Abstract:
A roller hemming system for hemming nested panels includes a single hemming workstation providing for tooling exchange operations simultaneous with hemming operations. A plurality of robots that perform tooling exchange at the hemming workstation, movement of nested panels through the system, and hemming operations on nested panels at the hemming workstation. Nested panels are inputted into the system and hemmed nested panel assemblies are outputted from the system.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority of U.S. Provisional Application No. 60/997,810 filed Oct. 5, 2007. 
    
    
     TECHNICAL FIELD 
     This invention relates to a roller hemming system, and more particularly to a robotic roller hemming system that allows for a flexible product mix. 
     BACKGROUND OF THE INVENTION 
     It is known in the art relating to roller hemming that traditional roller hemming cells for large production volumes have multiple stations. In these conventional roller hemming cells, the hemming process is distributed over these multiple stations in order to support line rate or production throughput. Dividing the hemming across multiple stations increases the potential for dimensional variations in the final part product. When a flexible product mix is required, automation is added to the stations for tooling exchange. The tooling exchange is typically done by multiple slide mechanisms that are typically expensive and consume a substantial amount of floor space. Additionally, the tooling exchange automation negatively impacts production throughput due to the machine time required for tool exchange. 
     SUMMARY OF THE INVENTION 
     The present invention provides a roller hemming system that allows for the running of parts for multiple models at a line rate of 90 parts per hour with a batch of one model mix. In contrast to automation systems used in conventional roller hemming cells that move a fixture into and out of a work zone, the present invention utilizes robots to change out anvils and spiders, thereby increasing the line rate and flexibility of the present hemming process relative to conventional methods. The anvils are indexed to the hemming robot position by a turntable, which maximizes hemming robot processing time and reduces the overall robot quantity required. 
     The present system utilizes a robot having a robotic tool exchange mechanism that exchanges hemming anvils on a frame that is mounted on a turntable. A second robot carries a spider clamping device that mounts married inner and outer closure panels. The second robot presents the spider and mounted parts to the anvil mounted on the turntable frame. At this time, the spider is then secured to the anvil through a single low cost and compact clamping mechanism. The robot releases the spider assembly and then the spider transfer robot and the anvil transfer robot activate robot motion driven cornering units to bend the hem flange in the corner areas of the part. Cornering on the load side of the turntable increases available hem time in front of the hemming robots. Once the corners are bent, the first and second robots exit the anvil/spider load clearance zone, and the turntable rotates 180 degrees to present the closure panel for roller hemming. Multiple hemming robots, preferably three to five hemming robots, complete all outer periphery hemming. If required, additional roller hemming also may be performed on inside portions of the panels in areas such as glass channels on door sash portions. This additional roller hemming may be performed with a pull pressure roller head working from the opposite side of the closure panel. 
     The present system also allows for flexible change out, for both flexible production of multiple parts in a single line and for future model introduction into an existing production line. New/additional anvils and spiders can be introduced into the present hemming cell via exchange stands. Also, the anvils are designed so as to match the existing turntable frame in the hemming cell for easy integration into the hemming process. 
     More particularly, a roller hemming system in accordance with the present invention includes a single hemming workstation providing for tooling exchange operations simultaneous with hemming operations on nested panels. A plurality of robots perform tooling exchange at the hemming workstation, movement of nested panels through the system, and hemming operations on nested panels at the hemming workstation. Nested panels are inputted into the system and hemmed nested panel assemblies are outputted from the system. 
     In one embodiment, a roller hemming system for hemming nested panels includes a panel load robot that introduces nested panels into the system. A clamping spider load robot is adapted to interchangeably mount clamping spiders. The clamping spider load robot is cooperable with the panel load robot to transfer nested panels. A plurality of clamping spider storage stands are provided in combination with the clamping spider load robot. The clamping spider storage stands are disposed in proximity to and within reaching distance of the clamping spider load robot. Each clamping spider storage stand is adapted to store at least one clamping spider. An anvil load robot is adapted to interchangeably mount anvils. A plurality of anvil storage stands are provided in combination with the anvil load robot. The anvil storage stands are disposed in proximity to and within reaching distance of the anvil load robot. Each anvil storage stand is adapted to store at least one anvil. A turntable is disposed in proximity to and within reaching distance of the clamping spider load robot and the anvil load robot. The turntable is adapted to interchangeably support anvils, clamping spiders, and nested panels thereon. A plurality of roller hemming robots are disposed in proximity to and within reaching distance of the turntable to perform hemming operations on nested panels. An unload robot is cooperable with the clamping spider load robot. The unload robot receives hemmed nested panel assemblies from the clamping spider load robot and releases the hemmed nested panel assemblies from the system. 
     A roller hemming system in accordance with the present invention embodies a method of hemming nested panels. The method includes providing a single hemming workstation having a turntable adapted to simultaneously mount at least two anvils thereon at a first anvil mounting position and a second anvil mounting position. An anvil is mounted on the first anvil mounting position of the turntable using an anvil load robot. A clamping spider and an engaged set of nested panels is mounted on the anvil at the first anvil mounting position using a clamping spider load robot. The turntable is rotated to present the anvil and the mounted clamping spider and nested panels to a plurality of roller hemming robots. Hemming operations are performed on the nested panels using the roller hemming robots. While performing the hemming operations, at least one of the following steps is performed: (a) unloading a clamping spider and an engaged hemmed nested panel assembly from an anvil mounted on the second anvil mounting position of the turntable using the clamping spider load robot, (b) unloading an anvil from the second anvil mounting position using the anvil load robot, (c) mounting an anvil on the second anvil mounting position using the anvil load robot, and (d) mounting a clamping spider and an engaged set of nested panels onto an anvil disposed at the second anvil mounting position using the clamping spider load robot. 
     Hemming operations may be simultaneously performed from a front side and a back side of the nested panels. 
     At least one anvil may be stored on at least one anvil storage stand disposed in proximity to and within reaching distance of the anvil load robot. At least one clamping spider may be stored on at least one clamping spider storage stand disposed in proximity to and within reaching distance of the clamping spider load robot. 
     A set of nested panels may be loaded onto the clamping spider held by the clamping spider load robot using a panel load robot that engages the nested panels and presents the nested panels to the clamping spider load robot, wherein the nested panels are mounted on the clamping spider and released from the panel load robot. A hemmed nested panel assembly may be unloaded from a clamping spider mounted on the clamping spider load robot using an unload robot, wherein the clamping spider load robot presents the hemmed nested panel assembly to the unload robot, the unload robot engages the hemmed nested panel assembly, and the clamping spider load robot releases the hemmed nested panel assembly. 
     The unload robot may manipulate the hemmed nested panel assembly relative to a pedestal mounted roller hemming head to perform localized hemming operations. Cornering may be performed on the load side of the turntable before rotating the turntable to present the panels for hemming. 
     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 schematic view of a roller hemming system embodying the method in accordance with the invention; 
         FIG. 2  is a side view of a turntable on which an anvil, clamping spider, and nested metal panels are mounted; 
         FIG. 3  is a perspective view of nested metal panels clamped to an anvil by a clamping spider, and a plurality of roller hemming robots simultaneously performing hemming operations from front and back sides of the nested metal panels; 
         FIG. 4  is a schematic view of a hemming workstation including a turntable frame on which an anvil, clamping spider, and nested metal panels are mounted; and 
         FIG. 5  is a perspective view of an unload robot performing localized hemming operations on a nested panel assembly using a pedestal mounted roller hemming head. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1 through 5 , in a specific embodiment, a roller hemming system  10  in accordance with the invention includes an anvil load robot  12  such as a multi-axis robotic arm, and a plurality of anvil storage stands  14 . Each anvil storage stand  14  holds at least one anvil  50 . In the embodiment shown in the drawings, each anvil storage stand  14  may hold two anvils  50 . Each anvil  50  may be product specific for hemming a specific type (i.e., door panel, hood panel, etc.) and model of closure panel assembly. The anvil load robot  12  includes a tool exchange end effector such as a tool exchanger  34  that allows the anvil load robot  12  to interchangeably pick and release the anvils  50 . For example, the anvil load robot  12  may choose an anvil  50  from an anvil storage stand  14  by engaging the tool exchanger  34  with the anvil  50  on the stand  14 . Once the tool exchanger  34  is engaged with the anvil  50 , the anvil load robot  12  can release the anvil  50  from the stand  14  and manipulate the anvil  50  to other positions in the hemming system  48  as described in more detail below. To exchange the anvil  50 , the anvil load robot  12  returns the engaged anvil to an empty position  52  on a stand  14 , releases the engaged anvil, and chooses another anvil  50  from one of the stands  14  in the hemming system  48 . 
     The anvil load robot  12  further uses the tool exchanger  34  to exchange the anvils  50  on a frame  18  that is mounted on a turntable  20 . The frame  18  has a plurality of sides  56 , and at least two of the sides are capable of receiving and mounting an anvil  50  thereon. The anvil load robot  12  secures an anvil  50  from one of the anvil storage stands  14  using the tool exchanger  34 , manipulates the secured anvil  50  to the turntable frame  18 , mounts the anvil  50  onto the turntable frame  18 , and then releases the tool exchanger  34  from the anvil  50 . 
     The hemming system  48  further includes a clamping spider load robot  22  such as a multi-axis robotic arm, and a plurality of clamping spider storage stands  26 . Each clamping spider storage stand  26  holds at least one clamping spider  16  that can releasably hold a workpiece such as nested closure panels  24  and/or secure nested closure panels  24  to an anvil  50 . Each clamping spider storage stand  26  may hold two clamping spiders  16 . Each clamping spider  16  may be product specific for hemming a specific type and model of closure panel assembly (e.g., nested closure panels  24 ). The clamping spider load robot  22  may include a tool exchange end effector such as a tool exchanger  34  that allows the spider load robot  22  to interchangeably pick and release the clamping spiders  16 . For example, the clamping spider load robot  22  may choose a clamping spider  16  from a stand  26  by engaging the tool exchanger  34  with the clamping spider  16  on the stand  26 . Once the tool exchanger  34  is engaged with the clamping spider  16 , the clamping spider load robot  22  can release the clamping spider  16  from the stand  26  and manipulate the clamping spider  16  to other positions in the hemming system  48  as described in more detail below. To exchange the clamping spider  16 , the clamping spider load robot  22  returns the engaged clamping spider  58  to an empty position  52  on a stand  26 , releases the clamping spider  16 , and chooses another clamping spider  16  from one of the stands  26  in the hemming system  48 . 
     A plurality of anvil storage stands  14  and a plurality of clamping spider storage stands  26  may be generally disposed in semi-circles  62 . Also, a plurality of anvil storage stands  14  may be disposed generally opposite a plurality of spider storage stands  26 . 
     A married assembly load robot  66  such as a multi-axis robotic arm introduces married assembly workpieces such as pairs of inner and outer nested closure panels  24  into the system. The married assembly load robot  66  cooperates with the clamping spider load robot  22  to secure the nested closure panels  24  to the clamping spider  16  held by the clamping spider load robot  22 . Once the nested closure panels  24  are secured on the clamping spider  16 , the clamping spider load robot  22  manipulates the clamping spider  16  and nested closure panels  24  towards an anvil  50  mounted on the turntable frame  18 . The clamping spider load robot  22  aligns the clamping spider  16  and nested closure panels  24  with the anvil  50 , and when the clamping spider  16  and nested closure panels  24  are in proximity with the anvil  50 , the clamping mechanism  28  on the frame  18  secures the clamping spider  16  to the frame  18 , thereby also mounting the nested closure panels  24  on the anvil  50 . The clamping spider  16  engages the anvil  50  with register pins  68  and register surfaces  70  to accurately control the position of the clamping spider  16  in reference to the anvil  50 . The inner panel and outer panel positions are controlled by engagement pins  72  and surfaces  74  on the anvil  50  and clamping spider  16  to accurately control part dimensional relationships during the hemming process. 
     The clamping spider load robot  22  then releases from the clamping spider  16  and moves away from the turntable frame  18 . The clamping spider load robot  22  and the anvil load robot  12  then engage and activate the robot motion driven cornering units  76  to bend the hem flange in the corner areas of the part. The clamping spider load robot  22  and the anvil load robot  12  then move to a clear position for turntable  20  activation. The turntable  20  rotates to present the nested closure panels  24  for roller hemming with some or all of the corner pre-hems completed. For example, the turntable  20  may rotate 180 degrees to move the anvil  50 , nested closure panels  24 , and clamping spider  16  from a loading position  30  into a hemming position  32 . When the anvil  50  and mounted nested closure panels  24  are rotated into the hemming position  32 , the anvil  50  and nested closure panels  24  are accessible by a plurality of roller hemming robots  36  such as a plurality of multi-axis robotic arms that each include roller hemming end-of-arm tooling  40 . For example, in the embodiment shown in the drawings, the hemming system  48  includes three hemming robots  36  that perform hemming along the outer periphery  38  of the nested closure panels  24  from the inside panel location of the assembly, and one hemming robot  36  that may perform hemming along inner portions of the nested closure panels  24  from the outside panel location of the assembly as necessary. The system in different embodiments allows up to two hemming robots  36  working on the outer panel side and up to four robots on the inner panel side of the assembly. 
     While the roller hemming robots  36  perform hemming operations on the nested closure panels  24 , the clamping spider load robot  22  will unload a clamping spider  16  and hemmed panel assembly from the anvil  50  that is mounted on the turntable frame  18  180 degrees from the anvil  50  that is currently in the hemming position  32 . The clamping spider load robot  22  first engages the clamping spider  16  and releases the clamping spider  16  from the anvil  50 . The clamping spider load robot  22  then manipulates the clamping spider  16  and secured panel assembly and presents the panel assembly to an unload/pedestal hem robot  42  such as a multi-axis robotic arm. The unload/pedestal hem robot secures the panel assembly, and the clamping spider load robot  22  then releases the clamping spider  16  from the panel assembly. 
     At this time, the clamping spider load robot  22  may exchange the clamping spider  16  with another clamping spider stored on one of the clamping spider storage stands  26 . The clamping spider load robot  22  returns the current clamping spider  16  to the clamping spider storage stands  26 , releases the clamping spider  16 , chooses another clamping spider from the storage stands  26 , engages the new clamping spider, and removes the new clamping spider from the clamping spider storage stand  26 . 
     In a similar manner, after the clamping spider load robot  22  has removed the clamping spider  16  and hemmed panel assembly from the turntable frame  18  as described in the preceding paragraph, the anvil load robot  12  may change the anvil  50  that is mounted on the turntable frame  18  180 degrees from the anvil  18  that is currently in the hemming position  32 . The anvil load robot  12  engages the anvil  50 , releases the anvil  50  from the turntable frame  18 , returns the anvil  50  to the anvil storage stands  14 , and chooses another anvil from the anvil storage stands  14 . 
     The unload/pedestal hem robot  42  may include a robotic tool exchange end effector such as a tool exchanger  34  that allows the unload robot  42  to interchangeably pick and release clamping and localized hem anvil end effectors  44  that are stored on one or more storage stands  78 . Similar to the clamping spider load robot  22 , the unload robot  42  may pick and release clamping and localized hem anvil end effectors  42  from the clamping and localized hem anvil end effector storage stands  78 . The unload robot  42  uses the clamping and localized hem anvil end effectors  44  to secure hemmed panel assemblies  80  that are passed to the unload robot  42  by the spider load robot  22  as described above. For example, the spider load robot  22  presents a hemmed panel assembly to the unload robot  42  as described above. The unload robot clamping and localized hem anvil end effectors  44  mounted on the tool exchanger  34  of the unload robot  42  grip the hemmed panel assembly  80 , at which time the clamping spider  16  on the clamping spider load robot  22  releases the panel assembly  80 . 
     When the unload robot  42  secures a panel assembly  80  with the clamping and localized hem anvil end effectors  44 , the unload robot  42  may manipulate the clamping and localized hem anvil end effectors  42  and mounted panel assembly  80  towards a pedestal mounted roller hemming head  82 . The unload robot  42  then positions the clamping and localized hem anvil end effectors  44  and panel assembly  80  relative to the pedestal mounted roller hemming head  82  and moves the clamping and localized hem anvil end effectors  44  and panel assembly  80  such that the pedestal mounted roller hemming head  82  performs localized hemming operations on a localized portion  84  of the panel assembly  80 . After localized hemming operations are performed, the unload robot  42  releases the hemmed panel assembly  80  from the hemming system  48 . For example, the unload robot  42  may place the hemmed panel assembly  80  on a part storage rack or similar (not shown). 
     Although the invention has been described by reference to a specific embodiment, 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 embodiment, but that it have the full scope defined by the language of the following claims.