JP2010240664A - Welding robot and method for controlling weaving operation in welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a technique for avoiding reduction in welding quality and damage of a tip part of a torch due to a fact that weaving operation in a scheduled locus is not performed by interference between the torch and a member to be welded accompanying the weaving operation in a welding robot having characteristics in the weaving operation, and a welding method. <P>SOLUTION: A correction angle θb for avoiding the interference between the tip part of the torch and the member to be welded due to the weaving operation is set in the controller of the welding robot. The controller of the welding robot calculates the correction angle θ=θbsinωt around an axis Yw on weaving coordinates and the torch is rocked by θ around the axis Yw to form a torch attitude after next minute time. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a welding robot and a welding method characterized by a weaving operation, and relates to a welding robot and a welding method characterized by a weaving operation when welding a workpiece (workpiece) having a deep groove. It is.

  The welding of a large structure is usually performed using a positioner and a welding robot that hold a temporarily welded workpiece and change the workpiece posture in a timely manner. A general welding robot is an articulated robot as shown in FIG. 3, and has six joint portions (coupled so as to be capable of turning or swinging) between the base 47 and the torch 1 attached to the tip of the arm. The position of the tip of the torch 1 (precisely, the tip of the wire) in the three-dimensional space and the attitude of the torch at that position (the angle in the three-dimensional direction) are used as teaching and CAD data. Based on the control, the torch 1 is caused to travel along the designated weld line.

  The welding robot moves the torch at the position xyz of the tip of the welding wire on the three-dimensional coordinates (base coordinates XYZ) of the robot itself and the orientation of the tip of the welding wire at the base coordinates (hereinafter referred to as “torch posture”) noa. Is controlling. Here, n, o, and a indicating the torch posture are the lengths in the X, Y, and Z axis directions on the base coordinates of the axis of the welding wire having a unit length (projection lengths on the YZ plane, ZX plane, and XY plane). That is).

  Note that the protruding length of the welding wire from the tip of the torch is registered in the controller in advance, and the controller knows the positional relationship between the tip of the torch and the tip of the welding wire from the protruding length and the torch posture. Therefore, the position and direction of the wire tip are set by correcting these values and setting the position of the torch tip and the posture of the torch body.

  In arc welding, there is a limit to the thickness that can be welded by one run (pass) of the torch along the workpiece welding line. Welding is performed in a plurality of passes by providing a groove on the surface. In this case, since the opening having a certain width is formed between the members to be welded to each other in the portion provided with the groove, it is necessary to fill this opening with a weld bead, and in order to perform wide overlaying A weaving operation is performed in which the wire tip is reciprocated in the width direction of the groove perpendicular to the direction of the welding line (traveling direction of the torch).

  As shown in FIG. 4, the weaving operation is performed by aligning the origin of the base coordinates XYZ with the welding start position, rotating the coordinate axis around the Z axis so that the projected line of the welding line L on the XY plane is in the Y direction, Next, rotate the coordinate axis around the rotated X axis (Xw axis) and align the Y axis (Yw axis) after the rotation with the welding progress direction of the welding line L on the weaving coordinate XwYwZw. This is an operation of moving in the Yw direction while meandering (generally a sine curve) on the XwYw plane (hereinafter referred to as “weaving plane”).

  Since the downward welding is desirable for good welding, the positioner holding the workpiece sets the orientation of the workpiece so that the downward welding is realized. Therefore, when the torch is downward and the weld line is horizontal, the weaving surface and the XY plane of the base coordinates are parallel. When the weaving surface is inclined with respect to the XY plane, the weaving width direction (Xw direction) is set by designating the inclination angle around the Yw axis of the weaving surface.

The weaving operation is set in the controller of the welding robot by inputting numerical values of the period given by the amplitude Wb and the angular velocity ω. The controller of the welding robot includes the weaving in the welding robot by converting the position of the wire tip after the next minute time including the weaving from the weaving coordinate system to the base coordinate system to obtain the movement target value of the wire tip. Perform welding operation. That is,
(1) The movement target position xyznoa of the wire tip after the next minute time on the base coordinates is calculated from the moving direction and speed (movement vector) of the torch along the weld line.
(2) From the weaving operation command, weaving relative amounts (components for performing the weaving operation) Wx, Wy, Wz of the sine wave are calculated and added to the xyz value.
The destination of the torch after a minute time is calculated by the procedure described above.

  As shown in FIG. 5, the weaving is performed by moving the torch in the Xw direction in the weaving coordinate system without changing the torch posture, that is, without changing the angle of the torch 1. For example, FIG. As shown, the wire 2 is made to swing linearly around the Yw axis of the weaving coordinate system, for example, centering on the tip of the torch body (referred to as swinging where the wire tip reciprocates on a straight line; the same applies hereinafter). Yes, but it's not common.

  Patent Document 1 below proposes a technique for performing a weaving operation so as to minimize the movement of the joint portion of the welding robot. In this case, the parallel weaving shown in FIG. 5 and the linear oscillation shown in FIG. 6 are proposed. It is considered that the weaving operation is performed in a manner in which dynamic weaving is combined. The angle around the Xw axis of the welding torch 1 is usually a direction perpendicular to Yw from the viewpoint of arc stability. However, the welding start position and the welding end position are shown in, for example, Patent Document 2. As described above, in order to avoid collision between the tip of the torch and the tab, welding may be performed by inclining the torch around the Xw axis.

Japanese Patent Laid-Open No. 2005-21971 JP-A-6-234074

  In the conventional weaving operation described above, the interference between the torch tip and the workpiece caused by the weaving including parallel weaving, linear swing weaving and the weaving operation proposed in Patent Document 1 is not considered at all. Not. When the thickness of the members 31 and 32 to be welded is increased, the depth of the groove 33 is also increased, and when the welding toward the bottom of the groove is performed, the torch tip 11 enters the groove, When the weaving is performed, the tip of the torch and the welded members 31 and 32 may interfere with each other.

  When such interference occurs, the welding operation hardly stops, and the movement of the tip of the torch is restricted by the member to be welded, and welding is usually performed without performing the desired weaving operation. is there. Such interference between the torch tip 11 and the members to be welded 31 and 32 is not only in the case of the parallel weaving shown in FIG. It can also happen.

  Such interference between the tip of the torch and the member to be welded usually occurs at the top of the peak of the sine curve of the weaving operation that is set so as to draw a sine curve. There is no problem. However, if the amount of interference is large, the wire tip trajectory deviates from the normal trajectory, which causes a problem in welding quality. In the case of parallel weaving, such interference can be avoided by increasing the protruding length of the wire from the tip of the torch, but it is not desirable because the arc becomes unstable and the welding quality may be deteriorated. .

  Further, recently, a technique for performing welding by correcting the position of the tip of the torch in the Xw direction in the weaving coordinate system so that the arc flies in an appropriate direction while observing the state of the arc with an arc sensor has been put into practice. When such a technique is adopted, the torch tip may swing in the Xw direction beyond the deflection width planned by the operator, and the possibility of interference between the torch tip and the member to be welded increases.

  An object of the present invention is to obtain technical means for avoiding deterioration in welding quality and damage to the tip of the torch due to the absence of the weaving operation at the planned locus due to the interference between the torch and the member to be welded accompanying the weaving operation. .

  The present invention sets the correction angle θb for avoiding the interference between the torch tip and the member to be welded based on the weaving operation during welding in the controller of the welding robot, so that the welding due to the interference between the torch tip and the member to be welded is set. This prevents quality degradation.

  The correction angle θb is a correction value of the torch angle around the axis in the torch traveling direction at the maximum amplitude position of the weaving operation. If the original weaving operation is parallel weaving, the upper portion of the torch at the maximum amplitude position of the weaving is If the original weaving motion is linear swing weaving, tilt the torch in the direction that reduces the torch angle around the axis of the torch travel direction at the maximum weaving amplitude position. This is the angle for linear rocking. The correction angle θ in the middle of the amplitude of the weaving operation is θbsinωt. If θb is set to 0, welding is performed by the conventional weaving operation that is the original weaving operation.

  The set correction angle θb is a correction component of the angle formed by the Zw axis and the line formed by projecting the axial center of the wire protruding from the tip of the torch on the ZwXw plane in the weaving coordinate system at the maximum amplitude. The welding robot calculates the position coordinate xyz of the wire tip in the base coordinate system and the torch posture noa by adding the correction amount θ to the original weaving operation.

That is, the controller of the welding robot
(1) The movement target position [xyznoa] of the wire tip after the next minute time on the base coordinates is calculated from the moving direction and speed (movement vector) of the torch along the weld line.
(2) From the weaving operation command, weaving relative amounts (components for performing the weaving operation) Wx, Wy, Wz of the sine wave are calculated, and added to the xyz value to determine the wire tip after the next minute time The target position.
(3) A correction angle θ = θbsinωt around the Yw axis on the weaving coordinates is calculated.
(4) The torch posture noa calculated in (1) is converted into a weaving coordinate system, and the torch is swung by θ around the Yw axis.
(5) The xyz value after adding Wx, Wy, and Wz calculated in (2) and the torch posture noa after the swing are set as the target position and torch posture of the wire tip after the next minute time.
(6) The wire tip is moved to the target position and the torch posture is set to the target posture.
The operations (1) to (6) are repeated at minute time intervals.

  By this invention, it is possible to avoid the interference between the tip of the torch and the work piece during welding and to perform higher quality automatic welding without changing the weaving command and the welding teaching method according to the conventional method. There is an effect of becoming. Regardless of whether the weaving operation before correction is parallel weaving, linear weaving weaving, or a combination of these weaving operations, the conventional weaving operation commands are applied. Interference between the torch and the member to be welded can be avoided, without impairing the advantages of the weaving operation in the conventional method, and without changing the command method of the weaving operation in the conventional method. There is an effect that it is possible to prevent deterioration of the welding quality due to.

Explanatory drawing which shows operation | movement of the torch tip before (a) and after correction (b) in parallel weaving The same figure as in Fig. 1 for linear rocking weaving A diagram schematically showing welding work using a welding robot Diagram showing weaving coordinate system and weaving operation on the coordinates The figure explaining interference of the tip of a torch and a member in parallel weaving Diagram similar to FIG. 4 for linear swing weaving

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a view showing a welding operation using a welding robot, and 3 is a workpiece. The workpiece 3 is a structure obtained by temporarily welding constituent members (members to be welded) 31 and 32 to be welded, and is supported by a positioner (not shown). A welding robot 4 shown in the figure is an articulated robot, and a first arm 42 is swingably connected to a main body 41 turning around a vertical axis, and a second arm 43 is connected to the tip of the first arm 42. The torch holder 44 is attached to the tip of the second arm 43 so as to be swingable in the vertical direction and pivotable about the axis, and the torch holder 44 is attached to the tip of the second arm 43 so as to be rotatable and swingable.

  The controller 45 controls the turning angle, the swing angle, and the turning angle of the welding robot 4 to maintain the predetermined torch posture while keeping the tip of the wire 2 protruding from the tip of the torch along the predetermined welding line L. To move. For example, in the case of teaching, the position and direction of the weld line L are determined by the operator inputting the coordinates of the start point and end point of the weld line L and the trajectory (straight line, arc, etc.) of the weld line between them to the controller. .

  The operation stored in the controller 45 by teaching is an operation not including weaving. The weaving operation is designated by numerically inputting the amplitude Wb, angular velocity ω, or frequency f (= 1 / ω) from the controller. The controller 45 performs a weaving operation given by W = Wbsinωt in the Xw direction in FIG. 4 while moving the torch in the movement direction (Yw direction in FIG. 4) taught by teaching.

The operator operates the welding robot 4 before starting actual welding after instructing the teaching and weaving operations as described above. At this time, as described above, the controller 45
(1) The movement target position [xyznoa] of the wire tip after the next minute time on the base coordinates is calculated from the moving direction and speed (movement vector) of the torch along the weld line,
(2) From the weaving operation command, weaving relative amounts of sine waves (components for performing the weaving operation) Wx, Wy, Wz are calculated, and added to the xyz value,
(3) Move the wire tip to the destination of the torch after the calculated next minute time,
By repeating this procedure, the welding operation with weaving is realized. The operator confirms the movement of the tip of the torch at this time, and if an interference between the tip of the torch and the members to be welded 31 and 32 is recognized, a correction angle θb considered to be necessary for avoiding the interference is input to the controller 45. To do.

When the correction angle θb is input, the controller 45 controls the position of the wire tip and the torch posture by a process including correction. That is, the target position xyz where the wire tip moves on the base coordinates after the next minute time, the torch posture noa at the target position, and the weaving relative amounts Wx, Wy, Wz of the sine wave are the conventional (1) and (2). After calculating by means,
(3) Calculate a correction angle θ = θbsinωt around the Yw axis on the weaving coordinates,
(4) The torch posture noa calculated in (1) is converted into a weaving coordinate system, and the torch is swung around the Yw axis by θ,
(5) The xyz value after adding Wx, Wy, and Wz calculated in (2) and the torch posture noa after the swing are set as the target position and posture after the next minute time,
(6) The operations of (1) to (6), in which the tip of the wire is moved to the target position and the torch posture is set to the target posture, are repeated at minute intervals.

  With this control, in the case of parallel weaving, the operation of the tip of the torch before correction in FIG. 1A is as shown in FIG. 1B, and the torch is moved inward by the correction angle θb at the position of the maximum weaving amplitude. That is, the welding is performed with the upper side of the torch inclined in a direction that becomes the inner side of the weaving width (the inner side of the groove). In the case of linear swing weaving, the posture of the torch before correction shown in FIG. 2A stands by the correction angle θb as shown in FIG. 2B (perpendicular to the XwYw plane in the weaving coordinate system). It is close to the state.

  That is, the correction angle θb is designated as a positive value in the case of parallel weaving and as a negative value in the case of swinging weaving. Whether the correction angle θb is input as a positive value or a negative value can be determined depending on which member and where the tip of the torch in the test run interferes.

  After inputting the correction angle θb, the operator makes the test run of the torch 1 again and confirms that interference has been avoided before starting the actual welding operation. By performing welding as described above, it is possible to avoid a situation in which the welding torch and the member to be welded interfere with each other during automatic welding by the welding robot and the welding quality is deteriorated or the tip of the torch is damaged.

DESCRIPTION OF SYMBOLS 1 Torch 3 Workpiece 4 Welding robot 31, 32 Welded member 33 Groove 45 Controller

Claims (4)

  In welding with a weaving operation, when mechanical interference between a welding torch and a member to be welded occurs, a tip of the torch is inclined in a direction to avoid the interference.   A correction angle setting means for setting a correction angle θb for avoiding a mechanical interference between a welding torch mounted on a torch mounting portion and a member to be welded when a specified weaving operation is performed, and a weaving An interference prevention means for tilting the torch mounting portion according to the amount of movement of the weaving in the amplitude direction so that the correction angle is tilted in a direction to avoid the interference when the amplitude of operation is maximum. robot. In a welding robot that sets an amplitude Wb and a frequency f or an angular velocity ω and performs a weaving operation at Wbsinωt, where t is the elapsed time from the start of welding
The welding robot according to claim 2, wherein the interference preventing means inclines the torch mounting portion at an angle calculated by θbsinωt. In a welding robot equipped with a controller that controls the position and posture of the torch mounting portion by calculating the next destination position of the torch tip and the torch posture at a set minute time interval,
When the next destination position and torch posture are calculated,
The interference preventing means calculates an angle θ = θbsinωt about the Yw axis on a weaving coordinate where the advancing direction of the torch tip is Yw and the amplitude direction of the weaving is Xw, and converts the torch posture into a weaving coordinate system. , Tilting the torch mounting portion around the Yw axis by the angle θ, and controlling the position and posture of the torch mounting portion after the next minute time as the torch posture after the next minute time. The welding robot according to claim 3, which is characterized.

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