The invention is generally related to welding operations and more particularly to the adaptive control of arc welding parameters.
Narrow groove welding is widely used in the construction of pipelines around the world. Although many automated systems utilize a variety of control systems and methods, the exact geometry of the weld joint is not known at the time of welding. The reason the exact weld geometry is not known is that the joint is comprised of a number of elements that individually and collectively produce errors with respect to the desired joint design. Among the contributing factors are:
Because joint geometry is a critical factor in determining optimum welding parameters, when exact joint geometry is unknown, weld quality is limited when using conventional systems. Discrepancies between the desired joint geometry and the actual joint geometry cannot be compensated for because the exact joint geometry is not known. This results in the potential for the creation of welding defects.
Additionally, inconsistency and changes in the actual bevel/weld geometry can also create the need for additional weld passes or “stripper” passes to properly fill the groove to allow the capping pass(es) to be run. For a production environment such as pipeline welding the time taken to run additional weld passes can be very costly.
The present invention addresses the shortcomings in the prior art and utilizes a laser sensor to scan the weld joint before welding begins as a pre-weld scanning operation to adjust pre-programmed arc welding parameters to provide adaptive control of the arc welding parameters. A “line” type laser sensor device projects a laser line within a fixed operating window. The line laser produces a reflective position of anything that the laser line “sees” within the operating window. By triangulation, the exact distance an object is from the laser can be measured at any point along the “line” of the laser. Certain parts of the weld bevel are targeted for measurement. The measurements are stored in an electronic storage medium and a data processor. The stored measurements and data processor are used in conjunction with automated welding equipment to adjust the welding parameters as required. Because the exact joint/weld geometry is then known for every portion of the weld, the welding equipment can then respond or “adapt” to variations in the weld joint between the work pieces.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming part of this disclosure. For a better understanding of the present invention, and the operating advantages attained by its use, reference is made to the accompanying drawings and descriptive matter, forming a part of this disclosure, in which a preferred embodiment of the invention is illustrated.
In the accompanying drawings, forming a part of this specification, and in which reference numerals shown in the drawings designate like or corresponding parts throughout the same:
As seen in
As seen in
These include the top edge 30 of each pipe 31, the tangent point 32 of the bevel angle, the top point 34 of each side of the bevel land, the volume to be welded, and any gap 36 between the two joints of pipe 31 (first pass only).
The information obtained from the measurements can be used with additional calculations to determine measurements such as high/low mismatch of the joint, pipe wall thickness, and bevel parameters.
In operation, the pipes 31 to be welded together are positioned adjacent and in contact with each other as in the normal manner when setting up work pieces for welding. The invention is used for a pre-weld scanning operation before the welding operation.
When used in a pre-weld scanning operation, the laser scanner 10 is positioned next to the joint between the pipes 31 and the entire circumference of the pipes 31 at the intended weld area is scanned and measured by triangulation of the laser reflections as referenced above. The measurements are recorded in an electronic data storage medium and data processor or computer 16. The computer contains software that is designed to work with the stored measurements for making adjustments to the welding operation. A person skilled in the art will understand how to write the software required for working with the stored measurements. The invention provides an advantage in that it is capable of being used with conventional automated welding equipment. The automated welding equipment illustrated in
In a pre-weld scanning operation the laser sensors 10 are positioned over the pipe 31 and weld joint as illustrated schematically in
The pre-welding scan of the entire circumference of the pipe joint obtains data that is processed to calculate various aspects of the joint groove that is to be welded. One use of the data is to determine the location of the weld groove for the entire circumference of the pipe joint to be welded. This data is used for pipe joint seam tracking in a similar fashion as taught by U.S. Pat. No. 5,347,101. The “line” type laser data obtained in the pre-welding scan also produces a three-dimensional representation of the weld groove. This three-dimensional representation can be used to check and adjust welding parameters that are pre-programmed for an ideal joint into a welding system.
The three-dimensional data can be used for joint tracking as well as parameter adjustments for multiple weld passes without re-scanning.
While the description generally references the use of the invention in relation to welding pipe joints, it should be understood that the invention is applicable to weld joints for other types of work pieces.
The invention provides a number of advantages.
Because the exact joint/weld geometry is known for every portion of the circumferential weld, the computer can cause the welding equipment to respond or adapt to variations in the joint bevel. The response or adaptive control of the welding equipment can include a change in any of the controlled welding parameters as required to insure the best weld in accordance with the recorded and calculated measurements of the pipe joint. These parameters include, but are not limited to, voltage, current, pulsing parameters when PGMAW (Pulsed Gas Metal Arc Welding) is used, wire feed rate, travel speed, oscillation parameters (width, speed, dwell angle, etc.), and position of the welding torch relative to the weld joint. The measurements and adaptive control of the invention can be used with any automated welding equipment.
The invention allows for compensation of any bevel and joint fit-up that is less than ideal. The stored measurements and calculations provide the ability to dynamically change any of the welding parameters listed above during welding. Combined with the detailed geometric information of the work pieces, adjustments may be made to one or more parameters to compensate for the bevel or fit-up variation.
An example of a required compensation would be a poor fit-up that results in one portion of the weld joint being wider than it should be. When welding the wider section of the joint, the invention can adjust the wire feed rate to increase the deposited weld metal to insure proper fill for each weld pass. At the same time, the arrangement can widen the oscillation width parameter to insure the arc obtains proper penetration into the side walls of the bevel (into the parent material).
The adaptive control of the invention can be developed for any variation from the ideal weld joint. The software may include specific parameters to be changed as well as the amount of change. The software may be designed to make adjustments proportionally as a function of the degree of error in the weld joint as measured by the laser sensors.
The invention reduces the risk of potential weld defects caused by variations in weld/bevel geometry for any location of a circumferential weld.
The invention improves consistency of root pass penetration and root profile.
The invention allows adjustment of weld volume deposited by each weld pass to insure proper filling of the weld groove within the planned number of weld passes.
The invention allows validation of joint fit-up by comparing the actual (measured) bevel geometry to pre-set allowable bevel geometry.
The invention reduces the scan time by utilizing multiple lasers for a given work piece (joint). A complete tracking model is generated using laser data from lasers on each weld head, with each weld head taking data for a portion of the circumference of the girth weld. This data is then joined together to produce a three-dimensional representation of the joint.
While specific embodiments and/or details of the invention have been shown and described above to illustrate the application of the principles of the invention, it is understood that this invention may be embodied as more fully described in the claims, or as otherwise known by those skilled in the art (including any and all equivalents), without departing from such principles.
This application is a continuation-in-part of application Ser. No. 12/650,596, filed Dec. 31, 2009.
Number | Date | Country | |
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Parent | 12650596 | Dec 2009 | US |
Child | 13662669 | US |