Abstract:
A system and method is provided to use a laser system to remove excess weld bead build up from a workpiece after a welding operation. After a weld bead is formed a weld bead can have a protrusion which extends above a surface of a workpiece and it is desirable to remove the protrusion. A system and method is provided which uses a laser beam oriented at an angle and delivered with an intensity sufficient eliminate or remove the excess weld bead build up.

Description:
PRIORITY 
       [0001]    The present application claims priority to U.S. Provisional Patent Application No. 61/679,481 filed Aug. 3, 2012, which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to systems and methods for post-weld processing. More specifically, the subject invention relates to methods and systems for eliminating post-weld build up (face or root enforcement) using a laser. 
       BACKGROUND 
       [0003]    Carrying out a welding operation results in a weld bead that generally projects above the workpiece surface, i.e., post-weld material (face or root reinforcement). Exemplary welding operations include electric arc welding, laser welding and hot wire welding. Shown in  FIG. 1  is an exemplary typical weld bead  10  which joins a first workpiece  12  and a second workpiece  14 . The weld bead  10  extends linearly (along the Y-Y axis) and further spans and fills the groove between the workpieces  12 ,  14  (along the X-X axis). Completion of the welding process provides for an excess weld material  10   a  having a thickness t which extends above the surface of the workpieces  12 ,  14 . The excess material  10   a  may be removed using know material removal tools such as for example, grinders. There is a need for alternative systems and methods to remove the post-weld material. 
         [0004]    Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present application with reference to the drawings. 
       SUMMARY 
       [0005]    Embodiments of the present invention provide for system and methods for post-weld removal of excess weld material for joined workpieces. In one aspect, the system includes a laser delivery assembly to deliver a laser beam at a weld-to-laser distance sufficient to melt or vaporize the excess material. One embodiment of the system includes a laser absorption element to absorb laser energy as it removes the excess weld material. Alternatively or in addition to, a fume extraction device is mounted to collect the fumes produced from the removal process. The subject removal process in one aspect provides for relative movement between the joined workpieces and the laser beam. In one aspect, the joined workpieces remains stationary and the laser beam is moved with respect to the workpieces. In alternative embodiments, the workpieces are moved relative to the laser beam. 
         [0006]    These and other features of the claimed invention, as well as details of illustrated embodiments thereof, will be more fully understood from the following description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The above and/or other aspects of the invention will be more apparent by describing in detail exemplary embodiments of the invention with reference to the accompanying drawings, in which: 
           [0008]      FIG. 1  is an illustrative embodiment of a typical weld bead with excess weld material; 
           [0009]      FIG. 2A  is an illustrative embodiment of a system for removing the excess weld material of  FIG. 1 ; 
           [0010]      FIG. 2B  is a plan view of an alternate arrangement of the system of  FIG. 2A ; 
           [0011]      FIG. 2C  is a cross-sectional view of an alternate embodiment of the system of  FIG. 2A ; 
           [0012]      FIG. 2D  is a cross-sectional view of an alternate embodiment of the system of  FIG. 2A . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Exemplary embodiments of the invention will now be described below by reference to the attached Figures. The described exemplary embodiments are intended to assist the understanding of the invention, and are not intended to limit the scope of the invention in any way. Like reference numerals refer to like elements throughout. 
         [0014]    Shown in  FIG. 2A  is a system  100  for removing the excess weld bead material  10   a.  Generally, the system  100  includes a laser delivery assembly  110  coupled to a laser source  115 . The laser delivery assembly  110  may be configured for fiber delivery so as to include appropriate laser optics  110   a  coupled to a fiber delivery  110   b  for delivery of a laser beam  125  from the laser source  115 . To control the intensity of the laser beam  125 , a controller  120  is coupled to the laser source  115 . In one aspect, the laser optics  110   a  are configured as a collimating and focusing laser optic assembly  110   a  to define a laser beam  125  sufficient to melt an amount of weld material and more particularly, weld metal. Other configurations of the laser optics  110   a  are possible to carry out the post-weld removal process. 
         [0015]    The laser optics assembly  110  in one embodiment is a substantially cylindrical member has a distal end from which a collimated and focused laser beam exits and a proximal end coupled to the laser beam delivery device  110   b.  Exemplary embodiments of the laser source  115  includes CO2, Nd:YAG; Fiber or Direct Diode for providing a wavelength from about 1 micron to about 11 microns and more particularly 0.8 microns to about 10.6 microns. In one exemplary embodiment, the laser source  115  provides a power density of about 500 W/cm 2 . In some embodiments, the laser optics subassembly  110   a  includes two lenses: a collimating lens and a focus lens which are spaced apart to form a laser beam  125  having a particular wavelength and energy at the weld joint. Of course, other optics configurations can be used. 
         [0016]    The system  100  is configured such that the laser beam  125  and joined workpieces  12 ,  14  can be moved relative to one another for removal of the excess weld bead material  10   a  which extends or projects above the surfaces of the workpieces. In one aspect, the joined workpieces  12 ,  14  can be mounted and affixed during the post-weld removal process. Accordingly, the laser subassembly  110  is moved about the workpiece so as to scan the laser beam  125  over the weld bead  10  to remove the excess material  10   a.  In one embodiment, the laser assembly  110  is configured to translate linearly along at least three axes: axis X-X horizontally transverse to the weld bead  10 ; axis Y-Y parallel to bead  10 ; and axis Z-Z vertically transverse to the weld bead  10 . In one exemplary embodiment, the optics assembly  110   a  is mounted for controlled translation along a first rail  130   a  extending parallel to axis X-X and a second rail  130   b  extending parallel to the Y-Y axis and perpendicular to the first rail  130   a.  To translate the laser subassembly  110  vertically, the optic assembly  110   a  can be, for example, mounted to a rack  132   a  by a pinion (not shown) for vertical translation along the Z-Z axis. Alternative arrangements for locating and translating the optics of a laser assembly are shown and described in U.S. Patent Publication No. 2011/0297658, which is attached incorporated herein by reference in its entirety. 
         [0017]    In an exemplary operation, the joined workpieces  12 ,  14  are affixed to, for example, a stationary material handling table  140 . The laser beam  125  is delivered and located at the weld  10  to melt and remove the excess material  10   a.  To properly locate the laser beam  125  along the weld  10 , the laser optics assembly  110  is translated in a controlled manner over the rails  130   a,    130   b  and/or rack and pinion  132   a  by, for example, appropriate motorized gearing, exemplary motorized gearing is shown and described in U.S. Pat. No. 5,227,601, which is incorporated fully herein by reference. 
         [0018]    To remove the excess weld material  10   a,  laser beam  125  is of sufficient intensity to melt, in some embodiments, or vaporize—in other embodiments—the excess weld material  10   a.  More particularly, the laser beam  125  is controlled by the controller  120  to deliver an intensity of laser energy at a laser-to-weld distance XX sufficient to melt and/or vaporize the excess material  10   a.  In one aspect, the excess weld material  10   a  is removed such that the resultant weld bead  10  is substantially flush with the surfaces of the workpieces  12 ,  14 . With reference to  FIG. 2A , the joined workpieces  12 ,  14  are arranged with respect to the laser subassembly  110  such that the laser beam  125  extends transverse to the weld bead  10  to define a substantially constant laser-to-weld distance. With reference to  FIG. 2B , the joined workpieces  12 ,  14  are alternatively arranged with respect to the laser subassembly  110  such that the laser beam  125  extends collinear to the weld bead  10  so that the laser-to-weld distance varies as the excess weld material  10   a  is removed. 
         [0019]    Referring again to  FIG. 2A , the system  100  may further include a laser absorption member  150  opposed the laser optics assembly  110   a  to absorb the laser beam energy while the laser is being located at the weld  10  or to absorb the energy when the removal process is completed. In addition, the system  100  may include a fume extraction assembly  160  for removal of fume materials produced from the melting and/or evaporating weld metal. 
         [0020]    In alternate system arrangements, the laser subassembly  110   a  remains stationary and the workpiece is moved to locate the weld bead  10  and excess material  10   a  in the path of the laser beam  125 . For example, as shown in  FIG. 2C , the laser subassembly  110  operates in fixed position to deliver the laser beam  125 . The laser beam  125  remains fixed with respect to a stationary reference point such as for example, the ground G at a distance H. To locate the weld bead  10  and its excess material in the path of the laser beam  125 , the joined workpieces  12 ,  14  mounted to a movable/rotatable work table  140 . Other alternate arrangements include where the workpieces, such as for example, a joint pipe assembly  12 ′,  14 ′ is rotated about axis X-X, as seen in  FIG. 2D . 
         [0021]    In further exemplary embodiments, rather than removing the excess material  10   a  from the weld  10 , embodiments of the present invention melt the excess material  10   a  so that is distributed flatter over the surface of the workpieces  12  and  14 . That is, after the welding process the laser  110  and beam  125  reheat the material  10   a  to allow the excess material to spread out over the surface of the workpieces, thus lowering the overall height of the bead  10 . 
         [0022]    While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed.