JPH01246016A - Machining control method utilizing arc discharge in electrolytic solution - Google Patents

Abstract

PURPOSE:To enable a good machining condition to be always maintained by constituting so that the near infrared rays generated during machining are detected for carrying out feedback, and that the output of a machining power supply is subjected to pulse- width control for maintaining the machining power supply output in a proper machining condition. CONSTITUTION:In the inside of a machining vessel 1 in which an electrolytic solution 2 is filled, a tool electrode 4 is arranged so as to be opposite to a workpiece 3, and also an auxiliary electrode 5 is arranged to carry out machining by means of arc discharge in the electrolytic solution. And the near infrared rays generated during machining is detected by a near infrared ray detecting device 6 for carrying out feedback thereof, and by subjecting the output of the machining power supply to pulse- width control, the machining power supply output is maintained in a proper machining condition. In this manner, by such a simple means that the output of a machining power supply is subjected to pulse-width control, the transfer from electrolysis to electric discharge can be ensured, and further the temperature rise of the tool electrode 4 in a high temperature is restricted, so that a proper machining condition can be maintained over a long period of time. As a result, machining efficiency can be remarkably improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a machining control method for electrical machining of ceramics, intermetallic compounds, and other difficult-to-machine materials using arc discharge in an electrolytic solution. It is related to.

[Prior Art] The present inventor previously published Japanese Patent Application No. 2-63371 titled "Method for Processing Non-Conductive Materials by Arc Discharge in Electrolyte"
is proposed. This processing method has already been proposed.

Non-conductive materials are processed using electrical discharge in an electrolytic cell, using a neutral salt electrolyte, and machining conditions are set so that the IA electrode placed opposite the workpiece does not melt in this electrolyte. , machining is performed by arc-shaped discharge in an electrolytic solution.

7III processing efficiency when processing using the above method.

It has been experimentally found that machining conditions are favorable in that the tool electrode is set and maintained at a relatively high temperature (400 to 800°C). However, this process is inherently unstable. For example, if the discharge current increases due to changes in external conditions, this will cause the °C discharge to become more intense and the temperature of the tool electrode to rise rapidly. This temperature rise also increases the discharge current, which causes the temperature of the tool electrode to rise, resulting in a vicious cycle that eventually leads to melting of the tool a'tam. On the other hand, if the addition conditions are set on the safe side, the temperature of the 1-liter electrode will not deviate much from L, and the addition efficiency will decrease.

Also, even if we set the temporally optimal addition condition,
As time passes, it becomes impossible to maintain this state due to changes in the temperature of the electrolytic solution, etc., so it is necessary to always consider returning the processing conditions to the optimal state.

Therefore, in order to deal with the above-mentioned problem of temperature increase, we tried using tungsten, silver-tungsten alloy, conductive ceramics, etc., which have excellent heat resistance, as tool electrode materials, but even these materials became red hot and melted. It didn't solve this problem.

Other methods for solving the problem include a method of suppressing the temperature rise by intermittent discharge with a period of discharge weight (see the example of the above-mentioned Japanese Patent Application No. 62-63371), or a method of suppressing the temperature rise by the presence of a rest period. This increases the time loss and does not essentially improve the instability of the discharge, so it is necessary to set conditions on the safe side, which is disadvantageous in terms of machining efficiency.

On the other hand, is it possible to consider methods such as limiting the current of the machining power supply, or should protection circuits such as constant voltage and constant current be used effectively due to the following specific requirements for the machining power supply for this machining method? Can not.

In other words, when an electric discharge occurs in an electrolytic solution, a large electrolytic current first flows, and the entire surface of the tool electrode is covered with gas generated by the electrolysis, which causes the transition to an electric discharge, or the luminescence phenomenon caused by the electric discharge and the machining current waveform. This has been revealed through research such as comparisons between Even when re-igniting when the discharge stops during machining,
The tool electrode material may need to be covered with a gas layer due to gas generated by electrolysis or water vapor generated by heat.

Therefore, if the set current value of the protection circuit is determined based on the current during discharge, the electrolytic current will be limited and will not reach the point where the tool electrode material is covered with a gas layer, making it impossible to proceed to discharge. On the other hand, if the set current value is adjusted to the peak value of the electrolytic current, it is impossible to limit a discharge current that is much smaller than that value, making it difficult to suppress the temperature rise of the tool electrode.

[I prefer to invent or solve the problem.] Il! Problem] Does machining using arc discharge in an electrolytic solution have the above-mentioned problems?The present inventor discovered that while researching the optical information generated during machining, It was discovered that the optical output in the near-infrared region, which can be easily detected in other methods, is an important parameter that represents the state of this processing. If the light output is too small, the machining efficiency will be poor, and on the other hand, if it is too large, the temperature of the tool electrode will tend to rise excessively.

Therefore, it is thought that if this optical output is fed back to control the output of the processing power source, a good processing state can be maintained.

The technical problems of the present invention are 1. Based on the above-mentioned knowledge, it is an object of the present invention to provide a machining control method that can always maintain a good machining state by controlling the output of a machining power source using near-infrared light output generated during machining.

[Means for Solving the Problems 1 Effect] In order to solve the problem 2, the machining control method according to the present invention is characterized in that the machining control method according to the present invention controls the machining by arc discharge of one electrode placed opposite to the workpiece in an electrolytic solution. In the method of processing objects, by detecting near-infrared rays generated during processing and feeding it back to control the pulse width of the output of the processing power source, the output of the processing power source can be maintained at an appropriate level. It is characterized by:

The present invention will be explained in more detail with reference to an example of the processing apparatus shown in FIG. In the tank 1 filled with the liquid 2, the workpiece 3 is provided with a tooling pole 4 facing the workpiece 3, and
An auxiliary electrode 5 made of an insoluble material such as a platinum plate is placed in the electrolyte, and in this state machining is performed by arc discharge in the electrolyte. As the machining of the workpiece 3 progresses, the tool electrode 4 receives the necessary feed.

The above machining can be efficiently performed under machining conditions in which the tool '', ii: 8i4 is in a relatively high temperature state. At that time, near-infrared rays are generated at the arc discharge part. This near-infrared rays are
It is detected and amplified by a near-infrared detector 6 equipped with an amplifier inside, and its output is input to an amplifier 7.

The amplifier 7 includes a reference voltage generator 8 and a sensitivity adjuster 9 for setting the feedback voltage level. The reference voltage generator 8 normally generates a DC voltage of opposite polarity to the output of the near-infrared detector 6, and by adjusting this voltage, a target value of the near-infrared intensity generated during processing can be set. Ru.

If the near-infrared intensity is set to be small, the efficiency will be increased, the wear rate of the tool electrode will be reduced, and the shape of the machined shape will be improved. On the other hand, if the near-infrared intensity is set to be large, the weighting efficiency will improve, or the IA main electrode will be more worn out, resulting in poor machined shape. In this way, by adjusting the voltage of the reference voltage generator 8, the machining situation can be selected. The sensitivity m@detector 9 is used to adjust the amplification degree of the amplifier 7 to perform appropriate IE feedback operation.7 The near-infrared detector 6 is L+ [equipped with a visible light cut filter]. Easy to use.

It is considered to be optimal in terms of spectral sensitivity characteristics and operating speed.

Is it possible to install this above the processing tank L and use a condensing lens to focus the light?If there is a risk that the light may be blocked due to operation of the processing machine, etc., place the cone tool' from the vicinity of pole 4. Detect C near-infrared rays using optical fiber! 16
It is also possible to use a method that leads to

As mentioned above, when a discharge occurs in an electrolytic solution, a large electrolytic current first flows, and the entire surface of the Gyokurou electrode is covered with the gas generated by electrolysis, which causes a transition to a discharge, but the electrolytic current and the discharge current Since the difference in output is large (one order of magnitude or more), controlling the output by controlling the resistance value of ordinary transistors is not practical, as it involves a large power loss and requires large-capacity transistors, heat sinks, etc. . For this reason, it adds 1? It uses a pulse width modulation method that allows the output of the source to be controlled.

That is, the FET power transistor 11 connected to the amplifier 7 via the comparator 12 is connected to a DC power source 13 that flows '7t& for machining between the tool electrode 4 and the auxiliary electrode 5, and is connected to a DC power source 13 that supplies a current of '7t& for machining between the tool electrode 4 and the auxiliary electrode 5. It repeats off, but the on time is determined by the comparator 12.6 The comparator 12 is connected to the output voltage of the triangular wave generator 14 and
! The output voltages of 17 are compared, and when the latter is smaller than the former, a positive voltage is output, and the F E 1' power transistor 11 is turned on for that time. The comparator 12, triangular wave generator 14, and FET power transistor +1 thus perform a so-called pulse width modulation operation.

FIG. 2 shows the machining voltage (voltage between the tool electrode 4 and the auxiliary electrode 5) when machining is performed using the apparatus shown in FIG. Detector 6 (silicon photodiode, sensitivity wavelength range 700-114
0 nm) is shown as an example of the output voltage waveform (displayed as 'F force direction increasing direction). The detector output is above a certain level (
In this case, when the voltage reaches about 7 mV, it can be seen that the machining voltage is low and the output is restricted. Note that the regular fluctuation in the IO+ms period observed in the machining voltage is due to the residual voltage of the DC power supply 13. Is it necessary to make the heating period of the triangular wave generated by the triangular wave generator 314 sufficiently small compared to the change in the output of the amplifier 7?Here, it was set to 30 LS.

According to the processing equipment described above, near-infrared rays generated during processing are detected, and this is fed back to control the pulse width of the output of the processing power source to maintain the processing output at appropriate processing conditions. I have something to do. Thereby,
It is important to ensure that discharge occurs and to limit the temperature rise of the hot tool electrode.

As mentioned above, the method of the present invention can be effectively used not only for machining ceramics, etc., but also for other machining methods that involve the generation of arc discharge in an electrolytic solution, such as electrolytic discharge machining of metals. This is clear from the explanation of the operating principle.

[Example 1] Processing was carried out in the same manner as in the case of Fig. 2 using the processing apparatus shown in Fig. 1 under the following conditions.

Experimental conditions Clove crops: Si, N.

1- Tool'ilt pole: Outer diameter 3.2-Copper inner diameter 1.6m-Copper vibe auxiliary electrode: Platinum plate 12hmX 50m11 Electrolyte
: Specific gravity: 1.20 ~ a N IJ, I aqueous solution Average processing current: 2 ~ 3 A As a result, the conventional method required 15 minutes and depth of about 1 to 2 mm inside the shell, but Despite the small number of attempts, it was improved to 1.8mm.

[χExample 2] The experimental conditions were: ``Gently circulating the electrolyte (exile 140c)
This is the same as in Example 1, except that it was made (m'/win).

The reference voltage generator 8 was set with priority given to improving the tool electrode wear ratio compared to the case of Example 1, and machining was performed for a long time. As a result, the machining depth was 1.9 @ s for 460 minutes of machining time, and the machining ft rate was inferior to Example 1, and the tool electrode consumption was 0:1 m + *.
This was about 1/10 of the 3.2 mwr in Example 1. It was difficult to perform stable machining for a long time using conventional methods, but it has become much easier with this method.

[Example 3] The applied voltage was increased from that in Example 2 to 192 V (160 V in Example 2), and the settings of the reference voltage generator 8 were changed in two ways, each applying for 15 minutes. [An experiment was conducted. As a result, the tool electrode was expended at a machining depth of 1.44 m5, and the tool electrode was expended at a machining depth of 1.90 mm. I got a result of U m+s.

In this case, if the trial was left without feedback, the tool electrode melted in 10 seconds. Note that a germanium photodiode (sensitivity wavelength range: 700 to 1900 ns) was used as the near-infrared detector in this case.

[Effects of the Invention] The control method of the present invention detects near-infrared rays generated during machining to control the pulse width of the output of the machining power source. In addition to ensuring the transition of the temperature, it is possible to limit the temperature rise of the high-temperature L-shaped electrode and maintain the processing conditions at 111LFE for a long time.As a result,
Machining efficiency is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a processing apparatus for implementing the method of the present invention, and FIG. 2 is a graph showing an example of waveforms of processing voltage and output voltage of a near-infrared detector. ■...Processing tank, 2...Electrolyte, 3...L crops,
4... ■Instrument electrode 25 - Auxiliary electrode, 6... Near infrared detector, 7... Amplifier, 8... Reference voltage generator, 9... Sensitivity adjuster, 11... FET power transistor, 12... Comparator, 13... DC power supply, 14... Square wave generator.

Claims (1)

[Claims] 1. In a method of machining a workpiece by arc discharge of a tool electrode placed opposite to the workpiece in an electrolytic solution, near-infrared rays generated during machining are detected and fed back to output the machining power source. A control method for machining using arc discharge in an electrolytic solution, characterized by maintaining the machining power output at appropriate machining conditions by controlling the pulse width.