Patent Publication Number: US-2004056069-A1

Title: Method of engineering a process line for a flexible manufacturing system

Description:
FIELD OF THE INVENTION  
       [0001] The field of the present invention is process lines for fabricating an assembly from a plurality of subassemblies generated from various workpieces. The inventive method of the present invention is particularly useful in the development of process lines for automotive vehicle body assemblies.  
       BACKGROUND OF THE INVENTION  
       [0002] In the genesis of automotive manufacturing, vehicle bodies were carriages fabricated from wood and leather. Hence the term “horseless carriage” came to describe automobiles. Subsequently, vehicles were developed having a steel frame chassis which was connected with the drive train of the vehicle. A steel vehicle body was then mated with the chassis.  
       [0003] Initially, steel vehicle bodies were connected together primarily by rivets and threaded fasteners. Welding was not an option in many situations since the sheet metal was too thin to absorb the heat of most welding techniques. In the mid-20 th  century a welding technique was developed which could weld together relatively thin overlapping members of sheet metal, commonly referred to as spot welding.  
       [0004] In spot welding, a weld gun compresses a small portion of a joint of overlapping workpieces of sheet metal and applies pressure. Thereafter, an electric charge is delivered through the joint. The joint is heated until the metal of the joint is partially melted. The electric charge is stopped and the joint is allowed to cool wherein the metal of the two sheet metal workpieces is fused together.  
       [0005] The development of spot welding facilitated a tremendous advancement in vehicle body design. Now, structural components of the body could be fabricated from sheet metal which was folded into a desired tubular or other structural form, and then be welded together to form a structural beam. Therefore, the utilization of heavier plate members to provide the structural components of the vehicle body could be minimized.  
       [0006] Initially, most spot welding of vehicles was performed with equipment which could be either manipulated manually or via manual controls. In the early 1980s more and more equipment became available so that the spot welding function could be done robotically. Typically, the process lines which form a body is referred to as a body shop and are part of an assembly plant. The body shop typically receives stamped workpieces from a stamping facility which may be an on-site facility or a plant that is distantly located and serves several assembly facilities.  
       [0007] Typically, each vehicle line has its own body shop. When an automotive vehicle is updated for a major redesign, the body shop is typically scrapped and a new body shop is built from scratch within the assembly plant facility. The paint shop of an automotive vehicle assembly plant which receives the body, typically is utilized over and over again. However, the body shop is typically rebuilt and is therefore a tremendous consumer of tooling capital. This expenditure of tooling capital not only reduces profits, but also discourages model changeover. The lack of model changeover often causes a lack of consumer demand. Therefore, body shop capital costs generate a vicious cycle which can lead to very negative financial results for a vehicle manufacturer.  
       [0008] Another reason why the body shop consumes a large amount of capital is that the body shop has typically been customized to a given vehicle. Therefore, in most instances vehicles which are dissimilar in size and function cannot be made on a common body process line. Even vehicles which are the same, but are built in geographically separated assembly locations typically have different body process lines since the process lines are typically built to accommodate a specific assembly plant specific.  
       [0009] The lack of flexibility of body process lines not only leads to increased capital cost, but is also less efficient in the utilization of maintenance equipment and purchasing. Maintenance and the associated training cost of operational personnel is also increased. Attempts have been made to provide more flexible equipment, but most of these attempts have dwelt on variation in the path programming of robotic operations and the utilization of robots whose end effecters can be modified. This has generally not saved money and time.  
       [0010] It is desirable to provide a process line where the process line can accommodate a vehicle after a major redesign with a minimum capital cost.  
       [0011] It is desirable to provide a process line with greater flexibility so that a wider range of vehicle bodies can be processed on the same processing line.  
       [0012] It is desirable to provide flexibility in the processing line such that it may produce different vehicles, such that the vehicles can be made sequentially with each other and not require a major maintenance operation to change over the tooling.  
       [0013] It is desirable to provide a process line wherein engineering, maintenance, training and purchasing costs can be reduced.  
       SUMMARY OF THE INVENTION  
       [0014] To make manifest the above-delineated and other desires, a revelation of the present invention is brought forth. In a preferred embodiment, the present invention provides a method of engineering a process line for fabricating an assembly from a plurality of subassemblies generated from various workpieces. The method of the present invention includes a step of providing a plurality of standardized task stations. A determination is made of at least first and second templates. Each template comprises a defined set of task stations for producing a subassembly. A combination of templates which includes at least the first and second templates in a predetermined alignment is made to form the process line to fabricate the assembly.  
       [0015] The present invention provides an advantage in that engineering costs are significantly reduced due to the standardization of task stations.  
       [0016] Other advantages of the present invention will become more apparent to those skilled in the art as the invention is further revealed in the accompanying drawings and detailed description. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0017]FIGS. 1, 2 and  3  are perspective views of a trunnion used in the flexible manufacturing system of the present invention.  
     [0018]FIGS. 1A and 4 are perspective views of the tooling plate utilized with the trunnion shown in FIG. 1.  
     [0019]FIG. 5 is a perspective view of a three sided trunnion.  
     [0020]FIGS. 6 and 7 are perspective views of the locater heel blocks utilized in the aforementioned tooling plates and trunnions.  
     [0021]FIG. 8 is a perspective view of a turntable.  
     [0022]FIG. 9 is a perspective view of a task station of the present invention.  
     [0023] FIGS.  10 - 62  are templates of defined sets of task stations of the manufacturing system of the present invention.  
     [0024] FIGS.  63 - 78  illustrate various task stations of the manufacturing system of the present invention.  
     [0025] FIGS.  79 - 87  list templates that are discrete to passenger cars.  
     [0026] FIGS.  88 - 106  list templates that are discrete to trucks.  
     [0027] FIGS.  107 - 132  list templates which are common to both cars and trucks.  
     [0028] FIGS.  133 - 140  illustrate transfer task stations in the manufacturing system of the present invention.  
     [0029]FIG. 141 is an enlargement of a portion of FIG. 1.  
     [0030]FIG. 142 illustrates a pallet type transfer station with a turntable.  
     [0031] FIGS.  143 - 145  graphically illustrate a process line for producing an automotive vehicle car body.  
     [0032] FIGS.  146 - 149  graphically illustrate a process line for a truck-like vehicle.  
     [0033] FIGS.  150 - 152  illustrate vehicle bodies for a rear wheel drive truck, a uniframe passenger front wheel drive vehicle and a rear body on frame chasiss type vehicle respectively. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0034] The flexible manufacturing system of the present invention is demonstrated in the environment of a weld process line for assembling a body of an automotive vehicle. Metal components of the body assembly for an automotive vehicle are first acted upon in a metal stamping facility. In some instances, the stamping facility will be located next to a vehicle assembly plant. However, most automotive manufacturers have fewer stamping facilities than assembly facilities. Therefore, often the stamped metal workpieces are shipped by rail or truck to an assembly plant.  
     [0035] Upon arrival at the assembly plant, the stamped workpieces are delivered to the body shop of the assembly facility. In the body shop, the body shell of the vehicle is assembly primarily on a weld processing line as will be further explained. After the body shell of the vehicle has been assembled in the weld processing line, the body is delivered to the paint shop of the assembly plant, wherein the body is painted. Often, a prime coat applied to the body shell is white; hence the term body-in-white is often utilized when referring to the body assembly.  
     [0036] After the prime coat has been applied the body is then color-coated and typically, multiple clear coats of paint are applied over the color coat. The painted body is later married with the chassis components and the powertrain which is inclusive of the engine, the transmission and final drive shafts. At this time, in a body-on-frame type vehicle, the body will be married to the frame. The vehicle is typically then delivered to the trim portion of the assembly plant wherein the interior components and the seating are added to the vehicle.  
     [0037] An example of the flexible manufacturing method of the present invention includes engineering to provide an automotive vehicle body wherein components are primarily joined together by welding processes. The process line produces an automotive vehicle from a plurality of subassemblies which are generated from various combinations of workpieces. The process line is provided by a plurality of standardized task stations. To enjoy the greatest benefit from the present invention, the number of different task stations is limited.  
     [0038] At least one of the task stations in a given process line has a workpiece presenter. The workpiece presenter has a platform which in some instances, can move. Connected to the platform in a repeatable manner and precision located thereon, is a tooling plate. To produce a given subassembly of a vehicle body a determination is made to define a set of task stations, which is referred to as a template. A combination of at least two or more templates is aligned in a predetermined manner to form a process line which fabricates the body assembly.  
     [0039] Referring to FIGS.  1 - 7 , a preferred embodiment tooling plate  7  (sometimes called a tooling tray) is provided. The tooling plate  7  is utilized to fixture a workpiece (not shown) of an automobile vehicle body weldment subassembly (not shown). The tooling plate  7  includes a planar body  10 . The planar body as shown is typically provided by 1800 mm by 2400 mm, 25 mm thick plate.  
     [0040] In an automotive vehicle body weldment process line according to the present invention, there is typically several tooling plates provided having planar bodies standardized into 4-6 standardized dimensions. Tooling plate  7 , as best shown in FIG. 1A, has a series of positionally predetermined holes  11  formed therein by drilling and tapping. The holes  11  receive threaded fasteners extending therethrough (not shown) that connect the base plates  14  of various fixture tools.  
     [0041] Referring specifically to FIG. 4, a back surface  16  of the tooling plate has two longitudinal weldably attached stiffening channels  18 . The tooling plate  7  supports various fixture tools  32 ,  34  via their respective base plates  14 ,  36 . The fixture tools are typically a combination of locating fixtures such as locating pin  38  along with a pneumatically actuated clamp  40 . Various weldment workpieces can be loaded to the fixture manually or, as in most cases, robotically by a robot (not shown). Appropriate control logic will be utilized to synchronize the loading robot with the various clamps  40  which are provided.  
     [0042] The tooling plate  7  will typically mount the appropriate pneumatic or electric actuators required along with any pneumatic control devices required. The fixture tooling can in some instances, be a geo positioning function wherein the tooling positions two separate workpieces which are welded together by a welding robot (not shown). In other configurations, the fixture tooling will hold just one workpiece for welding or other various metal working operations. These operations can additionally be spot welding, burr removing or weld finishing operations. In still other operations, fixture tooling will position a workpiece or a subassembly for sealant or adhesive application operations.  
     [0043] Referring specifically to FIG. 2, a trunnion  50  is provided. The trunnion provides a platform for two tooling plates  7 . The trunnion  50  includes a stand  52  which includes A-frame legs  54 . An opposite end of trunnion  50  has a motor stand  56 . Rotatably mounted to the stands  52 ,  56  is a drum  58 . The drum  58  has rigidly connected thereto a supporting frame  60 . The drum  58  can be rotated along a horizontal via a drive train driven by a motor  62 . Positioned on frame  60  is a locater mechanism which includes three axis abutment locater heel blocks  64 ,  66 ,  68 .  
     [0044] Referring back to FIG. 4, tooling plate  7  has three axis abutment system heel blocks (sometimes referred to as plates)  70 ,  72 ,  74 . All of the heel blocks have a hole  76  which allows for receipt of a shank of a fastener  78 . The heel block  66  has a longitudinal locating axis block portion  80 . The heel block  64  has a longitudinal groove formed by recess step  82 . Step  82  is configured to be operatively associated with the block portion  80 .  
     [0045] The heel block  68  has perpendicularly extending block portions  84 ,  86 . Heel block  74  has recessed steps  88 ,  90 . Recessed steps  88 ,  90  are provided to make abutting contact with respective block portions  84 ,  86 .  
     [0046] The heel blocks provided on the frame  60  and on the tooling plate  7  provide a locater mechanism to allow the tooling plate  7  to be positioned in a precise, repeatable manner. The edge  94  of the tooling plate is aligned with a lower edge  100  of the frame. The steps  82  of the heel block  64  are aligned with the block portion  80 . Additionally, the recessed steps  88  are aligned with the block portions  84 . At this point, alignment is achieved in the horizontal axis. The tooling plate is then slid to the left causing the recessed steps  90  to be abutted against the block portion  86 . Alignment is then achieved in the horizontal axis or the transverse axis of the tooling plate  7 .  
     [0047] Threaded fasteners are utilized to connect the tooling plate  7  with the frame  60  which extends through the holes  76 . The thicknesses of the heel plates, when the threaded fasteners are torqued, sets the position of the tooling plate  7  in the Z-axis (a direction generally perpendicular with the surface of the planar body  10  of the tooling plate). The tooling plate has eight standoffs  101 . The standoffs  101  (FIG. 4) extend outwardly further than the locater heel blocks. The standoffs  101  prevent the locater heel blocks from coming in contact with any flat surface, such as the factory floor, which the tooling plate  7  may be placed upon when the tooling plate is removed from the platform (frame  60 ). When the tooling plate is attached to the frame  60 , the standoff  101  will project through an aperture  102  provided in the trunnion frame  60 .  
     [0048] As shown in FIG. 1, trunnion  50  can have two identical tooling plates  7 . Often, one tooling plate will be utilized for loading a workpiece or workpieces to the tooling plate, while a robot is performing an operation on the workpiece or workpieces on the other tooling plate. In other applications, the two tooling plates can have fixture tools for workpieces which differ from one another. On one trunnion side, the fixture tools may fixture two workpieces for a passenger car. On the other trunnion side the workpieces may be for a truck.  
     [0049] A quick disconnection  111  for a line supplying air for the pneumatic actuators is made via a connector box  110  provided on the trunnion  50 . An enlargement of a multiple electrical quick connector  113  is shown in FIG. 141.  
     [0050] Referring in particular to FIG. 5, a three tooling plate trunnion  130  is provided. The trunnion  130  is very similar to that aforedescribed in FIGS.  1 - 3 , with the exception that it can hold three tooling plate (not shown). Typically, the tooling plates utilized in trunnion  130  will be smaller members than the tooling plates shown in FIG. 4. However, the same locating and connective principles will apply. Such a trunnion will typically be utilized for smaller subassemblies or operations associated with manual machines.  
     [0051] The trunnion  130  has a frame  132  which is provided with heel blocks  134 ,  136 . A motor is provided through appropriate gearing to turn a horizontally mounted shaft  140  which is journaled at one end by a bearing  142  supported on a stand  144 . An opposite side stand  148  supports an opposite end of the shaft  140 .  
     [0052] Referring to FIG. 8, a turntable  150  is provided. The turntable  150  has a base plate  151 . Supported on the base plate  151  is a rotary base  152 . A motor (not shown) turns a rotary table  153  about a vertical rotational axis. The rotary table  153  is rigidly connected to four geometrically spaced frames  154 . Frames  154  have a series of heel blocks  155  similar to those previously explained, to provide a three axis abutment locater system. Precision located in a repeatable manner by the heel blocks  155  on each frame  154 , are tooling plates  156 A,  156 B,  156 C and  156 D  
     [0053] Turntable  150  in some instances will have fixture tooling which may be exclusively dedicated to a given subassembly formed by two or more workpieces. In an alternative arrangement, the turntable will provide multiple tooling plates for a first subassembly which is materially different than that of a second subassembly. The difference can be that of between passenger cars and trucks and sports utility vehicles, front-wheel drive and rear-wheel drive vehicles, or vehicles having a body that is married to a chassis having its frame, or unibody type vehicles wherein a portion of the vehicle is formed to provide for its frame portion. In such situations, the turntable  150  will be programmed to present to an operational tool (such as a robot spot welder or a robot sealant or adhesive applicator) in a selective, non sequential manner, the intended workpiece.  
     [0054] A flexible manufacturing system according to the present invention preferably utilizes sixteen standardized flexible shop task stations.  
     [0055] Task station  1  (FIG. 64) is a tabletop fixture, having tilt platform  402  for mounting tooling plate  404 , and at least one robot  406 . Tilt platform  402  accommodates tooling plate  404  by tilting from the horizontal to a convenient easel-like angle as shown in FIG. 65. The tilting feature allows an operator, whether human or otherwise, to reach fixtures (not shown) mounted upon tooling plate  404  so as to mount a workpiece when tilt platform  402  and tooling place  404  are in the tilted position, with tooling plate  404  and platform  402  being returned to the horizontal position for welding or sealer application, or other operations performed by one or more robots  406 . If welding is desired, robots  406  may be equipped with a weld gun  436 , as shown in FIG. 67. The fixture shown in FIGS. 64 and 65 may preferably accommodate tooling plates ranging in size from about 900×1200 mm to about 1800×2400 mm.  
     [0056] The welder robot  406  employed in task station  1  (FIGS. 64 and 65) may be a completely robotic welder or otherwise. Other units which may be used with task station  1  include robotic material handling devices utilizing a custom design gripper to remove a part assembly from a fixture mounted upon tooling plate  404 , or a combined robotic material handler and welder combination. As another option, the work envelopes of robots  406  may be increased by using a 7th-axis slide.  
     [0057] Task station  2  (FIG. 63) is a hexapod manipulator task station. As used herein, the term “hexapod manipulator” means a compact robot having six electrically driven, computer operated ball screws,  409 , which hold and position a workpiece. Here, hexapod manipulator  410  uses clamps  414  and pins  416  to precisely hold a workpiece for welding by means of pedestal welding machine  418 . Unlike welders attached as an end effector to a movable robot, pedestal welder  418  does not move; rather the workpiece must be brought to welder  418 . Pedestal welder  418  may be supplemented or even supplanted by a projection weld gun unit (not shown) which includes a transformer, cables and weld controller, with hexapod  410  manipulating the workpiece into the weld gun of pedestal welder. As yet other alternatives for task station  2 , a sealer dispensing unit (not shown) may be used to place sealer on certain surfaces of a workpiece while the workpiece is positioned by hexapod manipulator  410 . Finally, a nut feeder with a hopper and a feeder tube (not shown) may be used to supply nuts which can be welded or mechanically fastened in place upon the work piece.  
     [0058] Task station  3  (FIG. 66) is a pedestal welding task station having robot  424  for positioning a workpiece. When task station  3  is employed, an operator, human or otherwise, will position the workpiece parts within fixtures  425  attached to tooling plate  426 , which is mounted at bench height. Then, end effector  428 , which is a gripper, and robot  424  will pick up the parts from tooling plate  426  and move them either to a pedestal welder of the type shown in FIG. 63 for task station  2 , or a projection welder or a sealer dispenser (not shown).  
     [0059] Task station  4  (FIG. 67) is a dual station having a seventh-axis slide to increase the work envelope of robot  432 . As shown, task station  4  may have dual tooling plates  434  and may utilize either a shared robot  432 , or multiple robots. A variety of tooling plates may be used, with several different sizes extending from approximately 900×1200 mm to the largest at about 1800×2400 mm. Welding gun  436  handles the task of supplying the localized current and electrodes needed for a spot or fusion welding operation.  
     [0060] As described above, robotic welding units or material handler robots or material and welder combination robots may be employed with this task station. Also, the tooling plate orientation may be zero° or flat, 30° angled or 70° angled. An important point here is that interchangeable tooling plates or plates allow repeatable and precise positioning of parts.  
     [0061] Task station  5  (FIGS. 5 and 68) includes a three-sided trunnion fixture  442 , which may be equipped with three tooling plates  444  (FIG. 68) and which rotates about a horizontal axis so as to present workpieces to welding robot  446 . FIG. 5 illustrates trunnion fixture  442  with the tooling plates removed, and without robot  446 .  
     [0062] FIGS.  1 - 3  illustrate the aforementioned two-sided trunnion  50 , which is a second larger version of task station  5 , and which too rotates about a horizontal axis, and which accepts a standard tooling plate  7 , albeit of a larger size than the tooling plates employed with the three-sided trunnion fixture  130 . Two-sided trunnion  50  also functions as a workpiece presenter, preferably for a welding or sealing operation.  
     [0063] As shown in FIG. 1, tooling plate  7  has a plurality of tooling fixtures  34  mounted thereon. Tooling fixtures  34  include a plurality of locating pins  38 . This tooling plate setup has quick disconnect  111  for pneumatic service (not shown).  
     [0064] Task station  6  (FIG. 8) is a four-sided turntable fixture  460  having four positions and which mounts four standard tooling plates  450 . Turntable  460  would be expected to be constructed in approximately three different capacity ranges from 6500 lbs. total capacity to 20,500 lbs. total capacity. This largest turntable could accommodate tooling plates up to 1800×2400 mm.  
     [0065] As shown in FIG. 69, robotic welding could be accomplished by at least one welding robot  464 . Although multiple tooling fixture modules  452  are shown as being attached to tooling plates  450 , those skilled in the art will appreciate in view of this disclosure that other types of tooling arrangements could be selected. Robotic material handling is another option as is a combination material handler and welder (not shown). Finally, a seventh-axis slide (not shown) may be used to increase the welding robot&#39;s work envelope.  
     [0066] Task station  7  (FIG. 70) is an indexing tooling plate task station having two tooling plates  468  which are independently controlled and which are preferably loaded by a human operator. Tooling plates  468  are mounted to indexing shuttle mechanism  470  which indexes the loaded tooling plates and attached workpieces into a welding or sealing zone. Up to five welding or sealing or machining robots  472  or other types of robot may be used with task station  7 . Because shuttle  470  travels perpendicular to the material system flow, operators may load parts from three sides of the fixture and one additional slide mechanism  474  and material handling robots  476  may be accommodated on the opposing side. Task station  7  may be used with robotic welders or robotic material handlers or combination robotic material handler and welder robots, as previously described.  
     [0067] Task station  8  (FIG. 71) is a laser welding task station equipped for receiving a very large tooling plate (not shown) by means of roller bed  482 . This large tooling plate is often termed a “pallet” in the trade. Although two laser welding robots  484  are shown, additional robots, or even a single robot, could be used with this task station. Additional equipment which could be employed with task station  8  according to the needs of someone wishing to practice the present invention could include a robot vision system to track a laser robot, or a seventh axis slide to increase the robot&#39;s work envelope.  
     [0068] Task station  9  (FIG. 72) includes press welding fixture  486  which allows many spot welds to be made in a short period of time. This type of fixture has been in use for many years in automotive assembly plant body shops, but without the addition of the inventive tooling plate system, and without being part of a standardized task station system according to the present invention.  
     [0069] Task station  10  (FIG. 73) is a schematic representation of a task station which may include either a conventional hemmer or a clincher or a piercer. A robotic material handler may be used with this task station to remove processed assemblies or subassemblies.  
     [0070] Task station  11  (FIG. 9) has two sliding tool plates  514  and multiple robots. Tooling plates  514  are mounted on common indexing shuttle  515 . The robots include four robots  516  for welding and three slide-mounted robots  518 ,  519 , and  520  for handling material. Robots  519  and  520  allow workpieces to be placed on either one of tool plates  514  depending on the mix of parts needed from task station  11 . It should be noted that the slides for robots  519  and  520  are neither parallel to each other nor perpendicular to the center axis of indexing shuttle  515 . Optionally, robots  516  may be either welding robots or could be other types of robots such as sealing or adhesive dispensing units.  
     [0071] Task station  11  provides a very high level of flexibility because the diverging arrangement of the slide mounts for material handling robots  519  and  520  allow for large, extensive feeder stations (not shown) which may accommodate a very wide range of component parts and sub-assemblies. This flexibility is extremely useful in conjunction with the capability to process multiple parts with tooling plates  514 .  
     [0072] Task station  12  (FIG. 74) which has provisions for receiving pallet  525  on roller bed  526 , is a vision task station containing optical measuring devices and fixtures for performing inspections using four robots  522  and cameras  524  with associated calibration equipment. Optionally, a smaller or larger number of cameras and robots could be employed with this task station.  
     [0073] Task station  13  (FIG. 75) is a sealer applying task station having two robots  506  which apply either adhesive, or sealer or mastic stored in tanks  508 . Although a larger tooling plate  507  is illustrated in FIG. 75, as with other task stations, either a smaller tooling plate or a large pallet could be employed for handling workpieces. If a pallet is used, task station  13  could have a roller bed for accommodating the pallet system.  
     [0074] Task station  14  (FIG. 76) is a welding task station including dual shuttling tooling plates (not shown) mounted upon shuttle drive  504 , and four robots  498  mounted on balconies  502  which allow robots  498  to reach down to operate on workpieces carried upon the tooling plates as they move back and forth under robots  498 . The sliding tooling plates provide model mix capability. In other words, different types of vehicles may be handled without the need for tooling change over.  
     [0075] Task station  15  (FIG. 77) is a welding task station used for large assemblies and includes roller bed  492  for accommodating a pallet (not shown) and may utilize not only the six illustrated robots  494 , but also robotic welders or sealing or adhesive application robots. Alternatively, a smaller number of weldbots (welding robots) could be employed, either alone or with adhesive or sealer applying robots.  
     [0076] Task station  16  (FIG. 78) is schematic representations framer which is used to join a vehicle body side to an underbody. In use, the underbody would be mounted upon a pallet and brought into a roller bed  550  that is incorporated in task station  16 . Gate fixture  552  is used to mate the body side with the underbody while the underbody is on the pallet, to permit welding of the body side and underbody. If desired, task station  16  equipment may be augmented by an overhead balcony holding additional robots or an indexing unit and extra gate so as to accommodate other body configurations.  
     [0077] The flexible manufacturing system also has standardized transfer task stations to move workpieces and subassemblies between various templates and operational task stations. A first transfer task station is provided by a robot  555  (FIG. 133) transferring between any of the aforementioned task stations  1 - 16 . Referring to FIG. 134, a second transfer task station comprises a gravity powered over and under conveyor  554 , which is typically supported by overhead hangers  556 . Referring to FIG. 135, a third transfer task station is provided by an electrically powered over and under conveyor  558 , which is suspended from overhead hangers  560 . A fourth transfer task station is provided by an enclosed track monorail  562  (FIG. 136). A fifth transfer task station is provided by an exposed monorail  564  (FIG. 137 partially shown). A sixth transfer task station is provided by an electrified monorail  570  (FIG. 138). A seventh transfer task station is provided by a pallet transfer system  572  (FIG. 139) which has a roller/chain delivery for heavier subassemblies. An eighth transfer task station is provided by an overhead bridge crane  574  (FIG. 140). A pallet  580  with a turntable is shown in FIG. 142.  
     [0078] As mentioned previously, the process line is formed by a plurality of templates which are combined in a predetermined alignment to form the process line. The process line can be made flexible in different ways. First, the process line can be made flexible so that a first set of different subassemblies can be manufactured on the process line which differ from one another. These different subassemblies can be manufactured simultaneously due to the presence on the process line of workpiece presenters which have a tooling plate for each separate subassembly. In rare instances where the process line is dedicated to one type of vehicle, the entire process line can be quickly retooled by changing the appropriate tooling plates and reprogramming the robotic operators. However, in most instances, flexibility is chiefly accomplished by having workpiece presenters with tooling plates for all types of subassemblies desired.  
     [0079] Examples of vehicle differences are two similar vehicles having different structures and various differences in body components, while having similar basic dimensions. Other examples are a process line for a different series of passenger vehicles.  
     [0080] In some instances it may be desirable for the process line to provide a body portion for two separate assembly lines which vastly differ from one another, such as a passenger car line assembly line and a light truck vehicle assembly line. In other instances, the different assembly plants may include a front-wheel drive vehicle assembly plant and a rear-wheel drive vehicle. In still other instances, the assembly plants may be for a unibody-type passenger vehicle and a body-on-frame-type passenger vehicle.  
     [0081] To minimize resources required, a determination is made of which task stations are required to form a given subassembly.  
     [0082]FIG. 61 provides an arrangement of template  700  for producing a lift gate assembly of the vehicle. The lift gate is a rear end enclosure of a hatchback. An outer panel is geopositioned (rigidly clamped and located) with reinforcements into a welding task station  6  noted as item  702 . From the task station  702 , via a number one transfer task station (robotic delivery not shown), the outer panel with its welded reinforcement is sent to a supplemental spot welding task station  3 , item  704 . From task station  3 ,  704  by robotic transfer the outer panel is delivered to a task station  3 ,  706  wherein sealant is applied. Simultaneously, the inner panel along with reinforcements is delivered to a geopositioning task station  6 ,  712  where welds are performed which fix the position of the inner panel and its reinforcements. The inner panel is then delivered to two supplemental weld task stations  3 ,  714  and  716 .  
     [0083] In a geopositioning weld task station  10 ,  718  the inner panel is mated with the outer panel. Subsequent to the weld task station  10  the mated panels are delivered to two supplemental weld task stations  10 ,  720  and  722 . By robotic transfer, the lift gate assembly is then delivered to a hemming task station  10 ,  724  wherein the outer panel is hemmed over the inner panel. The lift gate assembly is then delivered to a storage line  726  with queue  6  lift gate assemblies. The storage line acts as a buffer. The storage line is sometimes called a decouple.  
     [0084] The lift gate assembly is then robotically transferred from a storage station  726  to a task station  10 ,  730  which applies sealant. The lift gate assembly is then robotically transferred to a task station  3 ,  732  where additional sealant is applied. The lift gate assembly is then transferred to a task station  3 ,  734  where portions of the sealant are induction cured. The lift gate assembly is then transferred to another task station  3 ,  736  where there is a secondary induction cure. The lift gate assembly is then prepared to send to the closure of the main delivery line, shown in FIG. 145.  
     [0085] As mentioned previously, the lift gate assembly template  700  has two re-spotting task stations  10  noted as items  720  and  722 . The maximum feed rate of the lift gate assembly is approximately  40  lift gate assemblies per hour. If desired, re-spot task station  722  can be eliminated and the number of welds completed at the geopositioning weld task station  10 ,  718  can be increased along with an increased number of welds at re-spot task station  10 ,  720 . A thirty lift gate assembly feed rate will be established.  
     [0086] If a thirty lift gate assembly per hour completion rate is acceptable, then additional flexibility options may be realized. Task station  10 ,  720  may be dedicated to a first subassembly which is utilized for body-on-frame type vehicles (like rear wheel drive passenger car  742 , FIG. 152) and task station  10 ,  722  may be a dedicated task stations for unibody frame-type passenger car vehicles (like front wheel drive vehicle  744 , FIG. 151).  
     [0087] The lift gate assemblies in their initial phases of engineering will be stamped with holes so that the tooling prior to and including the weld geopositioning task station  10 ,  718  can be common to both types of passenger vehicle bodies. Thereafter, the differences in the lift gate assemblies will be accommodated in the task stations  724   730 ,  732 ,  734  and  736 .  
     [0088] Templates of subassemblies shown in FIGS.  10 - 18  are discrete for car body assemblies. Templates of subassemblies shown in FIGS.  19 - 37  are discrete for truck body assemblies. Templates shown in FIGS.  37 - 52  are common to car and truck bodies. By combining the templates in a predetermined manner, the process lines as shown in FIGS.  143 - 145  and  146 - 149  for the materially different cars and trucks are provided, resulting in a vehicle body which is delivered to the paint shop.  
     [0089] Referring to FIGS.  79 - 87 , the flexible manufacturing system of the present invention has a first set of templates drawn from a set of standardized task stations for manufacturing subassemblies of a portion of a first type of vehicle. In like manner, FIGS.  97 - 105  provide templates drawn from a defined set of task stations utilized to form a process line for certain subassemblies of a second type of vehicle which materially differs from the first type of vehicle. It should be noted that the subassemblies of FIG. 1 are not just for one first type of vehicle, which in the instance is a passenger car, but it can be for a family of passenger cars. In like manner, the templates noted in FIGS.  88 - 106  are for a family of truck vehicles  831  (FIG. 150).  
     [0090] FIGS.  107 - 132  are a listing of templates which have been determined to be common for a process line for making cars and for producing trucks. In engineering a process line, if it is desirable to produce cars, templates of FIGS.  79 - 87  will be combined to form the process line. If it is desirable to produce trucks, templates of FIGS.  89 - 106  will be combined to produce the process line. The templates which are discrete to cars and the templates which are discrete to trucks will both be combined with the templates of FIGS.  107 - 132  which are common to both sets of assemblies if it is desirable for the process line to produce both types of vehicle bodies. In some instances, a space can be reserved in a template for future models.  
     [0091] As mentioned previously, although the sets of vehicle assemblies have been explained in a situation of passenger cars and trucks, in other instances the families of vehicles will differ in that one family will be rear-wheel drive and the other family will be front-wheel drive. Another variation is for vehicles having a unibody construction and vehicles having a body mounted on frame type construction.  
     [0092] Various embodiments of the present invention have been shown in the application of a process line for automotive vehicle car bodies. It will be apparent to those skilled in the art of the various modifications and changes which can be made to the present invention without departing from the spirit and scope of the invention as it is embodied in the accompanying claims.