JPH0461751B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention applies a sensing voltage to a consumable electrode type welding torch in an automatic welding device that reproduces predetermined work contents, and uses this welding torch as a sensor. The present invention relates to a groove detection method for an automatic welding device that detects a groove in a weld line.

[Prior art] When welding a groove weld line using automatic welding equipment such as a welding robot, the position of the groove weld line is not necessarily constant depending on the workpiece, so it is difficult to accurately detect the position of the groove. This is an important matter in order to obtain accurate welding results.

Therefore, a groove detection method as shown in Japanese Patent Publication No. 58-39029 has been proposed. This conventional technology applies a sensing voltage to the welding torch, uses this welding torch as a sensor, and inputs the output to a computer to detect the groove in a short time. Detect the surface position z ₁ of the member, detect the surface position z ₂ that is a certain distance closer to the groove from the surface position z ₁ , and if z ₁ − z ₂ < zc (constant), z ₂ is While replacing z ₁ and repeating the same detection operation, z ₁ −z ₂ ≧
When zc is reached, it is determined that the welding torch has reached the groove, and the weld line position within the groove is detected.

[Problems to be Solved by the Invention] However, in the conventional groove detection method described above, detection inside/outside the groove is performed using z position data of two points detected intermittently from outside the groove (groove However, it is extremely difficult to set the constant zc based on the groove width, groove depth, and intermittent detection distance, so this setting If you make a mistake, it may not be possible to detect the groove, and depending on the constants, it may be incorrectly determined that the work has reached the groove when it is outside the groove when it is not set approximately horizontally in front of the robot.

The present invention was made to solve the above-mentioned problems, and it is possible to determine whether the groove is inside or outside without comparing the z-position data of two points with a constant, and even if the workpiece is not set approximately horizontally. It is an object of the present invention to provide a groove detection method for an automatic welding device that can be performed reliably and accurately detect the groove position of a workpiece.

[Means for Solving the Problems] In order to achieve the above object, the groove detection method for an automatic welding device of the present invention is such that a workpiece and a welding torch as a position sensor are controlled in position on three spatial axes. A method for detecting a groove in a weld line using an automatic welding device, the workpiece being arranged so that its member surface or groove intersection line is substantially orthogonal to one of the three axes, When detecting the groove by inputting the output of a position sensor by the welding torch provided in one axis direction to a computer, detecting the surface position P ₁ of the workpiece near the groove by the welding torch, and detecting the welding torch. The torch is pulled up by a predetermined distance from the position _P1 , and then moved by a predetermined distance l in the groove direction, and during the movement of the welding torch in the step, the welding torch detects the surface of the workpiece. If it is determined that the surface of the workpiece is not detected in the step, the welding torch is moved in the groove depth direction from the position reached by the welding torch, and the surface position of the workpiece is _P2
is detected by the welding torch, the welding torch is pulled up by a predetermined distance from the position _P2 , and then moved by a distance _{of 12 in} the direction of the vector _{P1P2 ---} →, so that the welding torch in the step During the movement, it is determined whether the welding torch has detected the surface of the workpiece, and if it is determined that the surface of the workpiece has not been detected in the step, replacing position _P2 with position _P1 , The welding torch is moved in the welding depth direction from the position reached by the welding torch, and the newly detected surface position of the workpiece is set as _P2 , and the step
While repeating, if it is determined that the workpiece surface is detected in the step or above, it is determined that the welding torch has reached the groove, and from the detected surface position, a predetermined position according to the groove shape is determined. The present invention is characterized in that the groove position sensing operation is executed to detect the intersection of the groove lines.

[Function] In the groove detection method of the automatic welding device of the present invention described above, two points on the workpiece surface spaced apart by a certain distance l are detected.
P ₁ and P ₂ are detected by the welding torch, and after the detection, the welding torch moves in the direction of the vector P ₁ P ₂ ---→. Therefore, if the second detection position P ₂ is within the groove of the workpiece, the groove depth direction positions z ₁ and z ₂ of positions P ₁ and P ₂ will be z ₁ < z ₂ , and the welding torch will be It will definitely move towards the inside of the groove. Also, 2
Even if the second detection position _P2 is not within the groove of the workpiece,
The welding torch is moved in the direction of the vector P ₁ P ₂ ---→, and if the workpiece is not set approximately horizontally, the welding torch can be moved along the surface of the workpiece. .

[Embodiments of the Invention] A groove detection method for an automatic welding apparatus as an embodiment of the present invention will be described below with reference to the drawings.

First, with reference to FIG. 4, the configuration of an arc welding robot, which is a type of automatic welding apparatus applied to the method of the present invention, will be explained. As shown in FIG. 4, a consumable electrode type welding torch 2 is attached to the wrist portion 1a of the multi-jointed arc welding robot 1, and its position and posture are controlled on three spatial axes. . This control is performed by the robot control panel 3 or a teaching box 4 attached to the robot control panel 3. In addition, the welding torch 2 includes
A wire (consumable electrode) is fed, and this wire
It is designed to always protrude from the welding torch 2 by an appropriate amount.

In order to use the welding torch 2 as a sensor, a welding voltage and a sensing voltage can be selectively applied between the welding torch 2 and the workpiece 7.
The welding power source 6 is equipped with a sensing power source (not shown).

Note that the workpiece 7 is fixed and supported at a suitable position and in a suitable posture by a positioner 8. Further, the welding work of the workpiece 7 by the arc welding robot 1 is performed in accordance with a program stored in the storage device of the robot control panel 3 after the contents of the welding work are taught in advance.

Below, steps 1 to 3 of the method for detecting a groove in a workpiece 7 according to this embodiment using the arc welding robot 1 described above will be described.
This will be explained using figures. In particular, in this example, a case will be described in which the method of the present invention is applied to a welded joint with a V-shaped groove butt.

First, various data necessary for groove detection will be taught. First, the protrusion length of the wire protruding from the welding torch 2 is set to a predetermined length, and then the workpiece 7
in the specified position and posture, and move it to the retracted position.
The welding torch 2 is moved and positioned to the intersection position Pf of PO and the groove line to be detected. Then, when positioning to the intersection position Pf, the following instruction code,
Input/set various data.

(a) Input a command to start stickiness sensing (which refers to a sensing operation characteristic of the present invention that detects when the groove has reached the groove in steps S5 to S23 in FIG. 1, which will be described later).

(b) Taking into account the predicted misalignment of the workpiece 7 in the x, y, and z directions, determine from which position P1 to start the stickiness sensing with respect to the intersection position Pf by determining the distance in the x, y, and z directions. Set as .

(c) Set the direction in which the sensing operation is to be performed from the stick sensing start position P1 (the direction in which the groove is present; that is, in this embodiment, the +x direction as shown in FIG. 2).

(d) Enter the shape of the welded joint to be detected. In addition,
The joint shapes for which the groove line intersection can be detected by this method are V-shaped groove butt, R-shaped groove butt, and downward fillet.

(e) Set the torch movement distance l (see Fig. 2) for stick sensing. This distance l is appropriately given to accommodate variations in groove width.

(f) After detecting that the wire has reached the groove using stick sensing, input a wire sensing command according to the weld joint shape to detect the groove line intersection Pf.

(g) Input welding conditions and welding power supply ON command.

Then, normal teaching is performed up to the welding end position of the welded joint, and a stiff sensing release command is input. As shown in Figure 2, the x, y, z coordinate system is set such that the x axis is in the direction perpendicular to the groove line, the y axis is in the groove line direction, and the z axis is in the groove depth direction. There is.

After completing the teaching operation as described above, the created teaching program is reproduced every time the workpiece 7 is set, and the intersection position Pf of the groove lines of the workpiece 7 is detected. The reproducing operation at this time will be explained with reference to the flowchart shown in FIG. 1 and FIGS. 2 and 3.

First, after setting the workpiece 7, welding torch 2
(step S1), and check whether the taught posture of the joint shape is downward (V-shaped groove butt, L-shaped groove butt, downward fillet). is determined (step S2).

If the joint posture is not downward (for example, in the case of a horizontal fillet or overlapped fillet), the command codes for the stick sensing start command and data e and f at the time of the above teaching are all ignored, and the joint shape (horizontal fillet) is ignored. A predetermined wire sensing operation corresponding to the groove (or overlapped fillet) is executed to detect the intersection of the groove and the groove line (step S3). This step S2, S
The operation content in 3 is to cope with the case where the Stuck Sensing Start command is input by mistake during teaching. Originally, the Stuck Sensing Start command was input only when the operator was in the downward joint posture. be.

Here, in step sensing, step S
As will be described later in steps 5 to S23, in order to efficiently reach the groove, it is necessary to obtain a vector P ₁ P ₂ ---→ having +x and +z components as shown in FIG. The method of the present invention is applied to a joint having a groove surface inclined with respect to the x-axis or the z-axis (the joint shape is downward). In other words, in a joint shape consisting only of groove surfaces orthogonal to the x-axis and z-axis, such as a horizontal fillet joint or a lap fillet joint, it is not possible to obtain the vector P ₁ P ₂ ---→ as described above. , it is not possible to perform stick sensing as in this embodiment. Therefore, for horizontal fillet joints, overlap fillet joints, etc., predetermined sensing is performed according to the shape of the joint by a well-known method.

When it is determined that the joint posture is downward (in this example, V-shaped groove butt) in the stick S2, the input x,
The welding torch 2 is positioned to the stiffness sensing start position P1, which is a composite of the distances in the y and z directions, and the stiffness sensing operation is started (step S
4).

That is, a sensing voltage is applied to the welding torch 2, and the welding torch 2 is moved in the +z direction toward the workpiece 7 at the first moving speed S _H (step S5).
At this time, the first moving speed S _H is selected to be high enough to prevent the wire from being plastically deformed when the workpiece 7 contacts, for example, about 300 cm/min. The movement in step S5 is continued until the wire comes into contact with the workpiece 7 and the welding torch 2 and the workpiece 7 are energized (step S6). When contact with the workpiece 7 is detected in step S6, the welding torch 2 is stopped, but at the time of this stop, the welding torch 2 was moving at high speed, so the welding torch 2 was moved at a high speed as shown by point P ₀₁ in FIG. The wire goes too far to the workpiece 7 side than the correct surface position of the workpiece 7, and the wire stops in an elastically deformed state.

Therefore, following the stop of the welding torch 2, the welding torch 2 is pulled up at a second moving speed S _L in the direction away from the workpiece 7 (in the -z direction) (step S
7). The second moving speed S _L at this time is the first
Select a moving speed slower than S _H , for example, about 30 cm/min. Then, the movement in step S7 causes the wire to separate from the workpiece 7 and the welding torch 2 and the workpiece 7 to move.
This continues until the wire becomes de-energized (step S8), and the position at which the wire separates from the workpiece 7 is detected and stored as the workpiece surface position _P1 (step S9). Since the welding torch 2 is moving at low speed when the wire separates from the workpiece 7 and becomes de-energized, the elastic deformation of the wire due to contact with the workpiece is gradually restored, and the welding torch 2 This means that the accurate workpiece surface position P ₁ at which the wire is almost in contact with the workpiece 7 has been detected.

After detecting the workpiece surface position P ₁ , move the welding torch from position P ₁ to the −z direction at the first moving speed S _H a distance zl
(Step S10; position shown in Figure 2)
_P02 ). The distance nl at this time is determined by the welding robot 1, and no teaching is required.
It is about 2.0mm. Subsequently, the welding torch 2 is moved in the taught detection operation direction (+x direction) by the taught torch movement distance l of stick sensing at the first moving speed S _H (step S11). In addition,
The torch moving distance l in step S11 may be determined in advance to be automatically switched to, for example, 1/2 of the taught distance, and the inclination of the workpiece surface may be determined first.

While the welding torch 2 is being moved in step S11, it is constantly determined whether or not a workpiece is detected, that is, whether the wire has come into contact with the workpiece 7 and has become energized (step S12). If the workpiece 7 is not detected, steps S11 and S12 are repeated until the welding torch 2 moves by the torch movement distance l (step S13), and the welding torch 2
is moved by a distance l in the +x direction and reaches position P ₀₃ . After reaching the position P ₀₃ , the work surface position P ₂ (in this example, the groove surface 7a of the work 7
(upper point) is detected and stored (step S14).

If the workpiece 7 is detected in step S12, it is determined that the welding torch 2 has reached the groove of the workpiece 7, and the process proceeds to step S24, which will be described later. Further, in this embodiment, a case will be explained in which the workpiece 7 is not detected in step S12 and the process proceeds to step S14.

As described above, two points P ₁ and P ₂ on the work surface
After obtaining _the position data, _calculate the _difference zc ₍ =z ₁ −
_z2 ) (step S15), and also calculates the number of times n of CP control to be performed in a predetermined control cycle when moving by the stiffness sensing movement amount l at the first movement speed S _H as l/Δl. (Step S1
6). Here, Δl is the distance by which the welding torch 2 should be moved in one control cycle in order to obtain the first movement speed S _H. Then, the difference zc obtained in step S15
By dividing by the number of times n obtained in step S16, the z-direction movement amount Δz (=zc/
n) is calculated (step S17).

Next, after lifting the welding torch 2 from position P ₂ by the distance zl in the -z direction at the first moving speed S _H (step S18), as shown in FIG. The welding torch 2 is moved at the first moving speed S _H to a position that is a combination of the distance Δl and the distance Δz in the z direction (step S19). As a result, the welding torch 2 moves from the pulled-up position P ₀₄ from the position P ₂ in the direction of the vector P ₁ P ₂ ---→. During the movement in step S17, it is constantly determined whether or not the workpiece is detected, that is, whether the wire has come into contact with the workpiece 7 and has become energized (step S20). If the workpiece 7 is not detected, steps S19 and S20 are repeated until the CP control is performed n times (step S21), and the welding torch 2 changes to the vector P ₁ P ₂ ---
→
It will be moved by a distance of _{1 2} in the direction of .
If the workpiece 7 is not detected even after n times of CP control, the workpiece surface position is detected and memorized again at the position reached by the welding torch 2 by the same procedure as steps S5 to S9 (step S2).
2), the detected position is replaced with the position P ₂ , and the position P ₂ is replaced with the position P ₁ (step S23), and the workpiece 7 is replaced in step S20.
Steps S15 to S23 are repeated until the detection is detected.

Note that the CP control in this embodiment refers to a control in which positions P ₁ and P ₂ are detected in FIG. 3, and the position is moved over the next horizontal distance l using the inclination thereof. usually,
The robot is controlled by further dividing the teaching points taught in advance and creating a target position for each dividing point.This kind of control is called CP control, but in this example, the following The target position for moving the horizontal distance l is not taught in advance, and the position P ₁ ,
Since it depends on the detection result of _P2 , CP control is intentionally defined as described above. Therefore, 1CP control refers to control that moves between each division point (Δl).

Now, when the workpiece 7 is detected in step S20 (in this embodiment, as shown in FIG.
It is assumed that the position Pk on the groove surface 7b of the workpiece 7 is detected while moving in the direction of the vector P ₁ P ₂ from P ₀₄ ), and the welding torch 2 is inside the groove of the workpiece 7. From the detected surface position Pk, it is judged that it has arrived.
Predetermined wire sensing is performed according to the groove shape (in this example, V-shaped groove butt) (step S).
24-S30).

That is, the welding torch 2 is pulled up in the -z direction from the reached position Pk by a predetermined distance zs (step S24), moved in the +x direction at the first moving speed S _H (step S25), and then steps S5 to S9 are carried out. The position _P3 on one groove surface 7b is detected and stored in a similar manner (step S26). After detecting the position _P3 , the welding torch 2 is moved in the -x direction at the first moving speed S _H (step S27), and then the welding torch 2 is moved in the -x direction at the first moving speed S H (step S27).
The position _P4 on the other groove surface 7a is detected and stored in the same manner as steps 5 to S9 (step S28). Then, the distance _{3 4} between the detected positions P ₃ and P ₄ is calculated, and the welding torch 2 is moved by 1/2 of this distance, _{3 4} /2, at the first moving speed S _H (step S29). At this time, the position Pc that the welding torch 2 has reached is directly above the intersection Pf of the groove lines, and from this position Pc, the welding torch 2 is moved in the +z direction at the first movement speed S _H , and steps S5 to S9 are performed. After detecting the intersection point Pf of the groove lines using the same procedure (step S30), the welding torch 2 is raised by 2 mm (step S31), this position is taken as the welding start position, and the groove detection is completed.

After detecting the intersection point Pf of the groove lines in this way, a welding voltage is applied to the welding torch 2, and welding is performed according to the welding conditions taught in advance.

In addition, in the above explanation, the case where the shape of the welded joint is a V-shaped groove butt is explained, but if the shape is a V-shaped groove butt, as shown in FIG. After detecting the position Pk on the workpiece 7 through steps S1 to S23, the intersection point Pf of the groove lines is detected in the following manner. That is,
In the case of matching the rectangular groove, as shown in FIG. 5, the position Pk detected by the procedure of steps S1 to S23 in FIG. 1 is on the vertical plate surface 7c of the rectangular groove,
After reaching position Pk, welding torch 2 is pulled up by a predetermined distance from this position Pk in the -z direction, and -x
direction at the first moving speed S _H (position P ₅ ), and detect position P ₆ on the groove surface 7a in the same manner as steps S5 to S9. And after detecting position P ₆ ,
Move the welding torch 2 in the +x direction at the first movement speed S _H to the groove center position P ₇ , and then move the welding torch 2 from this position P ₇ to the groove surface at a predetermined angle (∠P ₇ PfP ₅ ). By moving in the direction 7c at the first moving speed S _H and using the same procedure as steps S5 to S9, the intersection point Pf of the groove lines is detected. Here, the predetermined angle ∠P ₇ PfP ₅ is the angle required to go from the groove center position P ₇ to the intersection point Pf of the groove lines, and is the known angle of the rectangular groove ∠P ₆ PfP ₅ It can be easily calculated from

As described above, according to the groove detection method of this embodiment, two points P ₁ ,
P ₂ is detected by welding torch 2, and after that detection,
Since the welding torch 2 is moved in the direction of the vector P ₁ P ₂ ---→, if the second detection position P ₂ is within the groove of the workpiece 7, the groove depth direction of the positions P ₁ and P ₂ is position
z ₁ and z ₂ become z ₁ < z ₂ , and the welding torch 2 not only moves reliably toward the groove of the workpiece 7, but also welds even if the second detection position P ₂ is not within the groove of the workpiece 7. By moving the torch 2 in the direction of the vector P ₁ P ₂ ---→ as described above, the welding torch 2 can be moved along the surface of the workpiece when the workpiece 7 cannot be set approximately horizontally. . Therefore, without comparing the z position data of the two points P ₁ and P ₂ with a constant as in the past, and even if the work 7 is not set approximately horizontally, it is possible to reliably determine whether the groove is inside or outside the groove. The groove line intersection Pf of the workpiece 7 can be detected accurately.

Furthermore, in this embodiment, when detecting a point on the surface of the workpiece 7 with the welding torch 2, the procedure shown in steps S5 to S9 in FIG. With,
The sensing operation speed can be made extremely fast, and the sensing time can be significantly shortened.

Furthermore, in this embodiment, after detecting the intersection point Pf of the groove lines, the welding torch 2 is pulled up a predetermined distance (2 mm) and the positional information of the tip of the wire at that position is taken in as the welding start position. A good predetermined distance is provided between the wire and the workpiece 7 at the time of arc start, and detection errors due to bending (deflection) of the wire no longer occur.

In addition, in the above embodiment, the position on the work surface
P ₁ and P ₂ are detected to obtain the vector P ₁ P ₂ ---→, but _{the positions P 02 and} P ₀₄ where the welding torch 2 is lifted from the positions P 1 and P ₂ on the work surface are detected. Then, the vector P ₀₂ P ₀₄ ----> may be obtained and this vector P ₀₂ P ₀₄ ----> may be used in place of P ₁ P ₂ ---->.
At this time, the vector P ₀₂ P ₀₄ ---→ is P ₁ P ₂
―――→ is substantially the same.

Further, in the above embodiment, the arc welding robot 1
Although the case where detection is performed by moving the workpiece 7 side has been shown, the method of the present invention can be similarly used when the workpiece 7 side is moved and detected by the positioner 8.

Furthermore, in the above embodiment, the shape of the welded joint is V
Although the case of a type bevel and a rectangular bevel has been described, the method of the present invention can also be applied to a downward fillet in the same manner as in the case of a V-shaped bevel explained with reference to FIGS. 1 to 3. However, in the case of a downward fillet, the positions P ₁ and P ₂ corresponding to FIGS. 2 and 3 are detected on one of the groove surfaces forming the downward fillet.

[Effects of the Invention] As detailed above, according to the groove detection method of the automatic welding device of the present invention, two points P ₁ and P ₂ on the workpiece surface spaced apart by a certain distance l can be detected by the welding torch. After that, the welding torch is moved in the direction of the vector P ₁ P ₂ ---→, so if the second detection position P ₂ is inside the groove, the welding torch will surely move toward the inside of the groove, and Even if the second detection position _P2 is not within the groove, the welding torch can be moved along the workpiece surface when the workpiece cannot be set approximately horizontally, and the welding torch can be moved along the workpiece surface, unlike the conventional two-point detection position P2. ₁ ,
Without comparing the z position data of P ₂ with a constant,
Further, even if the workpiece is not set substantially horizontally, it is possible to reliably determine whether the groove is inside or outside the groove, and the intersection of the groove lines of the workpiece can be accurately detected.

[Brief explanation of the drawing]

Fig. 1 is a flowchart for explaining the procedure of a groove detection method for an automatic welding device as an embodiment of the present invention, and Figs. 2 and 3 show the method of the present invention applied to a welded joint with a V-shaped groove butt. Figure 4 is a perspective view showing an arc welding robot to which the method of the present invention is applied, and Figure 5 is a diagram showing an example of the moving state of the welding torch when the method of the present invention is applied. FIG. 6 is a diagram showing an example of a moving state of a welding torch when applied to a butt welded joint. In the figure, 1... arc welding robot (automatic welding device), 1a... wrist part, 2... welding torch, 3...
Robot control panel, 4...Teaching box, 6
... Welding power source, 7... Workpiece, 7a, 7b... Groove surface,
7c... Standing board surface, 8... Positioner.

Claims (1)

[Claims] 1. A method for detecting a groove in a welding line using an automatic welding device in which the position of a workpiece and a welding torch as a position sensor is controlled in three spatial axes, comprising:
The workpiece is arranged so that its member surface or groove intersection line is substantially perpendicular to one of the three axes, and the output of a position sensor from the welding torch provided in the direction of this one axis is input to a computer. A method for detecting a groove in an automatic welding device, characterized in that the groove is detected by a program having the following step order. (A) A step of detecting the surface position _P1 of the workpiece near the groove using the welding torch. (B) A step of lifting the welding torch by a predetermined distance from the position _P1 and then moving it by a predetermined distance l in the groove direction. (C) A step of determining whether or not the welding torch has detected the surface of the workpiece during the movement of the welding torch in step (B). (D) If it is determined that the surface of the workpiece is not detected in step (C), move the welding torch in the groove depth direction from the position reached by the welding torch to detect the surface position P of the workpiece. ₂
detecting the welding torch by the welding torch. (E) The step of raising the welding torch by a predetermined distance from the position P ₂ and then moving it by a distance _{1 2} in the direction of the vector P ₁ P ₂ --→. (F) A step of determining whether or not the welding torch has detected the surface of the workpiece during the movement of the welding torch in step (E). (G) If it is determined that the work surface was not detected in step (F), replace position P ₂ with position P ₁ , and move the welding torch in the welding depth direction from the position reached by the welding torch. Then, the newly detected surface position of the workpiece is set as _P2 , and the steps (E) and (F) are performed.
Steps to repeat. (H) If it is determined that the workpiece surface is detected in step (C) or (F), it is determined that the welding torch has reached the groove, and from the detected surface position, the workpiece surface is detected. A step of detecting the intersection of the groove lines by performing a predetermined groove position sensing operation according to the shape.