KR100992092B1 - Mechanical waveform control method and apparatus - Google Patents

Abstract

The present invention relates to a method and apparatus for controlling mechanical waveforms.

More specifically, the welding power supply unit for supplying power for welding, the first wire supply unit for supplying the wire for welding, and the wire supplied from the first wire supply unit by the reverse rotation and forward rotation operation as a base material A second wire supply unit for advancing and reversing, a buffer unit for storing a predetermined amount of wire to compensate for a difference in wire supply speed between the first wire supply unit and the second wire supply unit, and welding supplied from the welding power supply unit A short circuit state and an arc regeneration state are determined by using a detector that senses power, a driving drive that rotates the second wire supply unit in reverse and forward rotation, and a welding voltage sensed by the detector, and the second wire supply unit The drive to reverse rotation at the time of short circuit and forward rotation at the time of arc regeneration and to control the rotational speed of the second wire supply unit It relates to the mechanical main control waveform control method and apparatus that includes unit for controlling the drive.

The present invention can be attached to the existing welding power source can be used to reduce the cost of replacement, to prevent the generation of spatter generated during welding than the existing current control method, and to make ultra-thin welding at high speed The high quality welding is possible, and the productivity and the loss of the wire used in welding are reduced, thereby reducing the cost of welding.

Short circuit, arc regeneration, detector, buffer

Description

MECHANICAL WAVEFORM CONTROL METHOD AND APPARATUS}

The present invention relates to a method and apparatus for controlling a mechanical waveform, and more particularly, to detect a short circuit condition and an arc regeneration state generated during welding, and to control the short circuit and arc regeneration mechanically by advancing or reversing the wire and supplying the weld. The present invention relates to a method and apparatus for controlling a mechanical waveform which prevents occurrence of a short circuit and minimizes arc regeneration current by controlling a power supply.

In general, short-circuit performance in GMA (GAS METAL ARC) welding is a transition form that occurs under the condition of low current and low voltage regardless of the protective gas, and the volume grown at the tip of the wire by arc heat is melted as shown in FIG. The arc disappears in contact with the ground. At this time, the resistance becomes small due to a short circuit, the voltage drops momentarily below about 3V, and the current starts to rise rapidly. At this moment, the electromagnetic force (F _em ) acting on the volume in contact with the molten paper at the moment is as shown in Equation (1) (Ref .: The physics of welding, IIW, ed. By JF Lancaster, Pergammon Press, 1984, pp. 234 ( -) 237)).
[Equation 1]

Where I is the welding current, μ _o is the permeability at the free surface, R _e is the wire radius, and a is the radius of the surface where the volume contacts the molten pool as shown in FIG. Geometry factor F ₃ affects the direction of electromagnetic force as a function of R _e / a. In other words, when the radius of contact with the molten pool is relatively smaller than the radius of the electrode (R _a / a <1), the electromagnetic force acts upwards, and conversely, when the radius is large (R _a / a> 1), the electromagnetic forces act downward.

If R _e / a is less than 1 at the moment of short-circuit (the volume and the molten pool are not sufficiently in contact), the force of the electromagnetic force to push up the volume acts, and the volume is not fully transferred, but rather the pinch force When the contact is broken, the arc is regenerated, called an instantaneous short circuit (ISC). This short-circuit process is shown in FIG.

The short-circuit generates a large amount of spatter, because in the event of arc ash, a strong explosive force strikes the volume and the molten area, causing the volume and the part of the molten paper that have not been transferred to the molten area to be scattered. The spatter generated in the short circuit is very coarse and is attached to the base material in the molten state, so an additional process is required to remove it.

Therefore, the suppression of the short circuit can significantly reduce the spatter. The control of the instantaneous short circuit was proposed by Pinchuk (Svar. Proiz., 1976, pp. 52 (-) 54; 1980, pp. 9 (-) 10)) and the welding voltage could be below 8-12V. In this case, it is determined that a short circuit has occurred, and the current is reduced to 2 to 10 A for 0.7 to 1 msec time to delay the short circuit current rise.

In other words, by delaying the current rise in the short-circuit weakens the electromagnetic force to push up the volume to induce the instantaneous short circuit to become a normal short circuit.

In the case of a normal short circuit (NSC), when the molten paper and the volume sufficiently contact (R _a / a> 1) and crosslinking is formed as shown in FIG. 1B, the volume is transferred to the molten paper to break the crosslinking. Gravity, electromagnetic force and surface tension to maintain the bridge is acting. At low currents, however, the surface tension is very large compared to gravity and electromagnetic force, so bridging is difficult to break.

At the same time as the short circuit, the electromagnetic pinch force gradually increases due to the continuous increase of the current, and if the condition of Equation (2) is satisfied, as shown in (d) of FIG. 1, the bridge is broken and the arc is regenerated.
[Formula 2]

Where F _g is the gravity acting on the volume and F _v is the surface tension acting on the volume. The arc is regenerated when the current reaches a maximum during the short-circuit period, at which time the regenerated arc strikes the melt with a strong explosive force (arc repulsive force) and generates spatter of small particles. Therefore, in order to suppress the spatter generated during arc regeneration, the arc should be regenerated while maintaining a low current. In this concept, various current control waveforms have been proposed. For example, the initial current rise slope is increased, and the current rise rate is reduced above the set current to ultimately keep the current during arc regeneration and the initial current rise. There is a method of increasing the slope and limiting the rise above a certain current. But this too can't stop spatters.

In addition, since the current must be increased in order to break the bridge, the additional current is supplied, so that the smaller the thickness of the base material, the more limited the application to the ultra-thin welding due to the generation of welding deformation and melting.

For GMA welding to occur, short circuits must be satisfied as shown in Eq. (3). However, in reality, the forces acting on the volume are very large in terms of surface tension and electromagnetic force, so they cannot form a short circuit by drag and gravity alone. That is, it is difficult to satisfy the condition of the following formula (3).
[Equation 3]

In addition, the arc of the plasma jet continues to push the volume, making the short circuit more difficult. Therefore, in order to form a short circuit, when the molten pool reaches the volume by flow, it satisfies the condition of R _a / a> 1, so that the normal short circuit is smoothly performed. In addition, if a short circuit occurs or the arc period is increased and the volume grows further, the volume becomes very large and the volume is pushed up more strongly by the electromagnetic force, making the short circuit more difficult. That is, if the volume increases due to long-term arc, instantaneous short circuit occurs, and the arc voltage is increased by 4 ~ 5V instantaneously (about 1msec), and after the short circuit, the arc direction is changed irregularly like the arc regeneration phenomenon. Generate.

Therefore, in order to prevent such a long arc, the arc length is reduced by controlling the voltage at a constant speed during the arc period to facilitate contact with the molten pool.

However, this current control technique has a problem that it is difficult to induce a short circuit forcibly or periodically.

And mechanical control was published by Paton (Ref .: Avt. Svarka., 1977, pp. 1 (-) 5)), and the vibration frequency of the wire was optimally in the range of 15 ~ 100Hz. Liebiejev (Ref .: Automatic Welding, 1984, pp. 52 (-) 58) also reported mechanisms for various wire back and forth vibrations, but with limited control speed.

      Also, for mechanical control, a buffer must exist between the wire feed motor supplying the wire and the high speed motor (or other device) for the forward and backward wire attached to the end of the torch. In other words, the feeding motor is pushed at a constant speed according to the welding set current, the remnants of the wire occurs in the middle when the high speed motor is reversed, and the wire shortage occurs when the high speed motor is advanced.

Recently, a welding system capable of mechanical control has been commercialized. This is because servo motors and step motors capable of high speed control have become popular. Dual Jetline's CSC ^TM MIG (US patent: US6963048) consists of a torch with two step motors and a current controlled MIG pulsed welding power supply. This product is applicable to pulse MIG welding using inert protective gas. However, there is a problem that is generally difficult to apply in the domestic situation using the CO ₂ protective gas.

In addition, the above product is a disadvantage in that the torch is heavy, and it is impossible to apply the robot welding using a long cable.

     Another product, Fronius' CMT, is composed of one servomotor, wire buffer, and inverter welding power source capable of pulse welding.

The above products are wired forward and backward control and current control, and CO ₂ welding is possible, so domestic applicability is high, but the price is more than 10 times of existing inverter power supply, it is difficult to introduce easily.

In addition, the conventional welding power source has a problem that it is difficult to attach the product to the existing welding power source because it is a voltage controlled type.

The present invention has been made to solve the problems described above, can be attached to the existing welding power source can be used to reduce the cost of replacement, to prevent the occurrence of spatter generated during welding, ultra-thin welding The present invention provides a mechanical waveform control method and apparatus which enables high quality welding by enabling high speed, and reduces the cost of welding by increasing productivity and reducing the loss of wire used during welding. There is this.

An object of the present invention described above, the welding power supply for supplying power for welding, the first wire supply for supplying a wire for welding, and the reverse of the forward and forward rotation operation supplied from the first wire supply A second wire supply unit for advancing and retracting the wire with a base material, a buffer unit storing a predetermined amount of wire to compensate for a wire supply speed difference between the first wire supply unit and the second wire supply unit, and the welding power supply unit Detects a short circuit state and an arc regeneration state by using a sensing unit detecting a welding voltage supplied from a driving unit, a driving drive for rotating and forward rotating the second wire supply unit, and a welding voltage detected by the sensing unit. The second wire supply unit rotates in reverse at the time of short-circuit and forward rotates at the arc regeneration time, and adjusts the rotation speed of the second wire supply unit. It is achieved by providing a mechanical wave control apparatus including a main controller for controlling the driving machine drive.

The mechanical waveform control device according to a preferred feature of the present invention further includes a current controller for controlling the current supplied through the welding power supply so that the rise of the short circuit current is delayed.

Mechanical waveform control apparatus according to a preferred feature of the present invention includes a sensor for sensing the amount of the wire is stored in the buffer unit and the buffer unit for maintaining a constant curvature of the wire.

Mechanical waveform control apparatus according to a preferred feature of the present invention, by checking the amount of wire detected in the buffer unit, characterized in that for controlling the wire supply speed by the first wire supply unit to maintain a certain amount of wire stored in the buffer unit It includes the main control portion.

Mechanical waveform control apparatus according to a preferred feature of the present invention includes a buffer unit having a casing including an inlet guide and an outlet guide and a sensing sensor for sensing the amount of wire inside the casing.

Another object of the present invention described above is to (a) receive a control variable for mechanical waveform control during welding, (b) detect a welding voltage, and (c) use the detected welding power source. Determining whether the arc regeneration state or a short circuit state; and (d) rotating the second wire supply unit forward to short-circuit the arc regeneration state, and (e) the arc regeneration is performed when the short circuit state occurs. It is achieved by providing a mechanical waveform control method comprising the step of rotating the second wire supply in reverse.

In the mechanical waveform control method according to the preferred feature of the present invention, before the step (c), (c-1) determining whether the arc start mode, and (c-2) the determination result, the arc start mode, the wire Rotating the second wire supply unit to contact the base material, and (c-3) determining whether an arc start signal is generated from the welding machine after the forward rotation, and (c-4) if the arc start signal is generated. The method further includes rotating the second wire supply unit for a predetermined time.

The mechanical waveform control method according to a preferred feature of the present invention is characterized in that it further comprises the step of controlling the current of the welding power source so that the short-circuit current rise is delayed before the second wire supply unit reverses when the short-circuit point.

In the mechanical waveform control method according to the preferred feature of the present invention, (d-1) when the arc regeneration time, the step of forward rotation of the second wire supply unit at high speed, and (d-2) the predetermined forward rotation time has elapsed And (d-3) rotating the second wire supply unit at a low speed until a short time is reached after the predetermined forward rotation time has elapsed. do.

In the mechanical waveform control method according to the preferred feature of the present invention, (e-1) when the arc regeneration state, the step of forward rotation of the second wire supply unit at high speed, and (e-2) the predetermined forward rotation time has elapsed And (e-3) when the predetermined forward rotation time has elapsed, rotating the second wire supply unit at low speed until a short circuit time is reached. Include.

The present invention can be attached to the existing welding power source can be used to reduce the cost of replacement, significantly prevent the generation of spatter generated during welding than the existing current control method, by allowing ultra-thin plate welding at high speed High quality welding is possible, and there is an effect of reducing the cost of welding by increasing productivity and reducing the loss of the wire used during welding.

Hereinafter, a mechanical waveform control apparatus according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 is a block diagram of a mechanical waveform control apparatus according to an embodiment of the present invention.

Referring to FIG. 3, the present invention provides a welding power supply 101, an input 103, a display 105, a first wire supply 107, a detector 109, a drive drive 111, and a second wire supply. (113), the buffer unit 115 and the main control unit 117.

The welding power supply unit 101 supplies power required for welding.

The input unit 103 is a forward rotation (forward) and reverse rotation (reverse) speed and rotation time of the second wire supply unit 113 by the user's operation, such as the rising delay time for the control of the short-circuit current when the short circuit is detected. The control variable is input and output to the main control unit 117.

The display unit 105 displays the control variable and the control status input through the input unit 103.

The first wire supply unit 107 supplies a wire for welding. In this case, the wire supply speed by the first wire supply unit 107 is adjusted according to the welding current set in the welding power supply unit 101.

The detection unit 109 is connected to the welding power supply unit 101 detects a current welding voltage and transmits it to the main control unit 117.

The buffer unit 115 is positioned between the first wire supply unit 107 and the second wire supply unit 113 to store a predetermined amount of wires so that the first wire supply unit 107 and the second wire supply unit 113 are stored. This prevents the occurrence of wire residue or wire shortage due to the difference in feed speed between the wires.

That is, the first wire supply unit 107 supplies a wire to the welding torch 119 according to the wire supply speed value set in the welding power supply unit 101, and the supplied wire is the second wire supply unit. It is supplied to the welding torch 119 through the 113. At this time, the main control unit 117 controls the drive drive 111 according to the short circuit and the arc state detected by the detection unit 109, and reverses the forward rotation (forward) of the second wire supply unit 113. Control the rotation (reverse).
Particularly, for mechanical control, the wire promotion motor of the first wire supply unit 107 and the high speed motor of the second wire supply unit 113 are driven by the main control unit 117. Those skilled in the art to which this pertains will obviously know.
If the second wire supply unit 113 reversely rotates (backwards) when the first wire supply unit 107 supplies the wire at a constant speed during the process, the remaining portion of the wire is generated. When the two-wire supply unit 113 is rotated forward (advanced), the shortage of the wire occurs.

delete

For this reason, the buffer unit 115 includes a sensing sensor for sensing the amount of wires currently stored, so that the sensing sensor senses the amount of wires currently stored and transmits the amount of wires to the main control unit 117. As shown in FIG. 9, the buffer unit 115 according to the present invention includes a casing 905 including an inlet guide 901 and an outlet guide 903 to which a wire is supplied, and a wire inside the casing 905. And a sensing sensor for sensing the amount of 907.

The main control unit 117 pre-stores information on the amount of wires stored in the buffer unit 115. The main control unit 117 previously receives information on the amount of wires currently stored in the buffer unit 115 from the detection sensor. In comparison with the control, the wire feeding speed of the first wire supply unit 107 is controlled so that a certain amount of wire is stored in the buffer unit 115.

Here, the wire is wound around the buffer unit 115 in the form of a circle to maintain a constant helix (curvature of the wire), in which case the amount of wire stored in the buffer unit 115 may be represented by the size of the circle.

In addition, the main control unit 117 receives the welding voltage currently being welded from the detection unit 109 through a filter to determine the short circuit and arc regeneration time, and the second wire supply unit according to the determined short circuit and arc regeneration time The forward rotation (forward) and reverse rotation (reverse) of the 113 are controlled to prevent spatter generation.

In the short circuit, the supply voltage decreases rapidly, and when the voltage falls below 12 V to 14 V, the main control unit 117 determines that the short circuit occurs.

The mechanical waveform control device further comprises a current controller 123, by delaying the rise time of the supply current at the time of short-circuit through the current controller 123 to weaken the electromagnetic force, so that the volume of the wire end of the molten pool of the base material To ensure a smooth transition.

The second wire supply unit 113 according to the present invention is more preferably made of a servo motor.

4 is a view showing the relationship between the current rise delay control time and the rotation of the second wire supply unit according to the current waveform of the welding power source provided during the welding operation according to an embodiment of the present invention.

Referring to Figure 4, the waveform of the welding current and voltage supplied through the welding power supply unit 101 is as shown in (A).

Part (a) of the waveform of the welding current and voltage represents a current change in a short circuit state, and part (b) represents a current change in an arc regeneration state.

(B) shows the rotation direction of the second wire supply portion 113 controlled in accordance with the current supplied for welding.

As shown in FIG. 4, when the sensing unit 109 detects welding power supplied during welding, the main control unit 117 determines a short circuit and an arc regeneration time, and the second wire supply unit 113 reverses in a short circuit state. At the same time with a slight stop before the rotation, the current is maintained at about 50 to 100 A through the current controller 123, and the welding wire and the base material 121 are controlled to rotate in reverse when the volume of the welding wire end is sufficiently transferred to the molten pool. The separation causes the arc to be forced.

In addition, in the arc regeneration state, after the welding wire is melted by a certain amount, the second wire supply unit 113 is controlled to rotate forward at high speed so that a short circuit occurs by contacting the volume of the welding wire end and the molten pool of the base material 121. At this time, the short-circuit occurrence time is predicted, and the current is lowered to about 50 to 100A immediately before the short-circuit through the current controller 123 so that the short-circuit occurs more surely.

5 is a view showing a welding waveform of a general inverter welding power source, FIG. 6 is a view showing a welding waveform controlled by a current controller in a mechanical waveform control apparatus according to an embodiment of the present invention, and FIG. Figure 2 shows the welding waveform controlled by the mechanical waveform control and the current controller 123 according to an embodiment of the.

In the experiments of FIGS. 5 to 7, a 500 A class inverter welding power source was used, and the welding material used in the experiment was 1.2 mm of CO ₂ welding wire, and the protective gas was 100% CO _2. Was used. Welding was bead on plate welding on the mild steel sheet.

At this time, the distance between the tip and the base material (CTWD) was 14mm, the feeding speed was 4.5-5.5m / min, the welding speed was 0.5m / min. The welding waveform was measured for 5 seconds at a sampling rate of 20 kHz. Digital high speed camera was taken to observe the welding phenomenon. The shooting speed was set to 4,000 frames / sec and the shutter speed was set to 1 / 64,000 sec.

As shown in FIG. 5, when a general inverter welding power source is used, a momentary short circuit occurs somewhat, and a short circuit / arc of an irregular cycle can be seen.

6 is a welding waveform during welding controlled using only a mechanical waveform controller without attaching the current controller 123 to a general inverter welding power source.

Unlike FIG. 5, a short circuit occurs very regularly, and it can be seen that the occurrence of spatters is significantly reduced due to the normal short circuit. At this time, the normal / instantaneous short ratio was 93/7.

However, it is possible to suppress the short-circuit, but there is a limit to the reduction of the spatter due to the arc regeneration at high current. Therefore, the current reduction control is required during the arc regeneration.

7 is a welding waveform of the welding power source when the control is performed through the current controller 123, and when the rotation direction of the second wire supply unit 113 is controlled through the mechanical waveform control device as shown in FIG. Since the rise of cannot be suppressed, spatters are generated due to the arc explosion force. Therefore, by delaying the rise of the current applied in the short circuit through the current controller 123 it is possible to prevent the generation of spatters by arc regeneration at a low current as shown in FIG.

8 is a flow chart showing a process of mechanical waveform control according to an embodiment of the present invention.

Referring to FIG. 8, first, a user inputs a control variable necessary for mechanical waveform control through the input unit 103 (S801).

The control variable includes forward and reverse rotation speeds for the second wire supply unit 113, rotation time, short circuit current rise delay time through the current controller 123, reverse rotation speed and time at arc start, slow down speed, and the like. It includes.

When the user inputs the control variable and receives the welding start signal from the welding power source (S803), it is determined whether the arc start mode is used (S805). If the arc start mode is used, the second wire supply unit 113 is rotated forward for the arc start. (S807) and adjust the speed to the slow down speed.

At this time, the welding machine is in the state of raising the no-load voltage (about 70V) for the arc start, and when the welding wire touches the base material 121, it rises to the maximum current, and if it is 30A or more, the arc start signal is sent out from the welding power source. .

It is determined whether the arc start signal is generated (S809), and when the arc start signal is generated, the second wire supply unit 113 is rotated in reverse (S811) to increase the success rate of the arc start.

After the step S811, it is determined whether the initial reverse rotation time has elapsed (S813). If the initial reverse rotation time corresponds to the initial reverse rotation time, the second wire supply unit 113 continues to perform reverse rotation. Forward rotation of the 113 (S815).

The above process is performed to stabilize the arc generation.

After entering the main welding mode after the step S815, if the sensing unit 109 detects a welding voltage currently supplied for welding, it is determined whether the main control unit 117 is in a short circuit state or an arc regeneration state (S817). If it is a short time point, the current controller 123 is controlled to delay control (S819) a high current rise generated during a short circuit and reversely rotate the second wire supply unit 113 at high speed (S821).

In the step S819, since the welding current is rapidly increased when a short circuit occurs, spatter is generated due to the arc explosion force, thereby delaying the increase of the supply current through the current controller 123, thereby reducing the generation of spatter during arc regeneration.

After the step S821, it is determined whether the reverse rotation time has elapsed (S823). If the reverse rotation time has elapsed, the second wire supply unit 113 is rotated at a low speed (S825). Continue control.

If the arc regeneration point, the second wire supply unit 113 is rotated forward (forward) at high speed (S827) and it is determined whether the predetermined forward rotation time has elapsed (S829) If the forward rotation time has elapsed, the second wire supply unit 113 ) At a low speed (S831) and if the forward rotation time has not elapsed, the forward rotation of the second wire supply unit 113 is continued (S827).

After the above process, it is determined whether the end of welding (S833) If it is not the end of welding, it is determined whether the short-circuit state or the arc regeneration state again, and the end of the welding process if the end of welding.

Although one preferred embodiment of the present invention has been described above, it is apparent that the present invention may use various changes, modifications, and equivalents, and may be applied in the same manner by appropriately modifying the above embodiments. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

1 is a diagram showing welding current-voltage waveforms and displacement in a normal short circuit;

Fig. 2 is a diagram showing a spatter issue in the welding waveform and the instantaneous short circuit of the normal short circuit and the instantaneous short circuit.

Figure 3 is a block diagram of a mechanical waveform control device according to an embodiment of the present invention.

Figure 4 is a view showing the relationship between the welding current waveform provided during the welding operation and the current rise delay control timing and the rotation of the second wire supply unit according to an embodiment of the present invention.

5 is a view showing a welding waveform of a typical inverter welding power source.

6 is a view showing a welding waveform controlled through a mechanical waveform control device except the current controller according to an embodiment of the present invention.

7 is a view illustrating a welding waveform controlled through a mechanical waveform control and a current controller according to an embodiment of the present invention.

8 is a flow chart showing a process of mechanical waveform control according to an embodiment of the present invention.

      *** Description of the symbols for the main parts of the drawings ***

101: welding power supply unit 103: input unit

105: display unit 107: first wire supply unit

109: detector 111: drive drive

113: second wire supply unit 115: buffer unit

117: main fisherman 119: torch

121: base material 123: current controller

Claims (10)

A welding power supply unit 101 for supplying power for welding; A first wire supply unit 107 for supplying a wire for welding; A second wire supply unit 113 for advancing and reversing the wire supplied from the first wire supply unit 107 by a reverse rotation and forward rotation operation; A buffer 115 configured to store a predetermined amount of wire to compensate for a wire supply speed difference between the first wire supply unit 107 and the second wire supply unit 113; A detection unit 109 for detecting a welding voltage supplied from the welding power supply unit 101; A drive drive 111 for rotating the second wire supply part 113 in reverse and forward rotation; And The short circuit state and the arc regeneration state are determined using the welding voltage sensed by the detection unit 109, and the second wire supply unit 113 rotates reversely at a short time and forward rotates at an arc regeneration time. Including a main control unit 117 for controlling the drive drive 111 to adjust the rotational speed of the wire supply unit 113, The main control unit 117 drives the motors of the first wire supply unit 107 and the second wire supply unit 113, And the period of the short circuit and the arc is adjusted by the user. The method of claim 1, Mechanical waveform control device further comprises a current controller (123) for controlling the current supplied through the welding power supply (101) so that the rise of the short-circuit current is delayed. The method of claim 1, wherein the buffer unit 115, Mechanical waveform control device comprising a sensor for sensing the amount of the wire is stored in the buffer unit 115 and maintains the curvature of the wire constant The method of claim 3, wherein the main control unit 117, By checking the amount of wires detected by the buffer unit 115, the wire supply speed by the first wire supply unit 107 to control the amount of wires stored in the buffer unit 115 to maintain a certain amount of mechanical Waveform control device. The method of claim 3, wherein the buffer unit 115, And a sensing sensor having a casing including an inlet guide and an outlet guide, the sensing sensor sensing a quantity of wire in the casing. (a) receiving a control variable for controlling the mechanical waveform during welding; (b) detecting a welding voltage; (c) determining whether the arc is in a regeneration state or a short state by using the detected welding voltage; (d) forward rotating the second wire supply unit 113 to short-circuit the arc regeneration state; And (e) reversely rotating the second wire supply unit 113 to perform arc regeneration when the short circuit state occurs. The method of claim 6, wherein before step (c), (c-1) determining whether the operation is in an arc start mode; (c-2) as a result of the determination, in the arc start mode, rotating the second wire supply part 113 so that the wire contacts the base material; (c-3) determining whether an arc start signal is generated from the welding machine after the forward rotation; And (c-4) further comprising the step of reverse rotation of the second wire supply unit 113 for a predetermined time when the arc start signal is generated. The method of claim 6, And controlling the current of the welding power supply so that the short-circuit current rise is delayed before the second wire supply part 113 reversely rotates at the short-circuit point. The method of claim 6, wherein the step (d), (d-1) forward rotation of the second wire supply unit 113 at a high speed when the arc is regenerated; (d-2) determining whether a predetermined forward rotation time has elapsed; And and (d-3) forward rotating the second wire supply unit 113 at a low speed until a short time is reached when the predetermined forward rotation time elapses. The method of claim 6, wherein step (e) (e-1) rotating the second wire supply unit 113 at a high speed when the arc regeneration state is performed; (e-2) determining whether a predetermined forward rotation time has elapsed; And (e-3) when the predetermined forward rotation time elapses, rotating the second wire supply unit 113 at a low speed until a short circuit time is reached.

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