Abstract:
A horizontally mounted siding component for finishing of a top course of a vinyl siding installation while minimizing the lateral deformation of the vinyl siding. The invention additionally relates to the method for post-form extruding a thermoplastic dual undersill trim with complex geometry including extensive folding of the extruded material in a series of fixtures.

Description:
FIELD OF THE INVENTION 
     This invention relates to a method for post-form extruding a polyvinyl chloride component with a complex geometry that includes extensive folding of the extruded material by what is typically referred to as a water fixture or a calibrator. The invention also relates to dual undersill trim utilized for finishing a top course of siding installation. The dual undersill trim presents two positions for receiving the top course of siding thereby minimizing the vinyl siding deformation and which is manufactured through utilization of the post-form extrusion method. 
     BACKGROUND OF THE INVENTION 
     Vinyl siding currently has a 48 percent share of the U.S. siding market outpacing wood, stucco, stone, concrete, brick and metal. The vinyl siding market is expected to grow by an additional two percent by the year 2005. This explosive growth is the result of vinyl&#39;s outstanding durability and its versatility in terms of color, texture and patterns. Currently, many manufacturers of vinyl siding are having difficulty keeping up with market demand. The ability to extrude the polyvinyl chloride into the finished vinyl siding product is principally limited by the feed rate capacity of the production lines. For example, many vinyl siding components are profile extruded which requires extruding polyvinyl chloride through a die at a haul-off rate of between six and ten feet per minute. This compares with feed rates in excess of 150 feet per minute for some post-form extruded products. The dual undersill component had been profile extruded at a haul-off rate of approximately 3 meters per minute (10 feet per minute). A continuous loop version of the dual undersill which will be discussed in more detail below can now be post-form extruded at a haul off rate of approximately 18 meters per minute (60 feet per minute). 
     The principal drawback to the post-form extrusion process, at least until application of the present methodology, was its inability produce a product, such as the dual undersill, with a complex continuous loop configuration wherein a single sheet of polyvinyl chloride is bent or formed into the desired geometry by pressing it through one or more fixtures at a high rate of speed. 
     Profile-extrusion of polyvinyl chloride components is a common industrial practice across the globe. Numerous common items are produced from extruded polyvinyl chloride including, guttering, window frames and vinyl siding components. During the production process, the polyvinyl chloride resin is heated in an extrusion device and fed into a profile fixture where the desired shape is forced out of a die under considerable pressure. The process produces precisely dimensioned components, however, one major drawback to the process is the rate of production. It is common to experience a profile-extrusion process rate of no greater than 1.8 to 3 meters per minute (6 to 10 feet per minute). Profile-extrusion of polyvinyl chloride components is a relatively slow process and in the vinyl siding production business, companies must maintain high rates of production to remain profitable. 
     A second process for producing components manufactured from polyvinyl chloride is post-form extrusion. It is possible, utilizing post-form extrusion, to run production lines at speeds in excess of 45 meters per minute (150 feet per minute), or more than 10 times the speed of profile-extrusion production lines. With post-form extrusion, the extruded and heated polyvinyl chloride is formed into a flat sheet, embossed with a pattern or grain structure for aesthetic appeal, then depending upon the complexity of the desired finished product the sheet is first fed into a preform stage or directly into a fixture, also known as a calibrator, to achieve the desired profile and dimensions. Conventional wisdom has been that components with complex geometries, especially those that are characterized as having a continuous loop construction, wherein a first layer of the component is positioned in the fixture and then a second layer is wrapped back around in a continuous loop immediately atop the first layer could not be produced utilizing post-form extrusion if production rates were in excess of 3 meters per minute (10 feet per minute). Producing continuous loop components such as dual undersill trim having even a few critical bends has proven difficult for many siding manufacturers. 
     A vinyl siding component, referred to as dual undersill trim, is utilized to facilitate the installation of vinyl siding that is adjacent to a soffit. This is a commonly utilized component produced by many vinyl siding manufacturers, however, it is currently universally produced using the profile-extrusion process because it possesses a geometry considered too challenging to produce using post-form extrusion techniques if speeds much in excess of those utilized in profile-extrusion are sought. Numerous vinyl siding manufacturers have previously attempted to produce dual undersill trim utilizing post-form extrusion, however, the challenges of producing the component utilizing a continuous loop process at speeds approaching 18 meters per minute (60 feet per minute) have proven insurmountable up until now. 
     The function of dual undersill trim, as opposed to single undersill trim, is to minimize the deformation of the siding in proximity to the soffit or window sill, by providing the siding installer with two positions for placement of the cut edge of the top course of the siding within the dual undersill component. Minimizing deformation is particularly important for maintaining the aesthetic appeal of the siding in proximity to the soffit. Deformation of the siding will manifest itself in an uneven or bulging surface near the soffit. The dual undersill trim allows a siding installer to select between two positions for receiving, as well as obscuring, the cut edge of the siding. The entry point of the first slot of the dual undersill is in close proximity to the vertical wall that the siding is covering and the second slot is spaced away from the wall by approximately 8 mm (0.31 inches) or roughly the span of the center rib typically found on most vinyl siding. 
     During installation, when the top course of the vinyl siding is cut in proximity to the soffit such that the horizontally cut edge is closer to the plane perpendicular to the back edge of the center rib of the siding than with the front edge of the center rib, then the terminating edge of the vinyl siding is most easily inserted into the dual undersill position closest to the wall being sided. If, however, the cut edge of the siding is closer to the plane perpendicular to the front edge of the center rib than the vertical plane of the back edge of the center rib, then the cut edge should be inserted into the dual undersill position located furthest from the wall being sided with vinyl. 
     A need in the art therefore exists for a method of producing thermoplastic components of complex geometry at a high rate of speed without causing jamming of the production fixtures or sacrificing the dimensional requirements of the product. A further need exists for an undersill component that offers the vinyl siding installer the option of placing the cut edge of the top course of the vinyl siding in one of two positions within the undersill trim. The two placement options minimize the deformation experienced by the siding as it is installed adjacent the soffit, or beneath the sill of a window frame. 
     BRIEF SUMMARY OF THE INVENTION 
     This present invention pertains to a method for post forming extruded material from a single continuous sheet to produce a component such as the dual undersill trim of the present invention. The method comprises continuously feeding a raw material, preferably polyvinyl chloride, into an extrusion device where it is heated and then extruded under pressure. Following extrusion, the polyvinyl chloride is fed into a flat sheet die where a flat sheet, nominally 1 mm in thickness by 200 mm (8 inches) in width, is formed with opposed first and second edges coincident with the longitudinal axis of the sheet. During production set up and following formation of a length of sheet from the flat sheet die, the sheet is positioned on the surfaces of passages in a first section of a pre-form fixture separated into two sections. As the flat sheet passes through the passages of the fixture in production, the desired profile is formed. The sheet material is positioned atop the surfaces of the fixture passages and laid back atop itself in a continuous loop fashion to form the inner and outer layer of the dual undersill trim back panel. The two edges of the flat sheet are also positioned within the passages that will form the inwardly curving arcs extending from the inner and outer flanges of the dual undersill. Once the flat sheet is properly positioned within the fixture the second section of the fixture is secured in position adjacent the first section making ready the fixture to commence production. Once production commences the flat sheet material is pulled through the first fixture beginning the formation of the profile of the dual undersill trim. 
     Immediately following the pre-form fixture in the production process is a second fixture referred to a the calibrator fixture. As with the first fixture, the flat sheet is positioned atop the surfaces of the passages within a first section of the calibrator fixture. Once the sheet material is positioned atop the surfaces of the passages and laid back atop itself in a continuous fashion to form the inner and outer layer of the dual undersill trim and the two edges of the flat sheet are positioned within the passages that will form the inwardly curving arcs, the second section of the second fixture is secured in position adjacent the first section making ready the fixture to commence production. After the sheet material is positioned within the first and second fixtures and the fixture sections are secured to one another, the fixtures are fully configured for production. 
     As the polyvinyl chloride is extruded from the extrusion device it passes through the flat sheet die and then into the pre-form fixture where the linear segments comprising the inner and outer layers, the upper and lower flanges and the inner and outer flanges are formed. Additionally, the pre-form fixture commences formation of the non-linear segments which comprise the inwardly curving arcs that are positioned at one extreme of the inner and outer flanges. The calibrator fixture serves to refine the dimensions of the dual undersill trim that were produced in the pre-form fixture bringing those dimensions to within product tolerances. The calibrator fixture, unlike the pre-form fixture, utilizes a reduced air pressure, or vacuum assist, system to pull the polyvinyl chloride that is passing through the calibrator to the outer geometry of the fixture passages. The vacuum assist operates to eliminate jamming of the polyvinyl chloride in the calibrator by reducing the prospect for clogging the center of the fixture passages. After passing through the calibrator where the linear and non-linear segments are appropriately dimensioned and oriented the polyvinyl chloride passes into a water bath where it is cooled and fully hardens before slots are punched in the nail hem and the trim is cut to the desired length. 
     A product of the process described above is a dual undersill trim component formed from a single sheet of material. The dual undersill comprises, among other features, a back panel created from an inner layer and an outer layer of polyvinyl chloride. The outer layer is placed against the wall that is being sided with the vinyl. The back panel comprises an upper portion and a lower portion and a nail hem with integral nail slots disposed within the lower portion of the back panel. The inner layer of the back panel transitions to the outer layer at the lowermost extreme of the inner and outer layers in a continuous loop fashion. Opposite the lowermost extreme of the back panel, upper and lower flanges extend outwardly in a continuously transitioning fashion from the outer and inner layers respectively. The upper and lower flanges extend outwardly at an angle of approximately 90 degrees from the outer and inner layers. Extending downwardly from the outermost ends of the upper and lower flanges are outer and inner flanges with the flanges terminating in inwardly curving arcs. The inner and outer flanges in conjunction with the inwardly curving arcs receive and obscure the cut edge of the top course of vinyl siding, holding it in place in proximity to the soffit or window sill. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the dual undersill trim embodying features of the present invention as mounted to a wall adjacent a soffit, the soffit shown in phantom; 
         FIG. 2  is an enlarged view of  FIG. 1  of the trim embodying features of the present invention with the cut edge of the vinyl siding shown in phantom positioned between the inner flange and the inner layer of the back panel of the trim; 
         FIG. 3  is a cross sectional view of the trim embodying features of the present invention showing the cut edge of a sloping vinyl siding section inserted between the inner flange and the inner layer of the back panel of the trim taken along line  3 — 3  of  FIG. 2 ; 
         FIG. 4  is a perspective view of the trim embodying features of the present invention in an alternative position beneath a window sill; 
         FIG. 5  is an enlarged view of the selected features of  FIG. 4  of the trim embodying features of the present invention with the cut edge of the vinyl siding, shown in phantom, positioned between the inner and outer flanges; 
         FIG. 6  is a cross sectional view of the trim embodying features of the present invention showing the cut edge of sloping vinyl siding inserted between the inner and outer flange of the dual undersill taken along line  6 — 6  of  FIG. 5 ; 
         FIG. 7  is a process flow diagram detailing the steps of production of the dual undersill trim; 
         FIG. 8  is a sectional view of the pre-form fixture embodying features of the present invention, utilized for forming the trim embodying features of the present invention, showing the pre-form passages and means for securing together the pre-form fixture; 
         FIG. 9  is a sectional view of the pre-form fixture embodying features of the present invention separated and showing three stages for manipulating the sheet into the passages of the pre-form fixture; 
         FIG. 10  is a sectional view of the pre-form fixture embodying features of the present invention separated and showing the positioning of the thermoplastic sheet into the fixture prior to securing the pre-form fixture sections together; 
         FIG. 11  is a front view of the calibrator fixture showing the profile of the dual undersill trim and the vacuum ports; 
         FIG. 12  is a cross sectional view of the calibrator fixture embodying features of the present invention depicting the vacuum channels located within the calibrator taken along line  12 — 12  of  FIG. 11 ; 
         FIG. 13  is a cross sectional view of the calibrator fixture embodying features of the present invention depicting the direction of air flow created by the vacuum source and taken along line  13 — 13  of  FIG. 12 ; 
         FIG. 14  is a front view of the water cooling apparatus; 
         FIG. 15  is a cross sectional view of the water cooling apparatus taken along line  15 — 15  of  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Dual Undersill Trim Apparatus 
     As shown in  FIGS. 1 and 4 , the dual undersill trim  10  is typically positioned against the wall of a building adjacent the building soffit or beneath a window sill. The dual undersill trim provides a much needed approach to finishing off a top course of vinyl siding and simultaneously avoiding deformation of the top course when the upper edge is inserted into the trim. Depending upon whether the top course of siding is cut on a vertical section or a sloping section dictates which of the two positions of the dual undersill trim will be utilized. 
     As depicted in  FIGS. 2 ,  3  and  6  the dual undersill trim  10  is constructed from a single sheet of polyvinyl chloride thermoplastic nominally 1 mm thick and comprises, among other features to be discussed below, a back panel  12  with an inner layer  14  and an outer layer  16 . The outer layer  16  of the back panel  12  is mounted against a building wall  18  and beneath the building soffit  19  during installation of the dual undersill trim  10 . In the preferred embodiment set forth below specific dimensions are provided, however, these dimensions are not intended in any way to constrain alternative embodiments. 
     A preferred embodiment includes a gap of approximately 2.0 mm exists between the inner layer  14  and the outer layer  16  at the lower portion  20  of the back panel  12  to form a nail hem  22 . During production, slots  24  are punched into the nail hem  22  and during installation nails  26  are driven through the slots  24  and secured into the wall  28  being sided to hold the dual undersill trim  10  in position against the wall  18 . The nail hem  22  at the lower portion  20  of the back panel  12  extends for approximately 15 mm (0.6 inches) in length at which point the inner layer  14  and outer layer  16  of the back panel converge and are separated by less than a 0.1 mm (0.004 in) gap. 
     After converging, the inner and outer layers traverse together for approximately an additional 25 mm (1 inch) forming the upper portion  30  of the back panel. After traversing the approximately 25 mm (1 inch), the upper portion  30  of the back panel, including both the inner and outer layers commence an outward transition to a lower flange  32  and upper flange  34  respectively. The upper and lower flanges  32 ,  34  are both formed from the same continuous sheet of thermoplastic material as will be discussed in more detail below. Both flanges  32 ,  34  extend outwardly at approximately 90 degrees from the outer layer  16  and the inner layer  14  respectively. The outer layer  16  of the upper portion  30  of the back panel  12  folds atop the inner layer  14 . The upper flange  34  extends outwardly approximately 15 mm (0.6 inches) from the outer layer  16  while the lower flange  32  extends approximately 10 mm (0.4 inches) beyond the inner layer  14 . The upper flange  34  extends approximately 5 mm (0.2 inches) beyond the lower flange  32  before beginning a downward traverse at the point where it is most outwardly extended. The upper flange  34  at its outermost extent begins a downward traverse forming an outer flange  38  that extends downwardly approximately 25 mm (1 inch) before forming an inwardly curving arc  40  with a radius of curvature of approximately 2 mm (0.08 inches). The lower flange  32 , at its most outwardly extending point begins a downward traverse forming an inner flange  42  that extends approximately 24 mm (0.95 inches) before forming an inwardly curving arc  44  with a radius of curvature of approximately 2 mm (0.08 mm). 
     The dual undersill trim is typically cut into either 8 or 12 foot lengths at the factory. These entire lengths of trim  10 , or a section cut to the desired length, is then installed immediately beneath the soffit, or window sill, as depicted in  FIGS. 3 and 6 . For installation of the trim beneath a soffit the vinyl siding installer begins by securing a course of vinyl siding to the base of the wall nearest the ground. As the siding courses are installed one-a-top the other, they eventually approach the soffit or the window sill. Generally the final course, or top course, of siding to be installed must be cut or trimmed to a length that will allow it to fit under the soffit and be received into the undersill trim. 
     When the top course of the vinyl siding is cut in proximity to the soffit such that the horizontally cut edge  51  is closer to the plane perpendicular to the back edge  52  of the center rib  53  of the siding than with the front edge  54  of the center rib  53 , then the terminating edge  51  of the vinyl siding is most easily inserted between the inner layer  14  and the inner flange  42  as shown in  FIG. 3 . If, however, as shown in  FIGS. 5 and 6 , the cut edge  50  of the siding is closer to the plane perpendicular to the front  55  of the center rib  56  than the plane perpendicular to the back  57  of the center rib  56 , then the cut edge  50  should be inserted between the outer flange  38  and the inner flange  42  as shown in  FIG. 6 . 
     When the cut edge  51  is inserted between the inner layer  14  and the inner flange  42 , the inner flange flexes slightly outwardly, applying pressure to the siding  48 . The pressure applied to the siding assists in securing the siding within the trim  10  in proximity to the soffit  19  so that the cut edge  51  does not work loose during high winds but can be removed when necessary for repairs that may be required. When the cut edge  50  is inserted between the inner flange  42  and the outer flange  38 , both flanges  38 ,  42  flex slightly and apply pressure to the siding  46 . As with the inner position of the dual undersill, the outer position serves to secure the siding  46  in position. 
     Dual Undersill Trim Method of Production 
     As shown in  FIG. 7  the process for producing a dual undersill component through post-form extrusion includes feeding polyvinyl chloride resin, along with the desired coloring agents into the hopper of an extrusion device. An example of a preferred extrusion device is manufactured in Germany by Kraussmafei. The extrusion device is comprised of a large screw that augers the product forward inside of a barrel. The friction created by the rotation of the auger screw against the barrel produces heat. The heat produced by the friction along with the assistance of heater bands strapped around the barrel of the extrusion device melts the polyvinyl chloride resin. The heater bands also serve to maintain a constant temperature for the resin as it exits the barrel of the extrusion device. An example of a preferred heater band is also manufactured in Germany by Kraussmafei. 
     Melted polyvinyl chloride is then forced or extruded from the barrel and fed into a flat sheet die at a temperature of approximately 176° C. (350° F.). The flat sheet die compresses the extruded polyvinyl chloride into a thin sheet preferably about 200 mm (8 inches) wide and about 1 mm (0.04 inches) thick in preparation for further processing. The thin sheet has opposed first and second edges that are aligned with a longitudinal axis of the sheet. Examples of preferred flat sheet dies are manufactured by EDI or Production Components, Inc. 
     As will be discussed in more detail below, the flat sheet is ultimately formed into the desired dual undersill trim profile. The profiled dual undersill trim is captured by a haul-off machine at or very near the end of the production process that traditionally consists of two powered counter-rotating wheels that pinch the trim and pull it through the production process at the desired rate. It is the haul-off machine, coupled with the continuous extrusion of the material from the extrusion device that allows the thermoplastic material to be continuously formed into the desired profile. 
     Following the flat sheet die is an embossing station for adding texture to the surface of the flat sheet and preferably following that are one or more cooling rolls that serve to transfer heat from the vinyl siding through both conduction and convection. After passing through the cooling rolls the temperature of the vinyl siding is lowered to approximately 115° C. (240° F.) causing the polyvinyl chloride to stiffen. The stiffening of the polyvinyl chloride facilitates maintaining the material&#39;s shape during further processing and reduces its tackiness and hence propensity to adhere to itself when the thermoplastic is laid atop itself. 
     From the cooling rolls the flat sheet polyvinyl chloride moves to a preform fixture. The flat sheet passes from the cooling rolls into the preform fixture and begins the transition of the flat sheet into the desired dual undersill profile. The preferred construction of the pre-form fixture consists generally of a two section fixture produced from MICARTA®, an engineered thermoplastic. As depicted in  FIG. 8 , the preferred configuration of the pre-form fixture utilizes  60  a first section  62  and a second section  64  with dowel pins  66 , or some other suitable means, to ensure proper alignment of the two sections. The two sections  62 ,  64  are rigidly joined together preferably utilizing bolts  68 ,  70  or some other suitable means, such as clamps, prior to the flat sheet material passing through the pre-form fixture  60 . The preform fixture  60  is molded with tolerances of ±0.5 mm (0.02 inch). In addition, the surfaces  72 ,  74 ,  76 ,  78  of the pre-form fixture that come into contact with the polyvinyl chloride material are preferably polished to reduce the friction forces between those surfaces and the polyvinyl chloride sheet transitioning through the fixture. The smooth pre-form fixture surfaces  72 ,  74 ,  76 ,  78  serve to reduce the prospect for jamming of the polyvinyl chloride in the passages of the pre-form fixture. 
     As shown in  FIGS. 9 and 10 , during production set-up the first section  62  and the second section  64  of the preform fixture are separated from one another. Once the sections of the preform fixture are separated, the first edge  79  of the flat sheet  80  of polyvinyl chloride material is inserted into and laid against the surfaces  74 ,  84  of the first section  62  that form the inwardly curving arc  44  and the inner flange  42 . Next, the second edge  81  of the flat sheet  80  is inserted into and laid against the surfaces  72 ,  82  that form the inwardly curving arc  40  and the outer flange  38 . Following the insertion of both ends of the flat sheet  80  material into the preform fixture first section  62 , the flat sheet  80  material extending from the first edge  79  is wrapped around the surface  73  forming the lower flange  32 . Simultaneously, the flat sheet material extending from the second edge  81  is wrapped around the surface  75  forming the upper flange  34 . 
     As shown in  FIG. 10 , the remainder of the flat sheet  80  extending from both edges  79 ,  81  is wrapped, one layer atop the other, onto the surface  76  forming the back panel  12 . The inner layer  14  and the outer layer  16  travel atop one another until reaching the lowermost extreme  15  of the back panel  12 . At the lowermost extreme  15  of the back panel the inner layer  14  diverges from the outer layer  16  principally because of the resistance of the thermoplastic material to immediately fold upon itself. Attempting to force the inner layer  14  and outer layer  16  to immediately fold over at the lowermost extreme  15  would weaken the material at the lowermost extreme  15  and introduce undesirable stresses into the material. 
     Once the flat sheet  80  material is positioned as described above, the second section  64  of the preform fixture  60  is moved into position immediately adjacent the first section  62  as shown in  FIG. 10 . The second section  64  possesses a surface  78  that participates in the formation of the back panel  12  of the dual undersill. The surface  78  controls the formation of the outer layer  16  of the back panel  12 . 
     Since the flat sheet  80  is laid back on top of itself, it is preferable that the temperature of the material be lowered to the point where the surfaces laid atop one another are no longer tacky and adhere to one another. Once the flat sheet  80  is laid onto the surfaces  72 ,  73 ,  74 ,  75 ,  76  of the first section  62 , the second section  64  of the pre-form fixture is secured against the first section using threaded attachment devices  90 ,  92  or other appropriate securing means. Upon securing the first section  62  and the second section  64  together, the pre-form fixture  60  is ready to commence production. An example of a preferred pre-form fixture is manufactured by Teams Design, Inc. of 6750 West 75 th  Street, Overland Park, Kans. 
     After passing through the pre-form fixture the flat sheet has nominally attained the profile of the dual undersill trim  10 . The pre-form station  60  has served to bend the flat sheet  80  about the multiple axes that are all parallel to the longitudinal axis of the flat sheet. The bends about the multiple axes form the various linear and non-linear segments that comprise the dual undersill trim  10 . The linear segments include the inner layer  14  and the outer layer  16 , the upper flange  34  and the lower flange  32  as well as the outer flange  38  and the inner flange  42 . The formation of each of these linear segments will be discussed in more detail below. The nonlinear segments include the inwardly curving arc  44  extending from the inner flange  42  and the inwardly curving arc  40  extending from the outer flange  38 . The nonlinear segments will also be discussed in more detail below. 
     Though not dimensionally accurate after passing through the preform fixture  60 , the vast majority of the complex bending and folding has been accomplished in the preform fixture and the profile of the dual undersill is similar in appearance to the finished product. Immediately following the pre-form fixture  60  in the production sequence is a second fixture typically referred to as a calibrator  100 . 
     The calibrator  100 , as shown in  FIG. 11 , provides final dimensional refinement to the profile of the dual undersill  10  exiting the preform fixture  60 . The calibrator adjusts preformed bends, reduces angles and sizes every feature of the dual undersill trim discussed in detail above in order to attain product specifications. Unlike the preform fixture  60  which is preferably produced from MICARTA®, the calibrator  100  is preferably machined from STAVAX® or standard grade stainless steel. The calibrator  100  is preferably machined with dimensional tolerances of ±0.5 mm (0.02 inches) and the surfaces contacting the polyvinyl chloride material are preferably polished to a mirror finish. The polishing of the contact surfaces reduces the drag caused by the friction forces between the calibrator and the polyvinyl chloride material. As with the preform fixture  60 , the calibrator  100  can be separated into a first section  102  and a second section  104 . When separated, the internal surfaces  110 – 124  utilized for forming the profile of the dual undersill are exposed in a first section  102  and a second section  104 . 
     As previously discussed, the thermoplastic material is first extruded from the extrusion device and then into the flat sheet die. At production start-up an extended length of flat sheet material is extracted from the die. This provides the production personnel with sufficient material to load into the preform station, the calibrator, and ultimately the haul-off machine that pulls the material through the entire production process. 
     As shown in  FIG. 11 , during production set-up the calibrator first section  102  and the second section  104  are separated from one another. Once the sections of the calibrator are separated, the first edge  79  of the flat sheet  80  is inserted into and laid against the surfaces  120 ,  124  of the first section  102  that form the inwardly curving arc  44  and the inner flange  42 . Next, the second edge  81  of the flat sheet  80  is inserted into and laid against the surfaces  118 ,  122  that form the inwardly curving arc  40  and the outer flange  38 . Following the insertion of both ends of the flat sheet  80  into the calibrator first section  102 , the flat sheet  80  extending from the first edge  79  is wrapped around the surface  117  forming the lower flange  32 . Simultaneously, the flat sheet material extending from the second edge  81  is wrapped around the surface  119  forming the upper flange  34 . 
     As shown in  FIG. 11 , the remainder of the flat sheet  80  extending from both edges  79 ,  81  is wrapped, one layer atop the other, onto the surface  112  forming the back panel  12 . The two layers forming the inner layer  14  and the outer layer  16  are positioned atop one another until reaching the region of the nail hem  22  or the lowermost extreme  15  of the back panel. At that point the inner layer  14  diverges from the outer layer  16  principally because of the resistance of the thermoplastic material to immediately fold upon itself. Attempting to force the inner layer  14  and outer layer  16  to fold over after the direction change would weaken the material at the point of transition and introduce undesirable stresses into the material. After the thermoplastic material is placed into the designated spaces the two calibrator sections  102 ,  104  are secured together, with bolts  160 ,  162  or other appropriate securing means. 
     Once the thermoplastic material with the profile of the dual undersill trim exits the calibrator it passes through a water bath lowering the temperature of the material to approximately 38° C. (100° F.). The water removal apparatus  200  is shown in  FIG. 14 and 15 , detailing water inlet port  202  and water removal port  204 . Lowering of the temperature of the post formed thermoplastic material increases the rigidity of the trim component and once the component passes out of the calibrator no further changes in its dimensions can be tolerated. A preferred set up of the post-form production line utilizes a water bath immediately upon the undersill trim exiting the calibrator  100 . Heat is transferred more readily by using a water bath than attempting to transfer the heat through convection to the air. 
     As shown in  FIGS. 11–13 , the calibrator  100  utilizes an air pressure reduction system to pull the thermoplastic material against the internal calibrator surfaces  110 – 124  as the material passes through the calibrator.  FIG. 11  depicts the inlet  140  through which air is drawn, and water when additional cooling is necessary, into the calibrator  100 . Air is piped into the calibrator  100  and channeled through the passages formed by the surfaces  110 – 124 . Cross sectional drawing,  FIG. 12  reveals the channel  142  passing through the calibrator that routes the air into and then out of the profile passages  144 ,  146 ,  148 ,  150 ,  152  and out through the twin exit ports  154 ,  156 .  FIG. 13  reveals the lines of influence  190  that are produced by the reduced air pressure occurring adjacent the internal surfaces of the calibrator. The calibrator operates on the principle that an increase in velocity of a fluid passing over a surface causes a reduction in air pressure. As the thermoplastic material passes through the calibrator the reduced air pressure at the surface of the calibrator improves the flowability of the thermoplastic and reduces the incidence of jamming of the material in the calibrator. An air pressure differential of no less than 17 kpascals (5 inches of Hg) and no more than 34 kpascals (10 inches of Hg) is preferable at the calibrator inlet  140  to maximize flow of the thermoplastic material and yet avoid unnecessarily abrading the surface of the calibrator with excessive force being applied by the thermoplastic material passing through the calibrator. Utilization of the design described above with a reduced internal air pressure configuration allows for production speeds in excess of 18 meters per minute (60 feet per minute). 
     The foregoing specification describes only the embodiment of the invention shown and/or described. Other embodiments may be articulated as well. The terms and expressions used, therefore, serve only to describe the invention by example and not to limit the invention. It is expected that others will perceive differences which, while different from the foregoing, do not depart from the scope of the invention herein described and claimed. In particular, any of the specific constructional elements described may be replaced by any other known element having equivalent function.