Abstract:
A lower die or nest apparatus is described to create a hemming environment that locates and holds a metal panel to a frame using suction in a manner that substantially resists said loads on the panel without damage or deformation. The vacuum nest includes a frame made of a rigid material with an outer work surface and an interior region with a sealed elongated channel shaped to the contour of the metal panel. A polymeric rope is inlayed within a groove formed in the interior region to form the sealed elongated channel. A support member may be formed within the channel by inlaying additional polymeric ropes into grooves formed within the channel. A vacuum source is fluidly coupled with the sealed elongated channel to create a downward force by evacuating the volume of the channel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in part of pending U.S. Ser. No. 11/679,731, filed Feb. 27, 2007 which is a continuation in part of U.S. Ser. No. 10/521,655 filed on Jan. 14, 2005, now U.S. Pat. No. 7,254,973 issued Aug. 14, 2007 which is a National Phase of PCT/US04/38993 filed Nov. 19, 2004 which claims priority to U.S. Provisional Application No. 60/523,961 and to U.S. Provisional Application No. 60/524,080, both filed Nov. 21, 2003. This application is also a continuation in part of pending U.S. Ser. No. 10/521,652 filed Jan. 14, 2005 which is a National Phase of PCT/US04/034238 filed Oct. 15, 2004 which claims priority to U.S. Provisional Application No. 60/511,468 filed Oct. 15, 2003. The entire disclosure of the above-referenced applications are incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates to systems for holding and aligning a first sheet material and a second sheet material for the joining thereof. More particularly, the present invention relates to an apparatus for holding a first sheet material and a second sheet material that utilizes a vacuum assembly for holding the first sheet material in place during the alignment of the second sheet material thereto and during the joining of the first sheet material to the second sheet material. 
     BACKGROUND 
     One of the earliest operations required in the history of automobile assembly was the joining of an inner panel to an outer panel to form any of a variety of body parts, including doors, engine hoods, fuel tank doors and trunk lids, all referred to as “swing panels” which enclose an opening in the vehicle body. Known machines for the forming and joining of sheet materials include the press-and-die set, and the tabletop and roller-forming tool, the latter being the most-recently introduced device. 
     An unfortunate feature of joining materials is that the sheets tend to become misaligned with each other before or during the joining operation, in part due to the lateral forces applied to the panels during the hemming operation. Certain efforts have been undertaken to overcome this problem. 
     One known effort employed to prevent the skidding of one sheet relative to the other has been to apply an upper pressure ring from above the sheet materials, thereby pinching the upper and lower sheets between the upper pressure ring and the lower nest member. This practice leads to the consumption of much of the workspace above the sheet materials. In addition, the use of the upper pressure ring requires a high-powered overhead device to effect operation. All considered, the use of the upper pressure ring is costly, inefficient and inconvenient. 
     An additional known practice to prevent skidding of two sheets during joining is to align the two sheets relative to one another from the side using side gauges. This operation, while offering certain advantages over the use of the upper pressure ring in terms of cost, space and equipment, does a poor job of controlling movement of the sheet materials. Fixture in the form of clamps around the perimeter of the panels ring also be employed to secure the panels. The use of gauges and clamps also leads to defacing of the sheet material through scratching during loading and unloading of the sheet material. Importantly, during operation, the gauges interfere with the travel of the forming tool. In some instances, if the gauges are spring-loaded, the rolling tool may be shocked and may suffer a pressure bounce when struck. 
     An additional practice has been to simply position one sheet above the other without holding, this latter approach clearly being the least desirable. 
     Prior approaches to the problem of forming and joining two sheet materials together while restricting movement of the sheets relative to one another had failed. While improving the state of the art, the method and apparatus of co-pending application Ser. No. 10/521,652 to Campian still had remnant sheet material movement. Moreover, even with that improvement, the manufacturing and precise positioning of the vacuum chamber(s) is complex and repair difficult. 
     Accordingly, prior approaches to solving the problem of providing a method and apparatus for forming and joining two sheet materials together while restricting movement of the sheets relative to one another have failed to overcome the problem. 
     SUMMARY 
     The system and method described herein streamlines the fabrication process of conventional lower nest assembly as described in Ser. No. 10/521,652 to Campian, thereby improving its effectiveness. The manufacturing accuracy increases as a computer numerically controlled mill can precisely cut grooves into the rigid top surface of the lower nest member. Polymeric seals are positioned within these grooves to form sealed elongated chambers which seal against a metal panel. So configured, the elongated chambers are coupled to a vacuum system which evacuates the elongated chambers for generating a downward clamping force sufficient to laterally immobilize the metal panel prior to execution of a metal forming procedure such as a hemming operation. The use of a nest with a vacuum clamping assembly formed within the lower die by a series of polymeric seals streamlines manufacturing in comparison to the molded chambers of U.S. Ser. No. 10/521,652 which require detailed machining and assembly to form an adequate sealed chamber. 
     The system described herein overcomes the problems of known techniques for forming and joining a first sheet material to a second sheet material to create a swing panel for an automobile. The machine cell described herein provides a definite method for aligning and securing a first panel to the lower nest and for aligning and securing the second panel to the first panel. Specifically, the system includes a vacuum nest for securely holding a metal panel during an edge hemming operation. A frame having a material contacting surface along an outer boarder of the frame conforms to an edge of a metal panel for providing support during the edge hemming operation. A relieved surface located interior and subjacent to the material contacting surface has a groove formed therein adjacent said material contacting surface. A polymeric seal is partial located with the groove and extends above the relieved surface to define a sealed elongated channel adapted to conform to the metal panel. A vacuum source is in fluid communication with the elongated channel and operates to evacuate the sealed elongated channel for generating a downward clamping force sufficient to immobilize the metal panel during the edge hemming operation in a direction generally parallel to the material contacting surface. 
     The vacuum nest may be incorporated into a larger machine cell may includes an array of crowders to align the first panel on the vacuum nest. The machine cell may also include an upper gate for aligning and holding a second panel relative to the first panel. As a result, the system and method described herein provides a machine cell which is efficient, cost-effective, and flexible enough to accommodate panels of various sizes, shapes, and contours. 
    
    
     
       DRAWINGS 
       The present invention will be more fully understood by reference to the following detailed description of the preferred embodiments when read in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout the views, and in which: 
         FIG. 1  is a perspective view of the preferred embodiment of the present invention; 
         FIG. 2  is a sectional view taken along lines  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a perspective view of the upper gate of the present invention; 
         FIG. 4  is a sectional view of a spring plunger according to the present invention; 
         FIG. 5  is a top plan view substantially illustrating a sample inner sheet material or the support structure that forms the inner part of the resulting joined component; 
         FIG. 6  is a perspective view substantially illustrating the top of the lower nest member shown in  FIG. 2 ; 
         FIG. 7  is a perspective view substantially illustrating the top of an alternate lower nest member with sealed chambers similar to those illustrated in  FIGS. 2 and 6 ; 
         FIG. 8  is a sectional view taken along lines VIII-VIII of  FIG. 7 ; 
         FIG. 9  is a top plan view of an alternate seal configuration of the lower nest member illustrated in  FIG. 7  for supporting a vehicle roof panel having a sunroof opening; 
         FIG. 10  is a cross-sectional view through a portion of the nest shown in  FIG. 9  taken along line X-X; and 
         FIG. 11  is a top plan view of an alternate seal configuration of the nest illustrated in  FIG. 7  for supporting a vehicle hood. 
     
    
    
     DETAILED DESCRIPTION 
     The drawings disclose the preferred embodiment of the present invention. While the configurations according to the illustrated embodiment are preferred, it is envisioned that alternate configurations of the present invention may be adopted without deviating from the invention as portrayed. The preferred embodiment is discussed hereafter. 
     With reference first to  FIG. 1 , the preferred embodiment of a machine cell, generally referred to as  10 , is illustrated in a perspective view. The machine cell  10  includes an upper gate  100  and a lower nest  200 . It should be understood that the configuration of the machine cell  10  as illustrated is preferred, but is not to be interpreted as limiting as other configurations conceivable to those skilled in the art may also be suitable. 
     The present invention serves to hold two portions of sheet material so that a joining process may be undertaken without the sheet material portions being caused to shift or otherwise move out of position. The two portions of sheet material include a first sheet material A and a second sheet material B. The two sheets A and B, in a combination resulting from joining and forming becomes an integrated component, of which the first sheet material A is the outer part or the skin and the second sheet material B is the inner part or the support structure. (This latter material is illustrated, by way of example, in  FIG. 5 , discussed below.) As illustrated, the first sheet material A and the second sheet material B have a generally square configuration resulting in a generally square-shaped integrated component. However, it is to be understood that other shapes may be suitable for use in the present invention. 
     In brief, the married sheet materials A, B are approximated onto the lower nest  200 . The first sheet material A is then precisionly positioned by means of crowders, which will be discussed below primarily in relation to  FIG. 1 . Thereafter the upper gate  100  aligns the second sheet material B with respect to the first sheet material A by alignment pins as will be discussed below primarily in relation to  FIG. 3 . The first sheet material A is held in place by a vacuum applied to its under side. Thus held in place, a forming and joining operation may be effected for clinching the first sheet material A to the second sheet material B. 
     The upper gate  100  is shown in perspective view in relation to the entire machine cell  10  in  FIG. 1 , in sectional view in  FIG. 2 , and by itself in perspective view in  FIG. 3 . As illustrated in these figures, the upper gate  100  includes a main shaft  102  that is attached to a robotic arm or linear slide attachment shaft  101 . The main shaft  102  is fixed in a substantially perpendicular position with respect to the robotic arm attachment shaft  101 . 
     Pivotally attached to the main shaft  102  are three substantially parallel contact plunger support shafts  104 ,  104 ′,  104 ″. Each of the plunger support shafts  104 ,  104 ′,  104 ″ is attached to the main shaft  102  by a lockable swivel joint illustrated as lockable swivel joints  106 ,  106 ′,  106 ″. The lockable swivel joints  106 ,  106 ′,  106 ″ allow the support shafts  104 ,  104 ′,  104 ″ to be rotated with respect to the main shaft  102  thereby accommodating a variety of panels of different sizes and shapes. The composition of the shafts  102 ,  104 ,  104 ′,  104 ″ may be from a range of materials, including steel or aluminum. 
     Each of the plunger support shafts  104 ,  104 ′,  104 ″ preferably includes at least two contact plunger assemblies for firmly urging the second sheet material B against the first sheet material A. Specifically, contact plunger assemblies  108 ,  108 ′,  108 ″ are rotatably attached to the plunger support shaft  104 , plunger assemblies  110 ,  110 ′ are rotatably attached to the plunger support shaft  104 ′, and plunger assemblies  112 ,  112 ′,  112 ″ are rotatably attached to the plunger support shaft  104 ″. 
     Each of the contact plunger assemblies  108  . . .  108 ″,  110 ,  110 ′,  112  . . .  112 ″ includes a plunger body and an attachment shaft. Using plunger assembly  108 ′ as an example and as illustrated in  FIG. 4 , a plunger body  114  is pivotally attached to a plunger attachment shaft  116 , with the shaft  116  being rigidly fitted to the rotatable plunger support shaft  104 . It should be noted that while in operation the rotatable plunger support shaft  104  is locked to the swivel joint  106 . However, prior to operation, the swivel joint  106  may be loosened and the rotatable shaft  104  may be rotatably adjusted as needed to provide precise support for the second sheet material B. 
     Referring to  FIG. 4 , in addition to the plunger body  114 , the plunger assembly  108 ′ includes a plunger unit  118  which is preferably thread-fitted into the plunger body  114  thus allowing adjustability with respect to the plunger body  114 . To safely yet firmly urge the second sheet material B against the first sheet material A, each plunger unit  118  includes a spring-loaded nose  119 . The nose  119  may be made of a variety of materials, but is preferably made from a hard, non-marring material such as nylon. The plunger unit  118  could be of the type available from the Vlier Company of Brighton, Mass. 
     In addition to the function of applying pressure to urge the second sheet material B against the first sheet material A, the upper gate  100  also preferably provides an alignment function to align the second sheet material B with respect to the first sheet material A. The alignment function is accomplished by alignment pins acting in conjunction with circular and elongated alignment holes defined in the sheet material (in this case, sheet material B), which defines the inner part or the support structure of the resulting joined component. As illustrated in  FIG. 3 , certain ones of the plunger assemblies include alignment pins for engagement with the circular and elongated alignment holes of sheet material B. According to the preferred embodiment, the plunger assemblies  108  and  110 ′ each include alignment pins  120 ,  120 ′ respectively. The alignment pins  120 ,  120 ′ include generally conical or pointed ends and function to engage alignment holes a and b shown in the sample second sheet material B illustrated in  FIG. 5 . It should be understood to one skilled in the art that the placement and number of alignment holes may be varied according to need. 
     The lower nest  200  is partially illustrated in perspective view in  FIG. 1  in conjunction with the upper gate  100 , is illustrated in sectional view in  FIG. 2  as taken along lines  2 - 2  of  FIG. 1 , and is shown in perspective view in  FIG. 6  without the upper gate  100 , or sheet materials A and B. 
     Referring then to  FIGS. 1 ,  2  and  6 , the lower nest  200  generally includes a frame  202  and a vacuum assembly  204 . The frame  202 , also known as an anvil, is configured so as to provide maximum support to the vacuum assembly  204 , thus any one of a variety of configurations suitable for providing needed support may be adapted as known to one skilled in the art. The configuration shown is for illustrative purposes only. The frame  202  may be made from a variety of rigid materials, ranging from hard polymers to steel. The frame  202  includes an upper surface area  206  which provides support during the forming operation of the first sheet material A with the second sheet material B as is known in the art and as discussed further below with respect to the operation of the machine cell  10 . 
     The vacuum assembly  204  includes one or more vacuum pads  208 . Each of the vacuum pads  208  includes a series of vacuum channels  210 ,  210 ′,  210 ″,  210 ″′. This preferred arrangement allows for the appropriate degree of vacuum to be applied to the first sheet material A when positioned on the vacuum pads  208 . While it is possible that other arrangements may be applied, such as a series of vacuum holes formed in a substantially solid nest surface or a series of vacuum cups, the illustrated arrangement of the vacuum channels  210 ,  210 ′,  210 ″,  210 ″′ is preferred. Each of the vacuum pads  208  has an upper surface that is shaped to the contour of the first sheet material A. 
     Each vacuum pad  208  has a dual purpose—first, to provide a substantially air-tight seal with respect to the first sheet material A and, second, to provide a cushioned surface support for carefully supporting the first sheet material A while preventing its deformation. Accordingly, it is preferred that the vacuum pads  208  be composed of an elastic or semi-elastic polymerized material suitable for these purposes. 
     In addition to the vacuum pads  208 , the vacuum assembly  204  includes necessary elements appropriate to the creation of a working vacuum within the channels  210 ,  210 ′,  210 ″,  210 ″′.  FIG. 2  illustrates the preferred arrangement of vacuum lines for operation of the machine cell  10 . A vacuum source, generally illustrated as  212 , is provided and can be any one of such known sources. The source  212  is fluidly connected to a centrally located plenum  214 . A series of vacuum lines  216 ,  216 ′,  216 ″,  216 ″′, respectively fluidly connect the plenum  214  with the vacuum channels  210 ,  210 ′,  210 ″,  210 ″′. 
     Alignment of the second sheet material B with respect to the upper gate  100  is discussed above and is accomplished by use of alignment pins and alignment holes. Alignment of the first sheet material A with respect to the lower nest  200  may also be accomplished. To make the preferred alignment, two or more crowder assemblies  300 ,  300 ′,  300 ″,  300 ″′ are provided on the lower nest  200  to correctly align the sheet material A. Each of the crowder assemblies  300 ,  300 ′,  300 ″,  300 ″′ includes a movable alignment finger to effect alignment. Using the crowder assembly  300 ′ as an example, a finger  302  is pivotally provided and is movable between a substantially vertical aligning position, as shown in  FIGS. 1 and 4  and a substantially horizontal disengaged position, as shown in  FIG. 2 . 
     The crowder assemblies  300 ,  300 ′,  300 ″,  300 ″′ are pneumatically operated and are each fluidly connected to two pressure sources, one for moving the finger into its substantially vertical aligning position and one for moving the finger into its disengaged position. By way of example, the crowder assembly  300  is fluidly connected to a first air pressure source  304  by a fluid line  306  which operates to hold the finger in its disengaged position. A second air pressure source  308  is connected to the crowder assembly  300  by a fluid line  310  which operates to hold the finger in its aligning position. 
     Forming and joining of the first sheet material A with the second sheet material B is accomplished by a known forming unit. As illustrated in  FIG. 2 , a die/tabletop steel-type-forming unit  400  may be used. Alternatively, or in addition, a roller-tool type of forming unit  402  may accomplish the operation of forming and joining. Detail as to the configurations of the forming units  400 ,  402  will be omitted as such is well known to those skilled in the art. 
     With reference  FIG. 6  and  FIG. 7 , the two figures have a similar lower nest  200  that generally includes a frame  202  and an upper surface area  206  which provides support during the forming operation of the first sheet material A with the second sheet material B as is known in the art. They also have similar crowders  300 ,  300 ′,  300 ″, and  300 ″′. 
     With reference to  FIG. 2  and  FIG. 8 , the upper gate  100  is similar, including components  101 ,  102 ,  106 ,  106 ′,  106 ″,  112 ′ and  120 ′. Also die/tabletop steel-type-forming unit  400  and roller-tool type forming unit  402  accomplish their operation of forming and joining similarly. 
     The vacuum assembly  204  includes one or more vacuum pads  208 . Each of the vacuum pads  208  includes a series of vacuum channels  210 ,  210 ′,  210 ″,  210 ′″. The present invention presents a relieved surface  402  that is offset from the panel A surface approximately equal to the radius of ropes  404  and  406 . The ropes  404  and  406  are of urethane or similarly elastic material. The relieved surface  402  has grooves  408  cut into it approximately equal to the radius of the ropes  404  and  406 . The ropes  404  and  406  are laid in grooves  408  and adhered. The top of the exposed ropes  404  and  406  are thus in net contact with panel A throughout its length. A vacuum source is fluidly connected through hole  410 . The peripheral rope  404  forming a closed shape acts as an air-tight seal and the inner rope(s)  406  acts as a support for the panel to prevent panel deformation. 
     Each rope  404  and  406  thus has an upper surface that is shaped to the contour of the first sheet material A. The ropes rest or are permanently glued into the grooves machined into the stiff lower nest material, generally metal, however other stiff materials work as well such as resins and plastics. This configuration makes the vacuum holding characteristics more ridged than the pads  208 , permitting much less movement when side loading the panel A. Moreover, this configuration may be readily adapted to support and immobilize a wide variety of panel sizes and shapes. 
     For example, the lower nest  500  illustrated in  FIGS. 9 and 10  includes a frame  502  having a material contacting surface  504  along an outer border  506  of the frame  502 . The material contacting surface  504  conforms to an edge of metal panel A for providing support during an edge hemming operation. A relieved surface  508  is located interior and subjacent to the material contacting surface  504 . Grooves  510  (shown in  FIG. 10 ) are formed in the relieved surface  508  and receive polymeric seals  512 ,  514  in the form of a urethane rope. These seals may be of varying size to fill the space between the relieved surface  508  and the metal panel A, thereby forming an elongated sealed channel  516 . In  FIG. 10 , the polymeric seals  512 ,  514  are shown to have a generally circular cross-section fitting into a generally semi-circular groove. However, it is contemplated that the polymeric seals used to define the elongated channels may have different configurations including various elliptical cross-sections or various polygonal cross-sections including but not limited to triangular, square, rectangular, trapezoidal and the like. 
     A vacuum source (shown in  FIG. 8  as  212 ) is in fluid communication through passageway  518  with the elongated channel  516 . The vacuum source operates to evacuate the sealed elongated channel  516  for generating a downward clamping force sufficient to immobilize metal panel A during the edge hemming operation in a direction generally parallel to the material contacting surface  504 . 
     With reference now to  FIG. 9 , the frame  502  may include a number of numerous elongated sealed channels shown as  516   a - g . The location and shape of these channels  516  are determined by the size, shape and configuration of the metal panel A. For example, channel  516   a - d  are configured to circumscribe a sun roof opening formed in a roof panel. Likewise, channels  516   e - g  would accommodate longitudinally-extending rails typically formed in a roof. A channel  516  may be subdivided within an interior seal such as seal  520  in channel  516   a . The seal  520  functions to provide intermediate support across the width of the channel. Seal  520  is located with a groove (not shown) similar to that described above with reference to groove  510  and seals  512 ,  514 . 
     The frame  502  may also include a fixture or support  522  extending from the relieved surface  508 . The support  522  would be configured to extend into the sun roof opening. In this way, support  522  serves to located panel A onto the nest and further resist lateral movement during the forming operation. 
     The lower nest  600  illustrated in  FIG. 11  includes a frame  602  having a material contacting surface  604  along an outer border  606  of the frame  602 . The material contacting surface  604  conforms to an edge of metal panel (not shown) for providing support during an edge hemming operation. A relieved surface  608  is located interior and subjacent to the material contacting surface  604 . Polymeric seals  610 ,  612  extend from the relieved surface  606  to form elongated channels  614   a ,  614   b . A vacuum source (shown in  FIG. 8  as  212 ) is in fluid communication through passageways  616  with the elongated channel  614   a ,  614   b . The vacuum source operates to evacuate the sealed elongated channels formed by a metal panel and elongated channels  614   a ,  614   b  for generating a downward clamping force sufficient to immobilize the metal panel in a direction generally parallel to the material contacting surface  604  during a forming operation. 
     The vacuum assembly described herein, which includes the sealed elongated channel conforming to the metal panel and the vacuum source in fluid communication with said elongated channel, replaces conventional fixturing devices such as clamps to immobilize the metal panel in a direction generally parallel to said material contacting surface during the metal forming operation. A distinct advantage of this vacuum assembly is the ability to secure the metal panel to the frame and onto the material contacting surface, while at the same time to enable unobstructed lateral movement of a forming tool to and from the material-contacting area across a boundary defined by the perimeter of the frame. To this point, forming tools  400 ,  402  (as shown in  FIGS. 2 and 8 ) can move freely about the perimeter of the frame  200  and laterally with respect to the material contacting surface to engage and form the flanges on the metal panels. 
     The operation of the machine cell  10  will now be generally described. As the operation begins the upper gate  100  should already be in its elevated position, assuming that a joining operation has already been completed and the joined part has been removed, thus leaving the lower nest  200  empty. 
     Initially, a known quantity of mastic is applied to the approximate surface areas at which the first sheet material A will be joined to the second sheet material B. The mastic is utilized to provide a more complete joining of the sheet materials. The mastic may be joined to one of the sheets or to both as may be desired. Known mastics may include glass bead-filled compositions as are known in the art. 
     The machine cell  10  may then be operated by a human operator or by a programmable logic controller as is known in the art. Regardless of the form of the operator, reference shall be made hereafter generically to “the operator.” 
     Once the mastic has been selectively applied to the sheets A and B, the operator marries the first sheet material A to the second sheet material B then places the combined sheets on the vacuum pads  208  with the first sheet material A face down (that is, the outer surface of the sheet material A is placed onto the vacuum pads  208 ). The crowder assemblies  300 ,  300 ′,  300 ″,  300 ″′ are then activated by operation of the second air pressure source  308  to advance the alignment fingers to their engaged and aligning positions. So engaged, the first sheet metal A is in alignment relative to the lower nest  200 . This arrangement facilitates positive micro positioning of the first sheet material A. 
     The operator then engages the robotic arm or linear slide (neither shown) to lower the upper gate  100  into an engaged position. The robotic control provides that movement of the upper gate  100  with a precise attitude. As the upper gate  100  is lowered, the alignment pins  120 ,  120 ′ having generally conical or pointed tips as illustrated in  FIG. 3  engage the circular and elongated alignment holes a and b of the sheet material B. The pointed configurations of the alignment pins allow for some degree of initial play with the fit becoming tighter as the upper gate  100  is lowered. Accordingly, as the upper gate  100  is lowered, the pins  120 ,  120 ′ effect alignment by their engagement with the alignment holes a and b. 
     As the upper gate  100  is lowered and the alignment pins  120 ,  120 ′ engage the alignment holes a and b, the second sheet material B is moved into alignment with the first sheet material A. The polymerized noses of the contact plunger assemblies  108  . . .  108 ″,  110 ,  110 ′,  112  . . .  112 ″ apply a light pressure about the periphery of the second sheet material B, thus ensuring that the first sheet material A is nested onto the vacuum pads  208 . 
     After the first sheet material A and the second sheet material B are in position, the vacuum source  212  is activated to provide a vacuum between the surface of the first sheet material A and the vacuum channels  210 ,  210 ′,  210 ″,  210 ″′. The first sheet material A is thus immobilized. With the combined assembly of the first sheet material A and the second sheet material B secured within the machine cell  10 , the first air pressure source  304  is activated and the fingers of the crowder assemblies  300 ,  300 ′,  300 ″,  300 ″′,  300 ″′ are drawn away from their aligning positions to the substantially horizontal positions illustrated in  FIG. 2 . Thus positioned, the fingers will not interfere with the subsequent forming operation. 
     The joining operation then occurs, by which the upstanding flanges of material A are formed over onto material B resulting in clinched formation c. Formation c thus resides around part of or the entire periphery of the joined first sheet material A and the second sheet material B. As noted above, joining of the first sheet material A with the second sheet material B is accomplished by either the die/tabletop steel-type-forming unit  400  or the roller-tool-type-forming unit  402 . Regardless of the chosen forming unit, the surface  206  of the frame  202  provides a rigid surface upon which forming operations may take place. 
     Once forming and joining of the first sheet material A to the second sheet material B is complete, the upper gate  100  is removed from the second sheet material B and the vacuum source  212  is de-energized causing the first sheet material A to be re-mobilized from the vacuum pads  208 . The joined sheet materials A and B are unloaded from the top of the vacuum pads  208  and the next pair of married sheet materials A and B. is loaded. The forming and joining operation is thus repeated. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with the particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification and following claims.