and a machining electrode in a state where a minute machining gap between the workpiece and the machining electrode is filled with a machining fluid. In an electrical discharge machining apparatus that applies a pulsed voltage to machine a workpiece, the volume resistivity, which is a physical property of the machining fluid, a capacitance obtained by measurement according to JIS C2101, and a measurement according to JIS K2283 from at least one monitoring the monitoring results of the obtained viscosity and monitoring means for determining the corresponding physical property value, previously determined physical property values were as a physical value corresponding relationship between the monitoring means is determined in the processing speed A means for obtaining a processing speed at the time of monitoring, a means for obtaining a ratio between the obtained processing speed and a processing speed in a working fluid exhibiting good processing characteristics; It means for determining an optimum processing efficiency the reciprocal of the meta ratio is multiplied by the machining efficiency, of the optimum working efficiency becomes as pulse width, dwell time, that a control means for controlling a no-load voltage times Features.

According to the invention, the volume resistivity of machining liquid, the electrostatic capacitance, so that the optimum processing efficiency according to the physical properties of the at least one monitoring the by working fluid of viscosity is obtained, pulse width, holiday stop time, since the allow that you control the no-load voltage times, desired processing characteristics can be obtained irrespective of the kind and degree of degradation of the machining liquid.

  According to the present invention, there is an effect that desired processing characteristics can be obtained regardless of the type and degree of deterioration of the processing liquid.

  Exemplary embodiments of an electric discharge machining apparatus and a machining fluid for an electric discharge machining apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a block diagram showing a configuration of an electric discharge machining apparatus according to an embodiment of the present invention. Here, before explaining the electric discharge machining apparatus shown in FIG. The electric discharge machining apparatus targeted by the present invention is an electric discharge machining apparatus, but the performance required for the electric discharge machining fluid used in the electric discharge machining apparatus includes the following seven points. .

  That is, (1) The viscosity is low and it is easy to discharge processing waste, tar, and the like out of the discharge gap. (2) Excellent insulation. (3) Excellent cooling performance. (4) Low odor and no discomfort to workers. (5) High fire point and boiling point. (6) It is chemically stable and does not generate harmful gases. (7) Do not corrode the processing equipment or workpiece. In consideration of these performances, machining fluids in which an antioxidant or a cooling property improver is added to a low-viscosity hydrocarbon compound or a low-viscosity hydrocarbon compound are generally used in a sculpting electric discharge machine. .

  In general, the processing conditions are set in consideration of the physical properties such as volume resistivity and viscosity of a new processing fluid. However, in the processing fluid, thermal degradation or oxidative degradation occurs due to discharge energy, resulting in degradation products, polymers or fatty acids. Since a fatty acid metal salt or the like is produced, its physical properties change depending on the use time. And the physical property of a processing liquid changes according to use time, and volume resistivity falls. When the volume resistivity is lowered, a discharge occurs in a state where the insulation is not sufficiently recovered, so that a concentrated discharge occurs, and a spot (black spot) or the like is generated on the workpiece. As a result, the machining characteristics are degraded, and the default machining characteristics cannot be obtained. Therefore, it is necessary to take measures to obtain desired machining characteristics regardless of the type and degree of deterioration of the machining fluid.

  2 to 4 show detailed analysis and evaluation of machining fluid properties and machining characteristics (machining speed and finished surface roughness of workpiece after machining) for new and deteriorated sculpted electric discharge machining fluid. The results are shown. In each figure, the mark ◆ is the machining fluid A (new), the mark ■ is a deteriorated product of the machining fluid A (used for 3 years), and the mark ● is the machining fluid B (new). The symbol ▲ is the machining fluid C (new), the symbol X is a deteriorated product of the machining fluid C (used for one year), and the symbol + is the machining fluid D (new).

FIG. 2 shows the relationship between the rough machining speed and the volume resistivity. In FIG. 2, the horizontal axis represents the roughing speed (mm ³ / min), and the vertical axis represents the volume resistivity (Ω · cm). As shown in FIG. 2, it can be seen that the volume resistivity (JISC2101) decreases as the machining fluid deteriorates, but the rough machining speed tends to increase. FIG. 2 shows that when the volume resistivity is reduced from 1.5E + 14 Ω · cm to 1.5E + 13 Ω · cm, the roughing speed is increased by about 1.6 times.

  This means that in the working fluid, thermal degradation and oxidative degradation occur due to discharge energy, and decomposed products, polymers, fatty acids, fatty acid metal salts, etc. and processing waste (metal powder) are generated, so that the volume resistivity decreases. It is thought that it shows. At this time, from the viewpoint of electrical discharge machining, it can be said that since the time until the insulation recovery is shortened due to the improvement of the conductivity, the machining speed is improved by the amount of time until the dielectric breakdown is shortened. It is done.

  FIG. 3 shows the relationship between the finished surface roughness and the volume resistivity. In FIG. 3, the horizontal axis represents the finished surface roughness (μmRy), and the vertical axis represents the volume resistivity (Ω · cm). As shown in FIG. 3, it can be seen that when the volume resistivity (JISC2101) decreases as the working fluid deteriorates, the finished surface roughness tends to deteriorate.

  This is because when the machining fluid is deteriorated and the volume resistivity is lowered, the electric discharge is generated in a state where the insulation is not sufficiently recovered, so that the concentrated discharge occurs and the work surface is stained (black dots). It is considered that the quality is lowered and the surface roughness is lowered.

  FIG. 4 shows the relationship between the finished surface roughness and the capacitance. In FIG. 4, the horizontal axis represents the finished surface roughness (μmRy), and the vertical axis represents the capacitance (pF). As shown in FIG. 4, it can be seen that the finished surface roughness tends to deteriorate as the capacitance (JISC2101) decreases, as with the volume resistivity. FIG. 4 shows that when the capacitance is decreased from 2.068 pF to 1.96 pF, the finished surface roughness is deteriorated from 3.100 μmRy to 4.071 μmRy. This is considered to indicate that when the capacitance decreases, the charge charging time in the machining liquid, that is, the no-load voltage time is shortened, and the finished surface roughness is deteriorated because an arc is easily generated. .

  FIG. 5 shows the relationship between the finished surface roughness and the viscosity. In FIG. 5, the horizontal axis represents the finished surface roughness (μmRy), and the vertical axis represents the viscosity (cSt). As shown in FIG. 5, it can be seen that the finished surface roughness tends to deteriorate as the viscosity (JISK2283) increases. FIG. 5 shows that as the viscosity increases from 1.95 cSt to 2.67 cSt, the finished surface roughness deteriorates from 3.100 μm Ry to 4.071 μm Ry.

  This is considered to indicate that the lower the viscosity, the easier it is to discharge the processing waste, tar, and the like out of the discharge gap, thereby enabling stable discharge and improving the finished surface roughness. Further, it is considered that the roughness of the finished surface deteriorates because the viscosity increases when the low molecular component volatilizes due to the use of the working fluid over time.

  Thus, the influence of the physical properties of the machining fluid on the electrical discharge machining characteristics is great, and the machining speed and the finished surface roughness are affected by the properties of the machining fluid, but from the data shown in FIGS. A machining fluid capable of improving machining characteristics such as machining speed and finished surface roughness can be selected regardless of the combination of additives. That is, the working fluid has physical properties of a volume resistivity of 5.0E + 12 Ω · cm to 1.0E + 15 Ω · cm, a capacitance of 1.9 pF to 2.2 pF, and a viscosity of 1.5 cSt to 3.0 cSt.

  Therefore, if the current machining conditions are used because the current machining conditions cannot be changed, etc., if the machining fluid selected as described above is used, the machining speed and finish surface roughness will be increased regardless of the combination of base oil and additive. It can be seen that the processing characteristics such as the height can be improved.

  Specifically, for example, selection may be made as follows. In other words, when processing is performed with emphasis on the processing speed, a processing liquid having a low volume resistivity (for example, a processing liquid of about 5.02E + 12 Ω · cm) may be used. In addition, when processing with an emphasis on surface roughness is performed, a processing liquid having a high volume resistivity (for example, a processing liquid having a capacity of about 1.0E + 15 Ω · cm) or a processing liquid having a low capacitance (for example, processing of about 1.9 pF). Liquid) or a processing liquid having a high viscosity (for example, a processing liquid of about 2.5 cSt) may be used.

  In the electric discharge machining apparatus according to this embodiment shown in FIG. 1, machining conditions initially set using the data shown in FIGS. 2 to 5 can be changed in accordance with changes in physical properties of the machining fluid, and the machining fluid can be replaced. The time can be reported. First, the configuration of each part will be described with reference to FIG.

  In FIG. 1, a workpiece (workpiece) 1 is placed on a table 2. The processing electrode 4 attached to the main shaft 3 is disposed opposite to the work 1 with a slight gap. The workpiece 1 and the spindle 3 are each connected to a machining power source 5. Although not shown, the space between the workpiece 1 and the machining electrode 4 is filled with the machining liquid 7 stored in the machining liquid storage tank 6.

  A sensor 8 is immersed in the machining liquid 7 in the machining liquid storage tank 6. The sensor 8 only needs to monitor at least one of the volume resistivity, capacitance, and viscosity of the working fluid 7. The sensor 8 can detect at least a range of 5.0E + 12 Ω · cm to 1.0E + 15 Ω · cm in terms of volume resistivity, a range of 1.9 pF to 2.2 pF in terms of capacitance, and 1.5 cSt in terms of viscosity. If the range of 3.0 cSt can be detected, it can be used. A detection signal of the sensor 8 is input to the machining characteristic determination device 9.

  The machining characteristic discriminating apparatus 9 samples the detection signal of the sensor 8 in addition to the function of the conventional apparatus that monitors the machining progress status and notifies the machining condition generating apparatus 10 of whether or not stable machining is being performed. The volume resistivity, capacitance, and viscosity values of the machining liquid 7 that change from moment to moment are obtained, and the values are provided to the machining condition generation apparatus 10 as monitoring information.

The machining condition generation device 10 determines the quality of machining by monitoring the discharge pulse state during machining, and adapts based on the determination result and information on whether or not stable machining is performed from the machining characteristic discrimination device 9. In addition to the functions of the conventional apparatus that performs control, it has a machining condition database (FIG. 6) to be described later, and compares the monitoring information from the machining characteristic discriminating apparatus 9 to determine the time-dependent change state of the machining liquid 7, and accordingly selects the optimum machining conditions from the machining condition database Te, optimum applied voltage to the machining solution 7 based on the selected the optimum processing conditions, pulse width, and time that machining current characteristic (current value and current flows (IP-ON characteristics), and machining conditions such as downtime are generated to control the spindle 3 and the machining power supply 4.

  At this time, in the processing condition generating device 10, when the monitoring information from the processing property discriminating device 9 includes all physical property values of volume resistivity, capacitance, and viscosity, the target processing property is calculated from all the physical property values. In this case, the state of change over time in the machining fluid is determined. In this process, the deterioration state of the machining liquid is determined, and when the replacement time has come, the lamp of the display unit 11 is turned on to notify the replacement time of the machining liquid 7.

  Here, regarding the optimization of the processing conditions, it is necessary to pay attention to the following points from the data shown in FIGS. In other words, since the volume resistivity of the machining fluid varies depending on the type of machining fluid and the degree of degradation of the machining fluid, even if machining is performed under the same machining conditions, the same machining characteristics cannot be obtained if the physical properties of the machining fluid are different. is there. Therefore, in order to obtain the required processing characteristics, it is necessary to change the processing conditions according to the physical properties of the processing liquid.

  For example, in a degraded machining fluid with a reduced volume resistivity, insulation recovery is slower than in a new machining fluid, and thus concentrated discharge occurs. Therefore, in order to obtain machining characteristics equivalent to a new machining fluid, an OFF time (pause time) ) Is required. Similarly, when using a machining fluid with reduced electrostatic capacity or a machining fluid with increased viscosity, measures such as increasing the OFF time are required as one of the methods for obtaining machining characteristics equivalent to that of a new machining fluid. .

  Therefore, in order to be able to determine the processing conditions according to the physical properties of the machining fluid, the processing conditions optimized according to the physical properties of the machining fluid are obtained from the data shown in FIGS. It is set in advance in the condition generation device 10. FIG. 6 is a diagram for explaining a method for creating a machining condition database set in the machining condition generation apparatus 10. In FIG. 6, for example, volume resistivity is taken up as a physical property of the machining fluid, and FIG. 2 is used, and the machining fluid is roughly divided into three categories of classification A, classification B, and classification C by volume resistivity.

From the processing condition database shown in FIG. 6, the working fluid belonging to the class A as the processing properties, such as processing speed is optimal seek processing conditions such as applied voltage. Then, the machining conditions are optimized using the machining fluid belonging to the category A. The same is applied to the classification B and the classification C, and the optimum condition is obtained for each classification. Therefore, the larger the number of classifications, the finer the processing conditions can be set.

  Next, the operation of the electric discharge machining apparatus according to this embodiment will be described with reference to FIG. FIG. 7 is a flowchart for explaining various control operations performed in accordance with the degree of deterioration of the machining fluid.

  In FIG. 7, in step ST <b> 1, the machining condition generation device 10 selects and sets a machining condition according to the physical property of the machining liquid 7 stored in the machining liquid storage tank 6 from the machining condition database. As a result, the machining conditions such as the optimum applied voltage, pulse width, IP-ON characteristics and rest time for the machining fluid 7 are initialized, the spindle 3 and the machining power supply 4 are controlled, and machining of the workpiece 1 is started. Is done.

  In step ST2, when the machining of the workpiece 1 is started, the machining characteristic discriminating device 9 samples the monitor result from the sensor 8, and obtains the volume resistivity, capacitance, and viscosity of the machining liquid 7 that changes from time to time. Monitoring information including this is given to the machining condition generating apparatus 10.

  In step ST <b> 3, the machining condition generation device 10 determines whether or not the time or position that is the machining target has been reached. When the machining target is reached (step ST3: Yes), the machining is terminated as in the conventional electric discharge machining apparatus. On the other hand, if the machining target has not been reached (step ST3: No), whether or not the operator has selected the use of the adaptive control function in order to monitor the machining state and perform control that matches the machining state. Is determined (step ST4).

  If the use of the adaptive control function is not selected (step ST4: No), the machining condition generating apparatus 10 returns to step ST3, but if the use of the adaptive control function is selected (step ST4: Yes). Then, the discharge pulse state during machining is monitored, the quality of machining is judged and adaptive control is performed, and in the process, it is judged whether or not the machining characteristic discriminating device 9 shows a stable machining state (step ST5). .

  Then, when the machining characteristic discriminating device 9 does not indicate a stable machining state (Step ST5: No), the machining condition generation device 10 makes the machining pause time longer than the initial state, and raises the electrode of the spindle 3 One or both of the actions of reducing the down time of the jump control, which is the operation, are taken (step ST6) and waiting for the machining state to recover well, that is, in step ST5, the machining characteristic discriminating apparatus 9 is stable. The process returns to step ST2 after waiting for the processing state (step ST5: Yes).

  The two measures performed in step ST6 are both measures for reducing the machining efficiency. However, in conventional adaptive control (for example, Patent Documents 4 and 5), as described above, the discharge pulse state is monitored and machining is performed. The machining power supply 5 is controlled so that a good machining state can be obtained, and when the machining state deviates from the stable machining state, the avoidance operation is performed, and when the machining state is recovered satisfactorily, the avoidance operation is performed. Control is performed so as to return to the return operation.

  In this embodiment, when the machining characteristic discriminating apparatus 9 shows a stable machining state in step ST5 (step ST5: Yes), that is, when the conventional adaptive control function is operating, the machining condition generation is performed. In the apparatus 10, new adaptive control is performed in which the quality of the machining liquid 7 is determined based on the physical property values obtained by the machining characteristic determination apparatus 9 and the machining condition database. In the process, the process of step ST7 and the process of step ST8 are performed. That is, the conventional adaptive control is performed only by electrical changes in the machining state. In this embodiment, however, adaptive control is performed in consideration of the state quantity in addition to the state of the machining liquid.

The new adaptive control according to this embodiment is performed as follows. That is, the machining condition generation device 10 memorizes the time-varying state of the machining fluid indicated by the physical property value obtained by the machining characteristic discriminating device 9, and the physical property value of the machining fluid changes from the initial value to a preset threshold value. when, or, in accordance with the change of the machining fluid state every moment, with reference to the machining condition database according to physical properties of the working fluid, applied voltage, pulse width, machining current characteristics, machining conditions such as downtime The setting of one of the machining conditions is changed, or the setting of a plurality of machining conditions is changed, and control according to the machining state change from moment to moment is performed.

  In step ST7, it is determined whether or not the replacement time should be notified by turning on the lamp of the display unit 11. When the lamp of the display unit 11 is turned on (step ST7: Yes), the processing operation is performed from step ST2 after waiting for replacement of the machining liquid. The determination in step ST7 can be performed, for example, by the following two methods.

  That is, (1) the machining condition generation device 10 requires a time-dependent change state of the machining liquid 7 obtained from the values of volume resistivity, capacitance, and viscosity indicated by the monitoring information from the machining characteristic discrimination device 9 and a machining condition database. The lamp of the display unit 11 is turned on if it does not fall within the standard compared with the standard at which the machining characteristics to be obtained cannot be obtained (step ST7: Yes).

(2) Further, the machining condition generation apparatus 10 has data of machining fluid with good machining characteristics obtained in advance with the volume resistivity, capacitance and viscosity as evaluation items for the machining fluid 7 being used. The Mahalanobis distance from the group (processing condition database) is obtained, and if the Mahalanobis distance becomes worse than the reference value, the lamp of the display unit 11 is turned on (step ST7: Yes). Note that the Mahalanobis distance is a distance that takes into account the variation between the variables and the correlation between the variables, and the Mahalanobis distance of the data Xi is the variable X with an average m and a standard deviation σ, assuming that there is one variable. (Xi−m) ² / σ ² .

  Next, if it is determined in step ST7 that the working fluid 7 has deteriorated but it is not time for replacement (step ST7: No), the processing pause time is made shorter than the initial state, contrary to the processing in step 6. In addition, one or both of the measures for increasing the down time of the jump control, which is the electrode pulling operation of the main shaft 3, are taken (step ST8), and the process returns to step ST2.

  The contents of the measures in step ST8 will be specifically described. That is, when the machining fluid 7 is deteriorated but not replaced (step ST7: No), the machining condition generation device 10 first determines the machining speed based on the relationship between the volume resistivity and the machining speed corresponding to FIG. Obtain the rate of increase and calculate the ratio to the machining speed of the machining fluid in the new oil state. There is no problem even if this ratio is considered to be a difference in processing efficiency, so the OFF setting (resting time) is increased by a ratio.

For example, in FIG. 2, the machining fluid A is processed from the state of the new oil indicated by ♦, and the machining condition determination device 9 is the same as the deteriorated product in which the machining fluid A is indicated by the ■ mark from the detection signal of the sensor 8. Assume that a physical property value is output. At this time, looking at the relationship between the volume resistivity and the processing speed, the processing fluid A of the new oil deteriorated while the volume resistivity was 1.08E + 13 Ω · cm and the processing speed was 14 mm ³ / min. In the machining fluid A, the volume resistivity is 2.0E + 12 Ω · cm, and the machining speed is 19 mm ³ / min. Therefore, the machining speed improvement rate is 1.36.

In this case, there is a possibility that the processing efficiency is excessively improved at the processing speed of the deteriorated product with the processing liquid A. When this is improved by the operation of the downtime, the downtime of the deteriorated product in the working fluid A may be set so as to reduce the processing efficiency in the equation (1) for calculating the processing efficiency.

と計算して得られた休止時間を加工条件に用いればよいことになる。 In this example, the processing efficiency may be calculated to be 74% of the initial setting so that the processing speed is reduced from 19 mm ³ / min to 14 mm ³ / min.

It is sufficient to use the downtime obtained by calculating as the machining conditions.

  In other words, as described above, the decrease in volume resistivity means that degradation products, polymers, fatty acids, fatty acid metal salts, etc. generated by processing liquids that have caused thermal degradation or oxidative degradation have contaminated the processing gap. Think the same. In this case, if it is only necessary to perform a pause operation in the same manner as when dealing with a large amount of machining waste, the processing characteristics are improved by adopting the ratio of the processing speed of new oil and deteriorated oil as the pause operation amount. Conceivable.

Table 1 shows the results of processing with a processing fluid in a new oil state and a processing fluid that deteriorates and has a reduced volume resistivity.

  As shown in Table 1, in the machining fluid having a reduced volume resistivity, the machining speed was improved, but the machining surface quality was deteriorated. Therefore, when the machining time was changed so that the machining speed was lowered to the machining speed with the new oil state machining fluid, the machining speed was slightly reduced, but it was possible to prevent degradation of the machined surface quality.

As described above, according to this embodiment, the volume resistivity of machining liquid, the capacitance, at least one monitoring and applied voltage in accordance with the physical properties of the working fluid of the viscosity, the pulse width, IP- By controlling the processing conditions such as the ON characteristics and downtime, it is possible to perform processing under the processing conditions that can obtain the optimal processing characteristics , so that the best processing characteristics can always be obtained regardless of the type and degree of deterioration of the processing liquid. Can do.

  Further, a machining fluid for an electric discharge machining apparatus having a volume resistivity of 5.0E + 12Ω · cm to 1.0E + 15Ω · cm, a capacitance of 1.9 pF to 2.2 pF, and a viscosity of 1.5 cSt to 3.0 cSt. Because it is used, high-speed and high-precision processing can be realized even if the type and physical properties of the base oil and other components change. Further, when the current machining conditions cannot be changed, the machining fluid can be changed to an optimum one, so that machining characteristics can be improved.

  In addition, the time for exchanging the machining fluid is the time-dependent state of the machining fluid obtained by monitoring at least one of the volume resistivity, capacitance, and viscosity of the machining fluid, or the volume resistivity, capacitance of the machining fluid. The dispersion of discharge points is determined by comparing the processing fluid aging state in the target processing characteristics obtained from all the viscosity monitoring results and the processing liquid data group having good processing characteristics obtained in advance. Even when the machining fluid is not deteriorated, it is possible to correctly determine the replacement time, and to correctly notify the replacement time.

  In addition, the time for exchanging the machining fluid is the time-dependent state of the machining fluid obtained by monitoring at least one of the volume resistivity, capacitance, and viscosity of the machining fluid, or the volume resistivity, capacitance of the machining fluid. , Adaptive control method according to the processing state by comparing the processing fluid aging state in the target processing characteristics obtained from all the viscosity monitoring results and the processing fluid data group with good processing characteristics obtained in advance Therefore, it is possible to prevent excessive processing conditions from being added when the processing liquid is deteriorated and insulation is easily recovered.

  In addition, a database in which processing conditions optimized according to at least one physical property value among the volume resistivity, capacitance, and viscosity of the processing liquid based on a data group of processing liquids that show good processing characteristics prepared in advance are set. Therefore, it is possible to always obtain the best machining characteristics regardless of the type and degree of deterioration of the machining liquid simply by selecting the machining conditions according to the machining liquid.

  As described above, the electric discharge machining apparatus according to the present invention is suitable for diagnosing a machining fluid and improving machining characteristics in the die-sinking electric discharge machining apparatus. Moreover, the machining fluid for an electrical discharge machining apparatus according to the present invention is suitable for improving the machining speed and the finished surface roughness regardless of the combination of the base oil and the additive.

It is a block diagram which shows the structure of the electric discharge machining apparatus which is one embodiment of this invention. It is a characteristic view which shows the relationship between rough machining speed and volume resistivity. It is a characteristic view which shows the relationship between finished surface roughness and volume resistivity. It is a characteristic view which shows the relationship between finishing surface roughness and an electrostatic capacitance. It is a characteristic view which shows the relationship between finished surface roughness and a viscosity. It is a figure explaining the processing condition database creation method set to the processing condition production | generation apparatus shown in FIG. It is a flowchart explaining the various control operation | movement performed according to the deterioration degree of a working fluid in the electric discharge machining apparatus shown in FIG.

Explanation of symbols

1 Workpiece (work)
2 table 3 spindle 4 machining electrode 5 machining power supply 6 machining fluid storage tank 7 machining fluid 8 sensor 9 machining fluid characteristic judging device 10 machining condition generating device 11 display unit

Claims (7)

In an electric discharge machining apparatus for machining a workpiece by applying a pulse voltage between the workpiece and the machining electrode in a state where a minute machining gap between the workpiece and the machining electrode is filled with a machining fluid. ,
The volume resistivity is a property of the working fluid, the capacitance was determined by measuring in accordance with the provisions of JISC2101, monitoring at least one of the viscosity was determined by measuring in accordance with the provisions of JISK2283 properties corresponding from the monitoring results Monitoring means for determining the value;
Means for determining the processing speed at the time of monitoring, from the correspondence between the physical property value determined in advance and the processing speed and the physical property value determined by the monitoring means ;
Means for determining a ratio between the calculated processing speed and a processing speed with a processing liquid exhibiting good processing characteristics;
Means for multiplying the machining efficiency by the reciprocal of the obtained ratio to obtain the optimum machining efficiency;
Control means for controlling the pulse width, rest time, and no-load voltage time so as to obtain the optimum machining efficiency obtained above ;
An electrical discharge machining apparatus comprising: The processing efficiency controlled by the control means uses the pulse width, the pause time, and the no-load voltage time,
Processing efficiency = (pulse width) / {(pulse width) + (pause time) + (no load voltage time)}
Electric discharge machining apparatus according to claim 1, characterized by being represented as. The control means includes
A function for notifying the time for replacement of the working fluid based on a comparison between the physical property value obtained by the monitoring means and the physical property value of the working fluid showing good working characteristics obtained in advance;
The electric discharge machining apparatus according to claim 1, further comprising: The control means includes
The time-varying state of the working fluid indicated by the physical property value obtained by the monitoring means is stored every moment, and the ratio between the physical property value obtained by the monitoring means and the physical property value of the working liquid showing good working characteristics obtained in advance is When it changes to a preset threshold value, change the setting of one of the machining conditions such as applied voltage, pulse width, machining current characteristics, pause time, etc., or change the settings of multiple machining conditions , Function to perform adaptive control according to the machining state change every moment,
The electric discharge machining apparatus according to claim 1, wherein the electric discharge machining apparatus is provided. The control means includes
When the monitoring means obtains all physical property values of volume resistivity, electrostatic capacity, and viscosity, the time-dependent change state of the machining fluid in the intended machining characteristics is determined from all the physical property values. The electric discharge machining apparatus according to any one of 1 to 4 . The control means includes
A database in which processing conditions optimized according to at least one physical property value among the volume resistivity, capacitance, and viscosity of the processing liquid based on the data group of the processing liquid showing good processing characteristics prepared in advance,
The electrical discharge machining apparatus according to claim 1, wherein the electrical discharge machining apparatus is provided. The monitoring means includes
A function of measuring at least one of the volume resistivity, capacitance, and viscosity, which are physical properties of the machining fluid, to obtain a physical property value change every moment;
Electric discharge machining apparatus according to any one of claims 1-6, characterized in that it comprises a.

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