Abstract:
An apparatus and associated method for constructing prefabricated foam panels is provided. While making a longitudinal pass over a foam block, the apparatus flattens the foam block, cuts longitudinal kerfs in the foam block, and draws metal studs into the kerfs. The apparatus comprises a unique, heated blade having a shape similar to the cross section of a metal stud. The blade kerfs foam blocks, including blocks made of recycled or low-grade foam. The associated method includes kerfing the foam blocks by passing the blade through the foam blocks and drawing metal studs into the kerfs.

Description:
CROSS REFERENCES 
     None. 
     GOVERNMENTAL RIGHTS 
     None. 
     BACKGROUND OF THE INVENTION 
     Historically, buildings were constructed out of natural resources that were readily and locally available, such as mud, wood, sod, or stone. These materials present a number of disadvantages, including relatively low structural integrity, the requirement of skilled artisans to assemble the materials, the lengthy amount of time involved in assembling the materials, and the need to independently insulate the building. Recently, builders developed updated building materials, including prefabricated building panels made of metal studs and foam insulation. The invention relates to improved methods of constructing prefabricated metal stud and foam panels. 
     One type of foam panel is made by kerfing a block of foam using a hot wire cutter. As shown in U.S. Pat. No. 6,167,624, issued to Lanahan et al., hot wire cutters are machines that heat tensioned wires measuring slightly longer than the length of the foam blocks to be cut. The foam block is secured in place while the superheated wire enters the foam block, cuts a trace of the outline of the stud, and exits the foam block. The result is a kerf that is approximately the same size and shape as the cross-section of the stud. Because hot wire cutters span and kerf the entire length of a foam block at once, they leave a slug that also spans the length of the foam block that must be removed prior to inserting the stud. The removal of the longitudinal slug must be performed manually, which constitutes a disadvantage to the use of hot wire cutters. It is an object of the invention to provide a process for constructing a foam panel that does not require manual removal of a longitudinal slug or manual installation of a stud. 
     Hot wire cutters also produce an inconsistent cut across the entire length of a foam block. Hot wire cutters are supposed to perform a straight cut, but because wires stretch when heated, hot wire cutters require a tensioning mechanism to maintain a straight wire. The tensioning mechanism must be very precise, as too much tension will break a hot wire, and too little tension will result in a bowed wire and resulting erroneous kerf. In typical industrial applications, wires are fragile and must be replaced several times a week. It is thus an object of the invention to provide a process for constructing a foam panel that improves upon the relative unreliability of hot wire cutters of the prior art. 
     As hot wires used in foam cutting break easily due to tension fluctuations, great care must be taken with respect to the type of foam used. Hot wire cutters of the prior art are preferred only in cutting pure, new foam blocks because impurities in recycled foam cause varied tension of the wires, often breaking them. Even new foam, such as expanded polystyrene (“EPS”), that consists of millions of tiny beads can break hot wire cutters if the size of the beads are not substantially uniform. Generally speaking, foam (particularly EPS) is not easily recyclable and is not biodegradable, and hot wire cutters do nothing to alleviate this general concern. Thus, it is another object of the invention to provide a process for constructing a foam panel that is capable of utilizing recycled and lower-grade foam. 
     Because foam panels are in relatively wide use, especially in construction of commercial buildings, many localities have specific building codes directed to foam panels. These types of regulations address thermal bridging, which means that the heat conductivity of metal studs may allow heat to be transmitted into or out of a building. A typical regulation requires at least 1.5 inches of foam between a metal stud and the exterior surface of the panel. That is, the metal stud must be embedded at least 1.5 inches into the foam, as measured from the exterior surface, to meet typical regulations. It is another object of the invention to produce a metal stud and foam panel combination capable of reliably meeting building regulations. 
     Traditional methods of constructing foam panels are not well suited to meet regulations for metal studded foam panels. Foam, and particularly EPS, is produced in rectangular blocks, and the curing process creates a natural curvature in these blocks. Traditional processes measure to a depth of 1.5 inches on each side of a foam block and kerf a line between these two points; however, the wire-cutting method does not result in a uniform depth because it does not contemplate the natural and inconsistent curvature inherent in most if not all foam blocks. It is thus another object of the invention to provide a foam panel having a uniform kerf depth along the entire length of the foam block, regardless of the natural curvature of the initial foam block component. 
     Compounding the problem of irregularly curved foam blocks is the fact that the wires used in hot wire cutters bow when they are heated. That is, the center of the wire dips as the wire expands during heating. As a result, kerfs made using a hot wire cutter are typically bowed as well, thus exacerbating the unreliability of foam blocks cut by longitudinal wires. It is another object of the invention to provide a foam panel having straight and uniform kerfs for the insertion of metal studs along the entire length of the foam block. 
     The inventors have experimented with various methods of solving these problems of the prior art. In one prototype designed to kerf a foam block for receiving a metal stud, the inventors utilized a circular saw to kerf a channel for the main beam of a metal stud, and used a separate hot wire knife to form the portion of the kerf corresponding to the channel and lip of the stud. The inventors never considered this implementation ready to patent due to several serious drawbacks that rendered the implementation unfit for industrial use. The first drawback was that the circular saw created tiny particles of foam that were easily ignited by the saw, the hot wire, or both. Foam burns rapidly and reaches high temperatures quickly when ignited, and even more seriously, melted foam sticks to human skin, clothing, and any other surface. The saw can compound problems resulting from burning foam by discharging melted, burning foam as the saw continues to cut. Therefore, this implementation presented a serious industrial safety issue. The second drawback was that a hot wire had to be welded to a stiffener to assist in keeping the resulting knife in the appropriate shape. However, the wire portion of the knife still melted frequently (albeit not as frequently as a hot wire cutter alone) due to thinness, and the difference in expansion of the two different metals throughout the operating range of the knife accelerated the knife&#39;s failure. Furthermore, since the knife was comprised of two separate metals, the knife was more expensive to produce for a relatively small gain in reliability over hot wire cutters of the prior art. The third drawback of this implementation is that there was no way to ensure uniform depth of the studs from the outer surface of the foam. Fourth, metal studs still had to be inserted into the machine by hand, as the saws and knives remained stationary while the foam block was moved through the machine. It is thus an object of the invention to provide a safe, reliable, consistent automated foam panel-making machine. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides an apparatus and associated method of creating a foam panel that avoids the pitfalls associated with constructing foam panels using a hot wire cutter. The apparatus and method utilize a blade having a novel shape that maintains such shape while passing through and making a longitudinal cut through the foam block. The rigidity of the blade according to the invention provides several advantages, including that the invention is capable of producing metal studded foam panels with recycled foam. 
     To operate the apparatus, a foam block is secured to a deck. A cuffing unit moves longitudinally across the foam block, flattening the foam block with rollers immediately prior to cutting a kerf into the block using a heated blade. Such process creates kerfs of a uniform depth, and the heated blade configuration leaves no slug. The apparatus may preferentially insert the metal studs into the block following the cutting process in the same longitudinal pass, which is advantageous because the insertion of metal studs also assists in maintaining a flat foam block for uniform kerf depth. 
     These and other advantages provided by the invention will become apparent from the following detailed description which, when viewed in light of the accompanying drawings, disclose the embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a prefabricated foam panel. 
         FIG. 2  is a cross sectional view of a foam panel along the line  2 - 2  in  FIG. 1 . 
         FIG. 3  is a perspective view of the automated foam panel machine used to practice the method disclosed herein. 
         FIG. 4  is side view of the cutting unit used in the automated foam panel machine along the line  4 - 4  in  FIG. 3  showing the configuration of the stud clamp, blade, and roller in relation to a stud and foam block. 
         FIG. 5  is an exploded perspective view of the cutting unit showing the configuration of the stud roller, stud clamp, blade, and roller in relation to a stud, foam block, and kerf. 
         FIG. 6  is a side view of the stud clamp along the line  6 - 6  in  FIG. 5 . 
         FIG. 7  is a perspective view of an optional configuration of the pin used in the stud clamp. 
         FIG. 8  is a top view of the foam panel machine along the line  8 - 8  in  FIG. 4  with the cutting unit housing removed showing the configuration of stud rollers and cutting modules in relation to studs. 
         FIG. 9  is a rear view of the foam panel machine with the cutting unit housing removed along the line  9 - 9  in  FIG. 4  showing the configuration of blades and cutting modules in relation to a foam block. 
         FIG. 10  is a perspective view of the blade used in the automated foam panel machine. 
         FIG. 11  is a side view of the cutting unit that shows the motor and gearing used to move the cutting unit. 
         FIG. 12  is a rear view of the cutting unit that shows the motor and gearing used in the automated foam panel machine to feed foam blocks and studs into the machine. 
       
         
           
                 
               
                 
                 
                 
               
             
                 
                     
                 
                 
                   LISTING OF COMPONENTS 
                 
                 
                     
                 
               
               
                 
                     
                 
               
            
             
                 
                     
                   101  
                   foam panel 
                 
                 
                     
                   103  
                   top frame 
                 
                 
                     
                   105  
                   bottom frame 
                 
                 
                     
                   107  
                   studs 
                 
                 
                     
                   109  
                   foam block 
                 
                 
                     
                   111  
                   kerfs 
                 
                 
                     
                   113  
                   wallboard 
                 
                 
                     
                   115  
                   depth 
                 
                 
                     
                   117  
                   cavity 
                 
                 
                     
                   119  
                   foam panel machine 
                 
                 
                     
                   121  
                   deck 
                 
                 
                     
                   123  
                   stud rollers 
                 
                 
                     
                   125  
                   stud roller cross members 
                 
                 
                     
                   127  
                   base 
                 
                 
                     
                   129  
                   cutting unit 
                 
                 
                     
                   131  
                   cutting unit guides 
                 
                 
                     
                   133  
                   cutting unit movement 
                 
                 
                     
                   135  
                   cutting modules 
                 
                 
                     
                   137  
                   cutting module cross members 
                 
                 
                     
                   139  
                   cutting module clamps 
                 
                 
                     
                   141  
                   blades 
                 
                 
                     
                   143  
                   rollers 
                 
                 
                     
                   145  
                   stud clamps 
                 
                 
                     
                   147  
                   stud clamp cap 
                 
                 
                     
                   149  
                   stud channel 
                 
                 
                     
                   151  
                   pin 
                 
                 
                     
                   153  
                   aperture 
                 
                 
                     
                   155  
                   stud clamp brace 
                 
                 
                     
                   157  
                   stud beam 
                 
                 
                     
                   159  
                   stud lip 
                 
                 
                     
                   161  
                   bit 
                 
                 
                     
                   163  
                   driver 
                 
                 
                     
                   165  
                   shaft 
                 
                 
                     
                   167  
                   pneumatic actuators 
                 
                 
                     
                   169  
                   cutting module guides 
                 
                 
                     
                   171  
                   cutting module mounts 
                 
                 
                     
                   173  
                   anode 
                 
                 
                     
                   175  
                   cutter 
                 
                 
                     
                   177  
                   heat sink 
                 
                 
                     
                   179  
                   cathode 
                 
                 
                     
                   181  
                   insulator 
                 
                 
                     
                   183  
                   intersection 
                 
                 
                     
                   185  
                   gears 
                 
                 
                     
                   187  
                   teeth 
                 
                 
                     
                   189  
                   drive chain 
                 
                 
                     
                   191  
                   sprocket 
                 
                 
                     
                   193  
                   motor 
                 
                 
                     
                   195  
                   driveshaft 
                 
                 
                     
                   197  
                   cutting unit rollers 
                 
                 
                     
                   199  
                   cutting unit guide rollers 
                 
                 
                     
                   201  
                   temperature control unit 
                 
                 
                     
                     
                 
               
            
           
         
       
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention as disclosed herein provides a novel apparatus and method for constructing prefabricated foam panels for use in construction. As shown in  FIGS. 1 and 2 , foam panel  101  has four main components: top frame  103 , bottom frame  105 , one or more studs  107 , and foam block  109 . Studs  107  are inserted into kerfs  111  in foam block  109 , such kerfs having a substantially similar cross-sectional shape as studs  107 . Top frame  103  and bottom frame  105  are secured to studs  107  to form a strong, lightweight, insulated foam panel  101 . Foam block  109  forms the exterior surface of foam panel  101 . The interior of foam panel  101  is wallboard  113  or other like material such as drywall, fiberboard, or plywood, which is attached to studs  107  on the building site according to the specific architectural design of the building. In order to meet building codes of most locations, studs  107  must be recessed from the exterior of foam block  109  by a minimum predetermined depth  115 . In most applications, the attachment of wallboard  113  to studs  107  creates a hollow cavity  117  in which conduit (not pictured) or other in-wall building materials may be installed. 
     Turning now to  FIG. 3 , foam panel machine  119  assembles foam panel  101  in an automated fashion. Foam panel machine  119  is generally rectangular in shape, and such shape can be used to create foam panel  101  in virtually any shape. Foam panel machine  119  generally comprises a substantially rectangular deck  121 , one or more stud rollers  123 , one or more stud roller cross members  125 , a base  127 , a cutting unit  129 , and one or more cutting unit guides  131 . Deck  121  and cutting unit guides  131  are mounted to base  127 ; optionally, deck  121  may be integrated with base  127 . The distance between substantially parallel cutting unit guides  131  is equal to or greater in width than deck  121 , and the length of cutting unit guides is equal to or greater than the length of deck  121 . Cutting unit  129  is mounted between cutting unit guides  131  such that cutting unit  129  is substantially parallel to cutting unit guides  131 . Cutting unit  129  is movable along cutting unit guides  131  in a direction parallel to cutting unit guides  131 . Stud rollers  123  are selectably mounted to stud roller cross members  125 , which may be mounted to deck  121  or base  127 . 
     In order to assemble foam panel  101  using foam panel machine  119 , foam block  109  is placed on a deck  121  of foam panel machine  119 . Studs  107  are fed onto stud rollers  123  to maintain the studs  107  in a position substantially parallel to cutting unit guides  131  and other studs  107 . Cutting unit  129  receives studs  107  and, as cutting unit moves in the direction of cutting unit movement  133 , may preferentially push studs  107  into foam block  109  shortly after cutting unit  129  cuts kerfs  111  into foam block  109 . Once cutting unit  129  has traversed the length of cutting unit guides  131 , studs  107  will be fully inserted into kerfs  111  in foam block  109 . Partially assembled foam panel  101  may then be removed from foam panel machine  119 , or top frame  103  and bottom frame  105  may be secured to studs  107  while the partially assembled foam panel  101  remains on foam panel machine  119 . Optionally, either top frame  103  or bottom frame  105  may be secured to studs  107  prior to the activation of cutting unit  129 . 
     The components of cutting unit  129  are shown in more detail in  FIGS. 4-7 . Cutting unit  129  is comprised of one or more cutting modules  135 . Cutting modules  135  are movably attached to one or more cutting module cross members  137  such that each cutting module  135  may be separated from adjacent cutting modules at predetermined widths, such as sixteen (16″) or twenty-four inches (24″). Cutting module clamps  139  secure cutting modules  135  at the predetermined widths along cutting module cross members  137 . 
     Cutting modules  135  are comprised of one or more blades  141 . Blades  141  are heated to a temperature capable of vaporizing, or at least melting, a portion of foam block  109  contacting the leading edge of blade  141  to form kerf  111 . For a short period of time after blade  141  has formed kerf  111 , the foam surrounding kerf  111  remains liquefied. The liquid foam surrounding kerf  111  serves to lubricate the passage of stud  107  into kerf  111 . 
     An optional element of cutting module  135  is one or more rollers  143 . Rollers  143  flatten foam blocks  109  immediately prior to when blades  141  contact foam block  109  to ensure a uniform depth  115  of kerf  111 . In the best mode known to the inventors, at least two rollers  143  are spaced apart at a distance equal to or greater than the width of stud  107 . Such configuration enables the rollers  143  to more efficiently and effectively flatten a section of foam block  109  into which stud  107  will be inserted. 
     Another optional element of each cutting module  135  is one or more stud clamps  145 , which receive studs  107  fed into foam panel machine  119 . Stud clamps  145  secure studs  107  in a fixed position relative to cutting module  135  such that cutting unit  129  and studs  107  move substantially as a single unit. In order for stud clamps  145  to secure studs  107  with respect to cutting module  135 , stud clamps  145  preferentially maintain at least three points of contact with studs  107  in order to prevent movement in all three dimensions, x, y, and z. A first point of contact between stud clamp  145  and stud  107  is stud clamp cap  147 , which has a planar surface that communicates with a planar stud channel  149 . Stud clamp cap  147  secures stud  107  against movement in the y plane. A second point of contact between stud clamp  145  and stud  107  is pin  151 , which protrudes through an aperture  153  in stud  107 . Pin  151 , which may be operated pneumatically, hydraulically, or electrically, secures stud  107  against movement in the x plane and assists in limiting movement in the z plane. A third point of contact between stud clamp  145  and stud  107  is stud clamp brace  155 , which has a planar surface that communicates with a planar stud beam  157 . Stud clamp brace  155  secures stud  107  against movement in the z plane and against pivotal motion around pin  151  in the x plane. 
     Studs  107  are maintained in a position parallel to one another using one or more points of contact with stud rollers  123 , which work in conjunction with stud clamps  145 . Stud rollers  123  are preferentially designed to fit snugly within a generally “C”-shaped stud  107  such that stud rollers  123  roll along stud channel  149 , the sides of which are bounded by stud beam  157  and a stud lip  159 . By engaging studs  107  with stud clamps  145  and stud rollers  123  at separate places along the length of studs  107 , studs  107  can be maintained in a parallel configuration in the x, y, and z planes. 
     Optionally, pin  151  performs the additional step of forcibly punching or drilling aperture  153  in stud  107 , rather than requiring stud  107  to be predrilled. Pin  151  may be driven linearly with sufficient force to punch aperture  153  into stud  107 . Alternatively, pin  151  may comprise a bit  161  rotatably powered by driver  163  that creates aperture  153 . Either way, once aperture  153  is created in stud  107 , shaft  165  communicates with aperture  153  in order to create a point of contact with stud  107  in the manner described above. Driver  163  may be a self-powered electric or pneumatic motor, or may receive power from an external source. 
     For each cutting module  135 , stud clamp  145 , blade  141 , and/or roller  143  may be mounted to a single pneumatic actuator  167 , or such components may be mounted to separate pneumatic actuators  167 . Persons having skill in the art will recognize that pneumatic actuators  167  are interchangeable with other types of actuating devices, such as hydraulic, electrical, or mechanical devices. Pneumatic actuators  167  are useful in several components and may serve different functions. For instance, one function of pneumatic actuators  167  is to ensure that stud clamps  145  engage studs  107  with sufficient force to draw studs  107  through kerfs  111 . Another function of pneumatic actuators is to ensure that rollers  143  apply sufficient downward force to foam blocks  109  to ensure adequate flattening of foam blocks  109 . Yet another function of pneumatic actuators  167  is to lift stud clamps  145 , rollers  143 , and blades  141  so that once foam block  109  has been fully kerfed, cutting unit  129  may be positioned so that foam block  109  may be removed from foam panel machine  119 . 
     Turning now to  FIGS. 8-9 , cutting modules  135  are slidably mounted to one or more cutting module guides  169 . Cutting modules  135  are moveable along cutting module guides  169  so that each cutting module  135  may be positioned a predetermined distance from other cutting modules  135 . When cutting modules  135  are positioned in the desired predetermined location, cutting module clamps  139  engage cutting modules  135  in order to immobilize cutting modules  135  with respect to cutting module cross members  137 ; such configuration creates a fixed width between kerfs  111  when foam panel machine  119  is activated. By way of example, in residential construction, parallel studs are typically placed sixteen inches (16″) apart, a configuration known in the industry as “16-inch centers.” However, other types of construction call for 12-, 18, or 24-inch centers, hence the need for adjustable positions of cutting modules  135  (and stud rollers  123 ).  FIG. 8  demonstrates a foam panel machine  119  having a cutting module cross member  137  with cutting module mounts  171  at 16- and 24-inch centers, although centers of virtually any width may be used with foam panel machine  119 . 
     Blades  141  may be positioned throughout a range of positions in the y plane, two of which are depicted by  FIG. 9 . Pneumatic actuators  167  may movably position blades  141  (as well as stud clamps  145  and rollers  143 ) for at least two reasons. A first reason is that foam blocks  109  of different thicknesses may be utilized with foam panel machine  119 , or building codes may require a different depth  115 . A second reason is that blade  141  may be retractable in order for cutting unit  129  to be moved so that foam panel  101  may be removed from foam panel machine  119 . 
     The configuration of blade  141  is shown in more detail in  FIG. 10 . As stated above, blade  141  is preferably electrically heated. When electrical heat is used, blade  141  acts as a circuit. Such circuit is comprised of anode  173 , cutter  175 , heat sink  177 , and cathode  179 . The shape of blade  141  is critical in providing superior cutting properties over hot wire cutters of the prior art because the shape of blade  141  dictates the way in which each element of the circuit performs. During operation of foam panel machine  119 , electrical current flows into anode  173  and through cutter  175 . As seen in the drawing, cutter  175  is comprised of a relatively long, thin, and flat piece of conductive material. Heat sink  177  is comprised of a length of material that is approximately the same length as cutter  175 ; however, heat sink  177  is considerably wider, and preferably somewhat thicker, than cutter  175 . An electrical insulator  181 , which can be a ceramic or a non-conducting gas such as air, separates cutter  175  and heat sink  177  at all points except for intersection  183  of cutter  175  and heat sink  177 . The thickness and width of cutter  175  dictates that when current flows through cutter  175 , cutter  175  heats to a relatively uniform temperature because the cross section of the conductive material remains substantially the same throughout the length of cutter  175 , which means that cutter  175  yields uniform resistance. 
     After current exits cutter  175  and enters heat sink  177  at intersection  183 , which has substantially the same cross sectional area as cutter  175 , the cross section of conductive material comprising heat sink  177  increases. The increased cross section as between heat sink  177  and cutter  175  means that the resistance is lower in heat sink  177  than in cutter  175 , and thus the temperature of heat sink  177  is substantially lower than cutter  175 . The advantages of heat sink  177  are at least twofold: first, heat sink  177  provides a higher bandwidth for current than cutter  175 , which assists in maintaining uniform current and thus even temperature throughout cutter  175 . Second, because heat sink  177  is thicker and remains at a lower temperature than cutter  175 , it remains more rigid than cutter  175 ; the added thickness and rigidity of heat sink  177  assists in forming the proper shape of kerf  111 . After heating cutter  175  and heat sink  177 , current flows from heat sink  177  through cathode  179  and out of blade  141 . 
     Depending on the temperature of cutter  175 , kerf  111  is formed by vaporizing or melting a portion of foam block  109  around blade  141 . During such process, at least a portion of the foam surrounding kerf  111  remains melted after blade  141  continues to move and kerf additional portions of foam block  109 . Heat sink  177  may operate to cool such melted foam, which additionally assists in forming the proper shape of kerf  111 . 
     Various conductive materials may be used to construct blades  141 . High resistivity is necessary in order to construct a small, thin blade  141  capable of reaching high temperatures. Resistivity values of conductive metals change with temperature. The best mode known to the inventors is to construct blades  141  from Nichrome because Nichrome has a relatively high resistivity of 100×10 −8  Ω·m at 20° C., yet a relatively low temperature coefficient of 0.0004 (as compared with other readily available metals). The operating temperature ranges discovered to be ideal by the inventors for foam panel machine  119  are 700 to 1200° F. (370 to 650° C.) for cutter  175  and 250 to 500° F. (120 to 260° C.) for heat sink  177 , although other operable temperature ranges may be used by adjusting the thickness and width of both cutter  175  and heat sink  177 . Resistivity is given by the formula ρ=ρ 20 ·[1+α·(T C −20° C.)], where ρ is resistivity, ρ 20  is resistivity at 20° C., α is temperature coefficient of the metal, and T C  is the temperature of the metal in degrees Celsius. Thus, the resistivity of cutter  175  during operating temperature ranges is 114 to 125×10 −8  Ω·m, while the resistivity of heat sink  177  during operating temperature ranges is 104 to 110×10 −8  Ω·m. 
     The cross-sectional area of cutter  175  may depend on the size and shape of studs  107  to be used. Studs for use in building construction are commonly in the range of 14 to 24 gauge (0.0785 to 0.0276 inches), although sheet metal used in studs  107  can range from 3 to 30 gauge or beyond (0.2391 inches to 0.0100 inches). 
     For example, studs  107  constructed from 20 gauge galvanized steel have a thickness of 0.0396 inches (1.01 mm). When using 20 gauge galvanized steel, a blade  141  having a thickness of 0.0400 inches (1.02 mm) may be utilized to create kerf  111 . Cutter  175  has a length of 7.03 inches (176 mm) and a width of 0.240 inches (6.10 mm), and heat sink  177  has a length of 6.64 inches (169 mm) and a width of 0.710 inches (18.0 mm). The resistance of the parts of blade  141  is given by the formula R=ρL/A, where ρ is resistivity, L is length, and A is cross-sectional area (A=w·h, where w is width and h is thickness). The following table illustrates the resistances realized for cutter  175  and heat sink  177  at operating temperatures: 
                                                                                                               T min     T max     ρ min     ρ max     w   h   L   R min     R max         Part   (° C.)   (° C.)   (Ω · m)   (Ω · m)   (mm)   (mm)   (mm)   Ω   Ω                                cutter   370   650   1.14E−06   1.25E−06   6.1   1.02   176   3.22E−02   3.54E−02       heat sink   120   260   1.04E−06   1.10E−06   18   1.02   169   9.57E−03   1.01E−02       Ratio                               3.37   3.51                    
As demonstrated by the above table, the ratio of resistance as between cutter  175  and heat sink  177  is critical in ensuring that cutter  175  remains at proper temperatures during operation of foam panel machine  119 . The inventors have found that a ratio of resistance between cutter  175  and heat sink  177  of 3:1 to 4:1 will help to ensure proper heating of cutter  175 , and a ratio of 3.3:1 to 3.6:1 is ideal. Nichrome is an ideal metal for forming blade  141  because the ratio of resistance between cutter  175  and heat sink  177  does not vary greatly throughout the operating temperature range of blade  141 , although other materials may have suitable resistance characteristics over the operating temperature range of blade  141 .
 
     The movement of cutting unit  129  is shown in more detail in  FIGS. 11-12 . Cutting unit  129  has gears  185  that interface with teeth  187  on one or more of cutting unit guides  131 . A drive chain  189  passes over one or more gears and a sprocket  191 . Motor  193  provides rotary power to sprocket  191 , thus turning drive chain  189  and moving cutting unit  129 . Driveshaft  195  distributes rotary power equally between gears  185  on each side of cutting unit  129 . In the best mode known to the inventors, teeth  187  are mounted to the bottom of cutting unit guides  131 , and the weight of cutting unit  129  is supported by cutting unit rollers  197  that roll along the top of cutting unit guides  131 . This configuration reduces the force on gears  185  and teeth  187 . A cutting unit guide roller  199  may overlap the edges of cutting unit guides  131  to add lateral stability to cutting unit  129 . Cutting unit guide rollers  199  may be stand-alone components or may be integrated into cutting unit rollers  197 . 
     The process used to produce steel studded foam panels  101  requires at least four main steps: machine preparation, materials loading, machine activation, and capping. The process will be described as performed when all optional components are installed on foam panel machine  119 ; a person having skill in the art will recognize that steps relying on optional components are likewise optional. The machine preparation stage involves configuring the foam panel machine  119  for a particular job. The type and width of stud  107  may dictate the size of blade  141  used and/or the temperature of blade  141 . Studs  107  vary in thickness from 3 to 38 gauge and are made from a variety of materials, including regular steel, galvanized steel, stainless steel, and aluminum. Thickness of sheet metal, as measured in gauge, depends on the type of material; for instance, 14 gauge regular steel studs are 0.0747 inches thick, but 14-gauge aluminum studs are 0.0641 inches thick, a difference of 16.5%. A temperature control unit  201  (shown in  FIG. 3 ) for blades  141  is also configured for the type of foam block  109  used in the process, as high-grade EPS typically requires less heat to cut than low-grade recycled foam. The type and quality of foam block  109  will also dictate how much force is applied to flatten foam block  109  by rollers  143 . Cutting modules  135  are set to a predetermined width, such as 16″ centers. Cutting unit  129  is positioned in a starting location proximal to stud rollers  123 . The length and width of foam block  109  dictate how far cutting unit  129  must travel to fully cut kerf  111  into foam block  109 . For purposes of the disclosure of the inventive method, and because metal studded foam panels  101  are typically installed such that studs  107  are oriented in a vertical direction, throughout this specification the dimension of foam block  109  perpendicular to and between cutting unit guides  131  will be referred to as width, while the dimension of foam block  109  in the direction parallel to cutting unit guides  131  and cutting unit movement  133  will be referred to as length. Likewise, longitudinal movement refers to movement along the length of foam block  109 . Persons having skill in the art will recognize that such definitions are for the convenience of the reader and should not be construed as a limitation of the apparatus or method disclosed herein or the claims thereto. 
     The materials loading stage involves positioning materials upon foam panel machine  119  prior to activation. During the materials loading stage, foam block  109  is secured to deck  121 , and studs  107  are fed through stud rollers  123  and secured to stud clamps  145 . Either top frame  103  or bottom frame  105  may be secured to the end of studs  107  distal to stud clamps  145 . 
     The machine activation stage involves cutting kerf  111  into foam block  109  and inserting studs  107  into kerf  111 . Blades  141  are heated to a predetermined temperature dictated by the type of foam block  109  and/or stud  107  used. Cutting unit  129  moves from a starting location proximal to stud rollers  123  in a direction shown by cutting unit movement  133 . The best mode known to the inventors has cutting unit  129  moving in only one dimension; however, the inventors contemplate that cutting unit  129  could move in two dimensions to create complicated kerfs in foam blocks  109 . Rollers  143  flatten foam block  109 . Blades  141  longitudinally cut kerf  111  into foam block  109  by vaporizing and/or melting foam block  109  as cutting unit  129  moves along the length of foam block  109 . Temperature control unit  201  for blades  141  monitors the temperature of each blade  141  and adjusts the current flowing through each blade  141  in order to maintain a predetermined temperature. Studs  107  are drawn into kerf  111  as cutting unit  129  moves along the length of foam block  109 . Typically, foam block  109  and studs  107  are of substantially equal length; once kerf  111  has been fully formed into foam block  109 , blades  141  are cooled; cutting unit  129  continues to move along length of foam block  109  until studs  107  are fully inserted, at which time stud clamps  145  disengage studs  107 . Pneumatic actuators raise cutting unit  129  in order to avoid obstruction to completion and removal of foam panel  101  from foam panel machine  119 . Preferably, after cutting unit  129  is raised, cutting unit  129  moves to the starting location proximal to stud rollers  123 . 
     The capping stage involves installing top frame  103  and/or bottom frame  105  to studs  107 , if such installation was not performed during the materials loading stage. Top frame  103  and bottom frame  105  may be secured to studs  107  using a crimping tool or a rivet gun, although other methods of metal-to-metal joining are known in the art. 
     While the inventors have described above what they believe to be the preferred embodiments of the invention, persons having ordinary skill in the art will recognize that other and additional changes may be made in conformance with the spirit of the invention and the inventors intend to claim all such changes as may fall within the scope of the invention.