JP4780146B2 - Welding end control method - Google Patents

Description

  The present invention relates to a welding end control method and a welding method in arc welding in which an arc is generated between a wire as a consumable electrode and a base material as a workpiece to be welded.

  In recent years, in the welding industry, there is an increasing demand for shortening tact time required for production of welding and suppressing post-processing steps in order to improve productivity. Above all, since the production line is stopped due to an arc start error and an extra post-processing step occurs, there is an increasing demand for such suppression. The cause of the arc start mistake is often due to the presence of slag (insulator) between the wire and the base material, and an arc does not occur and an arc start does not occur. In this case, the wire can be cut to remove the slag at the tip of the wire, thereby starting the arc.

  Moreover, although an arc is generated, arc breaks frequently occur and the bead length of the welding start portion is insufficient, or spatter may adhere to the base material. In this case, post-processing and spatter removal work for adding a weld bead are required. In this case, the production line must be stopped or an extra post-processing step is required, resulting in a decrease in welding productivity.

  On the other hand, in order to suppress the influence of the slag formed at the wire tip, the suitability of the wire tip shape is performed by welding end control. For example, the current, voltage, and time settings in the welding end control portion different from the steady welding control portion are stored in the welding apparatus, and the welding end control is performed under the stored conditions. Then, a ball of an appropriate size is formed at the tip of the wire in a range of about 1.1 to 1.5 times the wire diameter. And by starting the ball of the proper size at the tip of the wire in this way, the arc start can be performed satisfactorily.

  However, as shown in FIG. 5, even if a ball having an appropriate shape is formed at the end of welding output, the wire tip and the molten pool are short-circuited due to vibration of the molten pool after the completion of welding and the formed ball is melted. In some cases, the ball is absorbed by the pool and a ball having a desired shape cannot be formed at the tip of the wire. In such a case, the tip of the wire has a sharp shape. In this case, the arc start cannot be performed satisfactorily. The reason is that the slag (insulator) concentrates on the pointed portion of the wire tip and inhibits arc start.

  Further, the wire tip and the melt pool may be short-circuited due to vibration of the melt pool after the end of welding and the wire tip and the melt pool may be fixed (hereinafter referred to as a stick). When the robot is welded with a welding torch, the robot cannot be moved.

  In the past, when a stick state is reached after welding is completed, a method is known in which a voltage is applied to release the stick state, a current is applied, and the sticking wire is melted and released (for example, patent document). 1). A specific example will be described below.

First, after the end of welding, as shown in step 2 of FIG. 7, a stick detection circuit for determining whether or not the stick is present is connected to the welding output path. Next, as shown in Step 4 of FIGS. 6 and 7, a predetermined voltage (DC voltage) is applied between the wire tip and the base material for a predetermined time. In the case of sticking, the voltage between the wire tip and the base material drops to near 0 V and current flows. Therefore, the voltage or current is monitored, and if the voltage is not lowered or no current is detected, the stick detection circuit is disconnected and the stick release process is performed as shown in step 6 of FIG. finish. On the other hand, when the stick state is detected, the stick detection circuit is disconnected as shown in step 7 of FIG. 7, and the stick release output is intentionally applied and sticked as shown in step 8 of FIGS. Fusing the wire that is. If the stick cannot be released by a single stick release process, the stick state is released multiple times.
JP-A-5-245638

  In the conventional welding output control, even if a ball having an appropriate shape is formed on the wire tip at the end of welding output, the wire tip and the molten pool are short-circuited due to vibration of the molten pool after the welding is finished, and the ball formed thereby There is a case where a ball having a desired shape cannot be maintained at the wire tip by being absorbed by the molten pool. In such a case, a good arc start cannot be performed, but it was not possible to determine that the ball formed by short-circuiting the wire tip and the molten pool was released after being absorbed by the molten pool.

  Further, in the conventional stick releasing method, for example, as shown in FIG. 6, the stick state is simply released. Therefore, a ball having a proper shape is not formed at the tip of the wire after releasing the stick, and in this case, a good arc start cannot be performed.

  In order to solve the above-described problem, the welding end control method of the present invention applies a voltage between a wire that is a consumable electrode and a workpiece to be welded for a predetermined time after the welding output is stopped, to establish a connection between the wire and the workpiece. A welding end control method for detecting contact, wherein the wire and the work piece are short-circuited when the detected voltage at the predetermined time is lower than the applied voltage and then increased after the decreased voltage. It is possible to determine the opened state later.

  In addition, the welding end control method of the present invention includes a step of storing the determined result in the storage unit and a step of displaying the determination result stored in the storage unit on the display unit.

  In addition, the welding end control method of the present invention includes a step of applying the second current and the third voltage for a fourth predetermined time immediately after determining that the wire and the workpiece are opened after being short-circuited. A ball of an appropriate size can be formed at the tip of the wire.

  As described above, according to the present invention, it is possible to determine whether or not the wire and the workpiece to be welded are opened after being short-circuited at the end of welding.

  In addition, when it is determined that the wire and the work piece are short-circuited at the end of welding, a voltage or current is applied between the wire and the work piece for a predetermined time to form a ball of the appropriate shape at the wire tip. can do. Thereby, generation | occurrence | production of an arc start mistake can be suppressed and productivity improvement can be implement | achieved by suppressing a production line stop and an extra post-process.

(Embodiment 1)
Hereinafter, the present embodiment will be described with reference to FIGS.

  FIG. 1 is a diagram showing a schematic configuration of a welding apparatus. The welding apparatus mainly includes a welding power source apparatus 1, a welding torch 6, a robot 7 that supports and carries the welding torch 6, a wire feeding unit 8 that feeds the wire 9 toward the base material 10, and the like. The The robot 7 operates based on an operation program stored in a robot control device (not shown).

  Further, the welding power source apparatus 1 mainly controls the welding output by controlling the power source unit 2 that supplies power between the wire 9 that is a consumable electrode and the base material 10 that is a welding target, and the power source unit 2. Control unit 3, output voltage detection unit 4 for detecting output voltage, output current detection unit 12 for detecting output current, and wire 9 and mother based on the output of output voltage detection unit 4 or output current detection unit 12. A short-circuit detecting unit 5 for determining whether or not the material 10 is short-circuited is provided. The control unit 3 controls the welding output by controlling the switching elements in the power supply unit 2 based on signals from the short circuit detection unit 5, the output voltage detection unit 4, the output current detection unit 12, and the like.

  Next, an example of control of the wire feed speed, welding current, and voltage at the end of welding will be described. FIG. 2A is a diagram showing a time change of the wire feed speed, FIG. 2B is a diagram showing a time change of the welding voltage, and FIG. 2C is a diagram showing a time change of the welding current. FIG. 2 (d) is a diagram showing the change over time of the wire tip situation.

  In FIG. 2A, when a welding start button (not shown) is turned off, a command to stop the rotation of the motor constituting the wire feeding unit 8 is output. However, since the motor continues to rotate due to inertia for a while, the wire feeding speed is decelerated from the wire feeding speed at the time of steady welding toward speed 0.

  Moreover, in order to form the front-end | tip part of the wire 9 in the spherical shape of a suitable magnitude | size, the control part 3 makes the welding voltage and welding current the 1st voltage or 1st shown in FIG.2 (b) and FIG.2 (c). The control to decrease toward the current is started, and after reaching each predetermined value, the application for the first predetermined time is continued in the state of the predetermined value. Then, when the first predetermined time has elapsed, the welding output is turned off to extinguish the arc. The control unit 3 controls the current so as to be the first current, and the first voltage is determined corresponding to this current. Alternatively, the control unit 3 may control the voltage so as to be the first voltage, and the first current may be determined corresponding to this voltage.

  Next, in order to determine whether or not the tip of the wire 9 and the base material 10 are short-circuited, when the second predetermined time elapses after the first predetermined time elapses, the power source unit 2 causes the wire 9 and the base material 10 to be connected. A second voltage is applied between the material 10. The reason for turning off the output for the second predetermined time is to completely eliminate the arc. If the arc has not completely disappeared, the arc may be generated when the voltage is applied next, and the tip of the wire 9 may be further melted. This is to prevent this. The second predetermined time is set to about 5 to 200 msec, for example.

  FIG. 2D shows a case where the tip of the wire 9 and the base material 10 are not short-circuited after the end of welding. In this case, there is no change in the detection voltage during the third predetermined time during which the second voltage is applied. However, as shown in FIG. 3D, when a short circuit occurs between the tip of the wire 9 and the molten pool due to the vibration of the molten pool or the like during the third predetermined time, the voltage is nearly 0 V when the short circuit occurs. Decreases and falls below a first threshold voltage. Therefore, occurrence of a short circuit can be detected by detecting the voltage. When the short circuit is opened after the short circuit has occurred, the detection voltage exceeds the first threshold value from near 0 V and returns to the original second voltage level. Therefore, by detecting the voltage for the third predetermined time, detecting that the voltage falls below the first threshold value from the second voltage and becomes the second voltage again, the circuit is opened after being short-circuited once. Can be determined.

  Note that the first predetermined time is, for example, about 10 ms to 200 ms, and the third predetermined time is about 10 to 200 msec. The first voltage is about 10 to 30V. The second voltage is about 5-30V. The first threshold voltage is about 2.5 to 15 V, which is about half of the second voltage. The first current is about 10 to 100 A, and the average value may be 10 to 100 A by outputting a pulsed current. These time, voltage value, and current value may be fixed from experiments, etc., or set welding current, set welding voltage, wire feed speed, shield gas type, wire material, wire You may make it set by the control part 3 based on a diameter, a welding method, etc.

  As described above, after the welding output is stopped, it can be determined that the wire 9 and the base material 10 are opened after being short-circuited. Then, in order to prevent a short circuit from occurring after the welding output is stopped, at least one of the first voltage, the first current, or the first predetermined time in the welding end control unit at the welding location is larger than the previous magnitude. Is set to be larger, it is possible to suppress the occurrence of a short circuit after the welding output is stopped. As a result, when welding is performed by replacing the base material 10 after the welding with another base material 10, a ball having an appropriate shape can be formed at the tip of the wire 9 at the end of the welding, and an arc start mistake is suppressed. As a result, production line stoppage and extra post-processing can be reduced to improve productivity.

  Note that the vibration of the molten pool is particularly large in the following cases. When the material of the base material 10 is a galvanized steel sheet, zinc vapor is released from the molten pool, so that the vibration of the molten pool is greater than that of a steel sheet that is not galvanized. Further, as the angle of the attitude of the welding torch 6 with respect to the base material 10 is inclined from a state of 90 degrees, the more the inclination is, the more inclined the base material 10 is inclined with respect to the welding torch 6, the arc The vibration of the molten pool tends to increase with force. In this way, it is affected by the material of the base material 10, the attitude of the welding torch 6, the arrangement of the base material 10, and the like.

  Therefore, when the base material 10 has a plurality of welding locations, an arc start error does not occur in all the welding locations, but often occurs at a specific welding location. Therefore, it is not necessary to uniformly change the current, voltage, time setting and the like in the welding end control in all the welding points of the base material 10, and only the welding point where the short circuit between the wire 9 and the base material 10 occurs at the end of welding. What is necessary is just to change an electric current, a voltage, time setting, etc.

  Further, since the vibration of the molten pool is greater in the galvanized steel plate than in the non-galvanized steel plate, the first voltage or the first current in the welding end control unit of the welded portion where the short circuit has occurred after the end of welding. Alternatively, when setting at least one of the first predetermined times to be larger than the previous size, it is desirable to make the galvanized steel sheet larger than the galvanized steel sheet, It is desirable that the angle between the welding torch 6 and the base material 10 increases as it is tilted from the 90 degree state.

  In the present embodiment, when a short circuit occurs between the tip of the wire 9 and the molten pool due to vibration of the molten pool or the like during the third predetermined time, the voltage drops to nearly 0 V when the short circuit occurs, When it is in a stick state where the wire 9 and the base material 10 remain short-circuited when the state continues to fall below the first threshold of the set voltage and the third predetermined time has elapsed. Judgment can be made.

(Embodiment 2)
This embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the location similar to Embodiment 1, and detailed description is abbreviate | omitted. The difference from the first embodiment is that the output of the control unit 3 is used as an input, the storage unit 13 for storing that the wire 9 and the base material 10 are opened after short-circuiting at the end of welding, and a display unit for displaying it 14.

  In a production site, it is common to weld many places to one work (base material 10) with one robot 7, and in many cases, the number of welding places may exceed 20 to 30 places. Then, in one workpiece, welding start control and welding end control are performed for each welding point. And when welding of all the places of one workpiece | work is complete | finished, it replaces | exchanges for the workpiece | work which is not welded of the same shape, and welds this exchanged workpiece | work next. And this is repeated and welding of a some workpiece | work is performed.

  Note that, in many welding locations of one workpiece, the welding states are different due to the influence of the welding posture of the robot 7, the torch angle, the joint shape, and the like. Therefore, a short circuit between the wire 9 and the base material 10 does not occur at the end of welding at a certain welding point, and a state where the wire 9 and the base material 10 are short-circuited at the end of welding at a certain welding point is opened. At the welding location, there may be a stick state in which the wire 9 and the base material 10 remain short-circuited at the end of welding. Thus, the state at the end of welding differs for each welding location. For this reason, it is not generated at all the welding locations just because the wire 9 and the base material 10 are opened after being short-circuited at the end of welding in one of the plurality of welding locations of one workpiece. Absent. However, when welding the next workpiece, it is necessary to adjust the welding end condition of the welded portion where the wire 9 and the base material 10 are short-circuited so that the wire 9 and the base material 10 are not short-circuited. However, if there are many welding locations, it is difficult to grasp the welding location where the wire 9 and the base material 10 are short-circuited. Therefore, the welding location where the short circuit between the wire 9 and the base material 10 is detected is stored in the storage unit 13 using the output of the control unit 3 as an input, and the contents of the storage unit 13 can be displayed on the display unit 14. As a result, it is possible to easily grasp and adjust the location where adjustment of the welding end conditions such as voltage and current is necessary. The short-circuited welding location is identified and stored in the storage unit 13 based on the operation program of the robot 7 stored in a robot control device (not shown) that controls the robot 7 and the determination result of the short-circuit detection unit 5. Can do. Further, a robot control device (not shown) may be provided in the welding power source device 1.

  Further, as the adjustment of the welding end condition, the first current is set higher than a preset initial value or the first voltage is set in advance so that a short circuit does not occur during the welding of the next workpiece. At least any one of setting higher than the set initial value or setting the first predetermined time longer than the preset initial value is set, or these are combined. And by performing such adjustment, the amount of melting at the tip of the wire 9 is increased, the distance between the tip of the wire 9 and the base material 10 is increased, and a short circuit hardly occurs. These initial values are, for example, about 20 to 50 A for the first current, about 10 to 20 V for the first voltage, and about 20 to 100 msec for the first predetermined time. is there. These adjustment amounts are about 20 to 50 A at the first current, about 5 to 10 V at the first voltage, and about 20 to 50 msec at the first predetermined time. . If these increases are insufficient, the adjustment amount may be further increased. The initial value and adjustment amount (increase amount) such as time, voltage value, and current value may be fixed values obtained from experiments or the like, or set welding current set in the welding power source device 1 when welding is performed. Alternatively, it may be determined by the control unit 3 based on the set welding voltage, wire feed speed, shield gas type, wire material, wire diameter, welding method, and the like.

  In addition, it is necessary to adjust the welding conditions so that the welding portion that is in a stick state at the end of welding does not become a stick state when the next workpiece is welded. Accordingly, the first current is set higher than a preset initial value, or the first voltage is set higher than a preset initial value, as in the case where the short circuit occurs and opens. Alternatively, the first predetermined time is set longer than a preset initial value, or a combination thereof. Thereby, the amount of melting at the tip of the wire 9 is increased, and the distance between the tip of the wire 9 and the base material 10 is increased. Here, the initial value is the same as when the short circuit occurs and is opened, but the adjustment amount in the stick state is larger than that when the short circuit occurs and is opened. The increase amount is about 40 to 70 A, the increase amount is about 15 to 20 V at the first voltage, and the increase amount is about 40 to 100 msec at the first predetermined time. The reason why the adjustment amount in the stick state is larger than that in the case where the short circuit occurs and is opened is that the shortage of energy for melting the wire 9 is less than in the case where the short circuit occurs and the wire is opened. This is because it is necessary to give more energy than when a short circuit occurs and opens.

  The initial value and adjustment amount (increase amount) such as time, voltage value, and current value may be fixed values obtained from experiments or the like, or set welding current set in the welding power source device 1 when welding is performed. Alternatively, it may be determined by the control unit 3 based on the set welding voltage, wire feed speed, shield gas type, wire material, wire diameter, welding method, and the like.

  The newly set first current, first voltage, and first predetermined time may be fixed values, or may be values obtained by adding an increase value to a preset initial value. Alternatively, it may be calculated by multiplying a preset initial value by a coefficient larger than 1, for example, 1.5.

(Embodiment 3)
This embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the location similar to Embodiment 2, and detailed description is abbreviate | omitted. The difference from the second embodiment is that a setting availability setting unit 15 is provided. FIG. 1 shows an example in which a setting availability setting unit 15 is provided on the display unit 14.

  In FIG. 1, the display unit 14 includes a setting availability setting unit 15 that sets availability of a new setting in the display area. The setting permission / inhibition setting unit 15 is implemented when the wire 9 and the base material 10 are short-circuited at the end of welding and then released, or when the wire 9 and the base material 10 remain in contact with each other. Instead of automatically performing the adjustment of the first current, the first voltage, and the first predetermined time described in the second embodiment, the operator selects and determines whether or not the adjustment can be performed. is there.

  Depending on the operator, although the welding condition is automatically adjusted to the suitability value, it may not be preferred that the welding condition is changed without the operator's knowledge, and the setting availability setting unit 15 is provided. Thus, it is possible to adjust the welding end condition at the operator's will.

  In addition, since this setting availability is automatically displayed only from the multiple welding locations where the welding end condition should be adjusted, the corresponding location can be selected from many welding locations in a short time, and productivity is improved. Can be improved.

(Embodiment 4)
This embodiment will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the location similar to Embodiment 1-3, and detailed description is abbreviate | omitted. The difference from the first to third embodiments is that after determining that the wire 9 and the base material 10 are opened after being short-circuited, the control unit 3 changes the second current and the third voltage shown in FIG. This is the point that the voltage is applied for a predetermined time. As a result, a ball of an appropriate size can be formed at the tip of the wire 9 after the short circuit is opened, and an arc start mistake is suppressed to reduce production line stoppage and extra post-processing, thereby improving productivity. can do. The control unit 3 controls the current so as to be the second current, and the third voltage is determined corresponding to this current. Further, the control unit 3 may control the voltage so as to be the third voltage, and the second current may be determined corresponding to this voltage.

  According to the above-described first to fourth embodiments, it can be determined that the wire 9 and the base material 10 are opened after being short-circuited after the end of welding. Then, in order to prevent a short circuit when welding the next workpiece, at least one of the first voltage, the first current, or the first predetermined time at the welding end portion of the welding location where the short circuit has occurred. This can suppress the occurrence of a short circuit. In addition, since the ball at the tip of the wire 9 at the end of welding can be formed in an appropriate shape, it is possible to suppress arc start mistakes and reduce production line stop and extra post-processing.

  The welding end control method and welding method of the present invention can suppress the influence of slag at the time of arc start by appropriately forming the shape of the wire tip at the end of welding, In order to improve welding productivity, arcs are generated but arc breaks frequently occur and the start part bead length is insufficient and spatter adheres to the base metal, and the production line is stopped and unnecessary post-processing steps are suppressed. This is industrially useful.

The figure which shows schematic structure of the welding apparatus in Embodiment 1. FIG. (A) The figure which shows the time change of the wire feeding speed in Embodiment 1 (b) The figure which shows the time change of the welding voltage in Embodiment 1 (c) The figure which shows the time change of the welding current in Embodiment 1 (D) The figure which shows the time change of the wire tip condition in Embodiment 1. (A) The figure which shows the time change of the wire feeding speed in Embodiment 1 (b) The figure which shows the time change of the welding voltage in Embodiment 1 (c) The figure which shows the time change of the welding current in Embodiment 1 (D) The figure which shows the time change of the wire tip condition in Embodiment 1. (A) The figure which shows the time change of the wire feeding speed in Embodiment 4, (b) The figure which shows the time change of the welding voltage in Embodiment 7, (c) The figure which shows the time change of the welding current in Embodiment 7. (D) The figure which shows the time change of the wire tip condition in Embodiment 7. (A) The figure which shows the time change of the conventional wire feeding speed (b) The figure which shows the time change of the conventional welding voltage (c) The figure which shows the time change of the conventional welding current (d) The conventional wire tip situation Diagram showing changes over time (A) The figure which shows the time change of the conventional wire feeding speed (b) The figure which shows the time change of the conventional welding voltage (c) The figure which shows the time change of the conventional welding current (d) The conventional wire tip situation Diagram showing changes over time Conventional process flowchart at the end of welding

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding power supply device 2 Power supply part 3 Control part 4 Output voltage detection part 5 Short circuit detection part 6 Welding torch 7 Robot 8 Wire feeding part 9 Wire 10 Base material 11 Arc 12 Output current detection part 13 Memory | storage part 14 Display part 15 Setting possibility Setting section

Claims (6)

A welding end control method for detecting contact between the wire and the workpiece by applying a voltage for a predetermined time between the wire that is a consumable electrode and the workpiece after the welding output is stopped,
When the detection voltage in the predetermined time is increased from the decreased voltage after being decreased from the applied voltage, it is determined that the wire and the workpiece are opened after being short-circuited, and the wire and the After it is determined that the workpiece is opened after being short-circuited, the second current and the third voltage are applied for a fourth predetermined time in a state where the wire and the workpiece are not short-circuited and opened. Then, a ball having an appropriate size is formed at the tip of the wire, and the third voltage is a voltage that is different from the detected voltage, the applied voltage, and the lowered voltage . The third voltage is different from the voltage applied to detect contact between the wire and the workpiece and is higher than the voltage applied to detect contact between the wire and the workpiece. The welding end control method according to claim 1. The predetermined time for applying a voltage between the wire and the workpiece after stopping the welding output in order to detect the contact between the wire and the workpiece is a period during which the molten pool vibrates after the welding output is stopped. The welding end control method according to claim 1 or 2 including. In order to detect contact between the wire and the workpiece, the welding arc is applied between a predetermined time during which a voltage is applied between the wire and the workpiece after the welding output is stopped and a fourth predetermined time. The welding end control method according to any one of claims 1 to 3, wherein a predetermined period for turning off the welding output is provided for complete disappearance. Storing the determined result in the storage unit;
The welding end control method according to any one of claims 1 to 4 , further comprising a step of displaying the determination result stored in the storage unit on a display unit. Among a plurality of welding locations, a contact is detected by detecting a contact between the wire and the workpiece to be welded by applying a voltage between the wire that is a consumable electrode and the workpiece to be welded for a predetermined time after the welding output is stopped. The welding end control method according to claim 5, wherein the welded part is stored in the storage unit.

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