JP2011156578A - Controller of arc welding robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of an arc welding robot, the controller capable of automatically adjusting a start timing of preflow in accordance with teaching data, welding environment, and the like. <P>SOLUTION: This invention is related to a controller 16 for an arc welding robot, in which welding starts by starting gas output at a time traced back by a preflow time from the time when a welding torch 7 reaches a welding starting position. A gas flow rate characteristic table is preliminarily stored in which a relation is determined between an interval time from gas stopping to outputting and an allowable flow rate-reaching time for the gas flow rate to reach an allowable value. When the next section exists through preceding interpretation of teaching data during the welding, a required time is computed from the completion of the welding until the start of the next welding. With this required time inputted in the gas flow rate characteristic table, feasibility is determined of securing the allowable flow rate-reaching time within the required time to compute a corrected preflow time. In accordance with this corrected preflow time, the gas output is controlled. Thus, a stable gas flow rate is constantly maintained in starting welding. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an improved arc welding robot controller for performing gas shielded arc welding.

  In consumable electrode type or non-consumable electrode type gas shielded arc welding, shield gas such as carbon dioxide gas and argon gas is blown out to the arc and molten pool to shield it from the atmosphere, and the atmosphere enters the welding atmosphere. It is necessary to prevent. It is important that the flow rate of the shielding gas is within a certain allowable range. When the gas flow rate is small, the arc state becomes unstable due to the intrusion of the atmosphere into the welding atmosphere, so that blowholes are generated or a large amount of spatter is generated. Conversely, if the gas flow rate is too high, turbulent flow may occur, resulting in poor shielding or insufficient melting. As a result, the appearance of the weld bead may be deteriorated, resulting in poor welding.

  Shielding from the atmosphere with shielding gas is not limited to arc welding, but is important at the welding start position. For example, in a conventional arc welding robot, after moving the welding torch to the welding start position, the shield gas is ejected while being stopped, and the arc is generated after the gas flow rate is stabilized. However, if the welding gas is ejected only after the welding torch reaches the welding start position, it takes a certain amount of time until the gas flow rate is stabilized, and this time becomes a delay factor of the cycle time.

  Patent Document 1 discloses a welding robot control device that ejects shield gas by a preset preflow time from a time when a welding torch reaches a welding start position. According to the prior art described in Patent Document 1, it is possible to reduce an extra time until the gas flow rate is stabilized. That is, the delay of the cycle time can be eliminated.

  By the way, in a general arc welding apparatus in which shield gas is turned on / off by a solenoid valve, an excessive flow of shield gas is ejected during the preflow process required when the solenoid valve is opened, that is, when welding is started. The This phenomenon is expressed as rush current below. The rush flow differs in peak flow rate and duration time depending on the pipe length, pressure, time elapsed since the last gas OFF, etc., and therefore the time from when the shield gas is jetted until the flow rate falls within the allowable range also differs. An example is shown below. Note that the elapsed time from the previous gas OFF means the elapsed time from the shield gas output stop in the previous welding section when there are a plurality of continuous welding sections.

  FIG. 6 is a diagram for explaining the state of the rush of shield gas. The figure shows how the gas flow rate changes with time depending on how many seconds have elapsed since the last gas OFF when the set flow rate is 15 liters / minute. FIG. 4A shows the flow rate change when the elapsed time from the previous gas OFF is 4 seconds. Similarly, FIG. 7B shows the flow rate change at 3 seconds, FIG. 10C shows 2 seconds, FIG. 10D shows 1 second, and FIG. 9E shows 0.5 seconds. . As shown in the figure, for a while after opening the solenoid valve, an excessive flow rate of gas is ejected by the rush flow, and approaches the set flow rate of 15 liters / minute with the passage of time. Assuming that the preflow time is set to 0.5 seconds, for example, in FIG. 5A, the arc start process is performed in a state where a shield gas of about 42 liters / minute is output. There is a possibility that poor welding as described above may occur.

JP 2006-21241 A

  In the above-described prior art, the time from the start of the injection of shield gas until the flow rate falls within the allowable range is determined in advance as the preflow time. The preflow time is a value set by the worker according to his / her own empirical rules, and is often set to a fixed value of about 0.1 to 0.5 seconds, for example. That is, the conventional technology does not take into consideration the fact that the gas flow rate changes depending on the influence of the rush flow described in FIG. 6 or how many seconds have elapsed since the previous gas OFF. For this reason, the gas flow rate at the time when the preflow time has elapsed is not necessarily within the allowable range. If the gas flow rate is outside the allowable range, poor welding may occur. In order to prevent the occurrence of poor welding, adjustment such as setting a long preflow time is necessary. However, if a long preflow time is set, it causes a delay in cycle time.

  Therefore, the present invention provides a control device for an arc welding robot capable of ensuring a necessary gas flow rate at the start of welding by automatically adjusting the start timing of preflow control according to teaching data, welding environment, and the like. It is an object.

The first invention is
The welding torch is moved based on a work program in which a plurality of sections for performing welding work are stored, and the shield gas is output at a time that is a predetermined preflow time from the time when the welding torch reaches the start position of the section. In the control device of the arc welding robot that sequentially executes the step of starting welding after the preflow time has elapsed and ending welding at the end position of the section, for each of the plurality of sections,
Storage means for storing a gas flow rate characteristic table defining a relationship between an interval time from stop of the shield gas to output and an allowable flow rate arrival time for the flow rate of the shield gas to reach an allowable value;
A required time calculating means for calculating a required time from the end of welding to the start of the next welding when the next section exists by pre-interpreting the work program during welding;
Determining means for inputting the required time into the gas flow rate characteristic table and determining whether the allowable flow rate arrival time can be secured within the required time;
Preflow time calculating means for calculating the allowable flow rate arrival time when the sum of the interval time and the allowable flow rate arrival time is the required time, as a corrected preflow time;
A welding control means for starting output of the shield gas at a timing according to the modified preflow time when the determination means determines that the allowable flow rate arrival time can be secured within the required time;
An arc welding robot control apparatus comprising:

  The second invention is characterized in that the welding control means does not stop the output of the shielding gas at the end of welding when the determination means determines that the allowable flow rate arrival time cannot be secured within the required time. It is a control apparatus of the arc welding robot as described in 1st invention.

  According to a third aspect of the present invention, the preflow time calculation means includes an approximate line of the gas flow rate characteristic table in which the interval time is the X axis and the allowable flow rate arrival time is the Y axis, and the required time is the X axis and the Y axis. The control device for an arc welding robot according to the first or second invention, wherein an intersection point with a straight line as each intercept value of an axis is calculated, and a Y coordinate value of the intersection point is calculated as the corrected preflow time. It is.

  According to the first invention, the optimum preflow time is automatically calculated in consideration of the flow rate change depending on the welding environment and the flow rate change due to the elapsed time from the end of the previous welding, and the timing based on this preflow time. The shield gas is output with This makes it possible to stabilize the gas flow rate required at the start of welding.

  According to the second invention, when it is determined that the shield gas cannot reach the allowable flow rate until the welding torch reaches the next welding start position, the output of the shield gas is not stopped at the end of welding. I am doing so. As a result, in addition to the effects exhibited by the first invention, the gas flow rate required at the start of welding can be further stabilized.

  According to the third aspect of the invention, since the corrected preflow time is calculated using the gas flow rate characteristic table, in addition to the effects exhibited by the first and second aspects of the invention, it is possible to optimize the gas flow rate. The preflow time can be easily calculated.

It is a lineblock diagram of an arc welding robot concerning an embodiment of the present invention. It is a functional block diagram which shows the internal structure of the robot control apparatus which concerns on this invention. It is a graph which shows an example of a gas flow rate characteristic table. It is a flowchart for demonstrating the flow of a process of a work program analysis part. It is a figure for demonstrating the concept which calculates whether correction | amendment preflow time while determining whether shield gas reaches | attains an allowable flow volume within required time based on a gas flow rate characteristic table. It is a figure for demonstrating the mode of the rush of gas.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on examples with reference to the drawings.

  FIG. 1 is a configuration diagram of an arc welding robot 1 according to the present invention. As shown in the figure, the arc welding robot 1 is roughly constituted by a manipulator 14, a teach pendant 15, a robot control device 16 and a welding power source 3.

  In the figure, a manipulator 14 automatically performs arc welding on a workpiece 2, and includes a plurality of arm portions and a wrist portion, and a plurality of servo motors (not shown) for rotationally driving them. And is composed of. A welding torch 7 is attached to the tip of the upper arm of the manipulator 14. The welding torch 7 is for guiding a welding wire 13 having a diameter of about 1 mm wound around a wire reel (not shown) to a taught welding line on the workpiece 2.

  The teach pendant 15 is used to input teaching points and welding conditions (welding current, welding voltage, welding speed, etc.) of a section for performing welding as a work program Dw and to set a preflow time Pt in advance. These are stored in the hard disk 22 to be described later.

  The robot control device 16 outputs an operation control signal Mc to the manipulator 14 based on the work program Dw input from the teach pendant 15 or outputs a welding control signal Ws to the welding power source 3.

  The welding power source 3 receives a gas output control signal Gs from the robot controller 16 and outputs a solenoid valve control signal Ds for injecting a shield gas from the welding torch 7 to a gas solenoid valve 19 described later. Further, an arc start process for starting power supply between the welding torch 7 and the workpiece 2 is performed with the welding control signal Ws from the robot control device 16 as an input. The gas solenoid valve 19 supplies the shield gas from the gas cylinder 20 to the welding torch 7 with the solenoid valve control signal Ds as an input.

  FIG. 2 is a functional block diagram showing the internal configuration of the robot control device 16. The robot control device 16 includes a microcomputer and various memories, and more specifically, a work program analysis unit 21, a hard disk 22, a trajectory planning unit 23, a RAM 8, a buffer 24, a servo control unit 25, and a servo drive unit. 26, a current position monitoring unit 27 and a welding control unit 28 are provided.

  The hard disk 22 corresponding to the storage means is a non-volatile memory, and previously stores welding control parameters such as a work program Dw and a preflow time Pt, and a gas flow rate characteristic table Gt. The gas flow rate characteristic table Gt is data in which a relationship between an interval time from the stop of shield gas to output and an allowable flow rate arrival time for the gas flow rate to reach an allowable value is determined in advance. Details of the gas flow rate characteristic table Gt will be described later.

  The work program analysis unit 21 reads the work program Dw stored in the hard disk 22 for each teaching step and analyzes the contents. For example, the work program analysis unit 21 reads a movement command (consisting of data such as coordinates and speed information) included in the work program and notifies the trajectory planning unit 23 of the movement command. Further, the teaching step for starting the gas output is obtained, and the timing for starting the gas output is obtained with reference to a predetermined preflow time Pt and notified to the trajectory planning unit 23. The work program analysis unit 21 corresponds to a required time calculation unit, a determination unit, and a preflow time calculation unit.

  The trajectory planning unit 23 stores various movement commands sent from the work program analysis unit 21 in the buffer 24. This movement command is also given gas output timing and the like. Further, the trajectory planning unit 23 reads out the movement command stored in the buffer 24, makes a trajectory plan for the welding torch 7 based on the command, and servo-controls information such as the rotation angle and rotation speed of each motor of the manipulator 14. Notify the unit 25.

  The buffer 24 includes a so-called first-in first-out (FIFO) memory, and stores a movement command sent from the trajectory planning unit 23.

  The servo control unit 25 sends a drive signal to the servo drive unit 26 to rotationally drive each motor of the manipulator 14 based on the track plan sent from the track planning unit 23. The servo control unit 25 acquires an output from an encoder (not shown) and sends the information to the current position monitoring unit 27.

  The servo drive unit 26 outputs an operation control signal Mc to each motor based on a command from the servo control unit 25.

  The current position monitoring unit 27 monitors the current position of the welding torch 7 based on a detection signal from an encoder (not shown) provided in each motor of the manipulator 14.

  The welding control unit 28 serving as a welding control means outputs various commands from the current position monitoring unit 27 to the welding power source 3 at an appropriate processing timing, thereby causing welding by the welding torch 7 and ejection of shield gas. is there. More specifically, the welding control unit 28 outputs a gas output control signal Gs for injecting the shield gas to the welding power source 3 at the processing timing designated by the current position monitoring unit 27. Based on this signal, the welding power source 3 outputs an electromagnetic valve control signal Ds to perform opening / closing control of the gas electromagnetic valve 19. Further, the welding control unit 28 outputs a welding control signal Ws for performing welding by the welding power source 3 based on the welding control command from the current position monitoring unit 27.

  The servo drive unit 26 sends an operation control signal Mc to each motor of the manipulator 14 based on a drive command from the servo control unit 25.

  Next, the operation of the arc welding robot 1 will be described. When the activation signal is input to the robot control device 16, the work program analysis unit 21 interprets the work program Dw and performs operations such as trajectory planning, and outputs an operation control signal Mc to each motor of the manipulator 14 based on the calculation results. In addition, a gas output control signal Gs, a welding control signal Ws, and the like are output to the welding power source 3. As a result, the plurality of shafts of the manipulator 14 rotate, and gas output is started at a time that is a predetermined preflow time Pt before the time when the manipulator 14 reaches the welding start position. When the welding torch 7 reaches the welding start position while performing gas output, welding is started, the welding torch 7 is moved to the welding end position, the welding is ended, and after the afterflow control is performed, the gas output is stopped. . A series of operations so far are the same as those of the above-described conventional technology.

  When a plurality of welding sections to be welded are taught in the work program Dw, the series of steps described above are sequentially executed for each of the plurality of welding sections. In the present invention, the welding of the next welding section is performed. In order to adjust the start timing of the preflow control at the start, the following configuration is provided.

  First, the gas flow rate characteristic table will be described. The gas flow rate characteristic table Gt is stored in the hard disk 22 as storage means.

  FIG. 3 is a graph showing an example of a gas flow rate characteristic table. In the figure, the X-axis indicates the interval time [second] from the previous gas OFF to the next gas ON (hereinafter referred to as the gas OFF / ON interval time). This gas OFF / ON interval time is equivalent to a required time from the gas output stop to the next gas output start in the case where a plurality of welding sections are continuously welded. The Y axis indicates the time until the gas flow rate reaches the allowable value (hereinafter referred to as the allowable flow rate arrival time) according to the time from gas OFF to the next gas ON.

  In the figure, the relationship between the gas OFF / ON interval time when the gas set flow rate is 16 to 20 liters / minute and the allowable flow rate arrival time when the gas flow rate reaches the allowable value is approximated by lines Ka to Ke. Respectively. The shaded area in the figure shows a portion where the allowable flow rate arrival time is longer than the gas OFF / ON interval time. In other words, since the gas OFF / ON interval time is short, it shows an area where the time required to reach the allowable flow rate cannot be secured. For example, looking at the approximate line Kc when the set flow rate is 18 liters / minute, when the gas OFF / ON interval time is 1 second, the allowable flow rate arrival time is about 1.1 seconds. That is, it indicates that the gas OFF / ON interval time for reaching the allowable flow rate is insufficient. On the contrary, in the shaded outer region, the allowable flow rate arrival time is about 1.5 seconds when the gas OFF / ON interval time is 2.0 seconds. That is, the gas OFF / ON interval time for reaching the allowable flow rate can be secured.

  The data shown in the gas flow rate characteristic table Gt is data acquired in an actual welding environment (gas pressure, pipe length, set flow rate, etc.). It is desirable to prepare a plurality of data acquired under various welding environments, and to select one data according to the actual welding environment from among them. If there is no data that matches the actual welding environment, an approximate expression such as linear interpolation may be used from two adjacent data so that the corresponding data can be generated.

  Next, calculation processing of the corrected preflow time Ptn for adjusting the start timing of the preflow control at the start of welding in the next welding section will be described using the gas flow rate characteristic table Gt described above. This process is performed by the work program analysis unit 21.

  FIG. 4 is a flowchart for explaining the processing flow of the work program analysis unit 21. Details of the processing of the work program analysis unit 21 will be described with reference to this flowchart.

(1. Advance analysis process)
First, the preceding analysis process will be described. In step S11 in the figure, one teaching step of the work program Dw is read in advance. In step S12, it is determined whether or not the read teaching step is a welding end command. If it is a welding end command, the process proceeds to step S13 to be described later for further prior analysis. If it is not a welding end command, the process proceeds to step S21. In step S21, the analysis result is notified to the trajectory planning unit 23. Further, in step S22, the number of steps is incremented by 1 in order to interpret the next teaching step, and the process is terminated.

(2. Required time calculation process)
Steps S13 to S19 are processes for calculating the required time from the end of welding to the start of the next welding. The time required from the end of welding described here to the start of the next welding is the time from the end of afterflow control at the welding end position until the welding torch 7 starts moving and reaches the next welding start position. Indicates the required time. Hereinafter, the required time calculation process will be described.

  In step S13, a counter (Td) for measuring time is set to zero. In step S14, the next teaching step is read and analyzed. In step S15, it is determined whether or not the read teaching step is a welding start command. When it determines with it being a welding start command, in order to calculate correction | amendment preflow time Ptn, it transfers to step S31 mentioned later. When it determines with it not being a welding start command, it transfers to step S16.

  In step S16, it is determined whether it is a movement command. If it is determined that the instruction is not a movement command, the process returns to step S14, and the next teaching step is further analyzed in advance. If it is determined that the instruction is a movement command, the process proceeds to step S17. In step S17, a movement time Tmv for moving the welding torch 7 to the teaching position of the movement command is calculated. In subsequent step S18, the counter Td is updated. This updated counter is the required time Td from the end of welding to the start of the next welding. In step S19, the previously analyzed information is stored in the RAM 8. Thereafter, the process returns to step S14, and steps S15 to S19 are repeated until the welding start command is read in step S15. The movement command described above includes an interpolation command for moving the welding torch 7 to the next teaching point and a timer command for waiting the welding torch 7 at the teaching point for a predetermined time.

(3. Judgment processing)
In step S31, the counted required time Td is input to the gas flow rate characteristic table Gt, and it is determined whether or not the time required for the shield gas to reach the allowable flow rate can be secured within the required time Td. Hereinafter, this determination process will be described.

  FIG. 5 is a diagram for explaining the concept of determining whether the shield gas reaches the allowable flow rate within the required time Td based on the gas flow rate characteristic table Gt and calculating the corrected preflow time. Referring to the figure, with reference to the case where the set flow rate of gas is 18 liters / minute and the required time from the end of welding to the start of the next welding is 3 seconds, the determination process and the calculation process of the corrected preflow time explain.

  When a straight line L with the required time (3 seconds) from the end of welding to the start of the next welding as the intercept values of the X axis and the Y axis is drawn on the gas flow rate characteristic table Gt, the set flow rate is 18 liters / min. The intersection C of the approximate line Kc is obtained. If the intersection C is located outside the shaded area, it is determined that the allowable flow rate arrival time can be secured. When the intersection C is located inside the shaded area, it is determined that the allowable flow rate arrival time cannot be secured.

(3.1 When it is determined that the allowable flow rate arrival time can be secured)
When it is determined in step S31 that the allowable flow rate arrival time can be ensured, the process proceeds to step S41, and a process for calculating a corrected preflow time is performed. This correction preflow time calculation process will be described with reference to FIG.

  The intersection C calculated in FIG. 5 is a point where the sum of the gas OFF / ON interval time and the allowable flow rate arrival time becomes equal to the required time from the end of welding to the start of the next welding. In other words, the required time from the end of welding to the start of the next welding is divided into the allowable flow rate arrival time and the gas OFF / ON interval time with reference to the intersection C, thereby allowing for a flow rate change due to the gas OFF / ON interval time. The flow rate arrival time can be obtained. Therefore, the allowable flow rate arrival time that is the Y coordinate value of the intersection C is set as a corrected preflow time Ptn. The X coordinate value of the intersection C is the gas OFF / ON interval time Gk.

  After the calculation process of the corrected preflow time Ptn is completed, in step S42, a welding end command is analyzed, a parameter for stopping gas output at the execution timing of this command is given, and the trajectory planning unit 23 is notified. To do. In subsequent step S43, the trajectory planning unit 23 is notified of the start timing of the preflow control based on the calculated corrected preflow time Ptn. Thereafter, the process proceeds to step S33. The start timing of the preflow control described above is the time when the gas OFF / ON interval time Gk has elapsed from the gas stop time according to the welding end command, or the time that has reached the next welding start position by the corrected preflow time Ptn. Either is good.

(3.2 When it is judged that the allowable flow rate arrival time cannot be secured)
If it is determined in step S31 described above that the allowable flow rate arrival time cannot be secured, the process proceeds to step S32. In step S32, a welding end command is analyzed, a parameter for continuing gas output at the execution timing of this command is given, and the trajectory planning unit 23 is notified.

(4. Prior analysis information notification process)
The information of the teaching step analyzed in advance in steps S16 to S18 remains stored in the buffer 24 in step S19, and has not been notified to the trajectory planning unit 23 yet. In step S33, the trajectory planning unit 23 is notified of the preceding analysis information stored in the buffer 24. In step S34, the teaching step is advanced to a welding start command.

  If the allowable flow rate arrival time can be ensured by performing the processing described above until the start of welding in the next welding section, a corrected preflow time Ptn for adjusting the start timing of the preflow control is calculated. Thereafter, the trajectory planning unit 23 formulates a trajectory plan for the welding torch 7 based on the analysis information sent from the work program analysis unit 21, and servos information such as the rotation angle and rotational speed of each motor of the manipulator 14. The control unit 25 is notified. The servo control unit 25 sends a drive signal to the servo drive unit 26 to rotationally drive each motor of the manipulator 14 based on the track plan sent from the track planning unit 23. The servo drive unit 26 outputs an operation control signal Mc to each motor based on a command from the servo control unit 25.

  Then, the welding control unit 28 outputs a gas output control signal Gs for injecting the shield gas to the welding power source 3 at the processing timing designated by the current position monitoring unit 27. Based on this signal, the welding power source 3 outputs an electromagnetic valve control signal Ds to control the opening of the gas electromagnetic valve 19. That is, the output of the shield gas is started at a time that is back by the corrected preflow time Ptn from the time when the welding torch 7 reaches the welding start position.

  When the allowable flow rate arrival time cannot be ensured by the start of welding in the next welding section, welding is performed by moving to the next welding start position without stopping the output of the shield gas.

  As described above, the optimum corrected preflow time Ptn is automatically calculated in consideration of the flow rate change depending on the welding environment and the flow rate change due to the elapsed time from the end of the previous welding, and based on the corrected preflow time Ptn. The shield gas is output at the correct timing. This makes it possible to always stabilize the gas flow rate required at the start of welding. Further, since it is not necessary for the operator to set an unnecessarily long preflow time, the tact time can be shortened. By the way, in order to always stabilize the gas flow rate at the welding start position, it is conceivable to continue to blow out the shielding gas from the welding end position. However, if the elapsed time from the end of the previous welding is long, By continuing to do so, the shielding gas is wasted. In the present invention, since the gas flow rate at the welding start position can be maintained using the minimum necessary consumption, the gas consumption can also be suppressed.

  Further, when it is determined that the shield gas cannot reach the allowable flow rate until the welding torch 7 reaches the next welding start position, the output of the shield gas is not stopped at the end of welding. This makes it possible to further stabilize the gas flow rate required at the start of welding.

  Furthermore, by calculating the corrected preflow time Ptn using the gas flow rate characteristic table Gt, the optimal corrected preflow time Ptn for stabilizing the gas flow rate can be easily calculated.

DESCRIPTION OF SYMBOLS 1 Arc welding robot 2 Workpiece 3 Welding power supply 7 Welding torch 13 Welding wire 14 Manipulator 15 Teach pendant 16 Robot controller 19 Gas electromagnetic valve 20 Gas cylinder 21 Work program analysis part 22 Hard disk 23 Trajectory plan part 24 Buffer 25 Servo control part 26 Servo Driving unit 27 Current position monitoring unit 28 Welding control unit C Intersection Ds Solenoid valve control signal Dw Work program Gs Gas output control signal Gt Gas flow rate characteristic table Gk Gas OFF / ON interval time Ka to Ke Approximate line L Straight line Mc Operation control signal Pt Preflow time Ptn Modified preflow time Td Required time Tmv Travel time Ws Welding control signal

Claims (3)

The welding torch is moved based on a work program in which a plurality of sections for performing welding work are stored, and the shield gas is output at a time that is a predetermined preflow time from the time when the welding torch reaches the start position of the section. In the control device of the arc welding robot that sequentially executes the step of starting welding after the preflow time has elapsed and ending welding at the end position of the section, for each of the plurality of sections,
Storage means for storing a gas flow rate characteristic table defining a relationship between an interval time from stop of the shield gas to output and an allowable flow rate arrival time for the flow rate of the shield gas to reach an allowable value;
A required time calculating means for calculating a required time from the end of welding to the start of the next welding when the next section exists by pre-interpreting the work program during welding;
Determining means for inputting the required time into the gas flow rate characteristic table and determining whether the allowable flow rate arrival time can be secured within the required time;
Preflow time calculating means for calculating the allowable flow rate arrival time when the sum of the interval time and the allowable flow rate arrival time is the required time, as a corrected preflow time;
A welding control means for starting output of the shield gas at a timing according to the modified preflow time when the determination means determines that the allowable flow rate arrival time can be secured within the required time;
An arc welding robot control apparatus comprising:   2. The arc according to claim 1, wherein the welding control means does not stop the output of the shielding gas at the end of welding when the determination means determines that the allowable flow rate arrival time cannot be secured within the required time. Control device for welding robot.   The preflow time calculation means includes an approximate line of the gas flow rate characteristic table with the interval time as the X axis and the allowable flow rate arrival time as the Y axis, and the required time as the intercept values of the X axis and the Y axis. 3. An arc welding robot control apparatus according to claim 1, wherein an intersection point with the straight line is calculated, and a Y coordinate value of the intersection point is calculated as the corrected preflow time.

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