JP2015016487A - Method for detecting wire tip grain size upon weld finish and method for controlling arc start - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an arc start performance by accurately detecting a wire tip grain size upon weld finish in consumable electrode arc welding.SOLUTION: When a weld start signal St changes to Low, a feeding motor is stopped to perform an anti-stick control for switching over a weld voltage setting signal to an anti-stick voltage setting value, so that welding is finished by extinguishing an arc with a grain formed at a wire tip. An integral value is detected, for time lengths Tb or weld currents Iw over a burning period of times t54 to t7, the period from release of the last normal short circuit generated during a period of the anti-stick control of times t5 to t8 until the extinguishment of the arc, to detect a grain size at the wire tip from these values. On the basis of the detected grain size at the wire tip, a parameter upon an arc start is optimized. In this way, constantly favorable arc start performances can be obtained even when variation occurs in the grain size at the wire tip.

Description

  According to the present invention, when the welding start signal changes to the end signal, a stop signal is output to the feed motor and an anti-stick control is performed to switch the welding voltage setting signal to the anti-stick voltage setting value, thereby forming grains at the wire tip and arcing. The present invention relates to a method for detecting the wire tip particle size at the end of welding and an arc start control method using the same.

  FIG. 5 is a general configuration diagram of a consumable electrode arc welding apparatus using a robot described in Patent Right 1. Hereinafter, each component will be described with reference to FIG.

  The teach pendant TP is connected to the robot controller RC, and plays an operation trajectory of the robot RM and sets welding conditions. The robot controller RC outputs an operation control signal Mc for controlling the operation of the robot RM to a plurality of servo motors (not shown) provided in the robot RM, and outputs a welding condition signal Wc to the welding power source PS. . The welding condition signal Wc includes at least a welding start signal St, a steady feed speed setting signal Fr, and a steady welding voltage setting signal Vr. A feed motor WM and a welding torch 4 are mounted on the robot RM.

  The welding power source PS receives the above welding condition signal Wc and outputs a welding voltage Vw and a welding current Iw for generating the arc 3, and a feed control signal Fc for controlling the feed motor WM. Is output. The welding wire 1 is fed through the welding torch 4 at the feeding speed Fw (cm / min) by the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. In the following description, when it is described as a feeding motor, it is used to include the entire feeding mechanism such as the motor itself, a speed reducer, and a feeding roll.

  FIG. 6 is a timing chart of sequence control from the start to the end of welding when arc welding is performed using the welding apparatus described above with reference to FIG. FIG. 4A shows the time change of the welding start signal St, FIG. 3B shows the time change of the feeding speed Fw of the welding wire 1, and FIG. 4C shows the time change of the welding current Iw. FIG. 4D shows the change over time in the welding voltage Vw. Hereinafter, the operation will be described with reference to FIG.

[When welding starts]
At time t1, when the welding start signal St becomes a high level (start signal) as shown in FIG. 9A, the welding wire 1 is set to a predetermined value of about 1 m / min as shown in FIG. Feeding at a slow slow-down feeding speed Fi is started. At the same time, since the output of the welding power source is also started, a welding voltage Vw having a maximum no-load voltage value is applied between the welding wire 1 and the base metal 2 as shown in FIG. In this state, the welding wire 1 and the base material 2 are separated from each other and are in a no-load state, so that the welding current Iw is not energized as shown in FIG.

  At time t2, when the tip of the welding wire 1 contacts the base material 2 by the slow-down feeding, the arc 3 is ignited. When the arc 3 is ignited, the welding current Iw is energized with a predetermined hot start current value Ih larger than the steady welding current value, as shown in FIG. This hot start current Ih is energized during a predetermined hot start period Th until time t3. At time t2, the welding voltage Vw becomes a hot start voltage value smaller than the no-load voltage value as shown in FIG. When the welding current Iw is energized at time t2, as shown in FIG. 5B, the feeding speed Fw is accelerated with an inclination and converges to a value determined by the steady feeding speed setting signal Fr at time t4. The period from time t2 to t4 is a predetermined acceleration period Tu. The reason why the hot start current Ih is energized is that the tip of the welding wire 1 is brought into contact with the base material 2 and then the hot start current Ih having a large current value is energized to rapidly melt the welding wire tip and instantaneously. This is to cause the arc 3 to fire. In order to smoothly shift from the instantaneous arc generation to the steady arc, the values of the hot start current Ih, the hot start period Th, and the acceleration period Tu are determined by the material, diameter, and welding of the welding wire 1. It is necessary to set an appropriate value according to the welding conditions such as the wire tip particle size before the start.

[Normal welding period]
The period from time t4 to t5 is the steady welding period. During this period, as shown in FIG. 5B, the feeding speed Fw becomes a value determined by the steady feeding speed setting signal Fr. During the short-circuit period from time t41 to t42, the welding current Iw gradually increases as shown in FIG. 8C, and the welding voltage Vw becomes a short-circuit voltage value of several volts as shown in FIG. . During the arc period from the time t42 to t43, the welding current Iw gradually decreases as shown in FIG. 10C, and the welding voltage Vw has an arc voltage value of several tens of volts as shown in FIG. Become. In the figure, three short-circuit periods and arc periods are drawn during the steady welding period from time t4 to t5. Actually, the short circuit occurs about 30 to 100 times per second. The average value of the welding current Iw during the steady welding period becomes the steady welding current value, and is set by the steady feeding speed setting signal Fr. Moreover, the average value of the welding voltage Vw during the steady welding period becomes the steady welding voltage value, and is set by the steady welding voltage setting signal Vr.

[At the end of welding (anti-stick control period)]
At time t5, when the welding start signal St becomes a low level (end signal) as shown in FIG. 9A, the feed motor WM is controlled to stop as shown in FIG. The feeding speed Fw is gradually decelerated due to inertia and stops at time t6. At the same time, the output from the welding power source PS is continued during a predetermined anti-stick control period Ta at times t5 to t8. During this anti-stick control period Ta, two short-circuits occur during the period from time t51 to t52 and from time t53 to t54. Actually, a short circuit occurs about 3 to 8 times. The short circuit from time t53 to t54 is the final short circuit. As shown in FIG. 6D, the welding voltage Vw becomes a short-circuit voltage value during the last short-circuit period from time t53 to t54, and gradually increases when the arc is regenerated at time t54, and time t6 when the feeding stops. The arc cannot be maintained at time t7 slightly later than the arc, and the arc is extinguished. When the arc is extinguished at time t7, the welding voltage Vw rises to the no-load voltage value as shown in FIG. 4D, and the no-load voltage is output until time t8. On the other hand, as shown in FIG. 5C, the welding current Iw gradually increases during the last short-circuit period from time t53 to t54, and becomes a small current value of about several tens of A during the burn-up period from time t54 to t7. And 0 at time t7.

  During the burn-up period from the time when the last short-circuit is released at time t54 and the arc is regenerated to the time when the arc is extinguished at t7, the tip of the welding wire 1 is melted and burned by the arc 3 to form grains. . The wire tip particle size increases in proportion to the length of the burn-up period. The average value of the welding voltage Vw during the period from time t5 to time t7 is a value determined by a predetermined anti-stick voltage setting signal Var. The value of the anti-stick voltage setting signal Var is set to a value smaller than the value of the steady welding voltage setting signal Vr. The length of the burn-up period is set by the anti-stick voltage setting signal Var. For this reason, the wire tip particle size at the end of welding can be adjusted by the anti-stick voltage setting signal Var. Therefore, the anti-stick voltage setting signal Var is set according to the welding conditions so that the wire tip particle size at the end of welding becomes an appropriate size. The wire tip particle size is an appropriate size when the welding is completed, the burn-up distance between the tip of the welding wire 1 and the base material 2 is an appropriate distance in the range of about 3 to 5 mm, and the wire tip particle The diameter is about 1.2 times the diameter of the welding wire 1. Thereby, the end of the welding wire 1 is not welded to the bead at the end of welding, and the wire tip particle size is an appropriate size, so that the arc start property at the start of the next welding is improved. When the wire tip particle size increases, a large amount of spatter is generated at the time of arc start, and from the time when the tip of the welding wire 1 comes into contact with the base metal 2 and the arc 3 is ignited until a steady arc state is reached. It will be frustrating. Conversely, when the wire tip particle size becomes small, slag, which is an insulator, tends to adhere to the wire tip, and even if the tip of the welding wire 1 comes into contact with the base metal 2 at time t2, the arc 3 does not start. Prone to start.

Japanese Patent No. 5160961

  As described above, in the prior art, the wire tip particle size at the end of welding is optimized by setting the anti-stick voltage setting signal Var to an appropriate value according to the welding conditions. However, even if the welding conditions remain the same, the wire tip particle size may sometimes be larger than the appropriate size. If it becomes like this, the arc start property at the time of the next welding start will worsen.

  Therefore, in the present invention, a method for detecting the wire tip particle size at the end of welding, which can detect the variation in the wire tip particle size at the end of welding and improve the arc start performance based on the detection result, and An object of the present invention is to provide an arc start control method used.

In order to solve the above-described problems, the invention of claim 1
In consumable electrode arc welding in which a short-circuit period and an arc period are alternately and repeatedly welded between a welding wire and a base material, when the welding start signal changes to an end signal, a stop signal is output to the feed motor. In the method for detecting the wire tip particle size at the end of welding, the anti-stick control is performed to switch the welding voltage setting signal to the anti-stick voltage setting value to form a grain at the wire tip, extinguish the arc and complete the welding. ,
A short circuit in which the short circuit period is a predetermined reference time or more is defined as a normal short circuit, and a short circuit that is less than the reference time is defined as a micro short circuit,
An index that correlates with the melting amount of the welding wire during the burn-up period from the release of the last normal short-circuit occurring during the anti-stick control period until the arc extinguishes is detected. Detect particle size,
This is a method for detecting the wire tip particle size at the end of welding.

In the invention of claim 2, the index is a time length of the burn-up period.
The wire tip particle size detection method at the end of welding according to claim 1.

In the invention of claim 3, the index is an integral value of the welding current during the burn-up period.
The wire tip particle size detection method at the end of welding according to claim 1.

According to a fourth aspect of the present invention, when the welding start signal changes to a start signal, an arc start control that drives the feeding motor to feed the welding wire and ignites the arc between the base material. In the method
Based on the wire tip particle size detected by the method according to any one of claims 1 to 3, the parameters at the time of arc start are changed.
An arc start control method characterized by the above.

According to a fifth aspect of the present invention, when the arc is ignited, the feeding speed is accelerated to a predetermined steady feeding speed, a predetermined hot start current is applied during a predetermined hot start period, and then the steady state is applied. The welding current of
The parameter is at least one of an acceleration period of the feed speed, the hot start period, or the hot start current;
The arc start control method according to claim 4, wherein:

  According to the present invention, an index that correlates with the melting amount of the welding wire during the burn-up period from the release of the last normal short circuit that occurred during the anti-stick control period until the arc is extinguished is detected. To detect the wire tip particle size. Thereby, the wire tip particle size at the end of welding can be accurately detected. In accordance with this index, at least one of a hot start current, a hot start period, or an acceleration period, which is a parameter at the time of arc start, is changed. For this reason, since the parameter at the time of arc start is optimized according to the size of the wire tip particle size, the arc start property at the start of the next welding can be improved.

It is a timing chart of each signal in a welding device for explaining a principle of a wire tip particle size detection method and an arc start control method concerning an embodiment of the invention. It is a relationship diagram of time length Tb (ms) of the burn-up period, hot start current Ih (a), hot start period Th (ms), and acceleration period Tu (ms). FIG. 6 is a relationship diagram of an integration value Si (A · ms) of a welding current during a burn-up period, a hot start current Ih (a), a hot start period Th (ms), and an acceleration period Tu (ms). It is a block diagram of welding power supply PS for implementing the detection method and the arc start control method of the wire tip particle size which concern on embodiment of this invention. It is a general block diagram of the consumable electrode arc welding apparatus using the robot in a prior art. 6 is a timing chart of sequence control from the start to the end of welding when arc welding is performed using the welding apparatus described above with reference to FIG. 5.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a timing chart of each signal in the welding apparatus of FIG. 5 for explaining the principle of the wire tip particle diameter detection method and arc start control method according to the embodiment of the present invention. FIG. 4A shows the time change of the welding start signal St, FIG. 3B shows the time change of the feeding speed Fw of the welding wire 1, and FIG. 4C shows the time change of the welding current Iw. FIG. 4D shows the change over time in the welding voltage Vw. This figure corresponds to FIG. 6 described above, and the operation in the period other than the times t54 to t8 is the same, so the description will not be repeated. In the following, with reference to the figure, the periods of different operations from time t54 to t8 will be described.

  The normal short circuit and the micro short circuit used in the following description are defined. The normal short circuit is a short circuit in which the length of the short circuit period is equal to or longer than a predetermined reference time. On the other hand, the micro short circuit is a short circuit in which the length of the short circuit period is less than the above-mentioned reference time, and the droplets at the wire tip do not move to the molten pool but remain at the wire tip. The reference time is set in a range of about 0.5 to 1.5 ms. This reference time is set to an appropriate value by experiment as a threshold value with or without the transfer of droplets, depending on the material, diameter, type of shield gas, and the like of the welding wire 1.

  In the figure, the last normal short circuit occurs at times t53 to t54 during the antistick control period Ta. The last normal short circuit is a normal short circuit that occurs during the anti-stick control period Ta and occurs last until the arc is extinguished. As shown in FIG. 4D, the welding voltage Vw becomes an arc voltage value when the last normal short circuit is released at time t54 and the arc 3 is regenerated, and during the minute short circuit from time t55 to t56, the short circuit voltage value is obtained. Thus, when the short circuit is released at time t56 and the arc 3 is regenerated, the arc voltage value is gradually increased. When the arc 3 is extinguished at time t7, the arc voltage value rapidly increases to the no-load voltage value. As shown in FIG. 5C, the welding current Iw becomes a substantially constant small current value during the burn-up period from time t54 to time t7, and becomes 0 at time t7. That is, in FIG. 6 described above, the short-circuit does not occur during the burn-up period from the time t54 when the last normal short circuit is released and the arc 3 is regenerated to the time t7 when the arc 3 is extinguished. On the other hand, in the figure, one minute short circuit occurs during the burn-up period Tb from time t54 to t7. The micro short circuit occurs about 0 to 7 times.

  Here, in order to clarify the cause of the variation in the wire tip particle size, the relationship between the short-circuit occurrence state during the anti-stick control period Ta and the wire tip particle size was investigated. As a result, when a micro short circuit does not occur during the burn-up period Tb, the wire tip particle size becomes an appropriate size, and the wire tip particle size increases substantially proportionally as the number of micro short circuit occurrences increases. I understood. This is because as the number of occurrences of micro short-circuit increases, the burn-up period Tb becomes longer, and the droplet does not migrate in the micro short-circuit, so the amount of melting at the wire tip increases and the wire tip particle size increases. In the prior art, the period from the time t56 when the last short circuit is released regardless of the normal short circuit or the minute short circuit to the time t7 when the arc 3 is extinguished is defined as the burn-up period. On the other hand, in the present invention, the period from the time t54 when the last normal short circuit is released to the time t7 when the arc 3 is extinguished is defined as a burn-up period Tb. The wire tip particle size is detected by detecting an index that correlates with the melting amount of the welding wire during the burn-up period Tb. As an index correlated with the melting amount of the welding wire, the time length of the burn-up period Tb or the integrated value of the welding current during the burn-up period Tb is used. As the time length of the burn-up period Tb and the integrated value of the welding current during the burn-up period Tb increase, the amount of melting at the wire tip increases and the wire tip particle size increases.

  In order to improve the arc start property at the start of the next welding even when the wire tip particle size becomes large, as described above, the hot start current Ih, the hot start period Th, or the acceleration period Tu of the feed speed Fw It is necessary to change at least one of them together. That is, as the index increases, at least one of these three arc start parameters may be increased.

  FIG. 2 is an example of a relationship diagram between the time length Tb (ms) of the burn-up period, the hot start current Ih (A), the hot start period Th (ms), and the acceleration period Tu (ms). The horizontal axis represents the time length Tb of the burn-up period, which is in the range of 50 to 100 ms. The left vertical axis indicates the hot start period Th and the acceleration period Tu, which are in the range of 0 to 50 ms. The right vertical axis indicates the hot start current Ih, which is in the range of 400 to 700A. In the figure, the material of the welding wire 1 is steel, the diameter is 1.2 mm, and the type of shielding gas is 100% carbon dioxide.

  The hot start current Ih indicated by the solid line is 500 A in the range of Tb ≦ 60, Ih increases as Tb increases, and 600 A in the range of Tb ≧ 90. The hot start period th indicated by the broken line is 5 ms in the range of Tb ≦ 60, Th increases as Tb increases, and 10 ms in the range of Tb ≧ 90. The acceleration period Tu indicated by the alternate long and short dash line is 20 ms in the range of Tb ≦ 60, Tu increases as Tb increases, and 40 ms in the range of Tb ≧ 90.

  When no micro short circuit occurs during the burn-up period Tb, Tb is in the range of 40 to 60 ms. As the number of micro shorts increases, Tb is in the range of 60 to 100 ms. The relationship as shown in the figure is set for each welding condition such as the material of the welding wire 1, the diameter, and the type of shield gas.

  FIG. 3 is an example of a relationship diagram of the integrated value Si (A · ms) of the welding current Iw during the burn-up period Tb, the hot start current Ih (A), the hot start period Th (ms), and the acceleration period Tu (ms). It is. The horizontal axis represents the integrated value Si, which is in the range of 1000 to 2000 A · ms. The left vertical axis indicates the hot start period Th and the acceleration period Tu, which are in the range of 0 to 50 ms. The right vertical axis indicates the hot start current Ih, which is in the range of 400 to 700A. In the figure, the material of the welding wire 1 is steel, the diameter is 1.2 mm, and the type of shielding gas is 100% carbon dioxide.

  The hot start current Ih indicated by the solid line is 500 A in the range of Si ≦ 1200, the Ih increases as Si increases, and 600 A in the range of Si ≧ 1800. The hot start period Th indicated by the broken line is 5 ms in the range of Si ≦ 1200, Th increases as Si increases, and 10 ms in the range of Si ≧ 1800. The acceleration period Tu indicated by the alternate long and short dash line is 20 ms in the range of Si ≦ 1200, Tu increases as Si increases, and 40 ms in the range of Si ≧ 1800.

  When no short-circuit occurs even once during the burn-up period Tb, Si is in the range of 800 to 1200 A · ms. As the number of micro shorts increases, Si is in the range of 1200 to 2000 A · ms. The relationship as shown in the figure is set for each welding condition such as the material of the welding wire 1, the diameter, and the type of shield gas.

  FIG. 4 is a block diagram of a welding power source PS for carrying out the wire tip particle size detection method and arc start control method according to the embodiment of the present invention. The overall configuration of the welding apparatus is the same as that in FIG. 5 described above, and the welding power source PS is a block diagram shown in FIG. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200 V, performs output control such as inverter control in accordance with a drive signal Dv described later, and generates a welding voltage Vw and a welding current for generating the arc 3. Iw is output. Although not shown, the power main circuit PM has a primary rectifier that rectifies commercial power, a capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current into high-frequency alternating current according to the drive signal Dv, A high-frequency transformer that steps down the alternating current to a voltage value suitable for arc welding, a secondary rectifier that rectifies the stepped-down high-frequency alternating current, and a reactor that smoothes the rectified direct current.

  The welding wire 1 is fed through the welding torch 4 by a feeding roll 5 coupled to a feeding motor WM, and an arc 3 is generated between the base metal 2 and the welding wire 1.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The current energization determination circuit CD receives the current detection signal Id and, when this value is equal to or greater than a predetermined current determination value, determines that the welding current Iw is energized and becomes a high level current energization determination signal. Cd is output. This current discrimination value is set to about 10 A, for example.

  The interface circuit IF receives the welding condition signal Wc from the robot controller RC and outputs a welding start signal St, a steady welding voltage setting signal Vr, and a steady feeding speed setting signal Fr included in this signal. The start-up circuit ON receives this welding start signal St and outputs an start-up signal On with an off-delay for a predetermined anti-stick control period, and at the same time, an anti-stick control period signal that is at a high level during the anti-stick control period. Ta is output.

The short circuit determination circuit sd receives the voltage detection signal Vd as described above, and outputs a short circuit determination signal Sd that is at a high level when this value is less than the short circuit determination value, and that is at a low level when the value is above. The short circuit discrimination value is set to about 15V. The index detection circuit HD receives the short-circuit determination signal Sd, the anti-stick control period signal Ta, the current energization determination signal Cd, and the current detection signal Id as input, and performs the following processing to generate the index detection signal Hd. Output.
1) When the short circuit determination signal Sd changes to High level during the period when the anti-stick control period signal Ta is at High level, a normal short circuit occurs when the period length of the High level is equal to or longer than a predetermined reference time. If it is less than the reference time, it is determined that a micro short circuit has occurred.
2) After the occurrence of the normal short circuit is determined, if the short circuit determination signal Sd is changed to the low level and it is determined that the normal short circuit is released, timing of the burn-up period and integration of the current detection signal Id are started, and the current conduction determination signal When Cd becomes the Low level, the timing and integration are stopped.
3) When the anti-stick control period signal Ta changes to the Low level, the above measured value is set as the time length Tb of the burn-up period, and the above integrated value is set as the integrated value Si of the welding current during the burn-up period.
4) Select either the time length Tb of the burn-up period or the integration value Si of the welding current during the burn-up period, and output it as the index detection signal Hd.

  The hot start current setting circuit IHR receives the index detection signal Hd as described above and outputs the hot start current setting signal Ihr calculated by a predetermined function as described above with reference to FIG. The current error amplification circuit EI amplifies an error between the hot start current setting signal Ihr and the current detection signal Id, and outputs a current error amplification signal Ei.

  The anti-stick voltage setting circuit VAR outputs a predetermined anti-stick voltage setting signal Var. The voltage control setting circuit VCR receives the above-mentioned steady welding voltage setting signal Vr, the anti-stick voltage setting signal Var and the anti-stick control period signal Ta, and the anti-stick control period signal Ta is at a low level (steady welding period). In this case, the steady welding voltage setting signal Vr is output as the voltage control setting signal Vcr, and when the level is High, the anti-stick voltage setting signal Var is output as the voltage control setting signal Vcr. The voltage error amplification circuit EV amplifies an error between the voltage control setting signal Vcr and the voltage detection signal Vd, and outputs a voltage error amplification signal Ev.

  The hot start period setting circuit tHR receives the index detection signal Hd as described above and outputs a hot start period setting signal thr calculated by a predetermined function as described above with reference to FIG. 2 or FIG. The hot start period timer circuit TH receives the hot start period setting signal tHR and the current energization determination signal Cd as input, and only the period determined by the hot start period setting signal tHR from the time when the current energization determination signal Cd changes to the High level. A hot start period signal Th that becomes a high level is output.

  The external characteristic switching circuit SW receives the current error amplification signal Ei, the voltage error amplification signal Ev, and the hot start period signal Th, and when the hot start period signal Th is at a high level, the current error amplification signal Ei. Is output as the error amplification signal Ea, and when it is at the Low level, the voltage error amplification signal Ev is output as the error amplification signal Ea. The drive circuit DV receives the error amplification signal Ea and the activation signal On, and when the activation signal On is at a high level, performs a pulse width modulation control based on the error amplification signal Ea and outputs the drive signal Dv. . As a result, when the welding start signal St becomes high level, the constant voltage characteristic is obtained and the output of the welding voltage Vw is started. When the welding current Iw starts energization, constant current characteristics are obtained, and the hot start current Ih is energized during the hot start period Th. When this period ends, the constant voltage characteristic is obtained, and the welding voltage Vw becomes a value determined by the steady welding voltage setting signal Vr. When the welding start signal St changes to the Low level, the welding voltage Vw becomes a value determined by the antistick voltage setting signal Var from this time point to the antistick control period.

  The acceleration period setting circuit TUR receives the index detection signal Hd and outputs the acceleration period setting signal Tur calculated by a predetermined function as described above with reference to FIG. 2 or FIG.

The feed speed control setting circuit FCR receives the welding start signal St, the current energization determination signal Cd, the steady feed speed setting signal Fr, and the acceleration period setting signal Tur, and receives the welding start signal St. When the high level is reached, a predetermined slow-down feed speed setting value is obtained, and when the current energization determination signal Cd is at the high level, the slow-down feed speed setting value is increased during the period determined by the acceleration period setting signal Tur and is constantly fed. A feed speed control setting signal Fcr that becomes a value determined by the speed setting signal Fr and becomes 0 when the welding start signal St becomes a low level is output. With this circuit, as shown in FIG. 1 (B), the feeding speed Fw becomes a slow-down feeding speed in the no-load state at times t1 to t2, and has an inclination during the acceleration period Tu at times t2 to t4. , And during the steady welding period from time t4 to t5, the steady feeding speed is reached, and when entering the anti-stick control period Ta from time t5, the speed gradually decreases due to inertia and stops.

  The feed control circuit FC receives the feed speed control setting signal Fcr as an input, and feeds a feed control signal Fc for feeding the welding wire 1 at a feed speed corresponding to this value to the feed motor WM. Output.

  This figure shows a case where the hot start current setting signal Ihr, the hot start period setting signal Thr, and the acceleration period setting signal Tur, which are parameters at the time of arc start, are changed according to the index detection signal Hd. At least one of them may be changed.

  According to the above-described embodiment, an index that correlates with the melting amount of the welding wire during the burn-up period from the release of the last normal short circuit that occurred during the anti-stick control period until the arc is extinguished is detected. The wire tip particle size is detected by this index. As this index, the time length of the burn-up period or the integrated value of the welding current during the burn-up period is used. Thereby, the wire tip particle size at the end of welding can be accurately detected. In accordance with this index, at least one of a hot start current, a hot start period, or an acceleration period, which is a parameter at the time of arc start, is changed. For this reason, since the parameter at the time of arc start is optimized according to the size of the wire tip particle size, the arc start property at the start of the next welding can be improved.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll CD Current energization discrimination circuit Cd Current energization discrimination signal DV Drive circuit Dv Drive signal Ea Error amplification signal EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC Feed control circuit Fc Feed control signal FCR Feed speed control setting circuit Fcr Feed speed control setting signal Fi Slow down feed speed Fr Steady feed speed setting signal Fw Feed speed HD Index detection circuit Hd index detection signal ID current detection circuit Id current detection signal IF interface circuit Ih hot start current IHR hot start current setting circuit Ihr hot start current setting signal Iw welding current Mc operation control signal ON start circuit On start signal PM power supply main circuit PS welding Power RC Robot controller RM Robot sd Short circuit Another circuit Sd short circuit determination signal Si kindling integral value St welding start signal SW external characteristic switching circuit Ta anti stick control period of the welding current during the period (signal)
Tb Time length of the burning period Th Hot start period tHR Hot start period setting circuit thr Hot start period setting signal TP Teach pendant Tu Acceleration period TUR Acceleration period setting circuit Tur Acceleration period setting signal VAR Antistick voltage setting circuit Var Antistick voltage setting Signal VCR Voltage control setting circuit Vcr Voltage control setting signal VD Voltage detection circuit Vd Voltage detection signal Vr Steady welding voltage setting signal Vw Welding voltage Wc Welding condition signal WM Feeding motor

Claims (5)

In consumable electrode arc welding in which a short-circuit period and an arc period are alternately and repeatedly welded between a welding wire and a base material, when the welding start signal changes to an end signal, a stop signal is output to the feed motor. In the method for detecting the wire tip particle size at the end of welding, the anti-stick control is performed to switch the welding voltage setting signal to the anti-stick voltage setting value to form a grain at the wire tip, extinguish the arc and complete the welding. ,
A short circuit in which the short circuit period is a predetermined reference time or more is defined as a normal short circuit, and a short circuit that is less than the reference time is defined as a micro short circuit,
An index that correlates with the melting amount of the welding wire during the burn-up period from the release of the last normal short-circuit occurring during the anti-stick control period until the arc extinguishes is detected. Detect particle size,
A method for detecting a wire tip particle size at the end of welding. The indicator is a time length of the burn-up period;
The method for detecting the wire tip particle size at the end of welding according to claim 1. The indicator is an integrated value of the welding current during the burn-up period.
The method for detecting the wire tip particle size at the end of welding according to claim 1. When the welding start signal changes to a start signal, the feed motor is driven to feed the welding wire, and the arc start control method of starting the arc between the base material,
Based on the wire tip particle size detected by the method according to any one of claims 1 to 3, the parameters at the time of arc start are changed.
An arc start control method characterized by the above. When the arc is ignited, the feeding speed is accelerated to a predetermined steady feeding speed, a predetermined hot start current is energized during a predetermined hot start period, and then a steady welding current is energized,
The parameter is at least one of an acceleration period of the feed speed, the hot start period, or the hot start current;
The arc start control method according to claim 4, wherein:

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