Electric heating – Metal heating – By arc
Patent
1995-09-07
1997-02-11
Shaw, Clifford C.
Electric heating
Metal heating
By arc
2191251, 21913021, 901 42, B23K 9095
Patent
active
056017391
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for controlling an arc welding robot which make it possible to determine welding failures in a welded region.
BACKGROUND ART
An industrial robot for arc welding operates at an instructed speed and in a pre-instructed. It commands a welding machine to start welding by dictating welding conditions (current, voltages, etc.) at the welding start point which is instructed in advance. Then, the welding machine starts welding and performs control so that the specified welding conditions are met until an end-welding command is received. Other types of controls, such as course control and I/O control, are performed by the robot. In general, until a stop request is received, the robot performs operations such as commanding the welding machine to change welding conditions in response to a welding condition change request and issuing an end-welding command to the welding machine in response to an end-welding request.
However, an interruption or failure in welding can occur unless such a robot is continuously monitored to see if the welding operation is being properly performed in accordance with the instructions. Since an interruption or failure can produce serious defects in the welded product, various monitoring functions are added to a robot.
For example, in order to ensure that a robot operates after an arc is generated when welding is started, the current flowing between the electrode and the base material to be worked on is checked at the robot or welding machine. The robot is allowed to start operating after it has been confirmed that the current has exceeded a preset value (after the generation of an arc). Interruption and failure during welding are avoided by the detection of failed arcing when the current between the electrode and the base material to be worked on falls below the preset value, or by checking the remaining amount of welding wire to spot any abnormality. The operator of the robot will be alerted to any abnormality, and will have welding continued again after eliminating the cause.
According to Japanese Patent Applications Nos. Hei 4-221970 and Hei 4-304951 made by the applicant, a robot does not stop even if arcing fails or is interrupted at the point where welding is started or in a region within the course of welding. Instead, the robot itself rewelds when such a problem occurs at the starting point, or returns to the position where arcing has been interrupted to reweld when the problem occurs in the course of welding. Thus, unwelded regions are eliminated and the robot can be continuously operated.
DISCLOSURE OF THE INVENTION
The former method makes it possible to detect an abnormality in welding and allows a welding operation to be continued if the operator performs a restart operation after eliminating the cause of the abnormality. However, it is inevitable that unwelded regions will remain in the workpiece if the operator makes an error in the restart operation or if welding is stopped and restarted without removing the cause of the abnormality.
The latter method is effective as a means for preventing operator errors as described above. However, if abnormal welding occurs and the robot is stopped after welding has been resumed automatically, because there is no way to eliminate the abnormality, it is inevitable that unwelded regions will be left in the workpiece to be welded, just as in the above-described case.
It is therefore an object of the present invention to provide a method and apparatus which will not leave unwelded regions in a workpiece to be welded even when abnormal welding occurs or the operator makes an error.
According to a first aspect of the present invention, there is provided a method of controlling an arc welding robot characterized in that the generation of an arc is detected to output an arc generation command by detecting an energized state wherein the arc current or arc voltage is equal to or greater than a predetermined value; the duration of the arc generation from the ou
REFERENCES:
patent: 3532853 (1970-10-01), MacKinney et al.
patent: 4132879 (1979-01-01), Glorioso
patent: 4772776 (1988-09-01), Siina
Hirayama Takahide
Morita Ryuichi
Okumura Shinji
Kabushiki Kaisha Yaskawa Denki
Shaw Clifford C.
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