JPH09216059A - Electrode non-consumption type welding robot and arc welding method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect the position of a work to be welded, to weld even a narrow part, to automatically measure the wear of a tungsten electrode, and to automatically exchange the tungsten electrode in a welding robot to automatically perform the arc welding. SOLUTION: In a welding robot, a tungsten electrode 8 for the arc welding which is fitted to a tip of a robot body 1 is used as a probe for the touch sensing to detect the position of a work to be welded. A reference block 9 is provided on the welding robot, its surface is touch-sensed by the tungsten electrode 8 to automatically measure the wear of the tungsten electrode 8, and when the measured value exceeds the prescribed value, the tungsten electrode is exchanged with a new one by a tungsten electrode exchanging device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding robot for performing 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. is there.

[0002]

2. Description of the Related Art Prior to the actual work of arc welding,
The operation sequence is stored in the welding robot body, the welding robot is controlled based on the operation program, and welding is performed 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 object to be welded.To detect the position of the object to be welded, a touch sensing method that is a well-known technique is generally used. It is used. With this touch sensing method, voltage is applied between the contact of the welding robot and the work piece whose position is to be detected, and the energization between the two that occurs when the contact makes contact with the work piece is detected. This is a method of recognizing the contact and detecting the position of the workpiece. By the way, in the conventional technique, as shown in FIG.
In the welding robot, a contact 12 is provided separately from the welding torch 3 and the tungsten electrode 8, and when the sensing is performed, the contact 12 shown in FIG.
As shown in (a), the contact 12 is connected to the tungsten electrode 8
The position of the object to be welded is detected by making the object to be welded touch-sensitive by projecting it further forward. Then, at the time of welding, as shown in FIG. 8B, the contact 12 is retracted, and arc welding is performed by the tungsten electrode 8.

By the way, electrode non-consumable welding, for example, T
In the case of the IG welding method (tungsten inert gas arc welding method), an arc is generated between the polished tip of the tungsten electrode 8 and the base material which is the object to be welded, and the base material is melted to join the metal. Of.

[0004]

However, in such a welding robot, since the contact 12 is provided separately from the welding torch 3, the area around the welding torch 3 becomes complicated and occupies a place. For example, as shown in FIG. 9, when welding the branch pipe 31 and the mother pipe 30 in the manufacture of a boiler, the branch pipe 31 and the contact 12 come into contact with each other because the pitch of the branch pipe 31 is narrow, and the welding is performed. There was a problem that the torch 3 and the tungsten electrode 8 did not reach the weld 32. Further, the relative positional relationship between the welding torch 3 and the contact 12 (see FIG. 8).
It is difficult to keep the dimensions A, B, and C in (a) constant, and for example, if the welding torch 3 is damaged, not only it takes time to recover, but also the welding torch 3 before damage is taken.
In some cases, the positional relationship between the contactor 12 and the contactor 12 cannot be reproduced correctly, the control data up to that point cannot be used as it is, and the data must be changed.

Further, in the conventional welding robot, the tip of the tungsten electrode 8 wears with time, but the wear state of the tip is manually checked.
However, the amount of wear was particularly severe, and if welding was continued with the tip worn without noticing it, the
As shown in (a) and (b), the concentration of the arc 33 is lowered, and the length of the arc 33 is changed, which causes a welding defect.

The present invention has been made in order to solve the above problems, and an electrode non-consumable welding robot capable of reliably detecting a relative positional relationship with an object to be welded by simplifying the circumference of a welding torch, and the same. It is an object to provide an arc welding method.

It is another object of the present invention to provide an electrode non-consumable welding robot capable of accurately measuring the amount of wear of the tip of a tungsten electrode and easily replacing the tungsten electrode, and an arc welding method using the same.

[0008]

To achieve this object, according to the present invention, in an electrode non-consumable welding robot for automatically performing arc welding, between a tungsten electrode for arc welding and an object to be welded. In addition, a power supply for applying a voltage and a current detector for detecting a current flowing at the moment when the tungsten electrode and the object to be welded contact each other. Then, prior to arc welding, the tungsten electrode is operated as a contactor for detecting the position of the workpiece by touch sensing.

Within the operating range of the welding robot,
An energizable reference block and a tungsten electrode automatic exchange device are provided. Then, before and after the arc welding with the tungsten electrode, by touch-sensing the fixed reference block with the tungsten electrode, the wear amount of the tungsten electrode due to the arc welding is measured, and the wear amount has a constant value. When it exceeds the value, the tungsten electrode is automatically replaced with a new one by the above-mentioned automatic tungsten changer.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an electrode non-consumable welding robot according to the present invention will be described below with reference to the drawings.

First, FIG. 1 is an overall view of a welding robot according to the present invention capable of measuring the amount of wear of a tungsten electrode tip. This welding robot is roughly composed of a robot body 1, a robot controller 2, a welding torch 3, a welding power source 4, a touch sensor controller 5, a tungsten electrode automatic exchange device 6, and the like.

The robot body 1 has a wrist shaft 7 extending 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 contacts the tip of the tungsten electrode 8 and that can be energized is installed within the operation range of the robot. The secondary side of the welding power source 4 is
A cable is connected to the welding torch 3 and the object to be welded, 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 object to be welded, and a current detection for detecting a current flowing when the tungsten electrode 8 mounted on the tip of the welding torch 3 and the object to be welded come into contact with each other. And vessels are provided. Further, the robot controller 2 controls the robot body 1, the welding power source 4, the touch sensor controller 5, the tungsten electrode automatic exchange device 6, and the like.

Next, FIGS. 2A and 2B show a welding torch 3.
FIG. 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 of the. The torch body 21 is fixed to the torch case 22, and the part of the torch body 21 protruding from the torch case 22 is covered with an alumina nozzle 23. The alumina nozzle 23 is a screw 2 provided on the torch body 21.
4 is screwed to 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 of the tungsten electrode 8 projects from the alumina nozzle 23. Then, as shown in FIG. 2B, the tungsten electrode 8 is pushed by the torch body 21 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.

Further, the torch body 21 is provided with an argon gas introduction joint 28 and a cooling water inlet / outlet joint 29. Then, during arc welding, argon gas is introduced by this, diffused by the gas lens 26, and the welding arc and the welding spot are uniformly wrapped with the inert gas. Further, the cooling water flows through the water cooling passage 20 and cools the torch body 21.

Next, the welding method, operation, effect, etc. by the apparatus of the above embodiment will be described.

First, in order to teach a welding robot to perform a welding operation, a touch sensing program for detecting the relative position between the robot body and the object to be welded is created by a known teaching method, and the welding object is further welded. Create a welding program. Then, the operation of the welding robot is stored in the robot control device 2 via the operation box 10 having the operation panel. Next, in order to cause the welding robot to perform the welding operation by the playback operation, welding conditions such as welding current, welding voltage, and welding speed are set in advance in the operation box 10, and the welding conditions are input to the robot controller 2. Keep it.

By the way, in the conventional teaching method,
The touch sensing for detecting the relative position between the robot and the object to be welded is performed by using the contactor 12 provided separately from the welding torch 3. However, with this method, the structure around the welding torch 3 becomes complicated, and for example, as shown in FIG. 9, for welding a narrow space where branch pipes 31 are forested,
There is a problem that the contact 12 is an obstacle and the welding torch 3 does not reach the weld 32. Further, the welding torch 3 and the contact 1
It is difficult to keep the relative positional relationship with 2 constant,
For example, it takes time to recover when the torch is damaged, and the positional relationship between the welding torch 3 and the contact 12 before the damage (see FIG. 8).
The dimensions (A), (B, C) in (a) may not be returned, and the teaching data up to that point cannot be used as they are, and there is a problem that the data must be changed. However, in the present invention, the tungsten electrode 8 of the welding torch 3 is
Since it is also used as a contactor as it is, the circumference of the welding torch 3 is simplified and such a problem does not occur.

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, a tungsten electrode 8 whose tip is polished is attached to the welding torch 3 by the tungsten electrode automatic exchange device 6. Then, a voltage is applied to the tungsten electrode 8 and the object to be welded, and when the tungsten electrode 8 comes into contact with the object to be welded, a current flows between the tungsten electrode 8 and the object to be welded, so that the position of the object to be welded. Is detected. Next, the steps of touch sensing will be described with reference to FIG. First, as shown in FIG.
The tungsten electrode 8 contacts the tube surface 30a of the mother tube 30. By contacting the tube surface 30a, it is detected by the current detector 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 is performed in the X and Y directions 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. Obtained by the above steps (X,
Y, Z) indicates the relative positions of the robot 1 and the branch pipe 31 and the mother pipe 30, and the robot 1 uses this data (X, Y, Z).
Based on the above, the branch pipe 31 and the mother pipe 30 are welded.

In the present invention, since it is not necessary to attach a contact around the welding torch 3, the welding torch 3 is simplified and the applicable range of welding is expanded.
It became possible to weld the mother pipe 30 and the branch pipe 31 in the process of manufacturing the boiler. Further, since the tungsten electrode 8 and the contact are the same, no error occurs in the position detection of the object to be welded. Even if the welding torch 3 is damaged, if the new welding torch 3 is restored to the reference position before the damage, it can be used without changing the existing teaching data.

Next, the measurement of the amount of wear that occurs during arc welding of the tip of the tungsten electrode 8 will be described.

By the way, the conventional wear state of the tip of the tungsten electrode is checked by the operator by stopping the automatic operation of the robot every time welding is completed, which causes a problem of poor productivity and insufficient confirmation. However, when the next welding is executed in the worn state, that is, the arc concentration is lowered and the arc length is changed, there is a problem that a welding defect occurs.

FIG. 5 is a diagram showing a flowchart for measuring the amount of wear of the tungsten electrode.

First, before starting welding, the tungsten electrode 8 whose tip is polished is mounted on 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 the detection voltage applied in advance,
The robot controller 2 stops the movement of the working arm, and the length of the tungsten electrode 8 (L
Measure 1). Then, this length is stored in the robot controller 2 and welding is performed.

Next, when the welding is completed, the tungsten electrode 8 is brought into contact with the reference block 9 again (FIG. 6 (b)).
The movement of the work arm is stopped by the short-circuit signal of the applied detection voltage, and the length (L2) of the tungsten electrode 8 after welding is detected from this stop position. This length is the robot controller 2
And the length after welding (L2) is subtracted (L1−L2 = ΔL) from the length before welding (L1). And
When the value of ΔL exceeds a predetermined constant value, the welding robot automatically replaces the tungsten electrode 8 by the tungsten electrode automatic replacement device 6.

The constant value for discriminating ΔL is inputted by the operator in advance, but can be inputted with an accuracy of 0.01 mm.

As described above, by automatically measuring the amount of wear of the tip of the tungsten electrode, it is possible to replace the tungsten electrode 8 with the welding robot without stopping the operation of the welding robot and inserting a step for the operator to check. Or, the welding is performed by determining whether to continue welding as it is, so that welding can be performed in a stable state at all times, and it is possible to prevent welding defects due to reduced arc concentration and changes in arc length, and at the same time, improve productivity. Can also be improved.

[0027]

As described above, in the electrode non-consumable welding robot and the arc welding method using the same according to the present invention, the tungsten electrode for welding has a function as a contact for touch sensing. As a result, the structure around the welding torch can be simplified, the position of the object to be welded can be reliably detected, and the narrow portion of the object to be welded can be welded.

Further, by providing a reference block that can be energized and an automatic tungsten electrode exchanging device within the operating range of the welding robot, the amount of wear of the tungsten electrode can be automatically measured, and the wear of the tungsten electrode can be measured. When the amount exceeds a certain value, the tungsten electrode can be automatically replaced with a new one, so that welding defects caused by wear of the tungsten electrode can be prevented.

[Brief description of 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 sectional view of a welding torch of the 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 illustrating 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 illustrating 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 changes in the welding arc when the tip of the tungsten electrode is worn.

FIG. 8 is a diagram showing a configuration of a touch sensing contactor according to a conventional technique.

FIG. 9 is a diagram illustrating a problem of the conventional technique.

[Explanation of symbols]

 1 Robot Main Body 2 Robot Control Device 3 Welding Torch 4 Welding Power Supply 5 Touch Sensor Control Device 6 Tungsten Electrode Automatic Replacement Device 7 Wrist Axis 8 Tungsten Electrode 9 Reference Block 10 Control Box 12 Contactor 20 Water Cooling Path 21 Torch Body 22 Torch Case 23 Alumina Nozzle 24 Screw 25 Electrode insertion hole 26 Gas lens 27 Tapered pin 28 Argon gas inlet joint 29 Cooling water inlet / outlet 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 Welded part 33 Arc

Claims (4)

[Claims] 1. In an electrode non-consumable welding robot for automatically performing arc welding, a power source for applying a voltage between a tungsten electrode for welding and an object to be welded, the tungsten electrode and the object to be welded are provided. An electrode non-consumable welding robot, comprising: a current detector that detects a current flowing when contacting. 2. The electrode non-consumable welding robot according to claim 1, wherein a reference block that can be energized and an automatic exchange device for the tungsten electrode are provided within an operating range of the welding robot. 3. The position of the object to be welded is detected by touch-sensing the object to be welded by the tungsten electrode prior to arc welding to the object to be welded. Arc Welding Method Using Non-consumable Welding Robot for Electrodes. 4. The amount of wear of the tungsten electrode is measured by performing touch sensing of the tungsten electrode with respect to the reference block before and after the arc welding, and when the amount of wear exceeds a certain value, The arc welding method according to claim 2, wherein the tungsten electrode is automatically replaced by the tungsten electrode automatic replacement device.