Abstract:
An apparatus and method for inspecting and analyzing welded structures includes a laser for directing at least one beam of light at a weld bead to define at least one visible profile line; a camera directed at the weld bead for capturing an image of the at least one profile line and generating a usable image signal based on the image; and a preprogrammed microprocessor assembly configured for receiving the usable image signal and processing the signal as an image to determine a dimension of the weld bead defined along the at least one profile line and comparing the dimension of the weld bead with a predetermined dimension set point to determine the quality of the weld bead.

Description:
BACKGROUND 
       [0001]    Relating broadly to equipment for testing the integrity of welds that join two or more structures together in a predetermined relationship and, more particularly, to a method and apparatus for inspection and analyzing such a welded structure utilizing a laser and camera for inspection and to generate a signal as a result of the inspection, a microprocessor is used for analyzing the results of the inspection based on the signal generated by the camera and laser apparatus. 
         [0002]    Welding is a fabrication process wherein two or more materials, usually metal or plastic, are joined by melting a portion of the workpieces and adding a filler material to form a pool of molten metal (or other workpiece material) known as the weld puddle that cools to become a strong joint. In industrial and manufacturing settings, robotic welding has become commonplace wherein machines position the work pieces for welding and a robotic welder applies the heat and material necessary to form the weld puddle. 
         [0003]    As may be expected, the integrity of the subsequent weld depends, among other things, on the positioning of the work pieces in relation to the position of the welder or heat source. In addition, the positioning of the filler material can also affect the quality and integrity of the subsequent welded joint. In the case of manual welding, the welder can adjust the position of the various materials in order to achieve what he or she feels is the best weld possible. Even then, a more precise inspection process could be useful. With robotic welding, when the machines have no independent capability to determine where to position the materials, other than their preprogrammed positions, certain tolerances may lapse and the weld may not be as good as it can be and, in fact, maybe dangerous with no one becoming the wiser until farther down the manufacturing process, if then. 
         [0004]    Accordingly, there exists a need for a welding system that provides an inspection and analysis process directed to the finished weld joint. Further, it is desirable to have such a method and apparatus that is applicable to virtually any welding process but is more particularly directed to welding vehicle wheels. 
         [0005]    Typically, during the manufacture of vehicle wheels such as those for automobiles and pickup trucks, the wheel is a two-piece unit having a wheel body, or rim joined to a disc. The wheel is typically mounted to the vehicle while the outer rim carries and seals the tire. As may be expected, such weld joints are extremely important in the safety of vehicle operation when the vehicles are equipped with such wheels. In the case of welded automobile wheels, safety becomes a primary concern because the wheels typically rotate at high rate and support the weight of the vehicle as is it propelled down the road. As can be imagined, catastrophic weld failure can have devastating results. 
         [0006]    It would therefore be helpful to have a method and apparatus for inspecting weld joints in wheels. Further, it would be beneficial to provide a method and apparatus whereby qualitative analysis can be performed on the weld joint to use an analysis of the entire welding process. 
       MULTIPLE EMBODIMENTS 
       [0007]    A method and apparatus is provided for inspecting and analyzing weld structures along the junction of wheel discs and wheel rims to determine the integrity of the weld bead or junction based on predetermined weld tolerances. 
         [0008]    Such a method and apparatus is provided that can be performed utilizing a microprocessor-based optical analysis. 
         [0009]    To these and other ends, an embodiment includes an apparatus for inspecting and analyzing welded structures including a laser for directing at least one beam of light at a weld bead formed on at least two workpieces joined by the weld bead in a predetermined manner to define at least one visible profile line, with the at least one profile line extending along at least a portion of each of the workpieces and along a full dimension of the weld bead. Also included is a camera directed at the weld bead for capturing an image of the at least one laser light beam forming the at least one profile line and generating a usable image signal based on the image. 
         [0010]    Also included is a preprogrammed microprocessor assembly configured for receiving the usable image signal and processing the signal as an image. The microprocessor assembly analyzes the image to determine the extent of a predetermined dimension of the weld bead. This is accomplished during processing by the microprocessor assembly being configured for locating at least one profile line on the image; locating the weld bead along the at least one profile line; determining a dimension of the weld bead defined along the at least one profile line; and comparing the dimension of the weld bead with a predetermined dimension set point to determine the quality of the weld bead. 
         [0011]    It is preferred that the apparatus for inspecting and analyzing welded structures include the preprogrammed microprocessor assembly being configured for locating a first straight portion of the at least one profile line extending for a predetermined length without curving on the image to identify a first workpiece portion; determining a weld start point by determining where the first straight portion of the at least one profile line begins to curve; defining a first weld dimension line extending tangent to the at least one profile line at the weld start point; locating a second straight portion of the at least one profile line extending for a predetermined length without curving on the image to identify a second workpiece portion; determining a weld bead endpoint by determining where the second straight portion of the at least one profile line begins to curve; defining a second weld dimension line extending tangent to the at least one profile line at the weld bead endpoint, wherein the first and second weld bead lines intersect at a weld bead midpoint; and determining a dimension of the weld bead defined as the sum of a distance from the weld start point to the weld bead midpoint and a distance from the weld bead midpoint to the weld endpoint. 
         [0012]    It is further preferred that the first workpiece is a wheel disc and the second workpiece is a wheel rim, and the laser is configured for producing at least one profile line directed laterally across the wheel disc and the wheel rim and a junction thereof. Preferably, the laser produces three generally parallel profile lines and the microprocessor assembly calculates a weld dimension as determined from an average of the results obtained from the three profile lines. 
         [0013]    It is preferable that the present apparatus for inspecting and analyzing welded structures is further configured to perform measurements of weld dimension at a plurality of positions along the workpieces. More particularly, it is preferred that the apparatus is configured to perform measurements of weld dimension at twelve positions disposed around the wheel rim and the wheel disc. 
         [0014]    It is further preferred that microprocessor assembly is configured to compare the weld dimension with at least two separate set points representing at least two separate failure modes to determine the quality of the weld bead. 
         [0015]    According to another, more detailed recitation, an apparatus is provided for inspecting and analyzing welded wheel structures including a laser for directing at least one beam of light at a weld bead formed on at least two workpieces comprising a wheel disc and a wheel rim joined by the weld bead in a predetermined manner to define at least one visible profile line, the at least one profile line extending along at least a portion of each of the wheel disc and the wheel rim and along a full dimension of the weld bead. Also included is a camera directed at the weld bead for capturing an image of the at least one laser light beam forming the at least one profile line and generating a usable image signal based on the image. 
         [0016]    Further included is a preprogrammed microprocessor assembly configured for receiving the usable image signal and processing the signal as an image. The microprocessor assembly analyzes the image to determine the extent of a dimension of the weld bead. This is accomplished during processing by the microprocessor assembly being configured for locating at least one profile line on the image; locating the weld bead along the at least one profile line; determining a dimension of the weld bead defined along the at least one profile line; and comparing the dimension of the weld bead with a predetermined dimension set point to determine the quality of the weld bead. 
         [0017]    It is preferred that the apparatus for inspecting and analyzing welded structures include the preprogrammed microprocessor assembly being configured for locating a first straight portion of the at least one profile line extending for a predetermined length without curving on the image to identify a wheel disc portion; determining the weld start point by determining where the first straight portion of the at least one profile line begins to curve; defining a first weld dimension line extending tangent to the at least one profile line at the weld start point; locating a second straight portion of the at least one profile line extending for a predetermined length without curving on the image to identify a wheel rim portion; determining a weld endpoint by determining where the second straight portion of the at least one profile line begins to curve; defining a second weld dimension line extending tangent to the at least one profile line at the weld bead end position, wherein the first and second weld bead lines intersect at a weld bead midpoint; and determining a dimension of the weld bead defined as the sum of a distance from the weld start point to the weld bead midpoint and a distance from the weld bead midpoint to the weld endpoint. 
         [0018]    Preferably, the laser is configured to produce at least one profile line directed laterally across the wheel disc and the wheel rim and a junction thereof. It is further preferred that the laser is configured to produce three generally parallel profile lines and the microprocessor assembly is configured to calculate a weld dimension as determined from an average of the results obtained from the three profile lines. 
         [0019]    Preferably, the apparatus is configured to perform measurements of weld dimension at a plurality of positions around the wheel disc and the wheel rim. More particularly, an embodiment of the apparatus is configured to perform measurements of weld dimension at twelve positions disposed around the wheel rim and the wheel disc. 
         [0020]    It is preferable that the microprocessor assembly is configured to compare the dimension of the weld bead with at least two separate set points to determine the quality of the weld bead. 
         [0021]    Also provided is a method for using the present apparatus. The method for inspecting and analyzing welded structures includes the steps of:
       providing a laser for directing at least one beam of light at a weld bead formed on at least two workpieces joined by the weld bead in a predetermined manner;   defining at least one visible profile line using the laser, the at least one profile line extending along at least a portion of each workpiece and along a full dimension of the weld bead;   providing a camera directed at the weld bead;   capturing an image, using the camera of the at least one laser light beam forming the at least one profile line and generating a usable image signal based on the image; and   providing a preprogrammed microprocessor assembly configured for receiving the usable image signal and processing the signal as an image to determine the quality of the weld bead, the processing including the steps of;   locating at least one profile line on the image;   locating the weld bead along the at least one profile line;   determining a dimension of the weld bead defined along the at least one profile line; and   comparing the dimension of the weld bead with a predetermined dimension set point to determine the quality of the weld bead.       
 
         [0031]    It is preferred that the present method include the following processing steps using the preprogrammed microprocessor assembly:
       locating a first straight portion of the at least one profile line extending for a predetermined length without curving on the image to identify a first workpiece portion;   determining where a weld bead start point is by determining where a first straight portion of the at least one profile line begins to curve;   defining a first weld dimension line extending tangent to the at least one profile line at the weld start point;   locating a second straight portion of the at least one profile line extending for a predetermined length without curving on the image to identify a second workpiece portion;   determining a weld endpoint by determining where the second straight portion of the at least one profile line begins to curve;   defining a second weld dimension line extending tangent to the at least one profile line at the weld endpoint, wherein the first and second weld bead lines intersect at a weld bead midpoint; and   determining a dimension of the weld bead defined as the sum of a distance from the weld start point to the weld bead midpoint and a distance from the weld bead midpoint to the weld endpoint.       
 
         [0039]    Preferably, of the at least two workpieces, the first workpiece is a wheel disc and the second workpiece is a wheel rim, and the step of defining at least one profile line includes defining at least one profile line directed laterally across the wheel disc and the wheel rim and a junction thereof. More particularly, it is preferred that the step of defining at least one profile line includes defining three generally parallel profile lines and that the step of determining the dimension of the weld bead includes determining a weld dimension from an average of the results obtained from the three profile lines. 
         [0040]    It is further preferred that the method steps are repeated to perform measurements of weld dimension at a plurality of positions along the workpieces. More particularly, in a preferred embodiment, the method steps are repeated to perform measurements of weld dimension at twelve positions disposed around the wheel rim and the wheel disc. 
         [0041]    A preferred embodiment provides a method for inspecting and analyzing welded structures wherein the step of comparing the dimension of the weld bead with at least one predetermined set point includes comparing the dimension of the weld bead with at least two separate set points to determine the quality of the weld bead. Furthermore, the step of comparing the dimension of the weld bead with at least two separate set points includes comparing the dimension of the weld bead to a first set point representing a welding torch position and a second set point representing a position of the workpieces to determine quality of the weld bead. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]      FIG. 1  is a diagrammatic representation of a method and apparatus for inspecting and analyzing welded structures according to one preferred embodiment of the present invention. 
           [0043]      FIG. 2  is a side view of the apparatus illustrated in  FIG. 1 ; 
           [0044]      FIG. 3  is a side view of a wheel rim illustrating the relationship of the laser and camera; 
           [0045]      FIG. 4  is a diagrammatic representation of a profile line generated by the laser in relation to the wheel portions and weld structure; 
           [0046]      FIG. 5  is a diagrammatic representation of the profile lines as use in analysis by the processor of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0047]    Turning now to the drawings and more particularly to  FIG. 1 , a wheel structure or wheel assembly is illustrated generally at  10  and includes a wheel disc  12  and a wheel rim  14  as seen in  FIG. 2 . The wheel  10  is formed by machining the disc  12  and the rim  14  out of, for example, a metal of choice such as, for example, steel, aluminum or some other material. The disc  12  is fitted to the rim  14  with four tack welds. A welder, preferably robotic (not shown) is then employed to apply a weld bead  16  continuously and circumferentially about the junction between the rim  14  and the disc  12 . In order to position the wheel  10  for use by an embodiment, a wheel support structure  18  is provided. 
         [0048]    With continued reference to  FIGS. 1 and 2 , an apparatus  20  for inspecting and analyzing the welded wheel structure  10  includes a laser  24 , a camera  30  and a microprocessor  21 . The laser  24  and camera  30  are supported on a frame structure  22  and each is supported by its own support tower with the camera  30  being supported by a camera support tower  32  and the laser  24  being supported by a laser support tower  26 . The microprocessor  21  may be one of a variety of microprocessors to include computers such as, for example, a production line computer or even a personal computer such as, for example, a laptop. The calculations necessary to determine the quality of a weld bead  16  and to otherwise perform the method of the present embodiments are not so complex as to require a great deal of computing capacity. Nevertheless, it is presumed that the microprocessor  21  will be somewhat remote from the laser  24  and camera  30 . The microprocessor  21  is in electrical communication with the camera  30  in order to receive and process an image from the camera  30 . 
         [0049]    The laser  24  is configured for generating and directing a laser beam  28  to a predetermined set point on the wheel assembly  10 , forming a profile line  34 . As shown in  FIG. 3 , it is preferred that the laser apply three profile lines,  34 ,  36 ,  38 , which will be explained in greater detail hereinafter, and that when the wheel  10  is mounted on a wheel support stand  18  such that the disc is oriented, for example, generally horizontal (See  FIG. 2 ), the profile lines  34 ,  26 , and  38  extend vertically up the wheel rim  14  and across the disc  12 . The camera  30  is aimed in such a manner as to capture the image of the profile lines  34 ,  36 ,  38 , as shown in  FIGS. 4 and 5 . 
         [0050]    In operation, and referring back to  FIGS. 1 and 2 , a laser beam  28  is transmitted from the laser  24  thereby projecting a beam of light on the wheel assembly  10  mounted to the wheel support  18 . Referring to  FIG. 3 , such projection results in three profile lines  34 ,  36 ,  38  being projected along the rim  14 , the weld bead  16 , and the disc  12 . The image of the profile lines  34 ,  36 ,  38  is captured by the camera  30  for analysis by the microprocessor  21 . If displayed on a screen, the profile lines  34 ,  36 ,  38  would appear generally as shown in  FIGS. 4 and 5 . The microprocessor  21  is employed to analyze the profile lines to determine the beginning and end of the weld points on the weld bead  16 .  FIG. 4  illustrates the correspondence between the wheel assembly  10  and the first profile line  34 . 
         [0051]    Turning first to the wheel assembly  10 , the weld bead  16  includes a wheel disc portion  52  and a wheel rim portion  56  as well as a weld bead midpoint  54 . Arrows indicate that on the profile line  34 , a location on the disc portion  12  prior to the weld bead  16  is illustrated at  40  and is formed as a straight line. Where the line begins to curve is the rim curve point  42  and which also corresponds to the wheel disc portion  52 . For the rim side, a straight portion of the profile line illustrated at  46  represents a location on the rim  14 , prior to the weld bead  16 . Where the rim line portion  46  of the profile line  34  begins to curve at  48  corresponds to the wheel rim portion  56  of the weld bead  16 . 
         [0052]    As shown in  FIGS. 4 and 5 , and as a part of the automated microprocessor analysis, a line  44  tangent to the rim curve point  42  is drawn by the microprocessor  21 . Similarly, a line  50  tangent to the wheel rim portion  56  is drawn. These lines intersect at the weld bead midpoint  54  as illustrated in  FIG. 4 . The length of the lines  44 ,  50  is the value of concern regarding the dimension of the weld bead  16 . The length is of concern because its analysis can determine the quality of the weld bead  16 . Each line  44 ,  50  is measured and each of the two length measurements for line  44  and line  50 , respectively, are compared to set points which are found to be in a range corresponding to the specifications of various customers. The microprocessor  21  determines a first length from profile line  34  and then performs the same activities on the remaining profiles lines  36 , and  38 , then averages the three results to achieve an average length of the weld bead  16  at the first point of measurement. Preferrably, the microprocessor  21  performs this process both for the rim  14  side of the weld  16 , and again for the disc  12  side of the weld  16 . The microprocessor  21  outputs the resulting averaged length for the rim  14  side and the microprocessor  21  also outputs the resulting averaged length for the disc  12  side, and both lengths are compared to the customer specifications. 
         [0053]    According to the method provided, the measurement is taken at multiple positions or locations, and in a preferred embodiment, at  12  positions or locations spaced equally about the wheel assembly  10  in order to obtain representative samples of the circumferential continuous weld bead  16  around the rim  14  and disc  12  juncture of the wheel assembly  10 . 
         [0054]    It should be noted that the provided weld inspection system should be calibrated using a known weld bead  16  of predetermined size to ensure that the measurements taken from the profile lines  34 ,  36  and  38  by the microprocessor  21  are valid. It will be apparent to those skilled in the art that calibrating the system in order to achieve accurate results using the present system is well within the skills of one possessing ordinary skill in the art. Therefore, in-depth discussions of the calibration of the system are beyond the scope of the present embodiments. 
         [0055]    Analysis has determined that there are two failure modes of the weld bead  16  that are readily identified in the eventuality of two maladjustments of the welding assembly. 
         [0056]    The first failure mode occurs if a robotic torch (not shown) is maladjusted and thereby out of position; either more to the rim  14  side or more to the disc  12  side, whereby the quality of the weld bead and accordingly, its measured dimension or length will be affected. The microprocessor  21  conducts this analysis and determines whether the torch is in the right position and also determines a correction factor for the torch. 
         [0057]    The second failure mode occurs if the wheel  10  is maladjusted and thereby out of position. Either the rim  14 , the disc  12 , or both, may be positioned incorrectly by the support structure  18  during the welding process also giving rise to poor weld bead  16  quality readings as determined by the aforesaid microprocessor  21  analysis. Accordingly, utilizing the present embodiments, at least these two failure modes of a weld bead  16  in a wheel assembly  10  may be measured and analyzed with correction factors applied as necessary to ensure the structural integrity of the rim/disc junction and, accordingly, the structural integrity of the wheel assembly  10 . Accordingly, the consistency of the wheels  10  produced by the manufacturing process is enhanced and overall wheel  10  quality is enhanced. It should be noted that the preferred embodiments do not directly inform the user which failure mode has occurred. Instead, the preferred embodiments inform the user if one leg length, for either the rim  12  side or the disc  14  side of the weld bead  16  is too short. Such short lengths correspond directly to the failure modes described above. 
         [0058]    In the past, a representative number of wheels  10  would be hand-measured to determine whether or not their welds  16  were within the required parameters as defined by the customer&#39;s specifications. For the sake of clarity in further teaching this concept, let us consider the OEM automotive parts supply industry where a particular manufacturing plant may be producing many different varieties of wheels  10  for a variety of customers—being various automobile companies who use the wheels  10  in the final assembly of automobiles. Let us designate “x” as a value corresponding to a particular customer&#39;s minimally acceptable weld leg length. Let us also designate “z” as a number larger than “x” and which corresponds to a particular wheel  10  manufacturing plant&#39;s preferred weld leg length. Furthermore, let us designate “y” as an acceptable weld leg length which corresponds to a range of numbers that fall in between “x” and “z.” In other words, “x” is less than the range “y” which is less than “z.” In practice, length values are expressed in millimeters or fractions of an inch, but other measurement systems may also be contemplated. Returning to our example, in the past, a typical representative wheel  10  was measured in four places around the wheel  10 . With these embodiments, every wheel  10  can be checked at a plurality of locations and, in a preferred embodiment, every wheel  10  is checked in 12 separate locations on the wheel  10 . For accuracy, good results have been obtained when the camera  30  resolution is 0.05 millimeters per pixel, although other resolution settings may work sufficiently without departing from the scope and spirit of the present embodiments. 
         [0059]    As an example, let us discuss a typical analysis of weld beads  16  that will cause a wheel  10  to fail testing under the present system and method. Using “x”, “y” and “z”, it has been determined that the dimension or length of the weld bead  16  should be greater than “x.” A wheel  10  is considered marginal and in need of further manual inspection if its weld beads  16  have dimensions less than “z.” Typically, such dimensions may be, but are not so limited, expressed as a percentage below “z.” For example, if the dimension of the weld bead  16  is found to be in a range of lengths corresponding to “y” that wheel  10  is marginal. A weld bead  16  length of less than “x” is further classified as a bad weld. 
         [0060]    Recall that, preferably, the wheel  10  is tested at  12  separate locations around the circumference thereof. The wheel  10  will fail its inspection if four or more inspection locations reveal lengths of weld beads  16  corresponding to “y.” In addition, if the testing reveals three marginal, or “y”, leg length locations in a row, then the wheel  10  will fail. If any particular location has a weld bead  16  length less than “x”, the entire wheel  10  will fail. Wheels  10  that have values of “z” or higher pass inspection but such values correspond to longer time in welding, thereby slowing down the assembly line, and increased use of welding rod and energy at the plant. In other words, once a plant&#39;s welding machines provide welds that exceed “z”, the plant is at risk of having reduced cost effectiveness, hence another reason why the current embodiments improve the efficiency of wheel  10  manufacturing. 
         [0061]    It will be apparent to those skilled in the art that the example is provided to illustrate certain predetermined values operable with the present embodiments or a certain wheel  10 . Other wheels  10  may provide different actual measurements and the test results of those wheels  10  may dictate the corresponding failure criteria. Nevertheless, the present example illustrates one use of the present embodiments for inspection of weld beads  16  on wheels  10 . 
         [0062]    It will therefore be readily understood by those persons skilled in the art that the present embodiments encompass a broad utility and application. While the present embodiments are described in all currently foreseeable manners, there may be other, unforeseeable embodiments and adaptation, as well as variations, modifications and equivalent arrangements, which do not depart from the substance or scope of the present embodiments. The foregoing disclosure is not intended or to be construed to limit the present embodiments or otherwise to exclude such other embodiments, adaptations, variations, modifications and equivalent arrangements, the embodiments provided herein being limited only by the claims appended hereto and the equivalents thereof.