Abstract:
An apparatus is adapted to form a plurality of apertures in a panel made from a meltable foamed plastic material. The apparatus has a movable panel support device for supporting said panel and a heating array. The heating array has a plurality of heating elements mounted to a support frame. The heating array is disposed opposite to the panel support device. Each of the heating elements is adapted to emit sufficient heat to melt the foamed plastic material when a panel is positioned proximate the heating elements. A driving mechanism is provided for moving the panel support device toward and away from said plurality of heating elements. The panel supporting device moves a panel supported thereon, towards and away from the plurality of heating elements and during them movement melts a plurality of apertures in the panel.

Description:
TECHNICAL FIELD 
   The present invention relates to methods and apparatus for forming apertures in foamed polystyrene, and other foamed plastic panels. 
   BACKGROUND OF THE INVENTION 
   Concrete walls and other concrete structures, are typically made by building a form. Unhardened concrete is poured into the form space provided by the form. Once the concrete hardens, the form walls can be removed. In some cases the form walls can remain in place after the structure has been made, and can for example serve an additional purpose such as providing insulation. 
   It is known to make the form walls from a series of interconnected panels. It is also known to use foamed plastic materials, including foamed polystyrene, for such panels. 
   Typically, the panels are held in place to provide the form when the concrete is poured in the form space, by providing tie-rods that stretch between two spaced panels. Typically the rods pass from an inner surface of the panels and join with some kind of end connector. 
   With reference to United States patent application publication no. 2002/0092253 published Jul. 18, 2002, a method is described whereby an anchor member is embedded in a foam panel. During the formation of the foam panel, the panel is injection formed so as to surround the anchor member. This may create a relatively strong connection between the panel and the anchor member. Despite the obvious advantages of such a connection, manufacturing of such plastic panels requires special molding equipment, which allows panels to be formed with installed anchor members. Such equipment and associated methods are expensive and don&#39;t allow the use of a common foam panel produced by industry for wall and roof thermal insulation. In some foamed panel applications for formwork, it is not desirable that the anchor member be fixed relative into the panel during the forming process. In particular, in some applications, it is desirable that the anchor member or connector be free to rotate relative to the panel so it can be secured firmly to an end of a tie-rod. 
   The building of forms using such foam plastic panels is assisted by the availability of numerous apertures in order to receive corresponding tie-rods and/or connectors. 
   It should be noted that known methods of forming apertures, such as milling, are not effective for forming apertures in foam plastic due to its low strength. Additionally, apertures formed with mechanical impacting on foam plastic, is very complicated to control because of the coarse structure of foam plastic. 
   U.S. PTO application Ser. No. 10/253,843 filed on Sep. 24, 2002 by the same applicant, the contents of which, are hereby incorporated by reference, discloses a method and a design for apparatus for forming apertures in foamed plastic panels. The method and apparatus include a carriage mounted on tracks to travel on the frame. The carriage is adapted to hold the panels and there is a mechanism mounted above the panel to move the aperture forming instruments towards the panel. The aperture forming instruments consist of a longitudinal tubular probe heated by an electrical resistance coil with no contact with the panel and cause apertures to be formed there through. The coil is heated by electrical current, using transformers. 
   However, this apparatus has a relatively low production output if a large number of apertures are required for the panel that will be used in the form. The design of the instrument results in a relatively unheated (“cold”) end. To heat the end portion of the instrument to generate a suitably hot thermal field under the instrument&#39;s end, the amount of beating of the main body of the instrument must be significantly increased. However, in heating the end for non-contact entering into a panel made of a foamed plastic material, the heat in the body is so high that it is difficult to form commensurable apertures with a diameter just a small amount larger than the diameter of the instrument. Additionally, this instrument doesn&#39;t allow forming the aperture with a complicated shape. Also, because the instrument is moving toward and through the panel, it becomes colder under the airflow movement and this causes a disruption to the thermal field around the heating instrument. This results in a decrease in temperature of the thermal field, which leads to a need to increase the consumed electrical power volume, to provide a given temperature and thermal field. In addition, use of the transformers as the electricity source for coils increases the cost of such a machine. 
   Accordingly, it is desirable to provide an improved method and apparatus for efficiently providing a plurality of apertures in foam plastic panels, particularly of the type that are used for construction. 
   SUMMARY OF INVENTION 
   According to one aspect of the present invention, there is provided an apparatus for forming a plurality of apertures in a panel made from a meltable foamed plastic material. The panel has first and second opposed surfaces defining a panel body there between. The apparatus comprises: (a) a movable panel supporting device for supporting the panel; (b) a heating array comprised of a plurality of heating elements mounted to a support frame. The heating array is disposed opposite to the panel supporting device and each of the heating elements is adapted to emit sufficient heat to melt the plastic material when a panel is positioned proximate the heating elements. A driving mechanism is provided for moving the panel supporting device toward and away from the plurality of heating elements. The driving apparatus is used to move the panel supporting device and a panel supported thereon, towards and away from the plurality of heating elements. The plurality of heating elements are positioned opposite and proximate the first surface of the panel held by the supporting device. This allows for the panel to be moved by the supporting device to a position proximate the plurality of heating elements enabling the heating elements to melt a plurality of apertures in the panel at the first surface of the panel. 
   According to another aspect of the present invention, there is provided a method of forming a plurality of apertures in a panel made from a meltable foamed plastic material. The panel has first and second opposed surfaces defining a panel body there between. The method comprises the step of moving the panel toward a plurality of heat elements in a first direction so that the first surface of the panel is heated by the plurality of heating elements to melt the plastic material at a plurality of locations. 
   According to another aspect of the present invention, there is provided a heating apparatus that comprises an outer tube having a hollow interior cavity and a first end and a second end. The first end has a hot tip. The apparatus also has a high resistance element extending in the cavity from proximate the first end to proximate the second end. The high resistance element is connected to a source for electricity to pass an electric current through the high resistance element to thereby generate heat capable of melting a plastic material when the plastic material is proximate the heating element. Also there is a heating disc mounted to the outer tube at a distance from the first end. The heating disc is adapted to generate heat capable of melting 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In drawings that illustrate by way of example only, preferred embodiments of the present invention: 
       FIG. 1  is a plan view of a machine in accordance with an embodiment of the invention; 
       FIG. 2  is a side elevation view of the machine of  FIG. 1 ; 
       FIG. 3  is a front elevation view of the machine of  FIG. 1 ; 
       FIG. 4  is a cross sectional view at  4 - 4  in  FIG. 1 ; 
       FIG. 5  is a cross sectional view at  5 - 5  in  FIG. 1 ; 
       FIG. 6  is a cross sectional view through a pre-form for an example of a heating element used to form part of a heating cartridge used in the machine of  FIG. 1 ; 
       FIG. 7  is a schematic view showing the bending operation carried out on the pre-form of  FIG. 6 ; and 
       FIG. 8  is a schematic view showing the shape of the heating element after the bending operation of  FIG. 7  has been carried out on the pre-form of  FIG. 6 ; 
       FIG. 9  is a front elevation view, partially cut away, of a heating cartridge employing the heating element of  FIG. 8 , and illustrating a preferred thermal heating field produced thereby; 
       FIG. 9   a  is a front view of an alternate embodiment to the heating cartridge of  FIG. 9 , and illustrating a preferred thermal heating field produced thereby 
       FIG. 10   a  is a cross sectional view of a secondary disk heating element used in the heating cartridge of  FIG. 9   a;    
       FIG. 10   b  is a plan view of disk heating element of  FIG. 10   a  with removed top part; 
       FIG. 11   a  is one example of a shaped aperture formed in a polystyrene panel by the machine of  FIG. 1  with a mounted heating cartridge in  FIG. 9  or  9   a;    
       FIG. 11   b  is another example of a shaped aperture formed in a polystyrene panel by the machine of  FIG. 1  with a mounted heating cartridge in  FIG. 9  or  9   a;    
       FIG. 11   c  is a third example of a shaped hole formed in a polystyrene panel by the machine of  FIG. 1  with a mounted heating cartridge in  FIG. 9   a;    
       FIG. 12   a  shows the initial step of one aperture forming in a foamed plastic panel by the machine of  FIG. 1  with a mounted heating cartridge in  FIG. 9  or  9   a;    
       FIG. 12   b  shows the intermediate step of one aperture forming in a foamed plastic panel by the machine of  FIG. 1  with a mounted heating cartridge in  FIG. 9  or  9   a;    
       FIG. 12   c  shows the final step of one aperture forming in a foamed plastic panel by the machine of  FIG. 1  with a mounted heating cartridge in  FIG. 9   a;    
       FIG. 13  is a perspective view of the frame and heating elements of the machine of  FIG. 1 ; 
       FIG. 14  is a perspective view of the lifting table which is another part of the machine of  FIG. 1 ; 
       FIG. 15  is an isolated view of several heating elements mounted to a supporting beam in the machine of  FIG. 1 ; 
       FIG. 16  is a perspective view showing a panel stripper forming another part of the machine of  FIG. 1 ; 
       FIG. 17  is a schematic layout showing the control console for the machine of  FIG. 1 ; and 
       FIG. 18  is a schematic functional layout of several of the components of the machine of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
   With reference first to  FIGS. 1 ,  2 ,  3 ,  4  and  5  a machine  30  for providing a plurality of apertures in a foamed plastic panel  31  is illustrated. Machine  30  can be adapted for use with a variety of foamed plastic panels, including expanded polystyrene panels (eg. grade EPS ASTM C 578-00 Type 1X) and extruded polystyrene panels (eg. grade XPS ATM C 578-00 Type VI). Panels  31  are typically in the range of approximately 2-20 cm in thickness, but can be larger and smaller in thickness. 
   Machine  30  includes a frame generally designed  39 , a lift table  41  movable relative to the frame, and a heating array generally designated  63  positioned above the lift table and immovably fixed to the frame  39 . Machine  30  also has a ventilation system generally designated  51 , a control system  61  and a transport conveyor system  37 . 
   As best shown in  FIGS. 14 and 16 , lift table  41  is generally formed from longitudinal beam members  46  interconnected with a series of transverse members  48 . Mounted at the four outer corners of lift table are bushing and block members  49 . A bushing  49   a  in block  49  is configured to receive a guide rail  43 . Bushing  49   a  and block  49  can thus slide up and down along guide rail  43 . An upper end of each guide rail  43  is affixed to a mounting block  42   a , which is mounted to frame  39 . Likewise, a lower end of each guide rail  43  is affixed to a mounting block  42   b , which is mounted to a lower part of frame  39 . Thus, lift table  41  is mounted for vertical movement relative to frame  39 , such movement restricted on guide rail  43  within the limits imposed by the abutment of block  49  with blocks  42   a  and  42   b . Various different configurations for lift table  41  are of course possible. By way of example only, lift table  41  in said machine  30  can be configured as a scissors lift table. 
   Also, as shown in  FIG. 16 , a panel stripper apparatus includes a plurality of transversely and horizontally mounted stripper bars  77  secured to vertical bars  78 . The vertical bars  78  have guides, which slide along vertical tracks or slots (not shown) in vertical bars  79 . Bars  79  are fixedly mounted to the frame  39  and have vertical movement stoppers  80  that restrict the vertical movement of bars  78  in the guides and thus the vertical movement of bars  77 . The stripper bars  77  and  78  are configured so that they can move vertically upward accompanying, and lifted by, the upward motion of lift table  41 . This lifting movement will preferably commence after the panel has already been lifted free of transport conveyor  37 , but before the panel comes into the vicinity any significant degree of heat generated by the thermal field from the heating array  63 . The upward movement of bars  77  however can continue as the heating elements penetrate the body of the panel. Once the apertures have been formed, the lift table  41  will move downward. During this movement of lift table  41 , bars  77  will likewise move down from their own weight, and apply a downward force on an upper surface of panel  31 , preferably until panel  31  has cleared the heating elements and most preferably exited the thermal field. This results in preventing the panels from staying in a position between the heating cartridges. Other devices or apparatus can be employed in machine  30  to provide a stripping mechanism for the panel. For example, a loose chain (possibly weighted) connected to frame  39  at two ends, can be employed that rests upon the top of the panel when lifted to heating array. When the lift table is lowered, it can apply a downward force onto panel  31 . 
   Returning to the construction and operation of lift table  41 , as shown in  FIG. 4 , lift table  41  also has a plurality of upstanding pusher members  73  which, as will be explained in detail hereinafter, are used to lift a panel  31  towards the heating array  63  in order to create the apertures in the panel. A plurality of pusher members  73  are mounted to each of transverse members  48  of table  41  (not shown in  FIG. 14 ). As is illustrated in  FIG. 5 , transverse members  48  of lift table  41  are positioned vertically below the belts  85  of conveyor  37 , and pusher members  73  extend between the belts. Thus, if a panel  31  is positioned on belts  85 , upward movement of pushers  73  will cause the panel to be raised upwards from belts  85 , toward heating array  63 . 
   Table  41  is vertically raised and lowered relative to heating array  63  and frame  39  by a table drive system generally designated  65 . Table drive  65  can, for example, comprise a DC elective drive motor interconnected to a typical gear mechanism, which translates the rotary movement of the drive motor into vertical upward and downward motion of the table. Other suitable linear drive mechanisms, which can be suitably controlled and drive lift table  41  up and down, can be used. 
   With reference to  FIG. 13 , frame  39  generally includes a series of pairs of longitudinal beams,  29   a ,  29   b  and  29   c  each pair being interconnected at its ends to an end of a transverse member, namely transverse members  53   a ,  53   b , and  53   c  respectively. Each combination of longitudinal beams and transverse members  29   a ,  53   a ;  29   b ,  53   b ; and  29   c ,  53   c  is attached to four columns  27 . Thus a frame  39  is formed and serves to support the lift table  41  for vertical movement in relation thereto. Frame  39  also supports heating array  63  having a plurality of heating cartridges  122 , from top beams  29   a.    
   With reference to  FIGS. 13 and 15 , heating array  63  comprises a plurality of transversely mounted heat array support beams  83 , secured at each end to a longitudinal beam  29   a . Secured to, and depending down from, each heat array support beam  83  are a plurality of heating cartridges  122 , which are described in detail hereinafter. 
   In this preferred embodiment, the heating array  63  is fixed in space. It will however be appreciated that in some embodiments, the heating array  63  might be capable of a small amount of movement, without substantially disrupting the thermal field around the heating cartridges  122 . Nevertheless, most of the movement between heating array  63  and the panel support apparatus that takes place relative to the surrounding environment, is movement by the panel support apparatus. 
   With reference to  FIGS. 1 and 2 , transport conveyor  37  is configured to be able to transport panels  31  from a loading station A, to an aperture forming station B, to an unloading station. Conveyor  37  comprises a pair of spaced apart continuous conveyor belts  85  driven around spaced drive wheels  87   a ,  87   b  which can be powered by conventional drive mechanisms. A plurality of freely rotating rollers  89 , affixed to frame  39 , are provided to support the belts  85  as they move from station A, to station B and finally to station C. Conveyor belts  85  are configured so as to be able to support thereon one or more panels  31  through stations A, B and C. Mounted at a leading position and trailing position on each belt  85 , are movable guide members or flights  81 , which guide the transverse edges of panels  31 . It will be appreciated that several sets of guides will be provided on belts  85 . Mounted longitudinally on frame  39  are also fixed guides  83  which serve to guide the longitudinal edges of panels  31 . Thus, each panel  31  is guided in its movement by a leading guides  81  and a trailing pair of guides  81 , such that each panel  31  will move with belts  85  and generally maintain its orientation. The guides  81  joined to the transport conveyer belt are used to fix the position said panels  31  in the loading position, lifting and lowering positions and the unloading position. Usually guides  81  are simply L-shaped metal profiles. 
   Ventilation system  51  includes a hood  35  with a centrally positioned opening  38  in communication with an exhaust duct  33 . A fan (not shown) is driven by a fan motor  36 . The exhaust fan is disposed at the opening  38  of hood  35  and is configured to be able to draw up into the exhaust duct  33 , air, noxious gases and other fine particle materials which it is desired to remove from the vicinity of the machine  30 , and which results from the operation of the machine, as described hereafter. 
   Heating array  63  includes a plurality of heating cartridges  122 , and in a preferred embodiment, there are a total of 72 cartridges arranged in longitudinally and transversely spaced orientation to provide a rectangular grid. The effect of employing machine  30  to a panel  31 , is to create a grid of apertures in a pattern shown at station C in  FIG. 1 . Of course, the specific arrangement of the heating cartridges in the heating array  63  can be modified to provide for any particular grid pattern that is required. 
   With reference to  FIG. 6 , a pre-form  101  component for one of several of the preferred heating elements  100  (See  FIG. 9   a ) employed in an example of a heating cartridge  122  used in heating array  63  is illustrated. Pre-form  101  includes a spiral wire  117  made from a material with a long-life durability and thermal stability having high electrical resistance such as Nichrome (nickel chromium alloy). Wire  117  has attached to each end a connector wire  115   a ,  115   b  which is a wire having much less resistance to permit electric current to be delivered to wire  117 . Wires  115   a ,  115   b  would typically be made of a material like copper with typical electrical resistivity in the order of 1.7 μOhms×cm. By comparison, wires  117  would typically have an electrical resistivity of in the range of 100-110 μOhms×cm. 
   The inner wall of tube  121  is also insulated with powdered ceramic material or other suitable insulator to ensure there is no short circuit between wire  117  and the inner wall of tube  121 . Wire  117  is thus held in inner cavity  119  of hollow steel tube  121  in an insulated state. Except for permitting the passage of wires  115   a  and  115   b  to extend from the ends of the tube  121 , the inner cavity is sealed at both ends  121   a  and  121   b  with a stopper  133  made with an insulating material such as a suitable ceramic material  123 . Wires  115   a ,  115   b  pass through apertures in stoppers  123  and are interconnected to a suitable source of electricity of a suitable voltage to provide the desired current and consequent heating. It is not necessary that the cavity  119  be air tight due to the fact that the tube is made from heat-resistant material. 
   To provide the apertures that are formed substantially commensurate with the diameter of the heating cartridge, a uniform temperature field is required around the heating cartridge tip. 
   To make the heating element  100  with a hot tip used in the heating array  63  from pre-form  101 , the pre-form  101  is folded about an axis x as shown in  FIGS. 7 and 8 . It will be appreciated that tube  121  will have a configuration that is suitable for such bending. It will be appreciated that heating element  100 , thus formed, is of a general U-shaped configuration and has, particularly at the bottom end portion of the U-shape, a generally intensified heat emission when electric current is passed through wire  117 . This results in a “hot-tip” heating element. 
   The cross section of tube  121  can take a variety of cross sectional shapes including half circles, triangles, rectangles, depending upon the desired configuration of the apertures to be formed in the panel  31 . The cross sectional shape of the initial tube  121 , will of course determine the cross sectional shape of the bent tube and thus heating element  100 . 
   With reference to  FIG. 9 , heating element  100  is shown housed in a holder  120  and thus forms a heating cartridge  122 . Holder  120  comprises a hollow tube, in which is held heating element  100 . Holder  120  is preferably made from stainless steel although other suitable materials can be used which include but are not limited to aluminum alloys. 
   Heating element  100  can be attached to holder  120  by, for example, spot welding. The upper end  120   a  of holder  120  is open to permit wires  115   a ,  115   b  to extend therefrom for connection to an electric circuit. 
   A flange member  124  is affixed (for example by spot welding) to holder  120  proximate upper end  121   a  of tube  121  and flange  124  assists in mounting the heating cartridge  122  to a beam member  83  as shown in  FIG. 15 . An aperture or bore in beam  83  permits cartridge  122  to be received there through and is suspended from the beam by the abutment of flange  124  with the upper surface of beam  83 . Cartridge can be attached to beam  83  securely or preferably with a relatively easy mechanism for detaching the cartridge from its supporting beam. This allows easy-to-do repairs to be performed on the heating array. It will be appreciated that it is quite beneficial if the heating cartridges can be replaced easily if for example, a cartridge burns out. 
   In a preferred embodiment, cartridge  122  comprises generally a WATT-FLEX (trade mark) split-sheath cartridge heater made and sold by Dalton Heating Co., Inc. of Ipswich Mass., employing a heated tip. This cartridge design can supply an appropriate thermal field for each cartridge  122  of heating array  63 . 
   It is preferred in cartridge  122  that a thermal field be provided that produces a thermal field which generally stretches ahead of the heating element  100 , so that heating of a panel in a relatively narrow area can be achieved without the heating element having to contact the panel surface. 
   With reference to  FIGS. 9   a  and  10   a , an alternate configuration for a heating cartridge is shown. Heating cartridge  222  employs a heating element  200  configured like heating element  100 . Cartridge  222  also has a tube  221  configured generally like tube  121 , with a flange  224  and wires  215   a ,  215   b  extending out from an upper end  221   a  thereof. In addition to heating element  200 , cartridge  222  includes a secondary heating disc  290 . As best shown in  FIG. 10   a , heating disc  290  essentially has three separate components: an upper cover member  292 , a lower holder member  294  and wire member  295 . Disc  290  also has a central bore  293  to permit the disc to be received onto tube  222 , which is preferably affixed thereto by for example spot welding. 
   Cover  292  is made from a relatively a material with relatively high degree of thermal insulation (ie. low thermal conductivity), such as for example aluminum oxide ceramic. Other possible materials for cover  292  include but are not limited to sintered and compact barium oxide ceramic, nickel alloy. On the other hand holder  294 , which is secured to cover  292 , is made from a material with relatively high thermal conductivity such as a metal like copper or aluminum. Holder  294  is preferably affixed to cover  292  by common fasteners (screw or bolt and nut). It is thus preferred that holder  294  can be detached from cover  292  to make repairs and the like. 
   Formed in an upper surface of holder  294 , is a continuous spiral groove  291  extending from a position near the outside perimeter of the disc, inward toward the center aperture  293 . Inset in groove  291  is a continuous spiral wire cartridge  295  made from a material, such as nickel-chrome alloys having a relatively high electric resistance When electric current is run from an electric power source through cartridge  295  from contacts  296   a  to  296   b  (or in the reverse direction) heat is generated in the cartridge  295 , which in turn heats holder  294 . However, as cover  292  is made from a material with a relatively high degree of thermal insulation, the cover itself will not become unduly heated. 
   An example of a suitable heater that can be incorporated as a heating disc  290  is a DIFF-THERM (trade mark) Platen Heater also made and sold by Dalton Electric Heating Co., Inc. 
   It is important that the heating elements and disc be able to heat the panel up to, or above its melting temperature (which for expanded polystyrene is about 250 degrees C.) but that the temperature not reach or exceed the flash point of that material. In other words, it is important that the material not be heated to such a degree that it ignites. 
   Preferably the supply of electrical current to each of the cartridges  122  and to discs  190 , is not by way of simply one or more transformers. Rather it is preferred that electronic devices (eg. teristor—triac with special IC) be associated with each cartridge. Each teristor (triac with special IC) can be provided with a specific duty cycle (eg. current on for 3 secs, current turned off for 2 secs, repeated). Alternatively, the teristor (triac with special IC) can be provided with a feedback look that is interconnected with temperature control device(s) [also provided]. In this way, the actual temperature of the heating elements can be monitored in real time and the teristor (triac with special IC) turned on and off as required. In this way, the supply of electric current to a particular cartridge can be turned off and on, to ensure that the temperature or thermal field emitted by the cartridge, stays within a desired range. This should have the effect of reducing the overall amount of electrical energy consumed by the machine  30 . 
   One safety feature that can also be provided, is a mechanism for detecting if a particular cartridge has failed. This can be conveyed to an operator by way of a light emitting diode which is activated if there is a failure in the circuit. For example could be set up so that the diode will alternately be illuminated and then turn off during normal operation as the heat of the heating cartridge is maintained within a desired range, but will stay un-illuminated if the cartridge has failed. 
   With reference to  FIG. 17 , an example layout for control console  61  (shown in  FIGS. 1 and 2 ) is illustrated in detail. 
   With reference to  FIG. 18 , an example schematic layout is shown of the operational features of machine  30 . 
   In general the control system, which can operate in either a manual or automatic mode, performs a number of functions. The control system, including the PLC:
         1. Provides for automatic temperature control for the heating cartridges and heating disc (if applicable), by controlling the supply of electricity to the heating elements therein.   2. Can control the movement of the panels on the conveyor  37  through stations, A, B and C.   3. Can operate the movement of the lift table up and down thus controlling the position of the panel in relation to the heating elements, including providing for intermittent motion during the aperture forming process caused by the heating elements.   4. Provides for machine shut-down or disablement in certain situations, particularly to ensure the safe operation of the machine  30 .       

   The control system can also be used to automatically operate the transport conveyor  37 , to deliver panels from station A, to B and to C. 
   With reference to  FIGS. 1   a ,  11   b  and  11   c , three different shaped apertures H 1 , H 2  and H 3  respectively, are shown in a panel  31 , as formed by machine  30 . 
   With respect to  FIG. 11   a , aperture H 1  is a straight forward cylindrical aperture extending from the upper surface  31   a  through the body of the panel to lower surface  31   b  and has cylindrical walls  71 . 
   With respect to aperture H 2  shown in  FIG. 11   b , this aperture has a cylindrical portion  171  like aperture H 1  in  FIG. 11   a . However, extending downward for a short distance from upper surface  31   a  is a frustum of cone or sphere portion  173 . Frustum of cone portion  173  provides an inset portion in the surface  131   a  of the panel that can be utilized for example to inset the leg of a connector element used to connect to a tie rod (not shown). Finally, with respect to  FIG. 11   c , aperture H 3  in panel  231  comprises an aperture which is similar to aperture H 2  in  FIG. 11   b  but includes an additional cylindrical disc portion  275  positioned above frustum of cone portion  273  and cylindrical portion  271 . Disk portion  275  has a much larger radius than cylinder portion  271  and cone portion  273  and can be utilized to provide an inset for a large mushroom-shaped connector nut or the like. 
   Now with reference to  FIG. 12   a , the formation of an aperture H 1  in  FIG. 11   a  is illustrated. When the lift table  41  is raised, the panel is brought gradually into the thermal field emitted from the element  100 . As the temperature reaches the melting point of the polystyrene at the surface, the emitted heat start to melt the polystyrene sheet and start to form the aperture H 1 . If the element  100  is held at a fixed distance from panel  131  for an extended period of time, this will tend to cause the formation of the frustum of insert portion  173 . Assuming that the thermal field around the bottom of the heating element is generally comprised of isotherms (akin to iso-lines—being positions in space having the same temperature) each formed to outline a semi-spherical shape, the opening  173  will tend to initially be formed in partial spherical shape as well. In a preferred embodiment, the tip of the heating element will be held approximately 0.5-2 cm from the upper surface of panel  31  for a time period in the range of 3-10 secs. Thereafter, as illustrated in  FIG. 12   b , as the panel is brought upwards the heating element  100 , the element will pass into the body of the panel melting the polystyrene as it moves into the body and forming the cylindrical portion  171  of aperture H 2 . The formation of the cylindrical portion is assisted by the shape of the thermal field. Around the exposed body portion of heating element  100  the thermal field has cylindrical shaped or cylinder defining isotherm. Preferably, the rate of movement of panel  31  relative to the heating element  100  during the cylinder portion ( 171  in  FIG. 11   b ) forming stage is in the range of 3-60 mm/sec. 
   It should be noted, that because the panel is moved relative to the environment, and the heating array  63  remains fixed relative to the environment, the disruption of the thermal field around each heating cartridge is minimized. This enable the desired shaped aperture in the panel to more easily form. 
   It will be appreciated that the particular shape and size of the aperture formed in the polystyrene sheet will be determined by features such as the amount of heat emitted from the heating element  100 , the particular shape of the cross section of heating element  100  as well as the duration of the application of heat at any particular position in the vicinity of the polystyrene panel. 
   With reference to  FIG. 12   c , the use of secondary heating disk  290  on a cartridge  122  is illustrated to form a disk portion  275  in upper surface  231   a  of panel  231 . 
   Generally, the operation of the machine is as follows. With reference again to  FIGS. 1 ,  2  and  5  in particular, first a polystyrene sheet  31  is positioned on transport conveyor  37  between guides  81  and guides  83 . This could be done manually or by a robot or other automated placement device. Conveyor  37  could be synchronized so that the loading at Station A of a panel  31  takes place at the same time as the other operations at Stations B and C as described hereinafter occur. In other words, loading, aperture forming and unloading can all take place while conveyor  37  is stationary, on three different panels  31 . 
   Once panel  31  has been loaded at Station A, the conveyor is advanced to move panel  31  to Station B where it is positioned immediately above lift table  41  and the pusher elements  73  thereof. Then, either manually or by automation controlled by the PLC, the lift table will operate such that pushers  73  extend between conveyor belts to lift panel  31  upwards towards the heating array  63 . In one embodiment, the lift table  41  will, as described above, stop for a period of time to permit a conical portion such as portion  173  in  FIG. 11   b  and  12   a  to be formed. Thereafter, once the appropriate amount of melting of the polystyrene has occurred, the lift table is raised either manually or automatically such that movement upwardly of the polystyrene sheet initiates melting but is at such a speed that there is no contact directly between heating element  100  or in the other part of cartridge  122 . Thus, the speed is controlled to ensure there is sufficient melting so that no contact occurs. 
   Once the heating element  100  has passed from the upper surface  131   a  to the lower surface  131   b  of the polystyrene sheet, it will be appreciated that there may be some dripping downwards of melted polystyrene material. However, because the heaters are below the heater ray  63 , there is no dripping of material onto the heating elements  100  or any other part of heating array  63 . 
   Once the aperture such as aperture H 2  or H 1  has been formed in the panel  31 , the lift table is then lowered such that the sheet  31  is positioned back on conveyor  37  between guides  81  and  83 . This preferably takes place relatively quickly so that no further melting of material occurs. Conveyor  37  can then be operated to move the sheet  37  to Station C where panel  31  is moved from machine  30  again either manually or automatically with a robot or the like. 
   When an aperture like H 3  shown in  FIG. 11   c  is desired, the movement of the cartridge  122  including heating element  100  and disk  290  is slightly varied. Once the panel has been pierced, and disk  290  is in a position above upper surface  231   a  (as shown in  FIG. 12   c ), the lift table is stopped for a predetermined period of time to allow the formation of the disk portion  275  in surface  231   a . The reverse movement through the panel to extract the cartridge  122  and heating element  100  is done at relatively high speed (preferably in the range of 50-150 mm/sec.) so that further melting and distortion of the opening is minimized. 
   Although preferred embodiments of the invention have been described in detail herein and illustrated in the drawings, it is to be understood that the invention is not limited to those precise embodiments and that various changes and modifications may be effected therein without departing from the scope or spirit of the invention.