JP2503448B2 - Non-consumable electrode arc processing method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an arc machining method and a machining apparatus in which an arc start of a non-consumable electrode inert gas arc machining apparatus (hereinafter referred to as TIG machining) is improved. .

[Prior Art] Conventionally, as an arc start method of TIG processing, there is a reverse polarity start method (Japanese Patent Publication No. 40-25241) in which a non-consumable electrode (hereinafter, referred to as an electrode) is connected to a positive polarity and a workpiece is connected to a negative polarity. There is a positive polarity start method (Japanese Patent Publication No. 52-46900) in which the electrode is connected to the negative polarity and the work piece is connected to the positive polarity.

[Problems to be Solved by the Invention] In the above method, when the arc is started, the polarities are reversed, so that even if a momentary arc is generated due to high frequency combined use, the electrodes are easily heated and the arc can be easily started. On the other hand, since the electrode is positive, it rapidly melts and scatters due to abrupt local heating of the electrode, and it easily migrates into the weld metal to form a defect in the start part, and the electrode is largely consumed. It also has the drawback of being

Next, in the method of (2), when the arc is started, there is no melting and consumption due to rapid heating of the electrode, but on the other hand, the electrode heating is delayed because the reverse polarity current flows only after the arc starts and the heating of the electrode is started. There is a drawback that workability is poor in processing such as arc welding in which arc start is frequently performed. Further, when the work piece has an oxide film such as aluminum and magnesium, a reverse polarity current does not flow at all at the time of arc start, so the cleaning action for removing the oxide film is not performed at all, It is also accompanied by the drawback that welding defects tend to occur at the start.

As a conventional non-consumable electrode arc machining method,
TIG welding, TIG cutting, plasma arc welding, plasma arc cutting, plasma arc spraying, etc.

[Means for Solving the Problems] A. Method of the Present Invention The method of the present invention is a non-consumable electrode arc machining method in which an arc is started by using a high frequency in combination. A positive polarity voltage Vs with a positive workpiece and a reverse polarity voltage Vr with a conduction time Tr shorter than the conduction time Ts of the positive polarity voltage are alternately applied, and after the arc starts, a DC voltage with a polarity suitable for arc machining is applied. The present invention proposes a non-consumable electrode arc machining method for switching to an alternating current having a positive polarity current application time and a reverse polarity current application time suitable for electric current or arc machining.

Further, as a first embodiment of the method of the present invention, a non-consumable electrode in which the energization time Ts of the positive voltage before the arc start is longer than the energization time Ts' of the positive voltage of the AC voltage after the arc start. This is a proposal for an arc processing method.

Further, as a second embodiment of the method of the present invention, a current obtained by superimposing a positive voltage Isp suitable for arc machining at the time of arc start and a positive pulse current Ip having a conduction time shorter than the conduction time of the positive current Isp. This is a non-consumable electrode arc machining method for energizing the.

B. First Apparatus of the Present Invention A first apparatus of an arc machining apparatus for carrying out the method of the present invention comprises the following means, as described in claims 4 and 4 of the claims.

In a non-consumable electrode arc machining system that uses both high frequency and arc start, a DC power supply that controls the output by an output setting signal and a non-consumable electrode 1 that switches the output of the DC power supply to the positive polarity current Isp and the reverse polarity current Irp The polarity changeover switch 12 supplied to the workpiece 2, the positive polarity current value setting signal Sis and the reverse polarity current value setting signal S
Positive current value setting circuit that supplies each ir to the DC power supply
21 and the reverse polarity current value setting circuit 22, the polarity switching signal output circuit 14 which alternately supplies the positive polarity current conduction signal Ss and the reverse polarity current conduction signal Sr to the polarity changeover switch 12, and detects the output current of the DC power supply. Output current detection circuit 13
And the positive voltage Vs depending on the output signal of the output current detection circuit 13.
And the reverse polarity voltage Vr of the reverse polarity voltage Vr of the conduction time Tr shorter than the conduction time Ts of the positive polarity voltage, the direct current of the polarity suitable for arc machining or the conduction time of the positive polarity current suitable for arc machining and the reverse polarity current A non-polarity current energization time setting switching circuit 15 and a reverse polarity current energization time setting switching circuit 16 for respectively switching the positive polarity current energization signal Ss and the reverse polarity current energization signal Sr so as to switch to the alternating current with the energization time. A consumable electrode arc machining apparatus is provided.

C. Second apparatus of the present invention The second apparatus of the arc processing apparatus for carrying out the method of the present invention comprises the following means as described in claims 5 and 11 of the claims. .

In a non-consumable electrode arc machining system that uses both high frequency and arc start, a DC power supply that controls the output by an output setting signal and a non-consumable electrode 1 that switches the output of the DC power supply to the positive polarity current Isp and the reverse polarity current Irp The polarity changeover switch 12 supplied to the workpiece 2, the positive polarity current value setting signal Sis and the reverse polarity current value setting signal S
Positive current value setting circuit that supplies each ir to the DC power supply
21 and the reverse polarity current value setting circuit 22, the polarity switching signal output circuit 14 which alternately supplies the positive polarity current conduction signal Ss and the reverse polarity current conduction signal Sr to the polarity changeover switch 12, and detects the output current of the DC power supply. According to the output current detection circuit 13 and the output signal of the output current detection circuit 13, the polarity suitable for arc machining from the AC voltage of the positive polarity voltage Vs and the reverse polarity voltage Vr of the conduction time Tr shorter than the conduction time Ts of the positive polarity voltage Positive current energization that switches the positive current energization signal Ss and the reverse polarity current energization signal Sr, respectively, so as to switch to the alternating current of the energization time of the positive current suitable for arc machining and the energization time of the reverse polarity Time setting switching circuit 15 and reverse polarity current conduction time setting switching circuit 16, output signal of output current detection circuit 13 and positive polarity current conduction signal
When Ss is input at the same time, the pulse current signal output circuit 17 that outputs the pulse current energization signal Sp that superimposes the single positive pulse current Ip to the positive current Isp to the DC power supply, and the current value of the positive pulse current Ip Pulse current value setting circuit 2 that sets and outputs the pulse current value setting signal Sip to the DC power supply
The present invention provides a non-consumable electrode arc machining device including the above.

[Operation] The operation of the method of the present invention will be described with reference to FIGS. 1 to 3.

FIGS. 1 (A) to 1 (C) are views showing a first embodiment of the method of the present invention, respectively. FIG. 1 (A) is an output voltage supplied between an electrode and a workpiece. Waveform diagram, (B) is a timing diagram of the high-frequency voltage for arc start supplied between the electrode and the workpiece, (C) is the waveform of the output current flowing between the electrode and the workpiece. It is a figure.

At time T ₀ shown in FIG. 1, when the torch switch for starting the work of the power supply device described later is pressed to start the arc machining work, as shown in FIG. In between, while supplying an alternating voltage consisting of a positive voltage Vs of the energization time Ts and a reverse polarity voltage Vr of the energization time Tr,
As shown in FIG. 3B, a high frequency voltage for arc start is supplied between the electrode and the workpiece. By applying the high-frequency voltage for arc start, the reverse polarity current Irp slightly flows at time T1 when the supply of the reverse polarity voltage Vr is started, and then at times T2 and T3, the reverse polarity current Irp larger than the previous time is supplied. Flow to heat the electrodes. Before the arc start, because the electrode is a cold cathode and the work piece in which the oxide exists is easier to emit electrons than the electrode, only when the reverse polarity voltage Vr is supplied, the above-mentioned Thus, only the reverse polarity current Irp flows and the positive polarity current Isp does not flow. In addition, the energization time Tr of the reverse polarity voltage can be selected as an appropriate value depending on the diameter of the electrode, the material of the electrode, the material of the workpiece, etc., regardless of the current of the polarity required during the machining operation.
It is possible to suppress the consumption of the electrode due to the reverse polarity current Irp until the arc start to a minimum, and to prevent unnecessary melting and melting of the electrode locally. In the case of workpieces such as aluminum and magnesium that are prone to oxide film formation, the reverse polarity current Irp or reverse polarity voltage energization time T
Proper selection of r will provide the required cleaning action.

As described above, when the electrode heating progresses due to the intermittent energization of the reverse polarity current Irp before the arc start, the positive polarity current Is
p flows and an arc start is performed. Already, since the positive current Isp flows and the arc start is performed after the electrode is heated by the intermittent conduction of the reverse polarity current Irp,
The arc stabilizes in an extremely short time after the arc starts.
Therefore, when the arc start greatly affects the workability such as tack welding, the workability is greatly improved. Furthermore, in the case of workpieces such as aluminum and magnesium, the necessary cleaning action has already been obtained by intermittent energization of the reverse polarity current Irp before arc start with the positive polarity current Isp, so at the processing start position The occurrence of processing defects can also be reduced.

When an arc start is performed at time Ta during the energization time of the positive current Isp, a positive or reverse polarity DC voltage suitable for arc machining work, a commercial frequency or double frequency sine wave AC voltage, or energization before arc start. The arc machining work is performed by switching to the rectangular wave AC voltage of the energization times Ts 'and Tr' different from the times Ts and Tr.

In FIG. 1, in order to prevent the arc start at the reverse polarity voltage Vr, the reverse polarity voltage energization time Tr is set shorter than the reverse polarity voltage energization time Tr ′ after the arc start. Prevents scattering and consumption due to local melting of the electrode within the time period for applying the polarity voltage, and shortens the cycle Tf of the output voltage before the arc start to be shorter than the cycle Tf ′ of the output voltage after the arc start, thereby reducing the reverse polarity current Irp. The intermittent energization cycle is shortened to promote heating of the electrodes.

FIGS. 2 (A) to (C) are diagrams showing a second embodiment of the method of the present invention, and are the first of FIGS. 1 (A) to (C).
The same parts as those described in the embodiment will be omitted, and only different parts will be described.

In the first embodiment of FIGS. 1 (A) to 1 (C), when the diameter of the electrode is large or the tip of the electrode is worn and rounded, the reverse polarity current Irp is applied to the electrode only intermittently. In some cases, the arc is not stable immediately because of insufficient heating, and the workability of tack welding is particularly poor.

Therefore, in the second embodiment shown in FIG. 2, when the positive current Isp starts to flow and the arc starts at time Ta, as shown in FIG. The current Isp is applied to the positive polarity current for the conduction time Ts ′
The positive pulse current Ip having a shorter energization time is superimposed. In the second embodiment of FIG. 2, the output voltage period Tf before the arc start and the output voltage period Tf ′ after the arc start are the same, but the reverse polarity voltage before the arc start is applied. To shorten the time Tr to suppress melting and scattering due to local heating of the electrode and increase the chance of arc start when outputting the positive voltage Vs, set the positive voltage energization time Ts before the arc start It is set to be longer than the energization time Ts ′ of the positive polarity voltage of the AC voltage.

FIGS. 3 (A) to 3 (C) are views showing a third embodiment of the method of the present invention, and are the first of FIGS. 1 (A) to 1 (C).
The same parts as those described in the embodiment will be omitted, and only different parts will be described.

In the third embodiment of FIG. 3, at time Ta,
When an arc start occurs when the positive current Isp starts to flow, as shown in FIG. 9A, the AC voltage is switched to the positive DC voltage for arc machining, and the positive voltage value before the arc start. After the arc starts from Vs, the positive voltage value Vs' of high voltage suitable for machining work is switched. This embodiment is effective when a high arc voltage is required such as plasma arc cutting.

[Examples] A. First apparatus of the present invention A fourth arc machining apparatus for carrying out the method of the present invention is a fourth apparatus.
This will be described with reference to FIGS.

FIG. 4 is an overall block diagram of the first device, and FIG.
FIGS. 9 to 10 are block diagrams showing the entire block diagram of FIG. 4 in detail, and FIG. 10 is an operation signal explanatory diagram of the first device of FIG.

(Explanation of FIG. 4) In FIG. 4, 1 is a non-consumable electrode, 2 is a workpiece, and 9 is a workpiece.
Is a high-frequency generation circuit for arc start, 10 is a power supply circuit for arc machining which has an output control circuit 11 for arc machining with a signal set by a setting circuit 21 or 22 described later as an input, 12 is a polarity changeover switch, 13 is an output Current detection circuit, 14 polarity switching signal output circuit, 15 positive polarity current conduction time setting switching circuit, 16 reverse polarity current conduction time setting switching circuit, 21 positive polarity current value setting circuit, 22 reverse polarity current value setting Circuit.

(Explanation of FIG. 5) FIG. 5 is a detailed view of the arc machining power supply circuit shown by reference numeral 10 in FIG. 4, in which the output current control element is connected to the thyristor.
Shows the case when TH is used. In FIG. 5, R, S, T are commercial three-phase AC power supply input terminals of the power supply circuit 10, the input power is converted to a voltage suitable for arc machining work by the machining transformer TF, and rectified and converted by the thyristor TH. It is controlled and output to the "+" and "-" DC output terminals through the smoothing reactor RA and the output current value detector CT. 11 is a circuit
10 is an output control circuit that inputs a signal Si set by an external setting circuit 21 or 22 of 10 and outputs a control signal St to a thyristor TH that is an output current control element. This output control circuit 11 is
Synchronous pulse generator PG, comparator CM11, operational amplifier AMP11,
It consists of a firing phase control circuit PH and a machining work operation relay CR that operates at the contacts of a relay CR1 described later.

(Explanation of FIG. 6) FIG. 6 is similar to FIG.
It is another detailed view of the power supply circuit for arc processing shown in,
The case where the analog control transistor TR is used for the output current control element is shown. 6, the same parts as those in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. In Fig. 6, the output of the processing transformer TF is the rectifier circuit DD1 and the capacitor C.
The output is controlled by the transistor TR through 11, and is output to the “+” and “−” DC output terminals through the output current value detector CT. Reference numeral 11 is an output control circuit that inputs the signal Si set by the setting circuit 21 or 22 outside the circuit 10 and outputs the control signal St to the transistor TR which is the arc control current control element. This output control circuit 11 includes a comparator CM11 and an operational amplifier.
It is composed of AMP11, AMP12, and a machining work operation relay CR that operates at the contacts of relay CR1 described later.

(Explanation of FIG. 7) FIG. 7 is the same as FIG.
FIG. 9 is still another detailed view of the arc machining power supply circuit shown in, showing a case where an inverter INV is used as an output current control element. 7, parts that are the same as those shown in FIG. 5 are given the same reference numerals, and descriptions thereof will be omitted. In FIG. 7, after the input power is converted into direct current by the first rectifier circuit DD2,
Converted to high frequency AC power by the inverter INV, further converted to a voltage suitable for arc machining work by the high frequency transformer HT, converted to DC again by the second rectifier circuit DD3, smoothing reactor RA and output current value detector CT Through the "+" and "-" DC output terminals. Reference numeral 11 denotes an output control circuit that inputs the signal Si set by the setting circuit 21 or 22 outside the circuit 10 and outputs the control signal St to the inverter INV that is an output current control element. This output control circuit
11 is a commercial switching regulator control circuit IC (for example, MB3759 made by Fujitsu) as the main component, and other field effect transistor EJT, pulse transformer PT, machining work relay CR that operates at the contacts of relay CR1 described later, etc. Composed of.

(Explanation of FIG. 8) FIG. 8 is an output current detection circuit indicated by reference numeral 13 in FIG. 4, where TS is a torch switch, which is pressed at the start of the machining operation to activate the machining operation relay CR1. If the torch switch TS is pressed again at the end of the machining work, the relay CR1 will be restored. RS is a reed switch installed in the magnetic field generated by the output current supplied to the DC output circuit of the arc processing power supply circuit 10 of FIG. 4, and detects the continuous supply of current and closes the contact. WCR is an output current detection relay operated by the operation of the reed switch RS.

(Explanation of FIG. 9) FIG. 9 is a detailed diagram of the polarity switching signal output circuit shown by reference numeral 14 in FIG. 4, in which a commercially available astable multivibrator IC (for example, M51841P manufactured by Mitsubishi Electric) is used. It is configured as a main component, and outputs a positive polarity current conduction signal Ss to the Qs terminal corresponding to the resistance value set by the positive polarity current conduction time setting switching circuit 15 and the reverse polarity current conduction time setting switching circuit 16,
The reverse polarity current energization signal Sr is output to the terminal. This output circuit
A positive current conduction time setting switching circuit 15 and a reverse polarity current conduction time setting switching circuit 16 are connected to 14. The setting switching circuit 15 includes a resistor R17, a variable resistor R7, and an output current detection relay WCR. Before the start of output current detection relay WCR before the arc start, resistor R17 and variable resistor R7
And are connected in series, the time corresponding to the resistance value connected in series (the time of energizing the positive polarity voltage before the arc start)
Only Ts outputs the positive current conduction time Ss to the Qs terminal of the output circuit 14, and after the operation of the output current detection relay WCR after the arc start, the resistor R17 is short-circuited by the WCR normally open contact and the variable resistor The time corresponding to the resistance value of R7 (the time of conducting the positive voltage after the arc start) Ts'
Output the positive current conduction signal Ss to the Qs terminal. At this time, the energization time Ts of the positive voltage before the arc start becomes longer than the energization time Ts' of the positive voltage after the arc start. Similarly, the setting switching circuit 16 includes a resistor R18, a variable resistor R8, and an output current detection relay WCR.
Before the output current detection relay WCR before the arc start, the resistor R18 and the variable resistor R8 are connected in parallel before the operation of the output current detection relay WCR. Time) Only the Tr outputs the reverse polarity current conduction signal Sr to the Qr terminal of the output circuit 14, and after the operation of the output current detection relay WCR after the arc start, the resistor R18 changes to WCR.
Opened by the normally closed contact of, the time corresponding to the resistance value of the variable resistor R8 (reverse polarity voltage energization time after arc start) Tr 'is output to the Qr terminal of the output circuit 14 with the reverse polarity current energization signal.
Output Sr. At this time, the conduction time Tr of the reverse polarity voltage before the arc start becomes shorter than the conduction time Tr 'of the reverse polarity voltage after the arc start.

(Explanation of Operation of FIG. 4) Next, the operation of FIG. 4 will be described with reference to the detailed diagram of the block diagram and the operation signal explanatory diagram of FIG.

To start the arc machining operation, when the torch switch TS of the output current detection circuit 13 of FIG. 8 is pushed at time T ₀ as shown in the operation explanatory diagram of FIG. 10, the operation explanatory diagram of FIG. 10 ( As shown in A) to (D), the supply of shield gas (not shown) is started by closing the relay contact CR1, and high frequency is supplied from the arc start high frequency generating circuit 9 between the electrode 1 and the workpiece 2. . Further, by closing the relay contact CR1, the arc machining power supply circuit 10 shown in FIGS. 5 to 7 operates to output DC power to the “+” and “−” terminals.

Polarity switching signal output circuit 1 by closing the relay contact CR1
From the output terminal Qs of 4 to the positive current conduction time setting switching circuit 1
The positive polarity current conduction signal Ss is output only for the time Ts set in 5, and the polarity changeover switch 12 is set as shown in FIG. 10 (G).
A base current flows through the transistors TR1 and TR3, and the transistors TR1 and TR3 are turned on to supply the positive voltage Vs before the arc start between the electrode 1 and the workpiece 2. However, since the electrode 1 is not heated at all, the positive current Isp does not yet flow between the electrode 1 and the workpiece 2. Next, since the output circuit 14 performs the operation of the astable multivibrator, the reverse polarity current conduction signal Sr is output from the output terminal Qr for the time Tr set by the reverse polarity current conduction time setting switching circuit 16, As shown in Fig. 10 (H), a base current flows through the transistors TR2 and TR4 of the polarity changeover switch 12, the transistors TR2 and TR4 become conductive, and the reverse polarity voltage Vr before the arc start is applied to the electrode 1 and the workpiece. Supply between 2 and. At this time, when the dielectric breakdown due to the high frequency voltage is performed between the electrode 1 and the workpiece 2, a slight reverse polarity current Irp flows to heat the electrode 1 at time T1 in FIG. . In this way, the output circuit 14 alternately outputs the signals Ss and Sr to the output terminals Qs and Qr to alternately supply the voltages Vs and Vr between the electrode 1 and the workpiece 2.

When the electrode 1 is slightly heated by the reverse polarity current Irp before the arc start, when the positive voltage Vs is supplied, as shown in FIG. 10 (I), the electrode 1 and the workpiece 2 are separated. A positive current Isp flows in between and an arc start occurs.

On the other hand, the output signals Ss and Sr of the polarity switching signal output circuit 14
Are supplied to the positive polarity current value setting circuit 21 and the reverse polarity current value setting circuit 22, respectively. The setting circuit 21 includes a variable resistor R4 for setting the positive current value, an analog switch SW1, and a resistor R21.
, Analog switch SW1 is input terminal IN,
Has output terminal OUT and control terminal C, and terminal C
From the polarity switching signal output circuit 14 to the positive current conduction signal Ss
Is input, the positive polarity current value setting signal Sis set by the resistor R4 is supplied to the output control circuit 11 of the arc processing power supply circuit 10 through the operational amplifier OPA. The setting circuit 22 includes a reverse polarity current value setting variable resistor R5, an analog switch SW2, a resistor R22, and the like. The analog switch SW2 has an input terminal IN, an output terminal OUT and a control terminal C, and the terminal C has a polarity switching signal output circuit 14
When the reverse polarity current energization signal Sr is input from
The reverse polarity current value setting signal Sir set by R5 is supplied to the output control circuit 11 of the arc machining power supply circuit 10 through the operational amplifier OPA. In this case, reverse polarity current value setting signal Si
When r is set to be larger than the positive polarity current value setting signal Sis, the input signal Si of the output control circuit 11 of the arc processing power supply circuit 10 becomes a signal having the waveform shown in FIG. 10 (E). ,
An output current having a waveform shown in FIG. 10 (I) is passed between the electrode 1 and the workpiece 2.

As described above, at time Ta, as shown in FIG. 10 (F), when the arc current is started and the output current detection relay WCR operates, the high-frequency output of the high-frequency generation circuit 9 for arc start is opened by the opening of the normally closed contact. Is stopped, and by closing the normally open contact WCR of the positive current conduction time setting switching circuit 15, the conduction time of the positive voltage is shortened by switching from the time Ts before the arc start to the time Ts' after the arc start. In addition, by opening the normally closed contact WCR of the reverse polarity current conduction time setting switching circuit 16, the conduction time of the reverse polarity voltage is changed from the time Tr before arc start to the time T after arc start.
It becomes longer by switching to r '.

The energization times Ts, Tr, Ts', Tr 'and the output voltage periods Tf, Tf' can be set arbitrarily within the scope of the purpose as described in the method of the first aspect of the present invention. As shown in Fig. 3, the output current after the arc start can be changed to positive DC current, and the positive voltage value can be changed from Vs before arc start to Vs' after arc start. Is.

B. Second device of the present invention An eleventh second arc machining device for carrying out the method of the present invention is
This will be described with reference to FIGS. 13 to 13 and 5 to 9.

FIG. 11 is an overall block diagram of the second device, and the same parts as those of the first device in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. FIG. 12 is a detailed block diagram of the pulse current signal output circuit 17, and FIG. 13 is an operation signal explanatory diagram of the second device of FIG.

(Explanation of FIG. 11) In addition to the same reference numerals 1, 2, 9 to 16, 21, and 22 as the first device of FIG. 4, the second device of FIG. The pulse current value setting circuit 23 is added, and the method shown in FIG. 2 can be implemented.

As described in FIG. 2 of the method invention, the pulse current signal output circuit 17 supplies an output signal to the pulse current signal output circuit 17 via the contact of the relay WCR as the arc start, when the output current detection circuit 13 supplies the output signal. The positive polarity pulse current Ip set by the pulse current value setting circuit 23 is changed to the positive polarity current Is.
An electric current is applied between the electrode 1 and the workpiece 2 so as to overlap with p. Furthermore, this output circuit 17 is for a monostable multivibrator.
Equipped with a positive current conduction signal detector consisting of IC, transistor TR17, relay CR2, etc., output current detection relay WCR
When the normally closed contact is opened and the positive current conduction signal Ss is output and the normally closed contact of the relay CR2 is opened, the output circuit 17 outputs the pulse current conduction signal Sp.

The pulse current value setting circuit 23 includes a pulse current value setting variable resistor R6, an analog switch SW3, a resistor R23, etc., and the analog switch SW3 has an input terminal IN and an output terminal OU.
It has a T and a control terminal C, and the output circuit 1 is connected to the terminal C.
When the pulse current energization signal Sp is input from 7, the pulse current value setting signal Sip set by the resistor R6 is output.

(Explanation of FIG. 12) FIG. 12 is a detailed diagram of the pulse current signal output circuit indicated by reference numeral 17 in FIG. 11, which is a commercially available monostable multivibrator IC (for example, M51814P manufactured by Mitsubishi Electric). Variable resistor for pulse current conduction time setting
The pulse current energization signal Sp is output to the Q terminal according to the resistance value set by R9. This output circuit 17 outputs the signal S when the normally closed contact of the output current detection relay WCR and the normally closed contact of the relay CR2 that operates with the positive current conduction signal Ss are opened at the same time.
Output p.

(Explanation of Operation of FIG. 11) Next, the operation of FIG. 11 will be described with reference to the detailed diagram of the block diagram of FIG. 12 and the operation signal explanatory diagram of FIG.

In order to start the arc machining work, as shown in the operation signal explanatory diagram of FIG. 13, at time T ₀ , the torch switch TS of the output current detection circuit 13 of FIG. 8 is pressed, and then at time Ta, the arc starts. The output current detection relay WCR operates, the high frequency output of the arc start high frequency generation circuit 9 is stopped, and the conduction time is changed from Ts by the positive current conduction time setting switching circuit 15 and the reverse polarity current conduction time setting switching circuit 16.
The operation until switching to Ts 'and from Tr to Tr' is the same as that of the first device in FIG. 4, and therefore its explanation is omitted.

The output current detection relay WCR operates, the normally closed contact WCR of the pulse current signal output circuit 17 is opened, and the positive current conduction signal Ss is output from the terminal Qs of the polarity switching signal output circuit 14, and the relay CR2 When the normally closed contact CR2 is opened, the pulse current energization signal Sp is output from the terminal Q of the pulse current signal output circuit 17 and supplied to the control terminal C of the analog switch SW3 of the pulse current value setting circuit 23. Terminal C
When the signal Sp is input to the pulse current value setting signal Sip, the pulse current value setting signal Sip set by the resistor R6 is supplied to the output control circuit 11 of the arc machining power supply circuit 10 through the operational amplifier OPA.
In this case, the input signal Si of the output control circuit 11 has a waveform in which the pulse current value setting signal Sip is superimposed on the positive polarity current value setting signal Sis, as shown in (E) of FIG. When the superimposed signal Si is input to the output control circuit 11, an output current having a waveform shown in FIG. 13 (I) is passed between the electrode 1 and the workpiece 2.

Also in the second device of FIG. 11, the energization time Ts, Tr, T
s', Tr 'and the periods Tf, Tf' of the output voltage can be arbitrarily set within the range of the purpose as described in the method of the first invention, and as shown in FIG. It is possible to arbitrarily change the output current after the arc start is set as the positive DC current and the positive voltage value is switched from Vs before the start to Vs ′ after the start. Further, in addition to the operation of the first device shown in FIG. 4, the second device has a function of superposing the pulse current Ip at the time of arc start, as shown in FIG.

In the first and second devices, the energization time Ts, Tr, T
Variable resistors R7 and R8 that set s ', Tr', variable resistor R9 that sets the pulse current energizing time, variable resistors R4 and R5 that set the positive or reverse polarity current value, and pulse current value The variable resistor R6 and the like can be replaced with a fixed resistance value or a semiconductor element or the like whose characteristics change according to the applied arc processing conditions. Further, the relays WCR, CR1, CR, CR2 used in the device of the present invention can be replaced with a semiconductor circuit.

[Effect] According to the method and the first device of the present invention, the electrode is heated at the time of starting the arc, the arc is easily stabilized even with a small current, and the workability of tack welding is good. In addition, even in arc machining of aluminum, magnesium, etc., the cleaning action holds the advantage of reverse polarity current that machining defects are less likely to occur at the machining start portion, and the electrode wear is large and the electrode tip melts and scatters. It is possible to solve the greatest drawback of the reverse polarity start, in which the startability deteriorates immediately because of the roundness.

Further, according to the method and the second device of the present invention, in addition to the advantages of the first device, by superimposing the pulse current at the start of the positive current, the heating of the electrode is promoted and the arc at the arc start is started. And the workability of tack welding can be improved.

[Brief description of drawings]

FIGS. 1, 2, and 3 are waveform diagrams for explaining the method of the present invention. FIG. 4 is an overall block diagram of the first device, and FIGS. 5 to 7 are first and second block diagrams.
FIG. 5 is a detailed view of the arc machining power supply circuit 10 common to the respective devices, FIG. 5 shows a case of thyristor control, FIG. 6 shows a case of transistor analog control, and FIG. 7 shows a case of inverter control. . FIG. 8 is a detailed view of the output current detection circuit 13, FIG. 9 is a detailed view of the polarity switching signal output circuit 14, and FIG.
FIG. 11 is an explanatory diagram of operation signals of the first device, FIG. 11 is an overall block diagram of the second device, FIG. 12 is a detailed diagram of the pulse current signal output circuit 17, and FIG. FIG. 3 is an explanatory diagram of operation signals of the device of FIG. 1 ... Non-consumable electrode, 2 ... Workpiece, 9 ... High frequency generating circuit for arc start, 10 ... Power circuit for arc machining, 11 ... Output control circuit, 12 ... Polarity change switch, 13 ... Output current detection circuit, 14 ... Polarity switching signal output circuit, 15 ... Positive current conduction time setting switching circuit, 16 ... Reverse polarity current conduction time setting switching circuit, 17 ... Pulse current signal output circuit, 21 ... Positive current value setting circuit, 22 ... Reverse polarity Current value setting circuit, 23 ... Pulse current value setting circuit, CR1, CR ... Machining work operation relay, WCR ... Output current detection relay, Sir ... Reverse polarity current value setting signal, Sis ...
Positive polarity current value setting signal, Sr ... Reverse polarity current conduction signal, Ss ...
Positive current conduction signal, Si ... Input signal of output control circuit 11,
Sp ... Pulse current energization signal, St ... Output control element control signal,
Ts: Positive voltage energization time before arc start, Tr ... Reverse polarity voltage energization time before arc start, Tf: Output voltage cycle before arc start, Ts' ... Positive voltage energization time after arc start , Tr '... Energization time of reverse polarity voltage after arc start, Tf' ... Output voltage cycle after arc start, Irp ... Reverse polarity current, Isp ... Positive current, Ip ... Positive pulse current (at arc start) , Vs ... arc before the start of the positive polarity voltage, Vr ... arc before the start of the reverse polarity voltage, Vs '... arc positive polarity voltage after the start, Vr' ... reverse polarity voltage after arc start, T ₀ ... work start time, T1, T2,
T3: reverse polarity current energization start time, Ta ... arc start time

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-55-120484 (JP, A) JP-A-52-22550 (JP, A) Actual development 61-92463 (JP, U)

Claims (5)

(57) [Claims] 1. A non-consumable electrode arc machining method in which a high frequency is used together with an arc start, and a positive polarity voltage (Vs) in which the non-consumable electrode is negative and the workpiece is positive until the arc is started, and the positive electrode. Conduction time of sexual voltage (Ts)
The reverse polarity voltage (Vr) with a shorter energization time (Tr) is alternately energized, and after the arc starts, the direct current with the polarity suitable for arc machining or the polarity with the positive polarity current suitable for arc machining and the opposite polarity A non-consumable electrode arc machining method that switches to alternating current with the current application time. 2. The method according to claim 1, wherein the energization time (Ts) of the positive voltage before the arc start is longer than the energization time (Ts') of the positive voltage of the AC voltage after the arc start. Non-consumable electrode arc machining method described. 3. A current in which a positive polarity current (Isp) suitable for arc machining and a positive polarity pulse current (Ip) having a conduction time shorter than the conduction time of the positive polarity current (Isp) are superposed at the time of arc start. The non-consumable electrode arc machining method according to claim 1 or 2. 4. A non-consumable electrode arc machining apparatus for starting an arc using high frequency in combination, a direct current power source for controlling output according to an output setting signal, and a positive polarity current (Isp) and a reverse polarity current (Isp) for the output of the direct current power source. Irp) to switch the non-consumable electrode (1) and the workpiece (2) to supply polarity switch (12), positive polarity current value setting signal (Sis) and reverse polarity current value setting signal (Sir) respectively Positive polarity current value setting circuit (21) and reverse polarity current value setting circuit (22) supplied to the DC power supply
And positive polarity current conduction signal (Ss) and reverse polarity current conduction signal (Ss
polarity switching signal output circuit (14) that alternately supplies r) to the polarity switching switch (12), an output current detection circuit (13) that detects the output current of the DC power supply, and an output current detection circuit (13). ) Output signal from a positive polarity voltage (Vs) and a reverse polarity voltage (Vr) with a conduction time (Tr) shorter than the conduction time (Ts) of the positive polarity voltage. The positive current conduction signal (S) is selected so as to switch to the alternating current of the conduction time of the positive current and the conduction time of the reverse polarity current suitable for electric current or arc machining.
s) and a reverse polarity current conduction time setting switching circuit (15) and a reverse polarity current conduction time setting switching circuit (16) for switching the reverse polarity current conduction signal (Sr), respectively. 5. A non-consumable electrode arc machining apparatus for starting an arc by using high frequency as well, a direct current power source for controlling output according to an output setting signal, and a positive polarity current (Isp) and a reverse polarity current (Isp) for the output of the direct current power source. Irp) to switch the non-consumable electrode (1) and the workpiece (2) to supply polarity switch (12), positive polarity current value setting signal (Sis) and reverse polarity current value setting signal (Sir) respectively Positive polarity current value setting circuit (21) and reverse polarity current value setting circuit (22) supplied to the DC power supply
And positive polarity current conduction signal (Ss) and reverse polarity current conduction signal (Ss
polarity switching signal output circuit (14) that alternately supplies r) to the polarity switching switch (12), an output current detection circuit (13) that detects the output current of the DC power supply, and an output current detection circuit (13). ) Output signal from a positive polarity voltage (Vs) and a reverse polarity voltage (Vr) with a conduction time (Tr) shorter than the conduction time (Ts) of the positive polarity voltage. The positive current conduction signal (S) is selected so as to switch to the alternating current of the conduction time of the positive current and the conduction time of the reverse polarity current suitable for electric current or arc machining.
s) and the reverse polarity current conduction time setting switching circuit (15) and the reverse polarity current conduction time setting switching circuit (16) for switching the reverse polarity current conduction signal (Sr) respectively, and the output of the output current detection circuit (13). A pulse current conduction signal (Sp) that superimposes a single positive polarity pulse current (Ip) on the positive polarity current (Isp) when a signal and the positive polarity current conduction signal (Ss) are input at the same time, is output to the DC power supply. And a pulse current signal output circuit (17) for setting a current value of the positive pulse current (Ip) and outputting a pulse current value setting signal (Sip) to the DC power supply (23). Non-consumable electrode arc machining equipment equipped with.