Patent Publication Number: US-2009235505-A1

Title: Hem flange control roller

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority of U.S. Provisional Application No. 61/070,552 filed Mar. 24, 2008. 
    
    
     TECHNICAL FIELD 
     This invention relates to roller hemming, such as roller hemming of wheelhouse openings and other vehicle closure panel assemblies. 
     BACKGROUND OF THE INVENTION 
     It is known in the art relating to roller hemming to hold a hem roller on a guide surface of a lower die which supports a set of panels for hemming. As shown in  FIG. 34 , a hem roller  20  for hemming a workpiece W is rotatably connected to a robot arm  22  having a predetermined traveling path. A die/anvil  24  is provided generally below the hem roller  20  and has a guide surface  26  formed by cutting a corner thereof in a descending manner. The workpiece W is positioned between the hem roller  20  and the anvil  24 . The workpiece W includes an outer panel WO and an inner panel WI. The outer panel WO has a peripheral edge bent substantially at right angles toward the inner panel WI to form an upturned edge WE, and the inner panel WI has a peripheral edge arranged along the inside of the upturned edge WE. To perform a pre-hem operation on the workpiece W, the guide surface  26  holds the hem roller  20  in a first position such that when the hem roller is moved along the guide surface, the hem roller abuts against the upturned edge WE of the outer panel WO at a desired distance from the bend in the outer panel. The guide surface  26  thereby controls the position of the hem roller  20  relative to the panels during hemming. 
     However, it is difficult to control and adjust the hem flange line when using this conventional method. Any build-up or wearing away of the guide surface  26  will undesirably change the position of the hem flange line as indicated by double-sided arrows in  FIG. 34 . In order to adjust the hem flange line, the guide surface  26  must be machined or altered in another mechanical manner. Further, the hem flange line cannot be adjusted in-process because it is predetermined by the configuration of the guide surface  26 . Moreover, any variation in the width of the panels WO and WI may affect the position of the hem flange line, and the position of the hem roller  20  must be corrected by machining or building-up the guide surface  26 . 
     SUMMARY OF THE INVENTION 
     The present invention provides a roller hemming apparatus and method that allows for simple and easy adjustment of the hem flange line by moving a hem roller axially and generally parallel to an anvil surface. 
     One or two hem rollers may be used to perform pre-hem operations, and one hem roller is used to perform final hem operations. In one embodiment, a roller hemming head includes three hem rollers, one for forming a 60 degree pre-hem, one for forming a 30 degree pre-hem, and one for forming a flat final hem. A sight line between the hem rollers and an edge of the anvil provides for accurate robot programming of the position of the hem rollers and control of the hem flange line. 
     A method of roller hemming an inner panel and an outer panel in accordance with the present invention includes the steps of providing a hem roller having an angled roller hemming surface, and adjusting a hem flange line by moving the hem roller axially and generally parallel to an anvil support surface. 
     More particularly, a method of roller hemming in accordance with the present invention includes disposing an inner panel and an outer panel on a support surface of an anvil. Pre-hem operations are performed, the pre-hem operations including aligning a control surface of a pre-hem roller with an edge of the anvil along a sight line defined by the anvil edge by moving the pre-hem roller axially along its axis and generally parallel to the anvil support surface, whereby a location of a hem flange line extending from an angular bend in the outer panel is set, and rotating the pre-hem roller along the anvil support surface in alignment with the sight line such that the angled roller hemming surface of the pre-hem roller contacts the outer panel to form an angled pre-hem bend in the outer panel. After the pre-hem operations, final hem operations are performed. The final hem operations include aligning a control surface of a final hem roller with the anvil edge along the sight line by moving the final hem roller axially along its axis and generally parallel to the anvil support surface, and rotating the final hem roller along the anvil support surface in alignment with the sight line such that the final hem roller contacts the outer panel to form a final hem between the inner and outer panels. 
     The pre-hem operations may include aligning a control surface of a first pre-hem roller with an edge of the anvil along a sight line defined by the anvil edge by moving the first pre-hem roller axially along its axis and generally parallel to the anvil support surface, whereby a location of a hem flange line extending from an angular bend in the outer panel is set; rotating the first pre-hem roller along the anvil support surface in alignment with the sight line to form an angled pre-hem bend in the outer panel; aligning a control surface of a second pre-hem roller with an edge of the anvil along a sight line defined by the anvil edge by moving the pre-hem roller axially along its axis and generally parallel to the anvil support surface, whereby a location of a hem flange line extending from an angular bend in the outer panel is set; and rotating the second pre-hem roller along the anvil support surface in alignment with the sight line to form an angled pre-hem bend in the outer panel. 
     Alternatively, the pre-hem operations may include aligning a control surface of a pre-hem roller with an edge of the anvil along a sight line defined by the anvil edge by moving the first pre-hem roller axially along its axis and generally parallel to the anvil support surface, whereby a location of a hem flange line extending from an angular bend in the outer panel is set; pivoting the pre-hem roller about a crown of the pre-hem roller to adjust the disposition of a angled surface of the pre-hem roller relative to the anvil support surface; rotating the pre-hem roller along the anvil support surface to form an angled pre-hem bend in the outer panel; pivoting the pre-hem roller about the crown to align the control surface of the pre-hem roller with the anvil edge; and rotating the pre-hem roller along the anvil support surface in alignment with the sight line to form an angled pre-hem bend in the outer panel. 
     A rope hem may be formed between the inner and outer panels. Alternatively, a flat hem may be formed between the inner and outer panels. 
     An apparatus for roller hemming an inner panel and an outer panel includes an anvil having a support surface for supporting the inner and outer panels and an edge adjacent the support surface. A hem roller is rotatable about an axis and has a roller hem surface for engaging the outer panel to effect a hem operation and a control surface for aligning the hem roller. The control surface is aligned with the anvil edge by moving the hem roller axially along the axis and generally parallel to the anvil support surface. 
     The hem roller surface for engaging the outer panel may be an angled surface for effecting a pre-hem bend in the outer panel. The angled surface may be a 30 degree angled surface or a 60 degree angled surface, although the roller may have any angle depending on the product and/or flange open angle of the flange to be hemmed. Alternatively, the hem roller surface for engaging the outer panel may be a flat surface for effecting a final hem bend in the outer panel. The roller may include a crown engagable with the anvil support surface, the roller being pivotable about the crown relative to the anvil support surface. 
     These and other features and advantages of the invention will be more fully understood from the following detailed description of the invention taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a side view of a 60 degree angle pre-hem roller performing a first hemming pass for a rope hem in accordance with a first embodiment of the present invention; 
         FIG. 2  is a side view of a 30 degree angle pre-hem roller performing a second hemming pass in accordance with the first embodiment; 
         FIG. 3  is a side view of a rope hem final hem roller performing a third hemming pass in accordance with the first embodiment; 
         FIG. 4  is a side view of a 30 degree angle pre-hem roller performing a 60 degree pre-hem operation for a rope hem in accordance with a second embodiment of the present invention; 
         FIG. 5  is a side view of the 30 degree angle pre-hem roller performing a 30 degree pre-hem operation in accordance with the second embodiment; 
         FIG. 6  is a side view of a rope hem final hem roller performing a final hemming pass in accordance with the second embodiment; 
         FIG. 7  is a side view of a 60 degree angle pre-hem roller performing a first hemming pass for a flat hem in accordance with a third embodiment of the present invention; 
         FIG. 8  is a side view of a 30 degree angle pre-hem roller performing a second hemming pass in accordance with the third embodiment; 
         FIG. 9  is a side view of a flat final hem roller performing a third hemming pass in accordance with the third embodiment; 
         FIG. 10  is a side view of a 30 degree angle pre-hem roller performing a 60 degree pre-hem operation for a flat hem in accordance with a fourth embodiment of the present invention; 
         FIG. 11  is a side view of the 30 degree angle pre-hem roller performing a 30 degree pre-hem operation in accordance with the fourth embodiment; 
         FIG. 12  is a side view of a flat final hem roller performing a final hemming pass in accordance with the fourth embodiment; 
         FIG. 13  is a side view of a 60 degree angle pre-hem roller performing a first hemming pass for a rope hem in accordance with a fifth embodiment of the present invention; 
         FIG. 14  is a side view of a 30 degree angle pre-hem roller performing a second hemming pass in accordance with the fifth embodiment; 
         FIG. 15  is a side view of a rope hem final hem roller performing a third hemming pass in accordance with the fifth embodiment; 
         FIG. 16  is a side view of a 60 degree angle pre-hem roller performing a first hemming pass for a flat hem in accordance with a sixth embodiment of the present invention; 
         FIG. 17  is a side view of a 30 degree angle pre-hem roller performing a second hemming pass in accordance with the sixth embodiment; 
         FIG. 18  is a side view of a flat final hem roller performing a third hemming pass in accordance with the sixth embodiment; 
         FIG. 19  is a side view of a 60 degree angle pre-hem roller performing a first hemming pass for a flat hem in accordance with a seventh embodiment of the present invention; 
         FIG. 20  is a side view of a 30 degree angle pre-hem roller performing a second hemming pass in accordance with the seventh embodiment; 
         FIG. 21  is a side view of a flat final hem roller performing a third hemming pass in accordance with the seventh embodiment; 
         FIG. 22  is a side view of a 60 degree angle pre-hem roller performing a first hemming pass for a flat hem in accordance with a eighth embodiment of the present invention; 
         FIG. 23  is a side view of a 30 degree angle pre-hem roller performing a second hemming pass in accordance with the eighth embodiment; 
         FIG. 24  is a side view of a flat final hem roller performing a third hemming pass in accordance with the eighth embodiment; 
         FIG. 25  is a side view of a 60 degree angle pre-hem roller performing a first hemming pass for a flat hem in accordance with a ninth embodiment of the present invention; 
         FIG. 26  is a side view of a 30 degree angle pre-hem roller performing a second hemming pass in accordance with the ninth embodiment; 
         FIG. 27  is a side view of a flat final hem roller performing a third hemming pass in accordance with the ninth embodiment; 
         FIG. 28  is a side view of a 60 degree angle pre-hem roller performing a first hemming pass for a rope hem in accordance with a tenth embodiment of the present invention; 
         FIG. 29  is a side view of a 30 degree angle pre-hem roller performing a second hemming pass in accordance with the tenth embodiment; 
         FIG. 30  is a side view of a rope hem final hem roller performing a third hemming pass in accordance with the tenth embodiment; 
         FIG. 31  is a side view of a 60 degree angle pre-hem roller performing a first hemming pass for a rope hem in accordance with a eleventh embodiment of the present invention; 
         FIG. 32  is a side view of a 30 degree angle pre-hem roller performing a second hemming pass in accordance with the eleventh embodiment; 
         FIG. 33  is a side view of a rope hem final hem roller performing a third hemming pass in accordance with the eleventh embodiment; and 
         FIG. 34  is a side view of a prior art flat hem roller performing a pre-hem operation by moving along a machined guide surface of a die. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings in detail, a hem flange control roller in accordance with the present invention controls the position of a hem flange line by moving along its axis relative to and generally parallel to a support surface of an anvil. A sight line exists between the hem flange control roller and the anvil surface for robot programming of the position of the roller. 
     In a first embodiment shown in  FIGS. 1 through 3 , a first pre-hem roller  130 , a second pre-hem roller  132 , and a final hem roller  134  may be rotatably mounted about their respective axes  136 ,  138 ,  140  to a roller hemming head which is carried by a programmable multi-axis robotic arm (not shown). An anvil  142  having a support surface  144  supports an inner panel  146  and outer panel  148  for hemming. 
     The hem rollers  130 ,  132 ,  134  are configured for forming a rope hem in the inner and outer panels  146 ,  148 . Each hem roller is dedicated for a specific roller hem pass. The first pre-hem roller  130  ( FIG. 1 ) includes a 60 degree angled surface  150  for forming a 60 degree pre-hem flange bend in the outer panel  148  during a first hem pass, a crown  152  for engagement with the anvil support surface  144 , and a control surface  154  for aligning the roller as described in more detail below. Similarly, the second pre-hem roller  132  ( FIG. 2 ) includes a 30 degree angled surface  156  for forming a 30 degree pre-hem flange bend in the outer panel  148  during a second hem pass, a crown  158  for engagement with the anvil support surface  144 , and a control surface  160 . It should be understood, however, that the pre-hem rollers may have any angle depending on the product formed by the inner and outer panels and/or the open angle of the flange to be hemmed. For example, the pre-hem rollers may have 80 degree and 40 degree angled surfaces, respectively. The following description discusses  60  degree and 30 degree angled pre-hem rollers, but the present invention is not limited to these specific dimensions. The final hem roller  134  ( FIG. 3 ) includes a flat surface  162  for bending the outer panel  148  against the inner panel  146  during a third hem pass, and a control surface  164 . 
     The support surface  144  of the anvil  142  assists in controlling the pre-hemming condition by directing pressure on the anvil  142  and having a tight control on the hem flange. The anvil support surface  144  may be made of the same material as the pre-hem rollers  130 ,  132 , and in this case the pre-hem roller crowns  152 ,  158  and the anvil support surface  144  may have different Rockwell hardness values. Alternatively, the support surface  144  may have an inserted, replaceable material that places the wear condition directly on the roller and that can be easily replaced. In yet another embodiment, polymer material(s) or high strength steel material(s) may be used to overcome the wear issues with respect to the anvil and rollers. 
     The control surface  154  of the first pre-hem roller  130  is aligned with an edge  166  of the anvil  142  along a straight sight line  168 . The alignment of the control surface  154  with the anvil edge  166  controls the distance d between the anvil edge  166  and the hem flange bend  170  in the outer panel  148 , thereby determining the position of the hem flange line. To adjust the position of the hem flange line, the first pre-hem roller  130  is moved axially along its axis  136  generally parallel to the anvil surface  144 , which in turn varies the position of the roller&#39;s angled hemming surface  150  relative to the outer panel  148 . Similarly, the control surface  160  of the second pre-hem roller  132  is aligned with the anvil edge  166  along the straight sight line  168 , and the control surface  164  of the final hem roller  134  is aligned with the anvil edge  144  along the straight sight line  168 . 
     To form a rope hem between the inner and outer panels  146 ,  148 , the robotic arm presses the first pre-hem roller  130  against the anvil support surface  144  and executes a first pass by moving the first pre-hem roller along a path in which the control surface  154  is aligned with the anvil edge  166 , thereby forming a 60 degree pre-hem flange bend in the outer panel ( FIG. 1 ). The robotic arm then presses the second pre-hem roller  132  against the anvil support surface  144  and executes a second pass by moving the second pre-hem roller along a path in which the control surface  160  is aligned with the anvil edge  166 , thereby forming a 30 degree pre-hem flange bend in the outer panel ( FIG. 2 ). The robotic arm then completes the rope hem by pressing the flat surface  162  of the final hem roller  134  against the outer panel  148  and executing a third pass by moving the final hem roller along a path in which the control surface  164  is aligned with the anvil edge  166  ( FIG. 3 ). 
     In a second embodiment shown in  FIGS. 4 through 6 , a single pre-hem roller  272  and a final hem roller  234  may be rotatably mounted about their respective axes  274 ,  240  to a roller hemming head which is carried by a programmable multi-axis robotic arm (not shown). An anvil  242  having a support surface  244  supports an inner panel  246  and outer panel  248  for hemming. 
     The hem rollers  234 ,  272  are configured for forming a rope hem in the inner and outer panels  246 ,  248 . The pre-hem roller  272  is utilized for first and second hem passes (pre-hem operations) and the final hem roller  234  is utilized for a third hem pass (final hem operation). The pre-hem roller  272  ( FIGS. 4 and 5 ) includes a 30 degree angled surface  276  for forming  60  and 30 degree pre-hem flange bends in the outer panel  248  during the first and second hem pass, a crown  278  for engagement with the anvil support surface  244 , and a control surface  280  for aligning the roller. The final hem roller  234  ( FIG. 6 ) includes a flat surface  262  for bending the outer panel  248  against the inner panel  246  during the third hem pass, and a control surface  264 . 
     The control surface  280  of the pre-hem roller  272  is aligned with an edge  266  of the anvil  242  along a straight sight line  268  ( FIG. 5 ). The alignment of the control surface  280  with the anvil edge  266  controls the distance d between the anvil edge  266  and the hem flange bend  270  in the outer panel  248 , thereby determining the position of the hem flange line. To adjust the position of the hem flange line, the pre-hem roller  272  is moved axially along its axis  274  generally parallel to the anvil surface  244 , which in turn varies the position of the roller&#39;s angled hemming surface  276  relative to the outer panel  248 . Similarly, the control surface  264  of the final hem roller  234  is aligned with the anvil edge  266  along the straight sight line  268 . 
     To form a rope hem between the inner and outer panels  246 ,  248 , the robotic arm first presses the pre-hem roller  272  against the anvil support surface  244  and aligns the control surface  280  with the anvil edge  266  along the sight line  268  ( FIG. 5 ). The robotic arm is then programmed to move the pre-hem roller  272  in a path along the sight line  268 . To begin hemming the panels  246 ,  248 , the robotic arm presses the pre-hem roller  272  against the anvil support surface  244  and pivots the pre-hem roller about the crown  278  until a desired angle is obtained between the roller&#39;s angled surface  276  and the anvil support surface  244 . In this case, the pre-hem roller  272  is pivoted 30 degrees about the crown  278  in order to pre-hem a 60 degree bend in the outer panel  248 . The robotic arm executes a first pass by moving the pivoted pre-hem roller  272  along the preprogrammed path, thereby forming a 60 degree pre-hem flange bend in the outer panel  248  ( FIG. 4 ). The robotic arm then returns the pre-hem roller  272  into a position in which the control surface  280  is aligned with the anvil edge  266  by pivoting the pre-hem roller 30 degrees in the opposite direction. The robotic arm executes a second pass by moving the pre-hem roller  272  along the preprogrammed path, thereby forming a 30 degree pre-hem flange bend in the outer panel  248  ( FIG. 5 ). The robotic arm then completes the rope hem by pressing the flat surface  262  of the final hem roller  234  against the outer panel  248  and executing a third pass by moving the final hem roller along a path in which the control surface  264  is aligned with the anvil edge  266  ( FIG. 6 ). 
     In a third embodiment shown in  FIGS. 7 through 9 , a first pre-hem roller  382 , a second pre-hem roller  372 , and a final hem roller  384  may be rotatably mounted about their respective axes  386 ,  374 ,  388  to a roller hemming head which is carried by a programmable multi-axis robotic arm (not shown). An anvil  342  having a support surface  344  supports an inner panel  346  and outer panel  348  for hemming. 
     The hem rollers  372 ,  382 ,  384  are configured for forming a flat hem in the inner and outer panels  346 ,  348 . Each hem roller is dedicated for a specific roller hem pass. The first pre-hem roller  382  ( FIG. 7 ) includes a 60 degree angled surface  390  for forming a 60 degree pre-hem flange bend in the outer panel  348  during a first hem pass, a crown  392  for engagement with the anvil support surface  344 , and a control surface  394  for aligning the roller. Similarly, the second pre-hem roller  372  ( FIG. 8 ) includes a 30 degree angled surface  376  for forming a 30 degree pre-hem flange bend in the outer panel  348  during a second hem pass, a crown  378  for engagement with the anvil support surface  344 , and a control surface  380 . The final hem roller  384  ( FIG. 9 ) includes a flat surface  396  for bending the outer panel  348  against the inner panel  346  during a third hem pass, and a control surface  398 . 
     The control surface  394  of the first pre-hem roller  382  is aligned with an edge  366  of the anvil  342  along a straight sight line  368 . The alignment of the control surface  394  with the anvil edge  366  controls the distance d between the anvil edge  366  and the hem flange bend  370  in the outer panel  348 , thereby determining the position of the hem flange line. To adjust the position of the hem flange line, the first pre-hem roller  382  is moved axially along its axis  386  generally parallel to the anvil surface  344 , which in turn varies the position of the roller&#39;s angled hemming surface  390  relative to the outer panel  348 . Similarly, the control surface  380  of the second pre-hem roller  372  is aligned with the anvil edge  366  along the straight sight line  368 , and the control surface  398  of the final hem roller  384  is aligned with the anvil edge  366  along the straight sight line  368 . 
     To form a flat hem between the inner and outer panels  346 ,  348 , the robotic arm presses the first pre-hem roller  382  against the anvil support surface  344  and executes a first pass by moving the first pre-hem roller along a path in which the control surface  394  is aligned with the anvil edge  366 , thereby forming a 60 degree pre-hem flange bend in the outer panel  348  ( FIG. 7 ). The robotic arm then presses the second pre-hem roller  372  against the anvil support surface  344  and executes a second pass by moving the second pre-hem roller along a path in which the control surface  380  is aligned with the anvil edge  366 , thereby forming a 30 degree pre-hem flange bend in the outer panel  348  ( FIG. 8 ). The robotic arm then completes the flat hem by pressing the flat surface  396  of the final hem roller  384  against the outer panel  348  and executing a third pass by moving the final hem roller along a path in which the control surface  398  is aligned with the anvil edge  366  ( FIG. 9 ). 
     In a fourth embodiment shown in  FIGS. 10 through 12 , a single pre-hem roller  472  and a final hem roller  484  may be rotatably mounted about their respective axes  474 ,  488  to a roller hemming head which is carried by a programmable multi-axis robotic arm (not shown). An anvil  442  having a support surface  444  supports an inner panel  446  and outer panel  448  for hemming. 
     The hem rollers  472 ,  484  are configured for forming a flat hem in the inner and outer panels  446 ,  448 . The pre-hem roller  472  is utilized for first and second hem passes (pre-hem operations) and the final hem roller  484  is utilized for a third hem pass (final hem operation). The pre-hem roller  472  ( FIGS. 10 and 11 ) includes a 30 degree angled surface  476  for forming  60  and 30 degree pre-hem flange bends in the outer panel  448  during the first and second hem pass, a crown  478  for engagement with the anvil support surface  444 , and a control surface  480  for aligning the roller. The final hem roller  484  ( FIG. 12 ) includes a flat surface  496  for bending the outer panel  448  against the inner panel  446  during the third hem pass, and a control surface  498 . 
     The control surface  480  of the pre-hem roller  472  is aligned with an edge  466  of the anvil  442  along a straight sight line  468  ( FIG. 11 ). The alignment of the control surface  480  with the anvil edge  466  controls the distance d between the anvil edge  466  and the hem flange bend  470  in the outer panel  448 , thereby determining the position of the hem flange line. To adjust the position of the hem flange line, the pre-hem roller  472  is moved axially along its axis  474  generally parallel to the anvil surface  444 , which in turn varies the position of the angled hemming surface  476  relative to the outer panel  448 . Similarly, the control surface  498  of the final hem roller  484  is aligned with the anvil edge  466  along a straight sight line  468 . 
     To form a flat hem between the inner and outer panels  446 ,  448 , the robotic arm first presses the pre-hem roller  472  against the anvil support surface  444  and aligns the control surface  480  with the anvil edge  466  along the sight line  468  ( FIG. 11 ). The robotic arm is then programmed to move the pre-hem roller  472  in a path along the sight line  468 . To begin hemming the panels  446 ,  448 , the robotic arm then presses the pre-hem roller  472  against the anvil support surface  444  and pivots the pre-hem roller about the crown  478  until a desired angle is obtained between the roller&#39;s angled surface  476  and the anvil support surface  444 . In this case, the pre-hem roller is pivoted 30 degrees about the crown  478  in order to pre-hem a 60 degree bend in the outer panel  448 . The robotic arm executes a first pass by moving the pivoted pre-hem roller  472  along the preprogrammed path, thereby forming a 60 degree pre-hem flange bend in the outer panel  448  ( FIG. 10 ). The robotic arm then returns the pre-hem roller  472  into a position in which the control surface  480  is aligned with the anvil edge  466  by pivoting the pre-hem roller 30 degrees in the opposite direction. The robotic arm executes a second pass by moving the pre-hem roller  472  along the preprogrammed path, thereby forming a 30 degree pre-hem flange bend in the outer panel  448  ( FIG. 11 ). The robotic arm then completes the flat hem by pressing the flat surface  496  of the final hem roller  484  against the outer panel  448  and executing a third pass by moving the final hem roller along a path in which the control surface  498  is aligned with the anvil edge  466  ( FIG. 12 ). 
     In a fifth embodiment shown in  FIGS. 13 through 15 , a first pre-hem roller  531 , a second pre-hem roller  533 , and a final hem roller  534  may be rotatably mounted about their respective axes  535 ,  537 ,  540  to a roller hemming head which is carried by a programmable multi-axis robotic arm (not shown). An anvil  542  having a support surface  544  supports an inner panel  546  and outer panel  548  for hemming. 
     The hem rollers  531 ,  533 ,  534  are configured for forming a rope hem in the inner and outer panels  546 ,  548 . Each hem roller is dedicated for a specific roller hem pass. The first pre-hem roller  531  ( FIG. 13 ) includes a 60 degree angled surface  539  for forming a 60 degree pre-hem flange bend in the outer panel  548  during a first hem pass, a crown  541  for engagement with the anvil support surface  544 , a cylindrical relief  543 , and a control surface  545  for aligning the roller. Similarly, the second pre-hem roller  533  ( FIG. 14 ) includes a 30 degree angled surface  547  for forming a 30 degree pre-hem flange bend in the outer panel  548  during a second hem pass, a crown  549  for engagement with the anvil support surface  544 , a cylindrical relief  551 , and a control surface  553 . The final hem roller  534  ( FIG. 15 ) includes a flat surface  562  for bending the outer panel  548  against the inner panel  546  during a third hem pass, and a control surface  564 . 
     The control surface  545  of the first pre-hem roller  531  is aligned with an edge  566  of the anvil  542  along a straight sight line  568 . Further, the crown  541  is positioned at and in engagement with a concave ride surface  555  on the anvil  542 . The concave ride surface  555  positions the pre-hem roller  531  at a proper distance d from the hem flange line, and the alignment of the control surface  545  with the sight line  568  sets the proper flange angle. The concave ride surface  555  also maintains proper roller position while the roller  531  moves through a hemming operation. Similarly, the control surface  553  of the second pre-hem roller  533  is aligned with the anvil edge  566  along the straight sight line  568 , and the crown  549  is positioned at and in engagement with a concave ride surface  555 . Also, the control surface  564  of the final hem roller  534  is aligned with the anvil edge  566  along the straight sight line  568 . 
     The cylindrical relief  543  of the first pre-hem roller  531  and the cylindrical relief  551  of the second pre-hem roller  533  compensates for variation in the width of the inner and outer panels  546 ,  548 . 
     To form a rope hem between the inner and outer panels  546 ,  548 , the robotic arm presses the first pre-hem roller  531  against the concave ride surface  555  and executes a first pass by moving the first pre-hem roller along a path in which the control surface  545  is aligned with the anvil edge  566 , thereby forming a 60 degree pre-hem flange bend in the outer panel  548  ( FIG. 13 ). The robotic arm then presses the second pre-hem roller  533  against the concave ride surface  555  and executes a second pass by moving the second pre-hem roller along a path in which the control surface  553  is aligned with the anvil edge  566 , thereby forming a 30 degree pre-hem flange bend in the outer panel  548  ( FIG. 14 ). The robotic arm then completes the rope hem by pressing the flat surface  562  of the final hem roller  534  against the outer panel  548  and executing a third pass by moving the final hem roller along a path in which the control surface  564  is aligned with the anvil edge  566  ( FIG. 15 ). 
     In a sixth embodiment shown in  FIGS. 16 through 18 , a first pre-hem roller  631 , a second pre-hem roller  633 , and a final hem roller  684  may be rotatably mounted about their respective axes  635 ,  637 ,  688  to a roller hemming head which is carried by a programmable multi-axis robotic arm (not shown). An anvil  642  having a support surface  644  supports an inner panel  646  and outer panel  648  for hemming. 
     The hem rollers  631 ,  633 ,  684  are configured for forming a flat hem in the inner and outer panels  646 ,  648 . Each hem roller is dedicated for a specific roller hem pass. The first pre-hem roller  631  ( FIG. 16 ) includes a 60 degree angled surface  639  for forming a 60 degree pre-hem flange bend in the outer panel  648  during a first hem pass, a crown  641  for engagement with the anvil support surface  644 , a cylindrical relief  643 , and a control surface  645  for aligning the roller. Similarly, the second pre-hem roller  533  ( FIG. 17 ) includes a 30 degree angled surface  647  for forming a 30 degree pre-hem flange bend in the outer panel  648  during a second hem pass, a crown  649  for engagement with the anvil support surface  644 , a cylindrical relief  651 , and a control surface  653 . The final hem roller  684  ( FIG. 18 ) includes a flat surface  696  for bending the outer panel  648  against the inner panel  646  during a third hem pass, and a control surface  698 . 
     The control surface  645  of the first pre-hem roller  631  is aligned with an edge  666  of the anvil  642  along a straight sight line  668 . Further, the crown  641  is positioned at and in engagement with a concave ride surface  655  on the anvil  642 . The concave ride surface  655  positions the pre-hem roller  631  at a proper distance d from the hem flange line, and the alignment of the control surface  645  with the sight line  668  sets the proper flange angle. The concave ride surface  655  also maintains proper roller position while the roller  631  moves through a hemming operation. Similarly, the control surface  653  of the second pre-hem roller  633  is aligned with the anvil edge  666  along the straight sight line  668 , and the crown  649  is positioned at and in engagement with a concave ride surface  655 . Also, the control surface  698  of the final hem roller  684  is aligned with the anvil edge  666  along the straight sight line  668 . 
     The cylindrical relief  643  of the first pre-hem roller  631  and the cylindrical relief  651  of the second pre-hem roller  633  compensates for variation in the width of the inner and outer panels  646 ,  648 . 
     To form a flat hem between the inner and outer panels  646 ,  648 , the robotic arm presses the first pre-hem roller  631  against the concave ride surface  655  and executes a first pass by moving the first pre-hem roller along a path in which the control surface  645  is aligned with the anvil edge  666 , thereby forming a 60 degree pre-hem flange bend in the outer panel  648  ( FIG. 16 ). The robotic arm then presses the second pre-hem roller  633  against the concave ride surface  655  and executes a second pass by moving the second pre-hem roller along a path in which the control surface  653  is aligned with the anvil edge  666 , thereby forming a 30 degree pre-hem flange bend in the outer panel  648  ( FIG. 17 ). The robotic arm then completes the flat hem by pressing the flat surface  696  of the final hem roller  684  against the outer panel  648  and executing a third pass by moving the final hem roller along a path in which the control surface  698  is aligned with the anvil edge  666  ( FIG. 18 ). 
     In a seventh embodiment shown in  FIGS. 19 through 21 , a first pre-hem roller  730 , a second pre-hem roller  732 , and a final hem roller  784  may be rotatably mounted about their respective axes  736 ,  738 ,  788  to a roller hemming head which is carried by a programmable multi-axis robotic arm (not shown). An anvil  742  having a support surface  744  supports an inner panel  746  and outer panel  748  for hemming. 
     The hem rollers  730 ,  732 ,  784  are configured for forming a flat hem in the inner and outer panels  746 ,  748 . Each hem roller is dedicated for a specific roller hem pass. The first pre-hem roller  730  ( FIG. 19 ) includes a 60 degree angled surface  750  for forming a 60 degree pre-hem flange bend in the outer panel  748  during a first hem pass, a crown  752  for engagement with the anvil support surface  744 , and a control surface  754  for aligning the roller. Similarly, the second pre-hem roller  732  ( FIG. 20 ) includes a 30 degree angled surface  756  for forming a 30 degree pre-hem flange bend in the outer panel  748  during a second hem pass, a crown  758  for engagement with the anvil support surface  744 , and a control surface  760 . The final hem roller  784  ( FIG. 21 ) includes a flat surface  796  for bending the outer panel  748  against the inner panel  746  during a third hem pass, and a control surface  798 . 
     The control surface  754  of the first pre-hem roller  730  is aligned with an edge  766  of the anvil  742  along a straight sight line  768 . The alignment of the control surface  754  with the anvil edge  766  controls the distance d between the anvil edge  766  and the hem flange bend  770  in the outer panel  748 , thereby determining the position of the hem flange line. To adjust the position of the hem flange line, the first pre-hem roller  730  is moved axially along its axis  736  generally parallel to the anvil surface  744 , which in turn varies the position of the roller&#39;s angled hemming surface  750  relative to the outer panel  748 . Similarly, the control surface  760  of the second pre-hem roller  732  is aligned with the anvil edge  766  along the straight sight line  768 , and the control surface  798  of the final hem roller  784  is aligned with the anvil edge  744  along the straight sight line  768 . 
     To form a flat hem between the inner and outer panels  746 ,  748 , the robotic arm presses the first pre-hem roller  730  against the anvil support surface  744  and executes a first pass by moving the first pre-hem roller along a path in which the control surface  754  is aligned with the anvil edge  766 , thereby forming a 60 degree pre-hem flange bend in the outer panel ( FIG. 19 ). The robotic arm then presses the second pre-hem roller  732  against the anvil support surface  744  and executes a second pass by moving the second pre-hem roller along a path in which the control surface  760  is aligned with the anvil edge  766 , thereby forming a 30 degree pre-hem flange bend in the outer panel ( FIG. 20 ). The robotic arm then completes the flat hem by pressing the flat surface  796  of the final hem roller  784  against the outer panel  748  and executing a third pass by moving the final hem roller along a path in which the control surface  794  is aligned with the anvil edge  766  ( FIG. 21 ). 
     In a eighth embodiment shown in  FIGS. 22 through 24 , a first pre-hem roller  857 , a second pre-hem roller  859 , and a final hem roller  884  may be rotatably mounted about their respective axes  861 ,  863 ,  888  to a roller hemming head which is carried by a programmable multi-axis robotic arm (not shown). An anvil  842  having a support surface  844  supports an inner panel  846  and outer panel  848  for hemming. 
     The hem rollers  857 ,  859 ,  884  are configured for forming a flat hem in the inner and outer panels  846 ,  848 . Each hem roller is dedicated for a specific roller hem pass. The first pre-hem roller  857  ( FIG. 22 ) includes an angled surface  865  for forming a pre-hem flange bend in the outer panel  848  during a first hem pass, a crown  867  for engagement with the anvil support surface  844 , and a control surface  869  for aligning the roller. The angle of the angled surface  865  is set approximately 15 degrees less than the flange angle requirement for the first hem pass. Similarly, the second pre-hem roller  859  ( FIG. 23 ) includes an angled surface  871  for forming a pre-hem flange bend in the outer panel  848  during a second hem pass, a crown  873  for engagement with the anvil support surface  844 , and a control surface  875 . The angle of the angled surface  871  is set approximately 15 degrees less than the flange angle requirement for the second hem pass. The final hem roller  884  ( FIG. 24 ) includes a flat surface  896  for bending the outer panel  848  against the inner panel  846  during a third hem pass, and a control surface  898 . 
     The control surface  869  of the first pre-hem roller  857  is aligned with an edge  866  of the anvil  842  along a straight sight line  868 . Further, the crown  867  is positioned at and in engagement with a concave ride surface  855  on the anvil  842 . The concave ride surface  855  positions the pre-hem roller  857  at a proper distance d from the hem flange line. The concave ride surface  855  and the sight line  868  maintain proper roller position while the roller  857  moves through a hemming operation. Similarly, the control surface  875  of the second pre-hem roller  859  is aligned with the anvil edge  866  along the straight sight line  868 , and the crown  873  is positioned at and in engagement with a concave ride surface  855 . Also, the control surface  898  of the final hem roller  884  is aligned with the anvil edge  866  along the straight sight line  868 . 
     When the first pre-hem roller  857  is aligned with the concave ride surface  855  and the sight line  868 , the angled surface  865  of the roller only contacts the hem flange at the end  877  of the outer panel  848 . Similarly, when the second pre-hem roller  859  is aligned with the concave ride surface  855  and the sight line  868 , the angle surface  871  of the roller only contacts the hem flange at the end  877  of the outer panel  848 . Therefore, variation in the width of the inner and outer panels  846 ,  848  does not affect the hem flange line or hem flange angle, and no reprogramming of the roller path is required. 
     To form a flat hem between the inner and outer panels  846 ,  848 , the robotic arm presses the first pre-hem roller  857  against the concave ride surface  855  and executes a first pass by moving the first pre-hem roller along a path in which the control surface  869  is aligned with the anvil edge  866 , thereby forming a 60 degree pre-hem flange bend in the outer panel  848  ( FIG. 22 ). The robotic arm then presses the second pre-hem roller  859  against the concave ride surface  855  and executes a second pass by moving the second pre-hem roller along a path in which the control surface  875  is aligned with the anvil edge  866 , thereby forming a 30 degree pre-hem flange bend in the outer panel  848  ( FIG. 23 ). The robotic arm then completes the flat hem by pressing the flat surface  896  of the final hem roller  884  against the outer panel  848  and executing a third pass by moving the final hem roller along a path in which the control surface  898  is aligned with the anvil edge  866  ( FIG. 24 ). 
     In a ninth embodiment shown in  FIGS. 25 through 27 , a first pre-hem roller  979 , a second pre-hem roller  981 , and a final hem roller  984  may be rotatably mounted about their respective axes  983 ,  985 ,  988  to a roller hemming head which is carried by a programmable multi-axis robotic arm (not shown). An anvil  942  having a support surface  944  supports an inner panel  946  and outer panel  948  for hemming. 
     The hem rollers  979 ,  981 ,  984  are configured for forming a flat hem in the inner and outer panels  946 ,  948 . Each hem roller is dedicated for a specific roller hem pass. The first pre-hem roller  979  ( FIG. 25 ) includes an angled surface  987  for forming a pre-hem flange bend in the outer panel  948  during a first hem pass, a crown  989  for engagement with the anvil support surface  944 , and a control surface  991  for aligning the roller. The angle of the angled surface  987  is set approximately 15 degrees less than the flange angle requirement for the first hem pass. Similarly, the second pre-hem roller  981  ( FIG. 26 ) includes an angled surface  993  for forming a pre-hem flange bend in the outer panel  948  during a second hem pass, a crown  995  for engagement with the anvil support surface  944 , and a control surface  997 . The angle of the angled surface  993  is set approximately 15 degrees less than the flange angle requirement for the second hem pass. The final hem roller  984  ( FIG. 27 ) includes a flat surface  996  for bending the outer panel  948  against the inner panel  946  during a third hem pass, and a control surface  998 . 
     The control surface  991  of the first pre-hem roller  979  is aligned with an edge  966  of the anvil  942  along a straight sight line  968 . The alignment of the control surface  991  with the anvil edge  966  controls the distance d between the anvil edge  966  and the hem flange bend  970  in the outer panel  948 , thereby maintaining an even hemming path. Similarly, the control surface  997  of the second pre-hem roller  981  is aligned with the anvil edge  966  along the straight sight line  968 , and the control surface  998  of the final hem roller  984  is aligned with the anvil edge  966  along the straight sight line  968 . 
     When the first pre-hem roller  979  is aligned with the sight line  968 , the angled surface  987  of the roller only contacts the hem flange at the end  977  of the outer panel  948 . Similarly, when the second pre-hem roller  981  is aligned with the sight line  968 , the angle surface  993  of the roller only contacts the hem flange at the end  977  of the outer panel  948 . Therefore, variation in the width of the inner and outer panels  946 ,  948  does not affect the hem flange line or hem flange angle, and no reprogramming of the roller path is required. 
     To form a flat hem between the inner and outer panels  946 ,  948 , the robotic arm presses the first pre-hem roller  979  against the anvil support surface  944  and executes a first pass by moving the first pre-hem roller along a path in which the control surface  991  is aligned with the anvil edge  966 , thereby forming a 60 degree pre-hem flange bend in the outer panel  948  ( FIG. 25 ). The robotic arm then presses the second pre-hem roller  981  against the anvil support surface  944  and executes a second pass by moving the second pre-hem roller along a path in which the control surface  997  is aligned with the anvil edge  966 , thereby forming a 30 degree pre-hem flange bend in the outer panel  948  ( FIG. 26 ). The robotic arm then completes the flat hem by pressing the flat surface  996  of the final hem roller  984  against the outer panel  948  and executing a third pass by moving the final hem roller along a path in which the control surface  998  is aligned with the anvil edge  966  ( FIG. 27 ). 
     In a tenth embodiment shown in  FIGS. 28 through 30 , a first pre-hem roller  1057 , a second pre-hem roller  1059 , and a final hem roller  1034  may be rotatably mounted about their respective axes  1061 ,  1063 ,  1040  to a roller hemming head which is carried by a programmable multi-axis robotic arm (not shown). An anvil  1042  having a support surface  1044  supports an inner panel  1046  and outer panel  1048  for hemming. 
     The hem rollers  1057 ,  1059 ,  1034  are configured for forming a rope hem in the inner and outer panels  1046 ,  1048 . Each hem roller is dedicated for a specific roller hem pass. The first pre-hem roller  1057  ( FIG. 28 ) includes an angled surface  1065  for forming a pre-hem flange bend in the outer panel  1048  during a first hem pass, a crown  1067  for engagement with the anvil support surface  1044 , and a control surface  1069  for aligning the roller. The angle of the angled surface  1065  is set approximately 15 degrees less than the flange angle requirement for the first hem pass. Similarly, the second pre-hem roller  1059  ( FIG. 29 ) includes an angled surface  1071  for forming a pre-hem flange bend in the outer panel  1048  during a second hem pass, a crown  1073  for engagement with the anvil support surface  1044 , and a control surface  1075 . The angle of the angled surface  1071  is set approximately 15 degrees less than the flange angle requirement for the second hem pass. The final hem roller  1034  ( FIG. 30 ) includes a flat surface  1062  for bending the outer panel  1048  against the inner panel  1046  during a third hem pass, and a control surface  1064 . 
     The control surface  1069  of the first pre-hem roller  1057  is aligned with an edge  1066  of the anvil  1042  along a straight sight line  1068 . Further, the crown  1067  is positioned at and in engagement with a concave ride surface  1055  on the anvil  1042 . The concave ride surface  1055  positions the pre-hem roller  1057  at a proper distance d from the hem flange line. The concave ride surface  1055  and the sight line  1068  maintain proper roller position while the roller  1057  moves through a hemming operation. Similarly, the control surface  1075  of the second pre-hem roller  1059  is aligned with the anvil edge  1066  along the straight sight line  1068 , and the crown  1073  is positioned at and in engagement with a concave ride surface  1055 . Also, the control surface  1064  of the final hem roller  1034  is aligned with the anvil edge  1066  along the straight sight line  1068 . 
     When the first pre-hem roller  1057  is aligned with the concave ride surface  1055  and the sight line  1068 , the angled surface  1065  of the roller only contacts the hem flange at the end  1077  of the outer panel  1048 . Similarly, when the second pre-hem roller  1059  is aligned with the concave ride surface  1055  and the sight line  1068 , the angle surface  1071  of the roller only contacts the hem flange at the end  1077  of the outer panel  1048 . Therefore, variation in the width of the inner and outer panels  1046 ,  1048  does not affect the hem flange line or hem flange angle, and no reprogramming of the roller path is required. 
     To form a rope hem between the inner and outer panels  1046 ,  1048 , the robotic arm presses the first pre-hem roller  1057  against the concave ride surface  1055  and executes a first pass by moving the first pre-hem roller along a path in which the control surface  1069  is aligned with the anvil edge  1066 , thereby forming a 60 degree pre-hem flange bend in the outer panel  1048  ( FIG. 28 ). The robotic arm then presses the second pre-hem roller  1059  against the concave ride surface  1055  and executes a second pass by moving the second pre-hem roller along a path in which the control surface  1075  is aligned with the anvil edge  1066 , thereby forming a 30 degree pre-hem flange bend in the outer panel  1048  ( FIG. 29 ). The robotic arm then completes the flat hem by pressing the flat surface  1096  of the final hem roller  1034  against the outer panel  1048  and executing a third pass by moving the final hem roller along a path in which the control surface  1064  is aligned with the anvil edge  1066  ( FIG. 30 ). 
     In an eleventh embodiment shown in  FIGS. 31 through 33 , a first pre-hem roller  1179 , a second pre-hem roller  1181 , and a final hem roller  1134  may be rotatably mounted about their respective axes  1183 ,  1185 ,  1140  to a roller hemming head which is carried by a programmable multi-axis robotic arm (not shown). An anvil  1142  having a support surface  1144  supports an inner panel  1146  and outer panel  1148  for hemming. 
     The hem rollers  1179 ,  1181 ,  1134  are configured for forming a rope hem in the inner and outer panels  1146 ,  1148 . Each hem roller is dedicated for a specific roller hem pass. The first pre-hem roller  1179  ( FIG. 31 ) includes an angled surface  1187  for forming a pre-hem flange bend in the outer panel  1148  during a first hem pass, a crown  1189  for engagement with the anvil support surface  1144 , and a control surface  1191  for aligning the roller. The angle of the angled surface  1187  is set approximately 15 degrees less than the flange angle requirement for the first hem pass. Similarly, the second pre-hem roller  1181  ( FIG. 32 ) includes an angled surface  1193  for forming a pre-hem flange bend in the outer panel  1148  during a second hem pass, a crown  1195  for engagement with the anvil support surface  1144 , and a control surface  1197 . The angle of the angled surface  1193  is set approximately 15 degrees less than the flange angle requirement for the second hem pass. The final hem roller  1134  ( FIG. 33 ) includes a flat surface  1162  for bending the outer panel  1148  against the inner panel  1146  during a third hem pass, and a control surface  1164 . 
     The control surface  1191  of the first pre-hem roller  1179  is aligned with an edge  1166  of the anvil  1142  along a straight sight line  1168 . The alignment of the control surface  1191  with the anvil edge  1166  controls the distance d between the anvil edge  1166  and the hem flange bend  1170  in the outer panel  1148 , thereby maintaining an even hemming path. Similarly, the control surface  1197  of the second pre-hem roller  1181  is aligned with the anvil edge  1166  along the straight sight line  1168 , and the control surface  1164  of the final hem roller  1134  is aligned with the anvil edge  1166  along the straight sight line  1168 . 
     When the first pre-hem roller  1179  is aligned with the sight line  1168 , the angled surface  1187  of the roller only contacts the hem flange at the end  1177  of the outer panel  1148 . Similarly, when the second pre-hem roller  1181  is aligned with the sight line  1168 , the angle surface  1193  of the roller only contacts the hem flange at the end  1177  of the outer panel  1148 . Therefore, variation in the width of the inner and outer panels  1146 ,  1148  does not affect the hem flange line or hem flange angle, and no reprogramming of the roller path is required. 
     To form a rope hem between the inner and outer panels  1146 ,  1148 , the robotic arm presses the first pre-hem roller  1179  against the anvil support surface  1144  and executes a first pass by moving the first pre-hem roller along a path in which the control surface  1191  is aligned with the anvil edge  1166 , thereby forming a 60 degree pre-hem flange bend in the outer panel  1148  ( FIG. 31 ). The robotic arm then presses the second pre-hem roller  1181  against the anvil support surface  1144  and executes a second pass by moving the second pre-hem roller along a path in which the control surface  1197  is aligned with the anvil edge  1166 , thereby forming a 30 degree pre-hem flange bend in the outer panel  1148  ( FIG. 32 ). The robotic arm then completes the rope hem by pressing the flat surface  1162  of the final hem roller  1134  against the outer panel  1148  and executing a third pass by moving the final hem roller along a path in which the control surface  1164  is aligned with the anvil edge  1166  ( FIG. 33 ). 
     Although the invention has been described by reference to specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.