JPS6128449B2 - - Google Patents

Description

[Detailed description of the invention] The present invention is carried out in electric discharge machining (including electrolytic erosion machining) in which machining is performed by repeatedly applying electric discharge using machining pulses to the machining gap where an electrode and a workpiece face each other. The purpose of this invention is to accurately detect and determine whether the state of discharge is good or bad, that is, change in the state of the machining gap, and whether it is good or bad, and further to optimally control the machining state.

In electrical discharge machining, machining pulses are controlled according to the gap state (discharge state), flow rate of machining fluid, control of electrical conductivity, electrode vibration when machining debris accumulates, cleaning work by pulling up the electrode, and gap length. It is necessary to optimally perform servo control, etc. to follow the machining. Conventionally, in order to detect the state of the machining gap, the discharge state, the quality of the discharge, etc., the voltage, current, impedance, etc. of the gap to which the machining pulse is applied have been detected and determined. There are two types of signal detection: one detects average voltage and current, and the other detects pulses that are repeatedly supplied and changes in voltage and current caused by each pulse. The former method of detecting average signals does not allow for quick state determination and quick response control. In the latter case, since pulses are digitally detected and discriminated, it is possible to respond quickly to changes, thereby increasing the machining effect. In addition, the machining pulse is set and controlled to the optimal conditions according to the target machining, and detection using this machining pulse, the state of the machining gap when the machining pulse is applied, and the discharge state are detected as voltage and current changes as signals. However, even if it is determined, it cannot be accurately determined. That is, unless changes in the applied machining pulses are also added to the signal, accurate discrimination cannot actually be made.

Therefore, the present invention aims to set a sufficient voltage and pulse width to generate electric discharge in the normal machining gap, and to set the peak value (
p), pulse width (τ~n), waveform, etc. are selected and set to a constant value, and the inspection pulse is incorporated into the machining pulse train and supplied to the machining gap. The feature is that the state is inspected, detected and determined.

As shown in Figure 1, the inspection pulse has a set wave height (p), pulse width (τon), or waveform that is different from the processing pulse, and is assembled into the processing pulse train. and feed it into the machining gap. The inspection pulses are incorporated into the machining pulse train at least in such a ratio that the number of inspection pulses is smaller than the number of machining pulses, and is supplied to the machining gap. Then, whether or not a discharge occurs due to this test pulse, and signals such as voltage and current when the discharge occurs are detected and determined.

(b) The figure shows a rectangular wave inspection pulse, and the wave height value is smaller than that of the processing pulse.

(b) The figure shows that the pulse width of the inspection pulse is longer than the processing pulse; of course, the pulse width of the inspection pulse may be shorter than that of the processing pulse.

(c) In the figure, one, two, or three test pulses are generated and supplied in succession, and various ways of supplying the test pulses can be considered. In either case, the number of inspection pulses is incorporated and supplied at a smaller ratio than the number of processing pulses.

In this way, the voltage and pulse width of the inspection pulse are set to a constant reference value that is sufficient to generate electric discharge in the machining gap. In the case of machining, the test pulse only needs to generate electric discharge in the machining gap to perform the test, so the voltage is set lower than the machining pulse as shown in the figure, and the test is performed with the set constant voltage and pulse width. Also, as shown in figure 2, when the voltage of the machining pulse is low, for example, for finishing machining (of course, the pulse width will be shorter in the case of finishing machining. The horizontal axis dimensions of figure 2 and figure 2 are different), the machining Since the voltage and pulse width of the pulse are small, the pulse width of the inspection pulse is set to be larger than the machining pulse, and is set to ensure that discharge occurs and inspection errors are eliminated.
In this way, the inspection pulse is independent of the processing pulse.
By setting the voltage and pulse width to constant reference values, it is possible to inspect everything from rough machining to finishing machining using constant pulses. Further, by inspecting using a constant set pulse, stable and accurate inspection can be performed even in the case of machining where the machining pulse is controlled to change. Since the test pulse is constant in determining the detection signal, the determination can be performed using a constant reference value and accurate determination can be performed at all times. In addition, as shown in Figure C, when the inspection pulses are generated while controlling one or more inspection pulses, generating multiple inspection pulses in succession eliminates inspection errors and also reduces the tendency of machining gaps to change. etc. can be known.

In addition, for the inspection pulse, one of the voltage and the pulse width can be set to a constant reference value, and the other can be changed according to the processing conditions. For example, when switching the machining pulse from a rough machining condition with a large pulse width to a finishing condition with a small pulse width, if the pulse width of the inspection pulse is set to a constant value that is optimal for inspection and the voltage remains unchanged, the machined surface will deteriorate due to the inspection pulse. In such cases, by lowering the voltage of the inspection pulse and reducing the peak value (p), the finished surface can be maintained and inspected.

Further, it is necessary to apply the inspection pulse when there is no processing pulse, during a pause, or after stopping the processing pulse.

An embodiment will be explained below with reference to the drawings. In FIG. 2, reference numerals 1 and 2 represent an electrode and a workpiece, which face each other and form a machining gap. 3 is a voltage source that supplies processing power, 4 is a switch element such as a transistor,
It is connected in series with the voltage source 3 and connected to the machining gap, and generates and supplies machining pulses by switching it on and off. 5 is a pulser that generates and applies switch control pulses to switch 4. Although an independent oscillator may be used in some cases, it is also a dependent oscillator whose pulse width, pause width, frequency, etc. change in response to detection signals such as voltage and current in the machining gap. is sometimes used. Further, a conversion circuit that converts the gap detection signal into a pulse may be used. The above-mentioned components 3, 4, 5, etc. form a processing pulse power source. 6 is a voltage source for testing, and 7 is a switch, which is turned on and off under the control of a pulser 8 to generate testing pulses.

The inspection pulse has sufficient voltage and pulse width to generate an electric discharge in the normal machining gap, and the peak value and pulse width of the electric discharge are set constant so that the inspection for detection and discrimination is easy and accurate. That is, the peak value (p) is selectively set by the voltage of the power source 6, and the pulse width (τon) is selectively set by the pulser 8. Peak value (p ⁺ is less than 200A, preferably around 10A,
or less, and pulse width (τon) 5 to 20μ
It is set to about s. The voltage and pulse width of the inspection pulse are set to constant reference values, but when the voltage or pulse width is set constant and the other is switched, the processing characteristics are controlled to be approximately equal to the processing conditions, if necessary. For example, the machined surface roughness is Ra≒K
For example, the machining pulse is expressed as τp.
When on3μs.p10A, the test pulse is τ
It is like setting on10μs.p44~5A. The waveform is normally a rectangular wave pulse, but by controlling the pulser 8, a triangular wave or other arbitrary waveform pulses can be generated. 9 is an AND gate circuit that incorporates the inspection pulse into the processing pulse train, and the output pulse of the pulser 5 and
The inspection pulse is incorporated into the machining pulse train by AND-combining the output pulse of the pulser 8, and the output pulse of the pulser 8 is inverted and combined with the not gate 10. During the pause of the machining pulse, or when the machining pulse is interrupted and paused, the inspection pulse is incorporated so as to be applied to the machining gap, and the state of the machining gap is determined while the machining pulse is not applied. 11 is a resistor for detecting the gap voltage signal; 12
is a detection signal discriminator which is controlled by the pulser 8 and operates to perform accurate inspection by discriminating the detection signal synchronously when a test pulse is applied to the gap.

The state of the machining gap is inspected by applying a test pulse of a predetermined size, detecting the gap voltage, and determining the detection signal, so the applied test pulse is always constant; The accuracy of detection and discrimination is extremely high because it detects and discriminates signals that change in response to the presence or absence of discharge and changes in the gap state when discharge occurs.Moreover, the test pulse has a peak value (p), a pulse width ( τon) is easy to test and is set to an optimal value for the test, which also facilitates the test and improves the test accuracy.

In addition, the inspection pulse is generated by an independent oscillation pulser 8 at predetermined time intervals, and in relation to the processing pulser 5, for example, the oscillation output of the pulser 5 is frequency-divided, and the inspection is performed every time how many processing pulses are generated. one pulse for
Or, generate a plurality of pulses, or control the pulser 8 according to the machining state of the gap,
The generated pulses are generated at time intervals according to the machining state, but the generated pulse is not limited to one pulse, and multiple pulses may be generated and supplied in succession.The generation interval and number of pulses of this inspection pulse are determined by the selection settings of the pulser 8. It can be generated arbitrarily, and the settings are controlled so that optimal inspection can be performed at all times. In normal electric discharge machining, it is preferable to generate test pulses by adding about 1 to 10 test pulses per second. Note that by setting the pulser 8 to oscillate at a lower frequency than the oscillation frequency of the processing pulser 5, the inspection pulse can be generated at a smaller rate than the processing pulse.

In addition, the signal detected from the machining gap by applying this inspection pulse may be voltage, current, impedance, or a temporal change thereof, or a generated high frequency, etc., and can be detected not only during the continuation of the inspection pulse but also at a certain period of the inspection pulse. It is also possible to check the signal immediately after the test pulse stops, such as voltage, current, resistance, impedance, or the vibration state of these, or to detect a change state, and the detection circuit is configured as appropriate, can be used. The detected signal can be determined by its size, smallness, level, or presence or absence.
In addition, by compound discrimination, for example, the detected and discriminated outputs are counted by a counter, preset counter, up-down counter, etc., and a plurality of them are collected and discriminated as a group, and when the preset counter etc. counts to the preset number, a discrimination calculation signal is output. The quality of the discharge state and the machining state are determined, the transition of the machining state, the overall trend, etc. are determined, and control is performed in accordance with the determination results. In this way, the detection/judgment, aggregation, and arithmetic processing are performed to determine the distribution of pass/fail in aggregation and to judge the whole. Also, 10
A test pulse with a pulse width of approximately μs is applied to cause a discharge, and a high frequency component of approximately 3 to 30 MHz contained in the discharge column is detected and contained approximately 3 to 5 μs after the discharge occurs. If the value is not included, it is determined to be good; if it is not included or below a certain level, it is determined to be defective.

In addition, detection judgment is performed by inputting a test pulse, that is,
The magnitude, number, waveform, etc. of the signal detected from the gap are compared with the magnitude, number, waveform, etc. of the inspection pulses applied to the machining gap. This allows the state, change, quality, etc. of the machining gap to be detected and determined.

FIG. 3 shows an embodiment in which a part of the processing pulse power source is also used to generate inspection pulses, and the same reference numerals as in FIG. 2 indicate the same parts. 13 is a counter that divides the output of the pulser 5;
When the preset counter counts up to the preset number, it outputs a signal and activates the pulser 14. The pulser 14 is a pulser for testing, and its output is applied to the switch 41 through the OR gate 17 to perform on/off switching control to generate testing pulses.

When this test pulse is generated, the output of the pulser 14 is inverted by the NOT gate 16, and the AND gate 1
5, the machining pulse is interrupted by AND-combining with the pulser 5 output of the machining pulse. Of course, there is no need to control the interruption of the machining pulse if the circuit is configured so that the relevant operation is performed so that the inspection pulse is generated during the pause of the machining pulse. Note that a plurality of switches 41 and 42 are connected in parallel, and the peak value (p) is controlled by the number of switches in parallel. A pulse with an arbitrary peak value can be obtained, and in the figure, when generating a processing pulse, switches 41 and 42 are operated in parallel, and when generating an inspection pulse, only switch 41 is operated from the OR gate 17 to set the peak value, and the processing It is configured to generate a pulse with a smaller peak value than the pulse. Of course, the same number of switches may be used for the processing pulse and the inspection pulse as long as they have the same peak value. The pulse width of the inspection pulse is arbitrarily controlled by the pulser 14, and the ratio relationship between the number of processing pulses and the number of inspection pulses is arbitrarily set by the preset of the counter 13. Further, in the case where the inspection pulse is generated by controlling in relation to the state of the machining gap, the preset of the counter 13 may be automatically controlled.

Further, the pulser 14 having this circuit configuration may be an independent pulser that is not controlled in relation to the pulser 5. or,
It may be controlled by the state of the machining gap. The output pulse waveform is arbitrary, such as a rectangular wave, a triangular wave, or a semicircular wave.

As described above, according to the present invention, an inspection pulse whose voltage and pulse width are set to a constant reference value and which is sufficient to generate an electric discharge in a normal gap different from the machining pulse is used; The condition of the machining gap is inspected by supplying it to the machining gap and generating electrical discharge.
Compared to conventional machining gap continuity tests using pulses that do not generate electric discharge in a normal gap, changes in the machining gap state can be tested extremely accurately by increasing the detection and discrimination parameter.

In addition, since the inspection pulse is generated independently from the machining pulse, it is easier to detect and discriminate compared to the conventional method that uses machining pulses.
In addition, the voltage and pulse width can be arbitrarily set constant to enable accurate discrimination, and signal detection and discrimination may change due to changes in processing conditions or changes in processing pulses, and errors may increase, resulting in inaccurate It is possible to always make accurate judgments using a fixed reference value without becoming unable to carry out a thorough inspection.

In addition, if the voltage or pulse width of the inspection pulse is set to a constant reference value that is sufficient to generate electric discharge in the normal gap, one of the pulse widths or voltages should be adjusted to match the machining conditions. By switching, accurate inspection can be performed without deteriorating machined surface roughness, machining accuracy, or electrode wear due to inspection pulses.

In addition, the inspection pulses are assigned to the machining pulse train at a smaller ratio than the number of machining pulses and are supplied to the machining gap, so electrical discharge machining is not sacrificed for inspection, and high-speed, high-performance processing is possible. Machining can be continued, and inspections can be performed to detect gaps, whether they are good or bad, trends, trends, etc. Then, this detection discrimination output is used as a signal,
By this signal and by the collective signal counted by a counter etc., for example, gap servo control, follow-up control, gap cleaning by reciprocating control, processing pulse width, pause width, duty factor control, etc. In addition, if you control the feed for approaching machining, the feed for inclined machining, etc., these controls will always be performed optimally. For example, when performing servo machining gap, the machining gap will be stopped at a normal gap, and when no electrical discharge occurs, the gap will be narrowed.
If the gap is narrow and abnormal discharge occurs, the gap can be controlled to be widened, so that stable machining can always be performed under optimal conditions, and machining effects such as machining speed, machining efficiency, and machining accuracy can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a pulse train waveform diagram for explaining one embodiment of the present invention, FIG. 2 is a circuit configuration diagram of one embodiment of the invention, and FIG. 3 is a circuit diagram of another embodiment. 1... Electrode, 2... Workpiece, 3... Processing electrode, 4... Switch, 5... Pulser, 6... Inspection power supply, 7... Switch, 8... Pulser, 9... AND gate , 10... Not gate, 11... Voltage detection resistor, 12... Discrimination device, 13... Preset counter, 14... Pulser, 15... AND gate, 16... Not gate, 41, 42...
Switch.

Claims (1)

[Scope of Claims] 1. In electric discharge machining in which a machining pulse is repeatedly applied to a gap between an electrode and a workpiece facing each other to produce a pulse discharge, a normal machining gap different from the machining pulse is used. Generate an inspection pulse whose voltage and pulse width are set to a constant reference value with a value sufficient to generate an electric discharge, and add the inspection pulse to a train of the processing pulses so that the number of inspection pulses is the number of processing pulses. Incorporate at a ratio smaller than that and supply it to the machining gap,
An electric discharge machining method characterized in that the state of a machining gap is detected by the inspection pulse. 2. In electric discharge machining, in which a machining re-pulse is used to repeatedly generate pulsed discharge in the gap between an electrode and a workpiece facing each other, the electric discharge is generated in a normal machining gap different from the machining pulse. Generate an inspection pulse with a voltage or pulse width set to a sufficient value and a constant reference value, and incorporate the inspection pulse into the processing pulse train at a ratio where the number of inspection pulses is smaller than the number of processing pulses. and supply it to the machining gap,
An electric discharge machining method characterized in that the state of a machining gap is detected by the inspection pulse. 3. A machining gap in which the electrode and the workpiece face each other, a machining pulse power source that supplies machining pulses to the machining gap, and a voltage and a constant reference value sufficient to generate electric discharge in the normal machining gap. A pulse generation power source which also serves as a part of the processing pulse power source or which generates an inspection pulse having a set pulse width or any of the pulse widths, and a pulse generation power source which is separate from the processing pulse power source and which generates an inspection pulse with a set pulse width or one of the pulse widths; Electrical discharge machining, characterized in that it is provided with a circuit that supplies a pulse train into the machining gap, the number of which is incorporated at a ratio smaller than the number of machining pulses, and a discriminator that detects and determines the state of the machining gap using the inspection pulses. Device. 4. A patent characterized in that a pulse generating power source that also serves as a part of the processing pulse power source that generates inspection pulses, or is separate from the processing pulse power source, generates inspection pulses at a number of pulses independent of the processing pulses. An electric discharge machining apparatus according to claim 3. 5. A patent characterized in that a pulse generating power source that also serves as a part of the processing pulse power source that generates inspection pulses, or is separate from the processing pulse power source, generates inspection pulses with a number of pulses dependent on the processing pulses. An electric discharge machining apparatus according to claim 3. 6. A pulse generating power source that also serves as a part of the processing pulse power source that generates inspection pulses, or is separate from this, is characterized in that it generates inspection pulses with a number of pulses corresponding to the machining state of the machining gap. An electric discharge machining apparatus according to claim 3. 7. Claims characterized in that a pulse generating power source that also serves as a part of the processing pulse power source that generates inspection pulses, or that is separate from this, generates a plurality of pulses successively when generating inspection pulses. The electric discharge machining apparatus according to item 3.