CA2359221A1 - Post weld inspection apparatus and method of using same - Google Patents
Post weld inspection apparatus and method of using same Download PDFInfo
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- CA2359221A1 CA2359221A1 CA 2359221 CA2359221A CA2359221A1 CA 2359221 A1 CA2359221 A1 CA 2359221A1 CA 2359221 CA2359221 CA 2359221 CA 2359221 A CA2359221 A CA 2359221A CA 2359221 A1 CA2359221 A1 CA 2359221A1
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Abstract
An apparatus for use in verifying weld seams, including weld seam sensors selected from a pin hole sensor, a weld surface topography sensor and a weld penetration sensor. The pin hole sensor includes a light emitter having a light source configured to project a beam at a first upper or lower surface of the weld seam, and a light receptor disposed on the second other side of the weld seam generally opposite to the light source. A lens is provided to focus the light generally perpendicular to the weld seam, and the weld seam is moved relative to the light source. As the blank weld seam and pin hole sensor are moved relative to each other, pin holes through the weld seam are detected by light passing from the light source through the weld seam and to the light receptor. The surface topography of the weld seam is sensed by a vision camera system laterally across the upper and/or lower surface of the weld seam to determine whether the weld seam possesses acceptable degrees of concavity. Weld penetration is sensed by analyzing the intensity of the weld flame which is emitted from the lower surface of the tailored blanks during welding.
The weld penetration sensor includes an optic sensor positioned on the underside of the weld seam, which is positioned to receive emitted light from the weld flame.
The weld penetration sensor includes an optic sensor positioned on the underside of the weld seam, which is positioned to receive emitted light from the weld flame.
Description
POST WELD INSPECTION APPARATUS AND METHOD OF USING SAME
SCOPE OF THE INVENTION
The present invention relates to an apparatus used in the verification and inspection of weld seams, and more particularly, an apparatus which permits the fully automated inspection of butt, lap or mash weld seams to determine the suitability of weld seam profiles, weld penetration and/or the presence of pin holes through the weld seam.
BACKGROUND OF THE INVENTION
Various welding systems have been proposed for the automated production of workpieces. United States Patent No. 6,011,240 to Bishop et al, which issued January 4, 2000, and which is incorporated herein by reference, discloses a system used in the automated welding of metal sheet components to form tailored blanks, as for example are used in the production of automotive body parts and the like. In United States Patent No. 6,011,240, the sheet components are moved via a magnetic conveyor into a position in an abutting orientation, and a laser is then activated to weld the abutting edges of the component parts along a longitudinally extending weld seam. Following welding, the completed blank is moved via the conveyors to output stacks.
Conventional welding systems suffer a disadvantage in that to date, there has been no accurate mechanism which can verify that the component parts have been successfully welded.
As a result, the completed tailored blanks may contain welds which contain pin holes, namely small holes extending through the weld seam which are produced by the improper cooling of the molten component material which melts together to form the seam. Further, the weld seam may itself possess an undesirable degree of concavity or incomplete penetration of the weld, either of which may lead to failure of the tailored blank in subsequent processing operations, such as stamping, dimpling or the like.
SCOPE OF THE INVENTION
The present invention relates to an apparatus used in the verification and inspection of weld seams, and more particularly, an apparatus which permits the fully automated inspection of butt, lap or mash weld seams to determine the suitability of weld seam profiles, weld penetration and/or the presence of pin holes through the weld seam.
BACKGROUND OF THE INVENTION
Various welding systems have been proposed for the automated production of workpieces. United States Patent No. 6,011,240 to Bishop et al, which issued January 4, 2000, and which is incorporated herein by reference, discloses a system used in the automated welding of metal sheet components to form tailored blanks, as for example are used in the production of automotive body parts and the like. In United States Patent No. 6,011,240, the sheet components are moved via a magnetic conveyor into a position in an abutting orientation, and a laser is then activated to weld the abutting edges of the component parts along a longitudinally extending weld seam. Following welding, the completed blank is moved via the conveyors to output stacks.
Conventional welding systems suffer a disadvantage in that to date, there has been no accurate mechanism which can verify that the component parts have been successfully welded.
As a result, the completed tailored blanks may contain welds which contain pin holes, namely small holes extending through the weld seam which are produced by the improper cooling of the molten component material which melts together to form the seam. Further, the weld seam may itself possess an undesirable degree of concavity or incomplete penetration of the weld, either of which may lead to failure of the tailored blank in subsequent processing operations, such as stamping, dimpling or the like.
While the random manual inspection of completed blanks has been proposed, this is both time consuming and expensive. Further, each component part typically will have edge characteristics which vary and may materially affect the quality of the weld formed. Random manual inspection, in addition to introducing the possibility of human error, increases the possibility that blanks containing incomplete or undesirable welds may pass from the system.
SUMMARY OF THE INVENTION
To at least partially overcome difficulties of prior art welding apparatus, the present invention provides an apparatus used to verify one or more weld seam characteristics to permit an assessment of whether or not the weld seam may be susceptible to failure.
In this regard, the apparatus is configured to sense one or more of the top surface topography of the weld seam, the bottom surface topography of the weld seam, the existence, number, size and/or spacing of pin holes extending through the weld seam, and/or the degree of weld penetration.
An object of the invention is to provide an apparatus which permits the fully automated inspection of weld seams formed in tailored blanks and other workpieces after or concurrently with the formation of the weld seam.
Another object of the invention is to provide an apparatus used to verify the integrity of a weld seam by analyzing one and preferably each of the weld seam surface topography, the presence, number or size of pin holes through the weld seam, as well as the degree of weld penetration.
Another object of the invention is to provide a weld inspection apparatus which may be used simultaneously with existing welding systems used to form tailored blanks, and which provides a substantially simultaneous indication of whether or not the characteristics of the weld seam produced fall within acceptable tolerances.
To achieve at least some of the foregoing objects, the present invention provides an apparatus for use in the verification of weld seams, and most preferably weld seams of tailored blanks. The seam verifying apparatus includes at least one and most preferably several weld seam sensors selected from a pin hole sensor, a weld surface topography sensor and a weld penetration sensor. While the apparatus is useful to verify weld seams formed by lap, mash or plasma welding apparatus, most preferably the apparatus is used to verify butt weld joints formed by laser welding.
As used herein, the upper surface of the weld seam refers to the side of the workpiece or blank which, in welding operations, is oriented closest to the weld energy source, such as for example a laser head where weld seams are formed with a coherent light beam.
Similarly, the lower surface of the weld seam refers to the side of the blank which, in welding operations, is oriented furthest away from the weld energy source. It is to be appreciated, however, that while both welding and seam verification is performed with the blank in a generally horizontal orientation in a most simplified construction, the invention is not so limited, and the present invention could equally be used with the blank in an inclined or vertical orientation.
The pin hole sensor includes a light emitter which includes an energy or light source configured to project a beam at a first upper or lower surface of the weld seam, and a light receptor disposed on the second other side of the weld seam generally opposite to the light source. Where ultraviolet, visible or infrared light is projected by the light source, a focusing element such as a lens or filter is preferably provided to focus the light generally perpendicular to the weld seam and the surface of the workpiece. The weld seam is moved relative to the light source and light receptor to enable the sensing of at least part and preferably the entire longitudinal length of the weld seam. As the blank weld seam and pin hole sensor are moved relative to each other, pin holes through the weld seam are detected by light passing from the light source through the weld seam and to the light receptor.
Most preferably, the light source consists of an elongated array of two, three, four or more infrared light lamps or projectors. Other light sources including lasers, ultraviolet and invisible light sources could, however, equally be used. The light lamps are spaced so as to emit an elongated substantially continuous linear beam of light, in an orientation generally transverse to the longitudinal length of the weld seam. With such a configuration, the light receptor preferably includes an infrared light sensor, a photodiode or photoelectric cell, and a collecting lens configured to refocus any light which passes through pin holes in the weld seam to the infrared light sensor, photodiode or photocell. Optionally, a reflective light guide may be provided on the second side of the weld seam to maximize the reflection and transmission of light travelling to the receiver.
Where the edges of the tailored blank are not precisely perpendicular to the longitudinal extent of the weld seam, the light emitter may be configured to permit the relative movement of the orientation of the emitted light beam relative to the orientation of the edges of the tailored blank at the weld seam. The repositioning of the light beam advantageously permits the alignment of the linear beam with the edge portion of the tailored blank to permit the effective operation of the pin hole sensor immediately adjacent to the edges of the tailored blank, without false readings.
The surface topography of the weld seam is preferably sensed by a vision camera system laterally across the upper and/or lower surface of the weld seam. Suitable vision camera systems include three dimensional vision systems which include a laser optic adapted to emit a laser stripe transversely across the lateral width of the seam weld, and a receptor positioned to detect laser light reflected from the blank. The surface topography of the weld seam is analyzed to determine the transverse weld surface profile. This permits an assessment of whether the weld seam possesses acceptable degrees of concavity. Most preferably both the upper and lower surface topographies are reviewed. The weld surface topography may be analyzed at a separate post weld inspection station remote from a welding station where the components are welded.
More preferably, however, weld topography analysis is performed substantially simultaneously with welding operations, as for example, by mounting the vision system on a gantry or robot arm which carries the weld head optics.
The weld penetration is preferably sensed by analyzing the intensity of the weld flame which is emitted from the lower surface of the tailored blanks during welding.
In particular, the applicant has appreciated that with laser welding, the presence and intensity of the emitted weld flame provides an indication of complete weld penetration to indicate whether the component sheets have been completely melted across their thickness. The weld penetration sensor preferably includes an optic sensor such as a photovolatic cell, photodiode or infrared sensor positioned on the underside of the weld seam, so as to receive emitted light from the weld flame.
Optionally, a gas suction and/or clearing gas flow may be provided along the lower surface of the weld seam to prevent smoke, vapours and other gases produced during the welding of component parts from obscuring the weld flame and otherwise interfering with the operation of the optic sensor. The penetration sensor may be either movable with the weld energy beam or mounted in a fixed position relative to the weld seam. When fixed, the apparatus preferably may also be provided with microprocessor circuitry or software which either logs and/or compensates for light intensity changes as the weld flame moves relative to the optic sensor.
Accordingly, in one aspect the present invention resides in an apparatus for verifying a weld seam of a workpiece blank comprising:
a pin hole sensor including a light emitter and a light receptor, the light emitter being disposed on a first side of said seam and including a light source for projecting a light beam at said first side, and a focusing element to focus said light beam generally perpendicular to said weld seam, the light receptor disposed on the second other side of the seam generally opposite to the light source whereby projected light which passes through said weld seam activates said light receptor, a drive for moving the blank relative to the light emitter and light receptor in the direction of said weld seam.
In another aspect, the present invention resides in an apparatus for verifying a weld seam of a workpiece blank formed from welding two component parts with a laser, said apparatus comprising, a light receptor disposed on a lower side of said weld seam remote from said laser, said light receptor operable substantially simultaneously with said laser to receive and sense light emitted by a weld flame produced during laser welding.
In a further aspect, the present invention resides in an apparatus for verifying a weld seam of a workpiece blank formed from welding at least two component parts with a laser, said apparatus comprising:
a pin hole sensor including a light emitter and a light receptor, the light emitter being disposed on a first side of said seam and including a light source for projecting an elongated light beam at said first side, and a focusing element to focus said light beam generally perpendicular to said weld seam, the light receptor disposed on the second other side of the seam generally opposite to the light source whereby projected light which passes through said weld seam activates said light receptor, said light receptor including a collecting lens configured to focus projected light which passes through said weld seam towards said pin hole light receiver , a reflective light guide and a pin hole light receiver providing an output signal when activated by said projected light, an infrared light sensor disposed on said second side of said seam, said infrared light sensor operable substantially simultaneously with said laser to receive and sense infrared light energy emitted by a weld flame produced during laser welding, and a surface topography sensor for sensing the concavity of at least one of the top or bottom of the weld seam.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of the invention will appear from the following description taken together with the accompanying drawings in which:
Figure 1 shows a schematic top view of a production assembly line for forming tailored blanks in accordance with the present invention;
Figure 2 is a schematic side view of the weld head, upper weld surface topography sensor and weld penetration sensor used in the production assembly line of Figure 1;
Figure 3 is a partial sectional view of the apparatus shown in Figure 1 taken along lines 3-3' illustrating the positioning weld penetration sensor;
Figure 4 illustrates graphically a preferred data output of the weld penetration sensor shown in Figure 3;
Figure 5 illustrates a cross-sectional view of the apparatus shown in Figure 1 taken along lines 5-5' illustrating the positioning of the pin hole sensor and bottom seam topography sensor relative to a tailored blank;
Figure 6 illustrates a schematic side view of the pin hole sensor used in the apparatus of Figure 1;
Figure 7 illustrates schematically a partial top view of the pin hole sensor of Figure 6; and Figure 8 illustrates graphically a preferred data output from the pin hole sensor of Figure 6.
DETAILED DESCRIPTION OF THE INVENTION
Reference is first made to Figure 1 which shows a system 10 used in the production of workpieces such as composite tailored blanks 12 which are used in the production of auto body parts and the like. With the system 10 shown, a vacuum operable lifting robot 18 is used to move a pair of metal component sheets 14,16 from respective supply stacks 20,22. The lifting robot 18 includes a movable telescoping lift arm 24 having a variable suction head 26 which is adapted to lift and move the pairs of blanks 14,16 onto a magnetic conveyor array used to convey the component sheets 14,16 and finished tailored blank 12 along the assembly system 10. The conveyor array consists of three sets of elongated magnetic stepping conveyors 32,34,36 which, in operation, move the pairs of component sheet blanks 14,16 and tailored blank 12 in the longitudinal direction of arrow 28. The magnetic stepping conveyors which comprise each conveyor set 32,34,36 are shown best in Figure 1 as being arranged in a parallel orientation to both each other and the conveyors of the remaining sets. It is to be appreciated, however, that other conveyor configurations are also possible and will vary with the final tailored blank 12 configuration.
The first set of conveyors 32 are used in the initial positioning of the component sheets 14,16 in the production system 10 and the conveyance of the positioned sheets 14,16 onto the second set of conveyors 34.
The conveyors 34 are provided as part of a laser welding and seam verifying station 42.
At station 42, the proximal edge portions of the blanks 14,16 are welded together along their abutting edge to form a weld seam 44 by a yttrium aluminum garnet (YAG) laser 46. As will be described, both during the welding process and following completion of the weld seam 44, characteristics of the formed weld seam 44 are verified to determine whether or not the weld seam 44 possesses defects or flows which may result in the failure of the tailored blank 12 in further processing operations. In particular, as will be described, to verify that the weld seam 44 possesses the desired properties, the welding and seam verifying station 42 includes a series of sensors used to evaluate the upper and lower weld seam surface topography profiles, the degree of weld penetration and the presence, size and/or number of pin holes which may exist through the formed seam 44.
The third set of conveyors 36 are used to convey the completed workpieces 12 to a lifting robot 48. The lifting robot 48 has the identical construction as the lifting robot 18 and includes a movable telescoping arm 50 and suction head 52 which are adapted to lift the completed workpiece blanks 12 from the conveyors 36 and move the blanks 12 either to an output stack 54 or a reject pile 56 depending upon the determined weld seam characteristics.
As shown in Figures 1 and 2, the YAG laser 46 includes a coherent light source generator 60 used to generate at least one, and preferably two coherent light sources or laser beams 30 (Figure 2) and a movable laser head assembly 62. The laser head assembly 62 is selectively driven in movement along on an overhead gantry 61 (Figure 1 ) by the operation of drive motors 63 with the assembly 62 adapted to travel longitudinally along the abutting edges of the components 14,16. Figure 2 shows best the laser head assembly 62 as including a light emitting laser head 66 from which laser energy is emitted. Although not essential, a support 68 is preferably provided which rotatably mounts the laser head 66 and a drive motor 70 is used to rotate the laser head 66 on the support 68. A fiber optic coupling 64 (Figure 3) is used to optically connect the generator 60 and laser head assembly 62. The fiber optic coupling 64 consists of a bundle of two fiber optic cables (not shown). The energy of the two coherent light sources produced in the generator 60 thus travels via a respective fiber optic cable to the laser head assembly 62, where it is directed towards the upper surface 65 of the components 14,16 to melt the edge portions and form the weld seam 44.
Figure 2 shows best a seam tracking sensor 72 and seam verifying upper surface topography sensor 74 as being mounted for movement with the laser head 66 in the direction of arrow 75, longitudinally along the weld seam 44. The seam tracking sensor 72 is used to sense the abutting edge portions of the sheet blanks 14,16 to be joined. The tracking sensor 74 includes a separate coherent light source 76 which directs a beam of coherent light 77 downwardly onto the proximal portions of the component sheet blanks 14,16. A
vision or optic sensor 78 is mounted adjacent the light source 76 used to sense light reflected from the upper surface 65 of the component sheets. By the absence of reflected light, the vision sensor 78 is used to provide an indication of the position and spacing of the abutting edge portions of the component sheets 14,16. The sensor 72 provides control signals to the drive motors 70 and 63 to automatically position the laser head 62 so that the composite beam is directed at the weld seam 44.
The seam verifying sensor 74 includes a separate coherent light source 88 which directs a second coherent light beam 89 downwardly onto the upper surface 65 of the blank 12 across the formed weld seam 44. The coherent light beam 89 from the second coherent light source 88 most preferably is elongated in a direction substantially transverse to the longitudinal direction of the weld seam 44 and is oriented approximately 30 mm behind the welding composite beam 30.
The upper surface topography sensor 74 includes a vision or optic sensor 90 used to sense light reflected from the upper surface of the weld seam 44. The light received by the sensor 90 is used to provide data representing the profile of the weld seam 44 in a transverse direction. Profile data is forwarded to a central processing unit (CPU) 92 (Figure 1 ) which controls the operations of the system 10. Most preferably, the CPU 92 includes stored data which is representative of a preferred upper weld surface topography profile, and which is selected having regard to the relative thicknesses of the components 14,16 and their metal composition. The CPU 92 includes software which compares the sensed upper surface profile data from the stored data to determine whether or not the upper topographic profile of the weld seam 44 falls within acceptable tolerances.
Figure 1 shows best the welding and seam verifying station 42 as including an enclosure 100, which is used to optically isolate the energy from the composite beam 30.
The enclosure is provided with mailbox-type entry and exit doors 102,104. The entry and exit doors 102,104 are opened to permit movement of the component blanks 14,16 and completed workpiece 12 on the conveyors 32,34,36 into and from the enclosure 100. It is to be appreciated that during welding operations, the entry and exit doors 102,104 remain closed to contain any potentially eye damaging YAG laser energy.
Figures 1 and 3 show best clamping units 110 as being provided within the enclosure 100 for maintaining the sheet blanks 14,16 in a fixed abutting position during welding operations.
The clamping units 110 are preferably of a magnetic clamping type, as disclosed in Canadian patent application serial No. 2,167,111, laid open 12 July 1997. It is to be appreciated, however, that other clamping mechanisms may also be used to maintain the component blanks 14,16 in the desired arrangement. Each of the clamping units 110 includes a pair of elongated arrays of electrically operable permanent magnets 112 which operate in conjunction with vertically movable ferromagnetic plates 113 (Figure3). The arrays of permanent magnets 112 are positioned so as to support the underside of each component 14,16 immediately adjacent to the abutting edge. Figures 2 and 3 show best an elongated laser dump 114 which extends between the magnetic arrays 112 in a position directly under the abutting edges of the blanks 14,16 and the weld seam 44. The laser dump 114 is formed as an elongated rectangular trough open along its uppermost edge. The laser dump 114 is preferably copper lined to absorb YAG laser energy which passes through the weld joint therein.
Figure 3 shows best the welding and seam verifying station 42 as including a weld penetration sensor 116 used to indicate whether or not the laser beam 30 has achieved complete melting of the blanks 14,16 across the vertical extent of the weld seam 44.
The weld penetration sensor 116 consists of an infrared light sensor 118 positioned towards one end of the laser dump 114. The infrared sensor 118 is electronically coupled to the CPU 92. The infrared sensor 118 is provided to sense the intensity of the flame 120 which is formed in the laser dump 114 on the lower side 122 of the weld seam 44 during welding operations. The applicant has appreciated that the presence of a flame 120 of a minimum intensity provides an indication that the weld seam 44 completely penetrates the joint. Most preferably, the sensor 118 is positioned at the end of the laser dump 114 to which the laser head 62 is moved during welding operations, however, other orientations remain possible. To prevent smoke and other weld vapours and gases from interfering with the proper operation of the infrared sensor 118, a pressurized gas is fed along the laser dump 114 via a gas line 124 and supply 126 from gas inlet immediately adjacent the sensor 118. An evacuation system consisting of a gas suction tube 128 and blower fan 130 is provided at the opposite end of the laser dump 114 to provide a gas flow along the dump 144 in a direction away from the sensor 118.
Data signals representative of the intensity of the flame 120 are transmitted to the CPU
92 and are output as a variable voltage display, as for example is shown in Figure 4. In Figure 4, the voltage output from the sensor 118 increases as the flame 120 moves towards the sensor 118.
Most preferably, the CPU 92 includes stored data signals which are indicative of a preferred flame intensity profile, and where software in the CPU 92 provides a comparison of the data signals received from the infrared sensor 118 with the stored profile to determine whether or not the intensity profile falls within acceptable tolerances. To avoid false readings, the weld penetration sensor 116 is most preferably activated by electronic optical sensors 132 (Figure 3) positioned on the gantry 61. Alternately, the sensor 116 could be activated by mechanical sensors and/or a central signal received from the CPU 92, in a timed sequence manner.
Figure 5 shows best the welding and seam verifying station 42 as also including a lower surface topography sensor 134 which is used to provide data indicative of the transverse profile of the bottom or lower surface 122 of the weld seam 44 simultaneously as the blank 12 is conveyed from the station 42 and outwardly through the exit door 104. The lower surface topography sensor 134 has essentially the identical construction as the sensor 74. The lower surface topography sensor 124 includes a separate coherent light source 136 which directs a beam of coherent light 138 upwardly onto the lower surface 122 of the weld seam 44, and a vision or optic sensor 140 used to sense light reflected from the underside of the weld seam 44.
The coherent light beam 138 projected by light source 130 consists of a linear beam which is oriented generally transversely to the longitudinal extent of the weld seam 44. The lower surface topography sensor 134 is provided in electronic communication with the CPU 92 and like the sensor 74 provides data signals indicative of the surface profile of the bottom of the weld seam 44 for comparison with a preferred profile data stored in the CPLJ 92.
Figures 5 to 7 show best the pin hole sensor 144 arrangement used to detect the existence of pin holes which may exist in the weld seam 34. Pin holes are minute holes typically having a diameter less then 0.5 mm which may be formed upon the freezing of the weld seam 44. The existence of pin holes, depending on their size and frequency, may possibly lead to failure of the weld seam 44. The pin hole sensor 144 is located adjacent to the exit door 104 directly in the path along which the weld seam 44 travels as the completed tailored blank 12 is conveyed from the welding and seam verifying station 42. In this position, the sensor 144 provides data respecting the weld seam 44 of the completed workpiece 12 as it is moved in the direction of arrow 146 (Figure 5) onto the conveyors 36. The pin hole sensor 144 consists of an infrared emitter assembly 148 and an infrared light receptor assembly 150. Figure 6 shows best the infrared emitter assembly 148 as including four infrared lamps 152a,152b,152c,152d and a cylindrical focusing lens 154. T'he lamps 152a,152b,152c,152d are laterally spaced from each other as an elongated array so as to project an elongated substantially continuous linear beam of infrared light towards the focusing lens 154, and in a direction substantially transverse to the longitudinal extent of the weld seam 44. The elongated cylindrical focusing lens 154 is positioned beneath the infrared lamps 152a,152b,152c,152d. The focusing lens 154 is configured to focus the infrared light beam emitted by the lamps 152a,152b,152c,152d as an elongated light beam which consists of a narrow elongated beam oriented generally perpendicular to the upper surface 65 of the workpiece 12. The infrared lamps 152a,152b,152c,152d and focusing lens 154 are mounted as a unit on a rotary bearing plate 1 S 8.
The plate 158, together with the lamps 152a,152b,152c,152d and lens 154, is driven in rotary movement about a vertical axis through preferably between S and 180° of rotation to either variable, or more preferably preset positions by the activation of an air cylinder 160.
The receptor assembly 1 SO includes a collecting lens 162, a reflective wave light guide 164 and an infrared light sensor 166. The light guide 164 is formed as a tapering cone having a generally frustoconical shape. The light guide 164 is extended along and concentric about a central axis A-A1 (Figure 6), and most preferably is positioned with the axis A-A~ of the guide 164 substantially perpendicular to the plane of the lower side 122 of each tailored blank 12 as they are moved therepast via the conveyors 34. The infrared sensor 166 is positioned in the narrow lowermost end of the light guide 164 substantially aligned with the axis A-Al. As seen best in Figure 6, the collecting lens 162 is formed as a generally circular disk with a radial size substantially corresponding to that of the upper enlarged end of the guide 164. The collecting lens 162 is configured to focus light emitted from the infrared lamps 152a,152b,152c,152d which passes through any pin holes 168 (Figure 6) in the weld seam 44 to the infrared sensor 166. It is to be appreciated that the light guide 164 is provided with a mirrored inner surface so as to minimize absorption of any infrared light which passes through the weld seam 44.
The infrared sensor 166 is electronically linked to the central processing unit 92 to provide data signals when light is detected by the sensor 166, indicative of the existence of pin holes 168 extending through the seam 44. Most preferably, as shown in Figure 8, the infrared sensor 166 preferably also outputs a variable voltage with light intensity.
Such variations in output voltage advantageously permit an analysis of pin hole size and location along the length of the weld seam.
To avoid false readings from the infrared sensor 166, optic proximity switches 172,174 (Figure 7) are provided in the path of movement of the conveyed blank 12 immediately adjacent to the pin hole sensor 144. The proximity switches 172,174 are used to sense the leading edge 176 and trailing edge 178 of the workpiece blank 12 as it moves along the conveyor 34 and through the exit door 104. The proximity switches 172,174 are positioned on each immediate side of the infrared sensor 166 in the direction of blank conveyance. In initial operation, the air cylinder 160 is activated to rotate the plate 158 so that the linear beam emitted by the infrared lamps 152a,152b,152c,152d are aligned with a leading edge 176 of the tailored blank 12 as it moves on the conveyor 34. As the workpiece 12 is conveyed towards the exit door 104, it moves across a first downstream proximity switch 172 to activate the infrared lamps 152a,152b,152c,152d and the light receptor assembly 144. Following a certain period of activation (as for example one second), the air cylinder 160 is again triggered to reposition the plate 158 and infrared lamps 152a,152b,152c,152d, so as to redirect the infrared beam emitted thereby in an orientation aligned with the trailing edge 178 of the workpiece 12. The pin hole sensor 144 remains activated until the blank 12 moves from the second other proximity switch 174. On deactivation, the second proximity switch 174 is used to provide a further control signal to the air cylinder 160 to reposition the plate 158 and infrared lamps 152a,152b,152c,152d to the initial start position. Although the simplified arrangement includes a pair of optic switches 172,174, the invention is not so limited. It is to be appreciated that other mechanical sensors could be used or alternately, in a less preferred embodiment, the operation of the pin hole sensor 144 could be programmed for initiation in a time sequence with respect to the conveyors 34 or system 10 as a whole.
Data from any or all of the upper surface topography sensor 74, the lower surface topography sensor 134, weld penetration sensor 116 or the pin hole sensor 144 is used to determine if the weld seam 44 characteristics remain within acceptable tolerances. The CPU 92 may then output either an audio or visual indication or warning to an operator that a potential problem exists with the weld seam 44, or depending upon the degree of deviation from the preferred pattern profiles, output signals may be forwarded directly from the CPU 92 to the off loading robot 48 to move the completed workpiece 12 to the reject pile 56 for manual inspection or reprocessing.
In operation, the component sheets 14,16 are moved via the lifting robot 18 from a respective supply stack 20,22. The pairs of blanks 14,16 are positioned on the parallel magnetic infeed conveyors 32. The lift robot 18 is used to move each component sheet 14,16 through an initial qualifying procedure to ensure the desired positioning of the sheets 14,16 on the feed conveyors 32 in the desired abutting orientation. Qualifying involves the sliding of the sheet blanks 14,16 against one or more sets of locating pins 180 (Figure 1 ) to ensure the component blanks 14,16 are in the desired position. Once qualified, the sheet blanks 14,16 are moved into the enclosure 100 via the inlet door 102 for laser welding. Conveyors 34 in turn move the blanks 14,16 into the magnetic clamping assemblies 110 which are then activated to clamp the sheet blanks 14,16 with their proximal edge portions in substantially abutting relationship. The laser 62 is thereafter moved in the direction of arrow 75 to weld the abutting edge portions of blanks 14,16 together and form the weld seam 44.
Substantially simultaneously with the welding operation, the upper surface topography sensor 74 and weld penetration sensor 116 are activated to provide data regarding the topography of the upper surface profile of the weld seam 44 and flame 120 intensity data, respectively, to the central processing unit 92. Although not essential, in a most preferred embodiment, the data respecting the flame 120 intensity received from the infrared sensor may be used by the CPU 92 to control the laser output power. For example, if the flame 120 intensity is indicated as being insufficient, the CPU 92 may be used to provide a control signal to the generator 60 to increase laser output. Similarly, if flame intensity is found to be excessive, the CPU
92 may be used to provide signals to the generator 60 to reduce laser power.
Following the formation of the weld seam 44, the magnetic clamping assemblies 110 are deactivated and the exit door 104 is opened. The conveyors 34 are used to move the completed workpiece 12 towards the exit door 12 while the pin hole sensor 144 and lower weld surface topography sensor 134 are simultaneously activated to provide pin hole and bottom topography data to the central processing unit 92.
As indicated, in the event any of the data signals received from the weld verifying sensors 74,116,134,144 indicate that weld seam 44 characteristics do not fall within acceptable limits, the CPU 92 may provide either a fail indication to an operator, or may provide control signals to the lift robot 78 to redirect the workpiece 12 to a reject pile. Furthermore, the CPU 92 may also provide signals or data output in the form of a caution, where some of the weld parameters may not fall within optimal ranges, however, are deemed to meet acceptable defect levels.
Although the preferred embodiment of the invention illustrates the post weld inspection apparatus as being provided as part of a welding station, the invention is not so limited. If desired, the pin hole sensor 144 and surface topography sensors 74,134 could be provided as part of a separate post weld inspection station remote from the welding apparatus either independently, or in conjunction with other blank working apparatus, including, dimpling apparatus, grinding apparatus, oiling apparatus and the like.
Although the detailed description describes the invention as being used to verify but weld joints performed by a YAG laser, the invention could also be used to verify welds from other laser welding apparatus including without limitation C02 lasers, and other welding laser systems including mash and plasma welding systems, as well as arc welding systems and the like.
While the preferred embodiment of the invention discloses the production line 10 as being used in the formation of tailored blanks 12, it is to be appreciated that the post weld inspection apparatus is not limited to tailored blank production and may equally be used to verify weld seams on numerous other types of finished and unfinished goods or workpieces.
Although the production assembly line shown in Figure 1 is configured for the manufacture of a single completed workpiece 12, it is to be appreciated that the invention is not so limited. The present apparatus could equally be modified for the concurrent manufacture of two, three or more workpieces. Examples of such production lines are disclosed in the applicant's international application No. PCT/CA98/00153, published as international publication No. WO 98/39136 on 11 September 1998.
While the detailed description discloses the weld penetration sensor 118 as including an infrared light sensor 114, it is to be appreciated that other sensors including UV and/or visible light sensors as well as temperature and other thermal sensors could equally be used.
Although the preferred embodiment illustrates the pin hole sensor 144 as including four infrared lamps 152a,152b,152c,152d, the invention is not so limited. It is to be appreciated that the sensor 144 could equally be provided with one, two, three or more than four lamps configured to emit infrared light, UV light, or visible light without departing from the spirit and scope of the invention. Similarly, although the preferred infrared collector assembly includes a light reflecting guide 164 and a collecting lens 162, the invention is not so limited. In a less preferred embodiment, the light sensor 162 by itself could be positioned beneath the weld seam 44.
While an air cylinder 160 is disclosed as rotating the infrared lamps 152 and focusing lens 154 between S and 180° of rotation, it is to be appreciated that other electric motor drives or belt drive arrangements may equally be used to rotate the infrared lamps and lens through greater or smaller increments of rotation. Similarly, if desired, the lamps 152a,152b,152c,152d could be individually operated and/or provided as part of a non-linear array. Further, in an alternate construction, the light source could be provided in a fixed arrangement and the focusing lens rotated alone.
While Figures 5 and 6 illustrate the pin hole sensor 144 as including a receptor assembly 150 positioned beneath the infrared emitter assembly 148, the invention is not so limited. If desired, the receptor assembly 150 and infrared emitter assembly 148 could be provided in an inverted configuration with the receptor assembly 150 positioned directly above the infrared assembly 148. Such a configuration would for example be advantageous where the pin hole sensor 144 is not positioned within an enclosure 100. In particular, the positioning of the receptor assembly 150 would advantageously minimize incidental light from overhead light fixtures and the like from providing false readings to the light sensor 166.
Although the detailed description of the invention describes and illustrates various preferred embodiments, the invention is not so limited. Many modifications and variations will now occur to a person skilled in the art. For a definition of the invention, reference may be had to the appended claims.
SUMMARY OF THE INVENTION
To at least partially overcome difficulties of prior art welding apparatus, the present invention provides an apparatus used to verify one or more weld seam characteristics to permit an assessment of whether or not the weld seam may be susceptible to failure.
In this regard, the apparatus is configured to sense one or more of the top surface topography of the weld seam, the bottom surface topography of the weld seam, the existence, number, size and/or spacing of pin holes extending through the weld seam, and/or the degree of weld penetration.
An object of the invention is to provide an apparatus which permits the fully automated inspection of weld seams formed in tailored blanks and other workpieces after or concurrently with the formation of the weld seam.
Another object of the invention is to provide an apparatus used to verify the integrity of a weld seam by analyzing one and preferably each of the weld seam surface topography, the presence, number or size of pin holes through the weld seam, as well as the degree of weld penetration.
Another object of the invention is to provide a weld inspection apparatus which may be used simultaneously with existing welding systems used to form tailored blanks, and which provides a substantially simultaneous indication of whether or not the characteristics of the weld seam produced fall within acceptable tolerances.
To achieve at least some of the foregoing objects, the present invention provides an apparatus for use in the verification of weld seams, and most preferably weld seams of tailored blanks. The seam verifying apparatus includes at least one and most preferably several weld seam sensors selected from a pin hole sensor, a weld surface topography sensor and a weld penetration sensor. While the apparatus is useful to verify weld seams formed by lap, mash or plasma welding apparatus, most preferably the apparatus is used to verify butt weld joints formed by laser welding.
As used herein, the upper surface of the weld seam refers to the side of the workpiece or blank which, in welding operations, is oriented closest to the weld energy source, such as for example a laser head where weld seams are formed with a coherent light beam.
Similarly, the lower surface of the weld seam refers to the side of the blank which, in welding operations, is oriented furthest away from the weld energy source. It is to be appreciated, however, that while both welding and seam verification is performed with the blank in a generally horizontal orientation in a most simplified construction, the invention is not so limited, and the present invention could equally be used with the blank in an inclined or vertical orientation.
The pin hole sensor includes a light emitter which includes an energy or light source configured to project a beam at a first upper or lower surface of the weld seam, and a light receptor disposed on the second other side of the weld seam generally opposite to the light source. Where ultraviolet, visible or infrared light is projected by the light source, a focusing element such as a lens or filter is preferably provided to focus the light generally perpendicular to the weld seam and the surface of the workpiece. The weld seam is moved relative to the light source and light receptor to enable the sensing of at least part and preferably the entire longitudinal length of the weld seam. As the blank weld seam and pin hole sensor are moved relative to each other, pin holes through the weld seam are detected by light passing from the light source through the weld seam and to the light receptor.
Most preferably, the light source consists of an elongated array of two, three, four or more infrared light lamps or projectors. Other light sources including lasers, ultraviolet and invisible light sources could, however, equally be used. The light lamps are spaced so as to emit an elongated substantially continuous linear beam of light, in an orientation generally transverse to the longitudinal length of the weld seam. With such a configuration, the light receptor preferably includes an infrared light sensor, a photodiode or photoelectric cell, and a collecting lens configured to refocus any light which passes through pin holes in the weld seam to the infrared light sensor, photodiode or photocell. Optionally, a reflective light guide may be provided on the second side of the weld seam to maximize the reflection and transmission of light travelling to the receiver.
Where the edges of the tailored blank are not precisely perpendicular to the longitudinal extent of the weld seam, the light emitter may be configured to permit the relative movement of the orientation of the emitted light beam relative to the orientation of the edges of the tailored blank at the weld seam. The repositioning of the light beam advantageously permits the alignment of the linear beam with the edge portion of the tailored blank to permit the effective operation of the pin hole sensor immediately adjacent to the edges of the tailored blank, without false readings.
The surface topography of the weld seam is preferably sensed by a vision camera system laterally across the upper and/or lower surface of the weld seam. Suitable vision camera systems include three dimensional vision systems which include a laser optic adapted to emit a laser stripe transversely across the lateral width of the seam weld, and a receptor positioned to detect laser light reflected from the blank. The surface topography of the weld seam is analyzed to determine the transverse weld surface profile. This permits an assessment of whether the weld seam possesses acceptable degrees of concavity. Most preferably both the upper and lower surface topographies are reviewed. The weld surface topography may be analyzed at a separate post weld inspection station remote from a welding station where the components are welded.
More preferably, however, weld topography analysis is performed substantially simultaneously with welding operations, as for example, by mounting the vision system on a gantry or robot arm which carries the weld head optics.
The weld penetration is preferably sensed by analyzing the intensity of the weld flame which is emitted from the lower surface of the tailored blanks during welding.
In particular, the applicant has appreciated that with laser welding, the presence and intensity of the emitted weld flame provides an indication of complete weld penetration to indicate whether the component sheets have been completely melted across their thickness. The weld penetration sensor preferably includes an optic sensor such as a photovolatic cell, photodiode or infrared sensor positioned on the underside of the weld seam, so as to receive emitted light from the weld flame.
Optionally, a gas suction and/or clearing gas flow may be provided along the lower surface of the weld seam to prevent smoke, vapours and other gases produced during the welding of component parts from obscuring the weld flame and otherwise interfering with the operation of the optic sensor. The penetration sensor may be either movable with the weld energy beam or mounted in a fixed position relative to the weld seam. When fixed, the apparatus preferably may also be provided with microprocessor circuitry or software which either logs and/or compensates for light intensity changes as the weld flame moves relative to the optic sensor.
Accordingly, in one aspect the present invention resides in an apparatus for verifying a weld seam of a workpiece blank comprising:
a pin hole sensor including a light emitter and a light receptor, the light emitter being disposed on a first side of said seam and including a light source for projecting a light beam at said first side, and a focusing element to focus said light beam generally perpendicular to said weld seam, the light receptor disposed on the second other side of the seam generally opposite to the light source whereby projected light which passes through said weld seam activates said light receptor, a drive for moving the blank relative to the light emitter and light receptor in the direction of said weld seam.
In another aspect, the present invention resides in an apparatus for verifying a weld seam of a workpiece blank formed from welding two component parts with a laser, said apparatus comprising, a light receptor disposed on a lower side of said weld seam remote from said laser, said light receptor operable substantially simultaneously with said laser to receive and sense light emitted by a weld flame produced during laser welding.
In a further aspect, the present invention resides in an apparatus for verifying a weld seam of a workpiece blank formed from welding at least two component parts with a laser, said apparatus comprising:
a pin hole sensor including a light emitter and a light receptor, the light emitter being disposed on a first side of said seam and including a light source for projecting an elongated light beam at said first side, and a focusing element to focus said light beam generally perpendicular to said weld seam, the light receptor disposed on the second other side of the seam generally opposite to the light source whereby projected light which passes through said weld seam activates said light receptor, said light receptor including a collecting lens configured to focus projected light which passes through said weld seam towards said pin hole light receiver , a reflective light guide and a pin hole light receiver providing an output signal when activated by said projected light, an infrared light sensor disposed on said second side of said seam, said infrared light sensor operable substantially simultaneously with said laser to receive and sense infrared light energy emitted by a weld flame produced during laser welding, and a surface topography sensor for sensing the concavity of at least one of the top or bottom of the weld seam.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of the invention will appear from the following description taken together with the accompanying drawings in which:
Figure 1 shows a schematic top view of a production assembly line for forming tailored blanks in accordance with the present invention;
Figure 2 is a schematic side view of the weld head, upper weld surface topography sensor and weld penetration sensor used in the production assembly line of Figure 1;
Figure 3 is a partial sectional view of the apparatus shown in Figure 1 taken along lines 3-3' illustrating the positioning weld penetration sensor;
Figure 4 illustrates graphically a preferred data output of the weld penetration sensor shown in Figure 3;
Figure 5 illustrates a cross-sectional view of the apparatus shown in Figure 1 taken along lines 5-5' illustrating the positioning of the pin hole sensor and bottom seam topography sensor relative to a tailored blank;
Figure 6 illustrates a schematic side view of the pin hole sensor used in the apparatus of Figure 1;
Figure 7 illustrates schematically a partial top view of the pin hole sensor of Figure 6; and Figure 8 illustrates graphically a preferred data output from the pin hole sensor of Figure 6.
DETAILED DESCRIPTION OF THE INVENTION
Reference is first made to Figure 1 which shows a system 10 used in the production of workpieces such as composite tailored blanks 12 which are used in the production of auto body parts and the like. With the system 10 shown, a vacuum operable lifting robot 18 is used to move a pair of metal component sheets 14,16 from respective supply stacks 20,22. The lifting robot 18 includes a movable telescoping lift arm 24 having a variable suction head 26 which is adapted to lift and move the pairs of blanks 14,16 onto a magnetic conveyor array used to convey the component sheets 14,16 and finished tailored blank 12 along the assembly system 10. The conveyor array consists of three sets of elongated magnetic stepping conveyors 32,34,36 which, in operation, move the pairs of component sheet blanks 14,16 and tailored blank 12 in the longitudinal direction of arrow 28. The magnetic stepping conveyors which comprise each conveyor set 32,34,36 are shown best in Figure 1 as being arranged in a parallel orientation to both each other and the conveyors of the remaining sets. It is to be appreciated, however, that other conveyor configurations are also possible and will vary with the final tailored blank 12 configuration.
The first set of conveyors 32 are used in the initial positioning of the component sheets 14,16 in the production system 10 and the conveyance of the positioned sheets 14,16 onto the second set of conveyors 34.
The conveyors 34 are provided as part of a laser welding and seam verifying station 42.
At station 42, the proximal edge portions of the blanks 14,16 are welded together along their abutting edge to form a weld seam 44 by a yttrium aluminum garnet (YAG) laser 46. As will be described, both during the welding process and following completion of the weld seam 44, characteristics of the formed weld seam 44 are verified to determine whether or not the weld seam 44 possesses defects or flows which may result in the failure of the tailored blank 12 in further processing operations. In particular, as will be described, to verify that the weld seam 44 possesses the desired properties, the welding and seam verifying station 42 includes a series of sensors used to evaluate the upper and lower weld seam surface topography profiles, the degree of weld penetration and the presence, size and/or number of pin holes which may exist through the formed seam 44.
The third set of conveyors 36 are used to convey the completed workpieces 12 to a lifting robot 48. The lifting robot 48 has the identical construction as the lifting robot 18 and includes a movable telescoping arm 50 and suction head 52 which are adapted to lift the completed workpiece blanks 12 from the conveyors 36 and move the blanks 12 either to an output stack 54 or a reject pile 56 depending upon the determined weld seam characteristics.
As shown in Figures 1 and 2, the YAG laser 46 includes a coherent light source generator 60 used to generate at least one, and preferably two coherent light sources or laser beams 30 (Figure 2) and a movable laser head assembly 62. The laser head assembly 62 is selectively driven in movement along on an overhead gantry 61 (Figure 1 ) by the operation of drive motors 63 with the assembly 62 adapted to travel longitudinally along the abutting edges of the components 14,16. Figure 2 shows best the laser head assembly 62 as including a light emitting laser head 66 from which laser energy is emitted. Although not essential, a support 68 is preferably provided which rotatably mounts the laser head 66 and a drive motor 70 is used to rotate the laser head 66 on the support 68. A fiber optic coupling 64 (Figure 3) is used to optically connect the generator 60 and laser head assembly 62. The fiber optic coupling 64 consists of a bundle of two fiber optic cables (not shown). The energy of the two coherent light sources produced in the generator 60 thus travels via a respective fiber optic cable to the laser head assembly 62, where it is directed towards the upper surface 65 of the components 14,16 to melt the edge portions and form the weld seam 44.
Figure 2 shows best a seam tracking sensor 72 and seam verifying upper surface topography sensor 74 as being mounted for movement with the laser head 66 in the direction of arrow 75, longitudinally along the weld seam 44. The seam tracking sensor 72 is used to sense the abutting edge portions of the sheet blanks 14,16 to be joined. The tracking sensor 74 includes a separate coherent light source 76 which directs a beam of coherent light 77 downwardly onto the proximal portions of the component sheet blanks 14,16. A
vision or optic sensor 78 is mounted adjacent the light source 76 used to sense light reflected from the upper surface 65 of the component sheets. By the absence of reflected light, the vision sensor 78 is used to provide an indication of the position and spacing of the abutting edge portions of the component sheets 14,16. The sensor 72 provides control signals to the drive motors 70 and 63 to automatically position the laser head 62 so that the composite beam is directed at the weld seam 44.
The seam verifying sensor 74 includes a separate coherent light source 88 which directs a second coherent light beam 89 downwardly onto the upper surface 65 of the blank 12 across the formed weld seam 44. The coherent light beam 89 from the second coherent light source 88 most preferably is elongated in a direction substantially transverse to the longitudinal direction of the weld seam 44 and is oriented approximately 30 mm behind the welding composite beam 30.
The upper surface topography sensor 74 includes a vision or optic sensor 90 used to sense light reflected from the upper surface of the weld seam 44. The light received by the sensor 90 is used to provide data representing the profile of the weld seam 44 in a transverse direction. Profile data is forwarded to a central processing unit (CPU) 92 (Figure 1 ) which controls the operations of the system 10. Most preferably, the CPU 92 includes stored data which is representative of a preferred upper weld surface topography profile, and which is selected having regard to the relative thicknesses of the components 14,16 and their metal composition. The CPU 92 includes software which compares the sensed upper surface profile data from the stored data to determine whether or not the upper topographic profile of the weld seam 44 falls within acceptable tolerances.
Figure 1 shows best the welding and seam verifying station 42 as including an enclosure 100, which is used to optically isolate the energy from the composite beam 30.
The enclosure is provided with mailbox-type entry and exit doors 102,104. The entry and exit doors 102,104 are opened to permit movement of the component blanks 14,16 and completed workpiece 12 on the conveyors 32,34,36 into and from the enclosure 100. It is to be appreciated that during welding operations, the entry and exit doors 102,104 remain closed to contain any potentially eye damaging YAG laser energy.
Figures 1 and 3 show best clamping units 110 as being provided within the enclosure 100 for maintaining the sheet blanks 14,16 in a fixed abutting position during welding operations.
The clamping units 110 are preferably of a magnetic clamping type, as disclosed in Canadian patent application serial No. 2,167,111, laid open 12 July 1997. It is to be appreciated, however, that other clamping mechanisms may also be used to maintain the component blanks 14,16 in the desired arrangement. Each of the clamping units 110 includes a pair of elongated arrays of electrically operable permanent magnets 112 which operate in conjunction with vertically movable ferromagnetic plates 113 (Figure3). The arrays of permanent magnets 112 are positioned so as to support the underside of each component 14,16 immediately adjacent to the abutting edge. Figures 2 and 3 show best an elongated laser dump 114 which extends between the magnetic arrays 112 in a position directly under the abutting edges of the blanks 14,16 and the weld seam 44. The laser dump 114 is formed as an elongated rectangular trough open along its uppermost edge. The laser dump 114 is preferably copper lined to absorb YAG laser energy which passes through the weld joint therein.
Figure 3 shows best the welding and seam verifying station 42 as including a weld penetration sensor 116 used to indicate whether or not the laser beam 30 has achieved complete melting of the blanks 14,16 across the vertical extent of the weld seam 44.
The weld penetration sensor 116 consists of an infrared light sensor 118 positioned towards one end of the laser dump 114. The infrared sensor 118 is electronically coupled to the CPU 92. The infrared sensor 118 is provided to sense the intensity of the flame 120 which is formed in the laser dump 114 on the lower side 122 of the weld seam 44 during welding operations. The applicant has appreciated that the presence of a flame 120 of a minimum intensity provides an indication that the weld seam 44 completely penetrates the joint. Most preferably, the sensor 118 is positioned at the end of the laser dump 114 to which the laser head 62 is moved during welding operations, however, other orientations remain possible. To prevent smoke and other weld vapours and gases from interfering with the proper operation of the infrared sensor 118, a pressurized gas is fed along the laser dump 114 via a gas line 124 and supply 126 from gas inlet immediately adjacent the sensor 118. An evacuation system consisting of a gas suction tube 128 and blower fan 130 is provided at the opposite end of the laser dump 114 to provide a gas flow along the dump 144 in a direction away from the sensor 118.
Data signals representative of the intensity of the flame 120 are transmitted to the CPU
92 and are output as a variable voltage display, as for example is shown in Figure 4. In Figure 4, the voltage output from the sensor 118 increases as the flame 120 moves towards the sensor 118.
Most preferably, the CPU 92 includes stored data signals which are indicative of a preferred flame intensity profile, and where software in the CPU 92 provides a comparison of the data signals received from the infrared sensor 118 with the stored profile to determine whether or not the intensity profile falls within acceptable tolerances. To avoid false readings, the weld penetration sensor 116 is most preferably activated by electronic optical sensors 132 (Figure 3) positioned on the gantry 61. Alternately, the sensor 116 could be activated by mechanical sensors and/or a central signal received from the CPU 92, in a timed sequence manner.
Figure 5 shows best the welding and seam verifying station 42 as also including a lower surface topography sensor 134 which is used to provide data indicative of the transverse profile of the bottom or lower surface 122 of the weld seam 44 simultaneously as the blank 12 is conveyed from the station 42 and outwardly through the exit door 104. The lower surface topography sensor 134 has essentially the identical construction as the sensor 74. The lower surface topography sensor 124 includes a separate coherent light source 136 which directs a beam of coherent light 138 upwardly onto the lower surface 122 of the weld seam 44, and a vision or optic sensor 140 used to sense light reflected from the underside of the weld seam 44.
The coherent light beam 138 projected by light source 130 consists of a linear beam which is oriented generally transversely to the longitudinal extent of the weld seam 44. The lower surface topography sensor 134 is provided in electronic communication with the CPU 92 and like the sensor 74 provides data signals indicative of the surface profile of the bottom of the weld seam 44 for comparison with a preferred profile data stored in the CPLJ 92.
Figures 5 to 7 show best the pin hole sensor 144 arrangement used to detect the existence of pin holes which may exist in the weld seam 34. Pin holes are minute holes typically having a diameter less then 0.5 mm which may be formed upon the freezing of the weld seam 44. The existence of pin holes, depending on their size and frequency, may possibly lead to failure of the weld seam 44. The pin hole sensor 144 is located adjacent to the exit door 104 directly in the path along which the weld seam 44 travels as the completed tailored blank 12 is conveyed from the welding and seam verifying station 42. In this position, the sensor 144 provides data respecting the weld seam 44 of the completed workpiece 12 as it is moved in the direction of arrow 146 (Figure 5) onto the conveyors 36. The pin hole sensor 144 consists of an infrared emitter assembly 148 and an infrared light receptor assembly 150. Figure 6 shows best the infrared emitter assembly 148 as including four infrared lamps 152a,152b,152c,152d and a cylindrical focusing lens 154. T'he lamps 152a,152b,152c,152d are laterally spaced from each other as an elongated array so as to project an elongated substantially continuous linear beam of infrared light towards the focusing lens 154, and in a direction substantially transverse to the longitudinal extent of the weld seam 44. The elongated cylindrical focusing lens 154 is positioned beneath the infrared lamps 152a,152b,152c,152d. The focusing lens 154 is configured to focus the infrared light beam emitted by the lamps 152a,152b,152c,152d as an elongated light beam which consists of a narrow elongated beam oriented generally perpendicular to the upper surface 65 of the workpiece 12. The infrared lamps 152a,152b,152c,152d and focusing lens 154 are mounted as a unit on a rotary bearing plate 1 S 8.
The plate 158, together with the lamps 152a,152b,152c,152d and lens 154, is driven in rotary movement about a vertical axis through preferably between S and 180° of rotation to either variable, or more preferably preset positions by the activation of an air cylinder 160.
The receptor assembly 1 SO includes a collecting lens 162, a reflective wave light guide 164 and an infrared light sensor 166. The light guide 164 is formed as a tapering cone having a generally frustoconical shape. The light guide 164 is extended along and concentric about a central axis A-A1 (Figure 6), and most preferably is positioned with the axis A-A~ of the guide 164 substantially perpendicular to the plane of the lower side 122 of each tailored blank 12 as they are moved therepast via the conveyors 34. The infrared sensor 166 is positioned in the narrow lowermost end of the light guide 164 substantially aligned with the axis A-Al. As seen best in Figure 6, the collecting lens 162 is formed as a generally circular disk with a radial size substantially corresponding to that of the upper enlarged end of the guide 164. The collecting lens 162 is configured to focus light emitted from the infrared lamps 152a,152b,152c,152d which passes through any pin holes 168 (Figure 6) in the weld seam 44 to the infrared sensor 166. It is to be appreciated that the light guide 164 is provided with a mirrored inner surface so as to minimize absorption of any infrared light which passes through the weld seam 44.
The infrared sensor 166 is electronically linked to the central processing unit 92 to provide data signals when light is detected by the sensor 166, indicative of the existence of pin holes 168 extending through the seam 44. Most preferably, as shown in Figure 8, the infrared sensor 166 preferably also outputs a variable voltage with light intensity.
Such variations in output voltage advantageously permit an analysis of pin hole size and location along the length of the weld seam.
To avoid false readings from the infrared sensor 166, optic proximity switches 172,174 (Figure 7) are provided in the path of movement of the conveyed blank 12 immediately adjacent to the pin hole sensor 144. The proximity switches 172,174 are used to sense the leading edge 176 and trailing edge 178 of the workpiece blank 12 as it moves along the conveyor 34 and through the exit door 104. The proximity switches 172,174 are positioned on each immediate side of the infrared sensor 166 in the direction of blank conveyance. In initial operation, the air cylinder 160 is activated to rotate the plate 158 so that the linear beam emitted by the infrared lamps 152a,152b,152c,152d are aligned with a leading edge 176 of the tailored blank 12 as it moves on the conveyor 34. As the workpiece 12 is conveyed towards the exit door 104, it moves across a first downstream proximity switch 172 to activate the infrared lamps 152a,152b,152c,152d and the light receptor assembly 144. Following a certain period of activation (as for example one second), the air cylinder 160 is again triggered to reposition the plate 158 and infrared lamps 152a,152b,152c,152d, so as to redirect the infrared beam emitted thereby in an orientation aligned with the trailing edge 178 of the workpiece 12. The pin hole sensor 144 remains activated until the blank 12 moves from the second other proximity switch 174. On deactivation, the second proximity switch 174 is used to provide a further control signal to the air cylinder 160 to reposition the plate 158 and infrared lamps 152a,152b,152c,152d to the initial start position. Although the simplified arrangement includes a pair of optic switches 172,174, the invention is not so limited. It is to be appreciated that other mechanical sensors could be used or alternately, in a less preferred embodiment, the operation of the pin hole sensor 144 could be programmed for initiation in a time sequence with respect to the conveyors 34 or system 10 as a whole.
Data from any or all of the upper surface topography sensor 74, the lower surface topography sensor 134, weld penetration sensor 116 or the pin hole sensor 144 is used to determine if the weld seam 44 characteristics remain within acceptable tolerances. The CPU 92 may then output either an audio or visual indication or warning to an operator that a potential problem exists with the weld seam 44, or depending upon the degree of deviation from the preferred pattern profiles, output signals may be forwarded directly from the CPU 92 to the off loading robot 48 to move the completed workpiece 12 to the reject pile 56 for manual inspection or reprocessing.
In operation, the component sheets 14,16 are moved via the lifting robot 18 from a respective supply stack 20,22. The pairs of blanks 14,16 are positioned on the parallel magnetic infeed conveyors 32. The lift robot 18 is used to move each component sheet 14,16 through an initial qualifying procedure to ensure the desired positioning of the sheets 14,16 on the feed conveyors 32 in the desired abutting orientation. Qualifying involves the sliding of the sheet blanks 14,16 against one or more sets of locating pins 180 (Figure 1 ) to ensure the component blanks 14,16 are in the desired position. Once qualified, the sheet blanks 14,16 are moved into the enclosure 100 via the inlet door 102 for laser welding. Conveyors 34 in turn move the blanks 14,16 into the magnetic clamping assemblies 110 which are then activated to clamp the sheet blanks 14,16 with their proximal edge portions in substantially abutting relationship. The laser 62 is thereafter moved in the direction of arrow 75 to weld the abutting edge portions of blanks 14,16 together and form the weld seam 44.
Substantially simultaneously with the welding operation, the upper surface topography sensor 74 and weld penetration sensor 116 are activated to provide data regarding the topography of the upper surface profile of the weld seam 44 and flame 120 intensity data, respectively, to the central processing unit 92. Although not essential, in a most preferred embodiment, the data respecting the flame 120 intensity received from the infrared sensor may be used by the CPU 92 to control the laser output power. For example, if the flame 120 intensity is indicated as being insufficient, the CPU 92 may be used to provide a control signal to the generator 60 to increase laser output. Similarly, if flame intensity is found to be excessive, the CPU
92 may be used to provide signals to the generator 60 to reduce laser power.
Following the formation of the weld seam 44, the magnetic clamping assemblies 110 are deactivated and the exit door 104 is opened. The conveyors 34 are used to move the completed workpiece 12 towards the exit door 12 while the pin hole sensor 144 and lower weld surface topography sensor 134 are simultaneously activated to provide pin hole and bottom topography data to the central processing unit 92.
As indicated, in the event any of the data signals received from the weld verifying sensors 74,116,134,144 indicate that weld seam 44 characteristics do not fall within acceptable limits, the CPU 92 may provide either a fail indication to an operator, or may provide control signals to the lift robot 78 to redirect the workpiece 12 to a reject pile. Furthermore, the CPU 92 may also provide signals or data output in the form of a caution, where some of the weld parameters may not fall within optimal ranges, however, are deemed to meet acceptable defect levels.
Although the preferred embodiment of the invention illustrates the post weld inspection apparatus as being provided as part of a welding station, the invention is not so limited. If desired, the pin hole sensor 144 and surface topography sensors 74,134 could be provided as part of a separate post weld inspection station remote from the welding apparatus either independently, or in conjunction with other blank working apparatus, including, dimpling apparatus, grinding apparatus, oiling apparatus and the like.
Although the detailed description describes the invention as being used to verify but weld joints performed by a YAG laser, the invention could also be used to verify welds from other laser welding apparatus including without limitation C02 lasers, and other welding laser systems including mash and plasma welding systems, as well as arc welding systems and the like.
While the preferred embodiment of the invention discloses the production line 10 as being used in the formation of tailored blanks 12, it is to be appreciated that the post weld inspection apparatus is not limited to tailored blank production and may equally be used to verify weld seams on numerous other types of finished and unfinished goods or workpieces.
Although the production assembly line shown in Figure 1 is configured for the manufacture of a single completed workpiece 12, it is to be appreciated that the invention is not so limited. The present apparatus could equally be modified for the concurrent manufacture of two, three or more workpieces. Examples of such production lines are disclosed in the applicant's international application No. PCT/CA98/00153, published as international publication No. WO 98/39136 on 11 September 1998.
While the detailed description discloses the weld penetration sensor 118 as including an infrared light sensor 114, it is to be appreciated that other sensors including UV and/or visible light sensors as well as temperature and other thermal sensors could equally be used.
Although the preferred embodiment illustrates the pin hole sensor 144 as including four infrared lamps 152a,152b,152c,152d, the invention is not so limited. It is to be appreciated that the sensor 144 could equally be provided with one, two, three or more than four lamps configured to emit infrared light, UV light, or visible light without departing from the spirit and scope of the invention. Similarly, although the preferred infrared collector assembly includes a light reflecting guide 164 and a collecting lens 162, the invention is not so limited. In a less preferred embodiment, the light sensor 162 by itself could be positioned beneath the weld seam 44.
While an air cylinder 160 is disclosed as rotating the infrared lamps 152 and focusing lens 154 between S and 180° of rotation, it is to be appreciated that other electric motor drives or belt drive arrangements may equally be used to rotate the infrared lamps and lens through greater or smaller increments of rotation. Similarly, if desired, the lamps 152a,152b,152c,152d could be individually operated and/or provided as part of a non-linear array. Further, in an alternate construction, the light source could be provided in a fixed arrangement and the focusing lens rotated alone.
While Figures 5 and 6 illustrate the pin hole sensor 144 as including a receptor assembly 150 positioned beneath the infrared emitter assembly 148, the invention is not so limited. If desired, the receptor assembly 150 and infrared emitter assembly 148 could be provided in an inverted configuration with the receptor assembly 150 positioned directly above the infrared assembly 148. Such a configuration would for example be advantageous where the pin hole sensor 144 is not positioned within an enclosure 100. In particular, the positioning of the receptor assembly 150 would advantageously minimize incidental light from overhead light fixtures and the like from providing false readings to the light sensor 166.
Although the detailed description of the invention describes and illustrates various preferred embodiments, the invention is not so limited. Many modifications and variations will now occur to a person skilled in the art. For a definition of the invention, reference may be had to the appended claims.
Claims (28)
1. An apparatus for verifying a weld seam of a workpiece blank comprising:
a pin hole sensor including a light emitter and a light receptor, the light emitter being disposed on a first side of said seam and including a light source for projecting a light beam at said first side, and a focusing element to focus said light beam generally perpendicular to said weld seam, the light receptor disposed on the second other side of the seam generally opposite to the light source whereby projected light which passes through said weld seam activates said light receptor, a drive for moving the blank relative to the light emitter and light receptor in the direction of said weld seam.
a pin hole sensor including a light emitter and a light receptor, the light emitter being disposed on a first side of said seam and including a light source for projecting a light beam at said first side, and a focusing element to focus said light beam generally perpendicular to said weld seam, the light receptor disposed on the second other side of the seam generally opposite to the light source whereby projected light which passes through said weld seam activates said light receptor, a drive for moving the blank relative to the light emitter and light receptor in the direction of said weld seam.
2. An apparatus as claimed in claim 1 wherein said light receptor includes a collecting lens, a generally conical light guide and a light receiver, said light receiver being disposed towards an innermost end of said taper and providing an output signal when activated by said projected light, said collecting lens comprising a generally circular lens configured to refocus projected light which passes through said weld seam towards said receiver.
3. An apparatus as claimed in claim 1 wherein said light beam comprises a linear beam of light which is elongated in a longitudinal direction, the apparatus further including a positioning mechanism used to selectively position the linear beam relative to said weld seam.
4. An apparatus as claimed in claim 2 wherein said light beam comprises a linear beam of light which is elongated in a longitudinal direction, the apparatus further including a positioning mechanism used to selectively position the linear beam relative to said weld seam.
5. An apparatus as claimed in claim 3 wherein said positioning mechanism comprises a rotatable support, said light source and focusing element being mounted to said rotatable support for movement therewith, whereby rotational movement of the support rotates the linear beam relative to the seamline, wherein said drive comprises a conveyor used to transport the blank following welding of the seam.
6. An apparatus as claimed in claim 5 wherein said light beam is selected from visible light, infrared light and ultraviolet light.
7. An apparatus as claimed in claim 2 wherein said light source comprises a plurality of infrared light projectors, said infrared emitters being provided as a longitudinally extending array, with each infrared emitter being spaced from a next adjacent infrared emitter by a distance selected to form the light beam as a substantially continuous linear beam of light at the focusing element.
8. An apparatus as claimed in claim 1 wherein the focusing element comprises a cylinder lens which is elongated in the longitudinal direction.
9. An apparatus as claimed in claim 3 further comprising a sensor for sensing an edge portion of said blank as said blank moves relative to said apparatus, the sensor being operable to provide a control signal to selectively actuate the positioning mechanism and position said light source relative to said edge portion on sensing the edge portion.
10. An apparatus as claimed in claim 4 further comprising a sensor for sensing an edge portion of said blank as said blank moves relative to said apparatus, the sensor being operable to provide a control signal to selectively actuate the positioning mechanism and position said light source relative to said seam on sensing the edge portion.
11. An apparatus as claimed in claim 7 wherein said infrared emitters are independently operable.
12. An apparatus as claimed in claim 1 further including a microprocessor electronically coupled to said light receptor for outputting data from said light receptor representative of at least one of the size of any located pin holes, the number of pin holes and the location of pin holes relative to the weld seam.
13. An apparatus as claimed in claim 9 further including a microprocessor electronically coupled to said light receptor for receiving and outputting data selected from the size of any located pin holes, the number of pin holes and the location of pin holes relative to the weld seam.
14. An apparatus for verifying a weld seam of a workpiece blank formed from welding two component parts with a laser, said apparatus comprising, a light receptor disposed on a lower side of said weld seam remote from said laser, said light receptor operable substantially simultaneously with said laser to receive and sense light emitted by a weld flame produced during laser welding.
15. An apparatus as claimed in claim 14 wherein said light receptor is disposed in a beam dump for laser energy.
16. An apparatus as claimed in claim 14 wherein said light receptor comprises an infrared sensor.
17. An apparatus as claimed in claim 14 further including a suction device of drawing smoke and vapours produced during welding away from the light receptor.
18. An apparatus as claimed in claim 17 further including a gas source for providing a pressurized gas flow in a direction away from the light receptor.
19. An apparatus as claimed in claim 14 wherein said laser is movable relative to said weld seam, said apparatus further comprising a controller operable to selectively operate the light receptor in response to the position of said laser.
20. An apparatus as claimed in claim 14 wherein said light receptor is operable to output a variable voltage signal in response to the light intensity sensed, said apparatus further including a microprocessor electronically coupled to said light receptor for comparing data representative of output signals received from the light receptor with stored data.
21. An apparatus as claimed in claim 14 further including a surface topography sensor for sensing the concavity of at least one of the top or bottom of the weld seam.
22. The apparatus as claimed in claim 21 wherein said topography sensor comprises a three-dimensional vision system including a laser emitter operable to emit a coherent light source, and a laser receptor for measuring coherent light source energy reflected from said seam.
23. An apparatus as claimed in claim 1 further including a surface topography sensor for sensing the concavity of at least one of the top or bottom of the weld seam.
24. The apparatus as claimed in claim 23 wherein said topography sensor comprises a three-dimensional vision system including a laser emitter operable to emit a coherent light source, and a laser receptor for measuring coherent light source energy reflected from said seam.
25. An apparatus for verifying a weld seam of a workpiece blank formed from welding at least two component parts with a laser, said apparatus comprising:
a pin hole sensor including a light emitter and a light receptor, the light emitter being disposed on a first side of said seam and including a light source for projecting an elongated light beam at said first side, and a focusing element to focus said light beam generally perpendicular to said weld seam, the light receptor disposed on the second other side of the seam generally opposite to the light source whereby projected light which passes through said weld seam activates said light receptor, said light receptor including a collecting lens configured to focus projected light which passes through said weld seam towards said pin hole light receiver , a reflective light guide and a pin hole light receiver providing an output signal when activated by said projected light, an infrared light sensor disposed on said second side of said seam, said infrared light sensor operable substantially simultaneously with said laser to receive and sense infrared light energy emitted by a weld flame produced during laser welding, and a surface topography sensor for sensing the concavity of at least one of the top or bottom of the weld seam.
a pin hole sensor including a light emitter and a light receptor, the light emitter being disposed on a first side of said seam and including a light source for projecting an elongated light beam at said first side, and a focusing element to focus said light beam generally perpendicular to said weld seam, the light receptor disposed on the second other side of the seam generally opposite to the light source whereby projected light which passes through said weld seam activates said light receptor, said light receptor including a collecting lens configured to focus projected light which passes through said weld seam towards said pin hole light receiver , a reflective light guide and a pin hole light receiver providing an output signal when activated by said projected light, an infrared light sensor disposed on said second side of said seam, said infrared light sensor operable substantially simultaneously with said laser to receive and sense infrared light energy emitted by a weld flame produced during laser welding, and a surface topography sensor for sensing the concavity of at least one of the top or bottom of the weld seam.
26. The apparatus as claimed in claim 25 wherein said topography sensor comprises a three-dimensional vision system including a coherent light source operable to emit a coherent light beam and a laser receptor for measuring coherent light source energy reflected from said seam.
27. An apparatus as claimed in claim 25 further including a surface topography sensor for sensing the concavity of each of the top and bottom surfaces of the weld seam.
28. An apparatus as claimed in claim 25 wherein said workpiece comprises a tailored blank.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US68883100A | 2000-10-17 | 2000-10-17 | |
| US09/688,831 | 2000-10-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2359221A1 true CA2359221A1 (en) | 2002-04-17 |
Family
ID=24765954
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2359221 Abandoned CA2359221A1 (en) | 2000-10-17 | 2001-10-16 | Post weld inspection apparatus and method of using same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2359221A1 (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106767408A (en) * | 2016-12-22 | 2017-05-31 | 河北卓然睿和自动化科技有限公司 | It is a kind of to seek gap sensor with sensitivity visualization regulation function |
| CN108714747A (en) * | 2018-08-01 | 2018-10-30 | 江苏逸飞激光设备有限公司 | A kind of sealing nail welding detecting system |
| CN111069845A (en) * | 2020-01-06 | 2020-04-28 | 山东力能重工有限公司 | Circular seam welding equipment |
| CN113984768A (en) * | 2021-12-24 | 2022-01-28 | 佛山隆深机器人有限公司 | Welding seam welding visual tracking detection device |
| CN114535801A (en) * | 2022-04-01 | 2022-05-27 | 柳州宏德激光科技有限公司 | Laser welding equipment for recycling power battery |
| CN114833074A (en) * | 2022-03-16 | 2022-08-02 | 杭州长川科技股份有限公司 | Electronic component appearance detection device |
| CN114888432A (en) * | 2022-01-24 | 2022-08-12 | 郑红菊 | Intelligent welding equipment and welding process for lithium battery punching sheet and lamination for new energy automobile |
| CN117705813A (en) * | 2024-02-05 | 2024-03-15 | 宁德时代新能源科技股份有限公司 | Welding quality detection system and method |
-
2001
- 2001-10-16 CA CA 2359221 patent/CA2359221A1/en not_active Abandoned
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106767408A (en) * | 2016-12-22 | 2017-05-31 | 河北卓然睿和自动化科技有限公司 | It is a kind of to seek gap sensor with sensitivity visualization regulation function |
| CN108714747A (en) * | 2018-08-01 | 2018-10-30 | 江苏逸飞激光设备有限公司 | A kind of sealing nail welding detecting system |
| CN111069845A (en) * | 2020-01-06 | 2020-04-28 | 山东力能重工有限公司 | Circular seam welding equipment |
| CN113984768A (en) * | 2021-12-24 | 2022-01-28 | 佛山隆深机器人有限公司 | Welding seam welding visual tracking detection device |
| CN114888432A (en) * | 2022-01-24 | 2022-08-12 | 郑红菊 | Intelligent welding equipment and welding process for lithium battery punching sheet and lamination for new energy automobile |
| CN114833074A (en) * | 2022-03-16 | 2022-08-02 | 杭州长川科技股份有限公司 | Electronic component appearance detection device |
| CN114833074B (en) * | 2022-03-16 | 2024-04-23 | 杭州长川科技股份有限公司 | Electronic component appearance detection device |
| CN114535801A (en) * | 2022-04-01 | 2022-05-27 | 柳州宏德激光科技有限公司 | Laser welding equipment for recycling power battery |
| CN117705813A (en) * | 2024-02-05 | 2024-03-15 | 宁德时代新能源科技股份有限公司 | Welding quality detection system and method |
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