JP3765861B2 - Electrode non-consumable welding robot and arc welding method using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a welding robot that performs arc welding, and more particularly to an electrode non-consumable welding robot using a tungsten electrode as an electrode for generating an arc and an arc welding method using the same.
[0002]
[Prior art]
Prior to the actual work of arc welding, the welding robot main body stores the operation sequence in advance, and the welding robot is controlled based on the operation program to perform welding on the workpiece. At this time, first, it is necessary to detect the relative positional relationship between the reference position of the welding robot and the workpiece, and generally, a touch sensing method that is a well-known technique is used to detect the position of the workpiece. It is used. In this touch sensing method, a voltage is applied between the contact of the welding robot and the workpiece to be position-detected, and the energization between the two when the contact contacts the workpiece is detected. This is a method for recognizing contact and detecting the position of the workpiece. By the way, in the prior art, as shown in FIG. 8, a contact 12 is provided separately from the welding torch 3 and the tungsten electrode 8 in the welding robot, and when sensing, as shown in FIG. The contact 12 is projected forward from the tungsten electrode 8 so that the workpiece is touch-sensing, and the position of the workpiece is detected. At the time of welding, as shown in FIG. 8B, the contact 12 is retracted and arc welding is performed with the tungsten electrode 8.
[0003]
By the way, in the case of non-consumable electrode welding, for example, TIG welding method (tungsten inert gas arc welding method), an arc is generated between the tip of the polished tungsten electrode 8 and the base material which is a workpiece to be welded, The base material is melted to join the metals.
[0004]
[Problems to be solved by the invention]
However, in such a welding robot, since the contact 12 is provided separately from the welding torch 3, the surroundings of the welding torch 3 are complicated and occupy a place. For example, as shown in FIG. In the manufacture of the boiler, when the branch pipe 31 and the mother pipe 30 are welded, the branch pipe 31 is in contact with the contact 12 because the pitch of the branch pipe 31 is narrow, and the welding torch 3 and the tungsten electrode 8 are welded. There was a problem of not reaching 32. In addition, it is difficult to keep the relative positional relationship between the welding torch 3 and the contact 12 (dimensions A, B, and C in FIG. 8A) constant, for example, recovery when the welding torch 3 is damaged. Not only takes time, but also the positional relationship between the welding torch 3 and the contact 12 before damage cannot be correctly reproduced. The control data up to that point cannot be used as it is, and the data must be changed. There was also a problem that was not possible.
[0005]
Furthermore, in the conventional welding robot, the tip of the tungsten electrode 8 is worn with time, but the wear state of the tip is checked manually. However, the amount of wear is particularly intense, and if welding is continued in a state where the tip is worn without noticing it, as shown in FIGS. 7 (a) and 7 (b), the concentration of the arc 33 decreases, The length of the arc 33 is changed, which causes a welding defect.
[0006]
The present invention has been made to solve the above-described problems. An electrode non-consumable welding robot capable of reliably detecting a relative positional relationship with an object to be welded by simplifying the periphery of a welding torch, and an arc welding method using the same. The purpose is to provide.
[0007]
It is another object of the present invention to provide an electrode non-consumable welding robot capable of accurately measuring the wear amount of the tip of the tungsten electrode and easily replacing the tungsten electrode, and an arc welding method using the same.
[0008]
[Means for Solving the Problems]
In order to achieve this object, in the present invention, in an electrode non-consumable welding robot that automatically performs arc welding, a power source for applying a voltage between a tungsten electrode for arc welding and a workpiece to be welded and tungsten A current detector that detects a current that flows at the moment when the electrode and the workpiece are in contact with each other is provided, and a reference block that can be energized and an automatic replacement device for the tungsten electrode are provided within the operation range of the welding robot. Prior to arc welding, the tungsten electrode is operated as a contact for detecting the position of the workpiece by touch sensing.
[0009]
Also, before and after arc welding with a tungsten electrode, the amount of wear due to arc welding of the tungsten electrode is measured by touch sensing the fixed reference block with the tungsten electrode, and the amount of wear is constant. If it exceeds the value, automatically replace it with a new tungsten electrodes by the tungsten autochanger.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an electrode non-consumable welding robot according to the present invention will be described with reference to the drawings.
[0011]
First, FIG. 1 is an overall view of a welding robot that can measure the amount of wear at the tip of a tungsten electrode according to the present invention. This welding robot is roughly composed of a robot body 1, a robot control device 2, a welding torch 3, a welding power source 4, a touch sensor control device 5, a tungsten electrode automatic exchange device 6, and the like.
[0012]
The robot body 1 includes a wrist shaft 7 in three axial directions, and a welding torch 3 is attached to the tip of the wrist shaft 7. In addition, a reference block 9 that can be energized to contact the tip of the tungsten electrode 8 is provided within the operating range of the robot. The secondary side of the welding power source 4 is connected to the welding torch 3 and the workpiece to be welded by a cable, and the welding torch 3 is also wired to the touch sensor control device 5. In this touch sensor control device 5, a power source for applying a voltage between the welding torch 3 and the work to be welded, a tungsten electrode 8 attached to the tip of the welding torch 3 and the work to be welded are in contact with each other. And a current detector for detecting a current flowing when the current flows. The robot control device 2 controls the robot body 1, the welding power source 4, the touch sensor control device 5, the tungsten electrode automatic exchange device 6 and the like.
[0013]
Next, FIGS. 2A and 2B are cross-sectional views of the welding torch 3. As shown in FIG. 2A, the torch body 21 is inserted into the torch case 22, and an alumina nozzle 23 is attached to the outside of the tip portion of the torch body 21. The torch body 21 is fixed to the torch case 22, and the portion of the torch body 21 protruding from the torch case 22 is covered with an alumina nozzle 23. The alumina nozzle 23 is screwed to the torch body 21 with a screw 24 provided on the torch body 21. The tungsten electrode 8 is detachably attached to the electrode insertion hole 25 on the central axis of the torch body 21 so that a part thereof protrudes from the alumina nozzle 23. Then, as shown in FIG. 2B, the tungsten electrode 8 is formed by the pressing force of the taper pin 27 set in the through hole provided in the tangential direction of the electrode insertion hole 25 of the torch body 21. It is supported and fixed to the main body 21.
[0014]
Further, the torch body 21 is provided with an argon gas introduction joint 28 and a cooling water in / out joint 29. When arc welding is performed, argon gas is introduced thereby and diffused by the gas lens 26, so that the welding arc and the welded portion are evenly wrapped with the inert gas. Further, the cooling water flows through the water cooling path 20 and cools the torch body 21.
[0015]
Next, a welding method, an operation, an effect, and the like by the apparatus of the above embodiment will be described.
[0016]
First, in order to teach the welding operation to the welding robot, a known sensing method is used to create a touch sensing program that detects the relative position between the robot body and the workpiece, and further welds the workpiece. Create a welding program. The operation of the welding robot is stored in the robot control device 2 via the operation box 10 having an operation panel. Next, in order to cause the welding robot to perform a welding operation by the playback operation, welding conditions such as a welding current, a welding voltage, and a welding speed are set in advance in the operation box 10 and are input to the robot controller 2. Keep it.
[0017]
By the way, in the conventional teaching method, the touch sensing for detecting the relative position between the robot and the workpiece is performed using the contact 12 provided separately from the welding torch 3. However, in this method, the structure around the welding torch 3 is complicated. For example, as shown in FIG. 9, the contact 12 becomes an obstacle for welding in a narrow part where the branch pipe 31 is standing. Thus, there is a problem that the welding torch 3 does not reach the welded portion 32. Further, it is difficult to keep the relative positional relationship between the welding torch 3 and the contact 12 constant. For example, it takes time to recover when the torch is damaged, and the welding torch 3 and the contact 12 before being damaged The positional relationship (dimensions A, B, and C in FIG. 8A) does not return, and the previous teaching data cannot be used as it is, causing a problem that the data must be changed. However, in the present invention, since the tungsten electrode 8 of the welding torch 3 is also used as a contact as it is, the periphery of the welding torch 3 is simplified and such a problem does not occur.
[0018]
Next, FIG. 8 is a diagram showing a position sensing method using the tungsten electrode 8 according to the present invention. Before performing this sensing, the tungsten electrode 8 whose tip is polished is attached to the welding torch 3 by the automatic tungsten electrode changer 6. A voltage is applied to the tungsten electrode 8 and the workpiece, and the tungsten electrode 8 comes into contact with the workpiece, so that a current flows between the tungsten electrode 8 and the workpiece, and the position of the workpiece. Is detected. Next, steps of touch sensing will be described with reference to FIG. First, as shown in FIG. 4A, the tungsten electrode 8 contacts the tube surface 30 a of the mother tube 30. By contacting the tube surface 30a, the current detector detects that a current flows between the tungsten electrode 8 and the mother tube 30, and the position of the tube surface 30a is detected. This position is stored in the robot controller 2 as a position in the Z direction. Next, sensing in the X and Y directions is performed following the Z direction. As shown in FIGS. 4B and 4C, when the tungsten electrode 8 contacts the branch pipe surfaces 31b and 31c, the positions in the X and Y directions are obtained and stored in the robot controller 2. (X, Y, Z) obtained in the above steps indicates a relative position between the robot 1, the branch pipe 31, and the mother pipe 30, and the robot 1 determines the branch pipe based on this data (X, Y, Z). 31 and the mother pipe 30 are welded.
[0019]
In the present invention, since it is not necessary to attach a contact around the welding torch 3, the welding torch 3 is simplified, the range in which welding can be applied is expanded, and the main pipe 30 in the boiler manufacturing process that has not been possible so far. And the branch pipe 31 can be welded. Further, since the tungsten electrode 8 and the contact are the same, no error occurs in the position detection of the workpiece. Even if the welding torch 3 is damaged, if the new welding torch 3 is restored to the reference position before the damage, the previous teaching data can be used without being changed.
[0020]
Next, measurement of the amount of wear that occurs during arc welding of the tip of the tungsten electrode 8 will be described.
[0021]
By the way, the confirmation of the wear state of the tip of the conventional tungsten electrode is confirmed by the operator that the automatic operation of the robot is stopped every time welding is finished, and the problem is that the productivity is poor, or the wear is not confirmed. When the next welding is performed in a state where the arc concentration is reduced and the arc length is changed, there is a problem that a welding defect occurs.
[0022]
FIG. 5 is a view showing a flowchart of the tungsten electrode wear amount measurement.
[0023]
First, before starting welding, the tungsten electrode 8 whose tip is polished is attached to the welding torch 3 attached to the work arm of the welding robot 1 by the tungsten electrode automatic exchange device 6. Then, as shown in FIG. 6A, the tungsten electrode 8 is brought into contact with the reference block 9. This contact is detected by a current detector in the touch sensor control device 5 as a short-circuit signal of a detection voltage applied in advance, and the movement of the work arm is stopped by the robot control device 2 and the tungsten electrode 8 is moved from the arm stop position. The length (L1) is measured. And this length is memorize | stored in the robot control apparatus 2, and welding is performed.
[0024]
Next, when welding is completed, the tungsten electrode 8 is brought into contact with the reference block 9 again (FIG. 6B), and the movement of the work arm is stopped by the applied detection voltage short-circuit signal. The length (L2) of the tungsten electrode 8 is detected. This length is stored in the robot controller 2, and the length after welding (L2) is subtracted from the length before welding (L1) (L1-L2 = ΔL). When the value of ΔL exceeds a predetermined value, the tungsten electrode 8 is automatically replaced by the tungsten electrode automatic replacement device 6 by the welding robot.
[0025]
The constant value for determining ΔL is input in advance by the operator, but can be input with an accuracy of 0.01 mm.
[0026]
As described above, by automatically measuring the amount of wear at the tip of the tungsten electrode, the welding robot can be replaced or subsequently replaced without stopping the operation of the welding robot and without the operator checking. Therefore, it is possible to always perform welding in a stable state, preventing welding defects due to reduced arc concentration and changes in arc length, and improving productivity. You can also.
[0027]
【The invention's effect】
As described above, in the electrode non-consumable welding robot and the arc welding method using the same according to the present invention, the welding tungsten electrode is provided with a function as a touch sensing contact so that the welding torch The position of the workpiece can be reliably detected, and the narrow portion of the workpiece can be welded.
[0028]
In addition, by providing a reference block that can be energized within the operating range of the welding robot and an automatic tungsten electrode changer, the wear amount of the tungsten electrode can be automatically measured and the wear amount is constant. When the value is exceeded, the tungsten electrode can be automatically replaced with a new one, so that it is possible to prevent a welding defect caused by wear of the tungsten electrode.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a welding robot capable of automatically measuring the wear amount of a tungsten electrode according to the present invention.
FIG. 2 is a cross-sectional view of a welding torch of a welding robot according to the present invention.
FIG. 3 is a diagram illustrating touch sensing using a tungsten electrode according to the present invention.
FIG. 4 is a diagram for explaining a touch sensing method in the welding robot according to the present invention.
FIG. 5 is a flowchart for measuring the wear amount of a tungsten electrode in the welding robot according to the present invention.
FIG. 6 is a diagram for explaining the measurement of the wear amount of the tungsten electrode of the welding robot according to the present invention.
FIG. 7 is a diagram showing a change in a welding arc when wear occurs at a tip portion of a tungsten electrode.
FIG. 8 is a diagram illustrating a configuration of a conventional touch sensing contact.
FIG. 9 is a diagram for explaining a problem of the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Robot main body 2 Robot control apparatus 3 Welding torch 4 Welding power supply 5 Touch sensor control apparatus 6 Tungsten electrode automatic change apparatus 7 Wrist axis 8 Tungsten electrode 9 Reference block 10 Operation box 12 Contact 20 Water cooling path 21 Torch main body 22 Torch case 23 Alumina Nozzle 24 Screw 25 Electrode insertion hole 26 Gas lens 27 Tapered pin 28 Argon gas introduction joint 29 Cooling water in / out joint 30 Mother pipe 30a Mother pipe surface (Z direction)
31 Branch pipe 31b Branch pipe surface (Y direction)
31c Branch pipe surface (X direction)
32 weld 33 arc

Claims (3)

In an electrode non-consumable welding robot that automatically performs arc welding, a power source that applies a voltage between a tungsten electrode for welding and a workpiece, and a current that flows when the tungsten electrode and the workpiece are in contact with each other A non-consumable welding robot comprising a reference block capable of energization and an automatic tungsten electrode exchange device within an operating range of the welding robot. 2. The electrode non-consumable welding robot according to claim 1, wherein prior to arc welding to the workpiece, the tungsten electrode performs touch sensing on the workpiece and detects the position of the workpiece. By arc welding method. Before and after the arc welding, the tungsten electrode is subjected to touch sensing with respect to the reference block to measure the wear amount of the tungsten electrode, and when the wear amount exceeds a certain value, the tungsten electrode is automatically 2. The arc welding method using an electrode non-consumable welding robot according to claim 1, wherein the tungsten electrode is automatically exchanged by an exchange device.

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