Control method in multi-layer welding

• US 6,023,044 A
• Filed: 12/12/1997
• Issued: 02/08/2000
• Est. Priority Date: 04/12/1996
• Status: Expired due to Fees

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Ikeda, Yoshitaka, Kosaka, Tetsuya
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US08/981,818
• Time in Patent Office: 788 Days
• Field of Search: 219/124.34, 219/125.1, 219/125.11, 219/125.12, 219/137 R, 219/137 PS, 901/42
• US Class Current: 219/124.34
• CPC Class Codes: B23K 9/025 for rectilinear seams
• CPC Class Codes: B23K 9/0956 using sensing means, e.g. optical
• CPC Class Codes: B23K 9/1274 Using non-contact, optical means, e.g. laser means

Abstract

In a multi-layer welding, weld line and a gap width of workpieces (A, B) to be welded are detected by a laser sensor mounted on a robot, during a welding for a first layer, whereby, a welding torch mounted on the robot is made to follow the weld line and welding conditions are adjusted in accordance with the detected gap width. The detected gap width is stored in the storage means together with the weld line data. Then, weldings for a second and subsequent layers are performed by using the stored data in such a manner that the welding torch is made to follow the weld line, and the welding conditions are adjusted in accordance with the gap width.

Claims

1. A control method in a multi-layer welding which uses a welding robot having an arc welding torch and a laser sensor mounted thereon, comprising steps of:

setting, in advance, relationships among a width of a gap existing in a portion to be welded and welding conditions;

continuously or successively detecting the width of the gap existing in the portion to be welded along a weld path by using the laser sensor while performing welding for a first layer, and storing detected data concerning the gap width in a memory; and

performing welding for a second layer and a subsequent layer or layers under said welding conditions determined in accordance with the gap width stored in said memory.

2. A control method in a multi-layer welding according to claim 1, further comprising a step of performing a tracking of the weld line with said welding robot on a real time basis, when welding for the first layer, and using data obtained by sensing said weld line in advance with a sensor mounted on said robot.

3. A control method in a multi-layer welding according to claim 2, further comprising steps of:

storing path correction data which was used in said real-time tracking of the weld line by said welding robot in said memory together with said gap width; and

performing correction of the path of said welding robot by using the path correction data stored in said memory, while weldings for the second and subsequent layer or layers are performed.

4. A control method in a multi-layer welding according to claim 3, further comprising a step of performing a welding with the welding conditions controlled in accordance with the gap width detected by the real-time tracking of said laser sensor.

5. A control method in a multi-layer welding according to claim 1, wherein said welding conditions include at least one of a welding voltage, a welding current, a welding speed, a path shift amount, a weaving condition and a torch attitude.

6. A control method in a multi-layer welding according to claim 1, wherein a path shift is performed separately from the control of said welding conditions in the welding for each of the layers.

7. A control method in a multi-layer welding according to claim 1, wherein said portion to be welded is a portion formed by work pieces to be welded, which are arranged to butt against each other.

8. A control method in a multi-layer welding according to claim 1, wherein said portion to be welded is a portion formed by work pieces to be welded, which are arranged to have a difference in level.

9. A welding control system comprising a welding robot mounting an arc welding torch and laser sensor thereon, and a robot controller for controlling the operation of said robot, said laser sensor being arranged in a manner such that a scanning beam may scan an area preceding a weld point with respect to an advancing direction of the robot, said robot controller comprising:

weld line and gap width calculating means for obtaining information on the weld line from a three-dimensional position information of the portion to be welded, which is detected by said laser sensor while performing welding for a first layer and calculating a width of the gap of the portion to be welded which lies on the weld line;

gap width storage means for storing data concerning the gap width of the portion to be welded which lies on said weld line;

welding condition storage means for storing predetermined relationships between the gap width of said portion to be welded and the welding conditions; and

welding condition outputting means for obtaining a gap width of the portion to be welded which lies on the weld line from a current position of the robot by using said gap width memory means, determining welding conditions in accordance with the gap width by using said welding condition storage means, and outputting the determining welding conditions to the robot for a second and a subsequent welding layer or layers.

10. A control method for multi-layer welding, comprising:

storing, in advance, relationships between a width of a gap in a portion to be welded and corresponding welding conditions;

detecting the width of the gap existing in the portion to be welded along a weld path while performing welding for a first layer, and storing the detected gap width data; and

performing welding for at least second and third additional layers under the welding conditions determined in accordance with the stored gap width data.