Abstract:
According to the present invention, an in-line compounding and extrusion deposition compression molding apparatus and method for producing a fiber-reinforced molded structural component is provided. The apparatus comprises an extruder device having an internal cavity formed therein and an extruder screw rotatably disposed within the internal cavity for producing a polymer melt. A deposition die head is disposed at a first end of the device, the deposition die head having a die channel disposed therein for receiving the polymer melt from the device. The apparatus includes at least one fiber element for feeding at least one reinforcing fiber element into the die channel for compounding the at least one reinforcing fiber element with the polymer melt to produce a fiber-reinforced polymer compound. The apparatus additionally includes a mold for receiving the fiber-reinforced polymer compound to form the fiber-reinforced molded structural component.

Description:
TECHNICAL FIELD 
     The present invention relates generally to the manufacture of fiber-reinforced thermoplastic polymeric structural components and, more particularly, to an apparatus and method for single step, in-line compounding, deposition and compression molding of fiber-reinforced thermoplastic polymeric structural components. 
     BACKGROUND OF THE INVENTION 
     Fiber-reinforced thermoplastic polymer structural components are most commonly manufactured from long fiber thermoplastic (LFT) granulates (pellets), glass mat thermoplastic (GMT) sheets, or pultruded sections. Long fiber-reinforced granulates typically consist of glass fiber bundles encapsulated with a thermoplastic through a cable coating or a pultrusion process. LFT granulates can be injection molded but are more commonly extrusion compression molded in order to preserve fiber length in the finished product. Although the damage to LFT granulates during processing is reduced when extrusion compression molded, some damage still occurs during the plastication process due to shear heating. 
     GMT sheets consist of a needle-punched glass mat impregnated with a thermoplastic polymer (typically polypropylene) to form a glass-reinforced thermoplastic sheet which is subsequently heated and compressed in a vertical compression press to obtain the final part shape. Desired mechanical properties of parts produced from GMT sheets can be custom tailored via the orientation of the glass fibers within the sheet. Overall mechanical properties are as good and many times improved over parts produced from LFT granulates, particularly in the area of impact strength. However, GMT sheets require preheating prior to compression molding and have flow limitations in the direction perpendicular to a die draw. 
     The pultrusion process is predominantly used in applications where the structural component requires optimal mechanical properties in one direction. Pultrusion typically involves impregnating fiber bundles with a polymer melt while the bundles are passed through a cross-head extrusion die, which also serves to shape the impregnated fibers into a predetermined section. Upon exiting the die, the polymer-impregnated fiber bundles are drawn into a cooling trough and cut to length upon exiting a haul-off unit. If it is desired to reshape these sections, as in compression molding, the sections must be reheated to the point where flow will occur under pressure. Also, the reheated sections require hand lay-up within the mold to obtain the desired fiber orientation. 
     Polymer components reinforced with fibers may also be manufactured using continuous in-line extrusion methods known in the art. Such methods involve the plastication of a polymer in a first single screw extruder from which the output is fed to a second single screw extruder. Fibers are introduced in the polymer melt in the second extruder either in chopped-segmented form or as continuous strands under a predetermined tension. The fiber-reinforced polymer compound is fed into an accumulator and then applied automatically or in a separate step to a compression molding tool wherein the fiber-reinforced polymer compound is shaped as required for a particular application. Alternatively, the fiber-reinforced polymer compound may be continuously extruded onto a conveyor and sectioned thereupon. The conveyor delivers the sectioned fiber-reinforced polymer compound to a placement assembly which removes the sectioned compound from the conveyor and places the compound upon the compression molding tool. 
     In-line extrusion methods used in the art to manufacture fiber-reinforced polymer compounds often damage the fibers during processing thus degrading the performance of the final reinforced composite structural component. Introducing fiber into the polymer melt within the extruder exposes the fiber to an extruder screw therein which rotates to create the polymer melt, mix the melt with the fibers, and move the resulting compound toward an outlet of the extruder. The rotation of the screw exerts shear forces upon the fiber resulting in wearing and eventually severance of the fiber. The forces within the extruder may also have an adverse effect upon the screw and the interior of the extruder barrel resulting in increased maintenance and cost. Additionally, the fiber may easily become tangled or otherwise mis-distributed within the extruder thus preventing a uniform distribution of the fiber throughout the polymer compound and resulting in an inconsistent disposition of individual fiber lengths. 
     Furthermore, the fibers within the extruder are exposed to the heat of the polymer melt for a substantial amount of time as the screw moves the fiber-reinforced polymer compound the length of the extruder. The temperature within the extruder can be, for example, in excess of three hundred and fifty degrees Fahrenheit. Natural fibers, which are lower in cost than synthetic fibers and are preferred for their recyclable properties, do not survive exposure to the magnitude of heat present within the extruder and thus tend to complicate the discussed extrusion methods of manufacturing fiber-reinforced polymer structural components discussed above. 
     Typical methods of extrusion manufacturing of fiber-reinforced polymer structural components do not permit the percentage of reinforcement fibers within the reinforced polymer compound to be varied during compounding or extrusion deposition. Various uses of fiber-reinforced polymer structural components may benefit from a controlled variation of fiber content within the reinforced polymer compound and hence throughout the resulting structural component. For instance, a portion of a particular structural component may require extra reinforcement whereas another portion of the same structural component may require little to no fiber reinforcement. Additionally, the structural component may call for various cross-weavings of the reinforcement fibers. Known extrusion methods allow neither variation of the percentage of fiber throughout the structural component during extrusion and deposition nor variation of the positioning of the fiber, i.e., cross-weaving, as applied to the reinforced structural component upon the compression mold thus limiting the effectiveness of such methods. 
     SUMMARY OF THE INVENTION 
     An in-line compounding and extrusion deposition compression molding apparatus for producing a fiber-reinforced molded structural component is provided. The apparatus allows a single step process for forming a polymer melt, extruding the polymer melt through a die channel, compounding the polymer melt in the die channel with at least one reinforcing fiber to form a fiber-reinforced polymer compound, depositing the fiber-reinforced polymer compound onto a compression mold, and molding the reinforced structural component therein. 
     In a preferred embodiment of the present invention the apparatus comprises a barrel having a body and an internal cavity formed therein. An extruder screw is rotatably disposed within the internal cavity to facilitate extrusion of a polymer melt which is also disposed within the internal cavity. The polymer melt is maintained at a predetermined temperature within the internal cavity of the extruder by the shear frictional forces of the rotating extruder screw and by a temperature mechanism disposed in the barrel. A deposition die head is disposed on a first end of the barrel for receiving the extruded polymer melt from the barrel. The deposition die head includes a die channel with a first opening proximate the barrel, connectively related to the internal cavity, and a second opening distal the barrel. The deposition die head may be releasably mounted to the barrel and the deposition die head, itself, may be comprised of a plurality of releasably mounted parts to facilitate operator access to the die channel. The apparatus further includes at least one fiber element for feeding at least one reinforcing fiber into the die channel of the deposition die head to form a fiber-reinforced polymer compound which is released from the second opening of the deposition die head onto a cavity of an open compression mold. The compression mold closes to form the fiber-reinforced molded structural component. 
     The apparatus, in a preferred embodiment, is movably disposed such that the apparatus may be maneuvered within the open compression mold in three dimensions, commonly understood to be the x, y, and z coordinate planes. The ambulatory nature of the apparatus allows disposition of the fiber-reinforced polymer compound in various concentrations and arrangements throughout the compression mold cavity. Thus, the amount of fiber reinforcement may be varied within the cavity of the compression mold resulting in a polymer structural component having enhanced reinforcement where desired. 
     The percentage of fiber within the reinforced polymer compound may also be varied through a simple adjustment of the deposition die head. The deposition die head may be fitted with a die lip which includes a deposition opening through which the fiber-reinforced polymer compound is passed during deposition thereof onto the cavity of the compression molding tool. Utilizing a die lip with a smaller opening allows less of the polymer melt to pass through the deposition opening thus increasing the percentage of reinforcing fibers relative to the volume of polymer melt. Contrariwise, a die lip with a larger opening will produce a fiber-reinforced polymer compound with a lesser percentage of reinforcing fiber relative to the volume of polymer melt. 
     The present invention further allows the percentage of reinforcing fibers within the fiber-reinforced compound to be varied by introducing additional reinforcing fibers or terminating existing reinforcing fibers mid-stream during formation and deposition of the fiber-reinforced polymer compound. In other words, the number of reinforcing fibers present in the fiber-reinforced compound may be varied in situ thus altering the percentage of fibers within the reinforced compound, hence ultimately in the structural component. 
     The disposition of fiber within the structural component may also be designated, as alluded to above, by the maneuvering capabilities of the apparatus of the present invention thus allowing, for example, continuous elongated fibers to be positioned congruent with one another or varied creating a cross-weaving fiber arrangement as desired. 
     Further, the integrity of the fiber is preserved prior to compounding by not introducing the fiber into the extruder barrel at an upstream location thus not subjecting the fiber to damage within the extruder due to the mechanical shear forces induced by the rotation of the screw within the barrel and the heat resulting therefrom. Correspondingly, the extruder is spared the undesired wear associated with introducing the fiber directly into the extruder. Also, the fiber may be maintained at a predetermined tension throughout the compounding process enhancing the alignment of fiber and facilitating the wet-out process while ensuring consistent and uniform distribution of the fiber, thus maximizing the structural benefits of the final reinforced molded component. 
     The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
     FIG. 1 is a side elevation view of an extrusion deposition compression molding assembly of the present invention; 
     FIG. 2 is a perspective view of an exemplary extrusion deposition compounding device of the present invention with an exploded view of a deposition die head; 
     FIG. 3 is a front elevation view of an upper portion of the deposition die head in an exemplary embodiment; 
     FIG. 4 is a bottom plan view of the upper portion of the deposition die head in an exemplary embodiment; 
     FIG. 5 is a perspective view of a second lower portion of the deposition die head; 
     FIGS. 6-8 depict bottom plan views of the deposition die head showing various die lips mounted thereon; 
     FIG. 9 is a cross-section view of an exemplary fiber bundle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 depicts an exemplary embodiment of the extrusion deposition compression molding (EDCM) assembly  10  in accordance with the present invention. The EDCM assembly  10  includes a compression mold  12  having a female half  14  and a male half  16 , each including a contact surface  18 . The female and male halves,  14  and  16  respectively, are complimentary in shape to mate with each other. The compression mold  12  may be a conventional mold generally used for molding polymers to desired shapes and forms. The compression mold  12  is disposed movably on a frame (not shown) so that the contact surfaces  18  may be moved into proximity, the male half  16  moving towards and being received by the female half  14  thus shaping a fiber-reinforced polymer compound  25  disposed therein. More specifically, the fiber-reinforced polymer compound  25  is shaped according to the contour of the contact surfaces  18  of the compression mold  12 . 
     The EDCM assembly  10  further includes an extrusion deposition compounding device  20 . The extrusion deposition compounding device  20  includes an extruder  22  which has a body  24  and a neck  26  extending from the body  24 . The body  24  includes a screw  28  disposed on an interior thereof. In one embodiment of the present invention, the screw  28  rotates to move a polymer melt  30  towards the neck  26  of the extruder  22 . The neck  26  has a channel (not shown) located therein for receiving the polymer melt  30  from the body  24 . The screw  28  advances the polymer melt  30  into and through the channel of the neck  26 . Another embodiment, according to the present invention, may include a reciprocating screw (not shown) which rotates within the body  24  to extrude the polymer melt  30  towards the neck  26 , the reciprocating screw simultaneously moving in a direction away from the neck  26  of the extruder  22  to form a volume of plastic shot proximate the neck  26  of the extruder  22 . The reciprocating screw then moves toward the neck  26  plunging the plastic shot of polymer melt  30  into the channel of the neck  26 . 
     The polymer melt  30  is disposed in the interior of the extruder  22  and maintained at a predetermined temperature as discussed herein. A polymer material (not shown) used to form the polymer melt  30  is introduced into the extrusion deposition compounding device  20  by any number of techniques including the use of a hopper (not shown) into which the polymer material is fed. Often, the polymer material is in the form of plastic pellets. 
     The extrusion deposition compounding device  20  further includes a deposition die head  32  for forming the fiber-reinforced polymer compound  25 . The deposition die head  32  is disposed adjacent the neck  26  of the extruder  22  and includes a deposition opening  100  through which the fiber-reinforced polymer compound  25  passes in deposition. FIG. 2 depicts an exploded perspective view of the deposition die head  32 . 
     Referring again to FIG. 1, the extrusion deposition compounding device  20  also includes a fiber assembly  34  disposed on a first side  36  of the extrusion deposition compounding device  20 . The fiber assembly  34  includes a fiber supply reel  38  disposed on the first side  36  of the extruder  22 . The fiber supply reel  38  contains at least one fiber  40  wound thereabout at a predetermined tension. The at least one fiber may be of synthetic or natural composition. The at least one fiber  40  may further be defined as a needle punched fiber mat strip or any of a plurality of reinforcing materials having a tape form. The at least one fiber  40  traverses the extrusion deposition compounding device  20 , through a fiber preheat die  42  to a tension pulley  44  where the at least one fiber  40  enters the deposition die head  32 . The at least one fiber  40  may comprise at least one fiber bundle  41  (see FIG.  9 ). The fiber bundle  41  includes a plurality of individual reinforcing fibers  43 . The extrusion deposition compounding device  20  may include a plurality of fiber assemblies  34  depending upon a particular desired reinforcement application. Further, in another embodiment, the fiber assemblies  34  may be disposed on equipment external to the extrusion deposition compounding device  20  including a mobile device (not shown) which correspondingly moves with the device  20  as the fiber-reinforced polymer  25  is deposited upon the compression mold as taught herein. Additionally, the fiber assemblies  34  may be disposed on fixed equipment external to the extrusion deposition compounding device  20 , the fiber being translated to the device  20  through, for example, a piped network. 
     The preheat die  42  is disposed on the first side  36  of the extruder  22  and serves to heat the at least one fiber  40  to a predetermined temperature. The tension pulley  44  is disposed on the first side  36  of the deposition die head  32  and allows the at least one fiber  40  to enter the deposition die head  32  at a predetermined tension as discussed herein. The preheat die  42  may be disposed on the first side  36  between the fiber supply reel  38  and the tension pulley  44 . 
     The extrusion deposition compounding device  20  further includes a severing assembly  46  disposed on a second side  48  of the extrusion deposition compounding device  20 . The second side  48  of the extrusion deposition compounding device  20 , in a preferred embodiment, is opposite the first side  36 . The severing assembly  46  includes a cutting member  50  and an actuator  52 , the actuator  52  being disposed connectively with the cutting member  50  so that activation of the actuator  52  causes movement of the cutting member  50 . 
     The deposition die head  32 , as depicted in FIG. 2, includes an upper portion  54 , a first lower portion  56 , and a second lower portion  58 . Referring to FIG. 3, the upper portion  54  of the deposition die head  32  includes a top face  60  and a bottom face  62 . The bottom face  62 , in a preferred embodiment, is opposite the top face  60 . The tension pulley  44  is mounted on the top face  60 . A plurality of mountings  45  are used to secure the tension pulley  44  to the upper portion  54  and allow the tension pulley  44  to rotate about a longitudinal axis x—x, thus facilitating the introduction of the at least one fiber  40  into the deposition die head  32 . The at least one fiber  40  traverses tension pulley  44  and descends in a direction from the top face  60  towards the bottom face  62 . 
     Referring to FIGS. 1 and 4, the bottom face  62  of the upper portion  54  of the deposition die head  32  includes a first polymer melt channel  64  for receiving the polymer melt  30  from the extruder  22 . The first polymer melt channel  64  includes a neck portion  66  which meets the neck  26  of the extruder  22  when the deposition die head  32  is fully assembled and mounted upon the extruder  22  as shown in FIG.  1 . The first polymer melt channel  64  further includes a stream portion  68  disposed on the bottom face  62  adjacent the neck portion  66 . The neck portion  66  and the stream portion  68  of the first polymer melt channel  64  are of a width sufficient to receive the flow of the polymer melt  30  from the extruder  22  and, in a preferred embodiment, the stream portion  68  has a width greater than that of the neck portion  66 . The first polymer melt channel  64 , as well, is of sufficient depth to receive the flow of the polymer melt  30  from the extruder  22 . 
     Referring again to FIG. 2, the first lower portion  56  of the deposition die head  32  includes a top surface  70  and a first contoured surface  72 . The top surface  70  is disposed substantially perpendicular to the first contoured surface  72 . The top surface  70  contacts the bottom face  62  of the upper portion  54  when the deposition die head  32  is assembled. The first lower portion  56  further includes a second polymer melt channel  74  which traverses the top and contoured surfaces  70  and  72 , respectively. The second polymer melt channel  74  includes a neck portion  76  disposed on the top surface  70  such that the neck portion  76  is proximate the neck  26  of the extruder  22  and opposite the neck portion  66  of the first polymer melt channel  64  when the deposition die head  32  is fully assembled. The second polymer melt channel  74  also includes a stream portion  78  which is disposed on the top surface  70  adjacent the neck portion  76  such that when the deposition die head  32  is assembled the stream portion  78  of the second polymer melt channel is disposed opposite the stream portion  68  of the first polymer melt channel  64 . The first polymer melt channel  64  of the upper portion  54  mates with the second polymer melt channel  74  of the top surface  70  of the first lower portion  56  to form a generally annular die channel  110  (see FIG. 1) when the deposition die head  32  is assembled. More specifically, the neck portion  66  and the stream portion  68  of the first portion  54  mate with the neck portion  76  and the stream portion  78  of the first lower portion  56 , respectively, to form the die channel  110 . The stream portion  78  of the second channel  74  continues along the first contoured surface  72  toward a bottom surface  80  of the first lower portion  56 . 
     The neck portion  76  and the stream portion  78  are each of a width sufficient to receive the polymer melt  30  from the extruder  22 . Likewise, the second polymer melt channel  74  is of sufficient depth to accommodate the polymer melt  30 . In one embodiment, the neck portion  76  is narrower in width than the stream portion  78 . 
     The first lower portion  56  of the deposition die head  32  also includes a first die lip  82  releasably disposed at the bottom surface  80 . The first die lip  82  includes a tailored polymer melt channel  83  disposed in the first die lip  82  such that when the first die lip  82  is releasably fitted on the first lower portion  56  of the deposition die head  32 , the tailored polymer melt channel  83  is aligned with the stream portion  78  of the polymer melt channel  74  thus providing continuity of the channel  74  with the deposition opening  100 . The tailored polymer melt channel  83  may descend from the stream portion  78  of the polymer melt channel  74  in a variety of shapes and sizes thereby allowing the width and form of the fiber-reinforced polymer compound  25  to be varied as desired in the formation of particular fiber-reinforced polymer structural components. A plurality of die lips  82  may be used with the EDCM assembly  10 , each having tailored polymer melt channels  83  of different geometries thus producing various shaped fiber-reinforced polymer melts  25  from a single EDCM assembly  10 . 
     The first contoured surface  72  further includes a first shear pulley  84  and a second shear pulley  86  each disposed on the first contoured surface  72  to effect a predetermined shear force upon the at least one fibers  40  within the polymer melt  30 . In one embodiment, the at least one fiber  40  traverses the first shear pulley  84  such that the first shear pulley  84  is disposed between the at least one fiber  40  and the first contoured surface  72 . The at least one fiber  40  further traverses the second shear pulley  86  such that the at least one fiber  40  is disposed between the second shear pulley  86  and the first polymer melt channel  74 . 
     The second lower portion  58  of the deposition die head  32  includes a second contoured surface  88  as shown in FIG.  5 . The second contoured surface  88  is shaped symmetrical and complementary the first contoured surface  72  such that when the deposition die head  32  is assembled the first and second contoured surfaces  72  and  88 , respectively, are received into one another. The second contoured surface  88  includes a third polymer melt channel  90  shaped congruent to the second polymer melt channel  74  formed in the first contoured surface  72 . The third polymer melt channel  90  is formed in the second lower portion  58  to lie opposite the second polymer melt channel  74  upon full assemblage of the deposition die head  32 . The second polymer melt channel  74  of the first contoured surface  72  mates with the third polymer melt channel  90  of second contoured surface  88  forming the generally annular die channel  110  when the deposition die head  32  is assembled. 
     The second lower portion  58  of the deposition die head  32  further includes a second die lip  102  releasably disposed at a lower end  81  of the second lower portion  58 . The second die lip  102  includes a tailored polymer melt channel  104  disposed so as to align with the third polymer melt channel  90  to provide continuity of the channel  90  with the deposition opening  100 . The tailored polymer melt channel  104  may be of a variety of shapes and sizes thus providing for variation of the shape, size, etc. of the fiber-reinforced polymer compound  25 , as discussed above with reference to the first die lip  82 . The second die lip  102  is disposed on the second lower portion  58  and the tailored polymer melt channel  104  is disposed upon the second die lip  102  such that when the deposition die head  32  is fully assembled, the second die lip  102  and the tailored polymer melt channel  104  are adjacent the first die lip  82  and the tailored polymer melt channel  83 , respectively. The interface of the tailored polymer melt channels  83 ,  98  forms the deposition opening  100 . 
     When assembling the deposition die head  32 , the upper portion  54  is secured to the first lower portion  56  with a first set of fasteners  92  such that the bottom face  62  of the upper portion  54  contacts the top surface  70  of the first lower portion  56 . The second lower portion  58  is also preferably secured to the first lower portion  56  by a second set of fasteners  94 . The first and second sets of fasteners  92  and  94  may be any conventional devices suitable for the use intended. The die lips  82 ,  102  are fastened to the first lower portion  56  and the second lower portion  58 , respectively, by any conventional fastening means suitable for the purposes herein described. Finally, the deposition die head  32  is secured to the neck  26  of the extruder  22  by conventional techniques. In a preferred embodiment, the deposition die head  32  is designed to fit a variety of extruders  22  known and commonly used in the art, thus allowing retro-fit of existing extruders and implementation of the EDCM assembly  10 . 
     A die channel  110 , shown in broken lines in FIG. 1, is formed within the deposition die head  32  by the interfacing of the first, second, and third polymer melt channels  64 ,  74 , and  90 , respectively. The at least one fiber  40  undergoes the wet-out process and is compounded with the polymer melt  30  within the die channel  110 . 
     The first and second contoured surfaces  72  and  88 , respectively, of the deposition die head  32  may include non-planar contours giving the die channel  110  a desired shape to facilitate a wet-out process. The non-planar contours of the first and second contoured surfaces  72  and  88 , respectively, may be designed to bend the at least one fiber bundle  41  exposing the individual fibers therein to the polymer melt  30  thereby inducing the wet-out process. In one embodiment, the first and second contoured surfaces  72  and  88 , respectively, may be shaped to traverse the die channel  110  first in a vertical manner, then non-vertical, and then again in a vertical manner to the termination of the die channel  110  at the deposition opening  100 . 
     The use of the EDCM assembly  10 , in accordance with the present invention, is now described. A polymer or combination of polymers is introduced to the extruder  22  to form the polymer melt  30 . In one embodiment the polymer may be a thermoplastic. At least one heating element (not shown) located, preferably, on the exterior of the barrel  22  of the extruder  20 , in combination with the shear heat introduced by the rotation of the screw  28 , forms the polymer melt  30 . The screw  28  rotates in such a manner as to move the polymer melt  30  toward the neck  26  of the extruder  22  and eventually into the deposition die head  32  for compounding with the at least one fiber  40 . The heating element maintains the temperature of the polymer melt  30  as required for proper compounding and deposition onto the compression mold  12 . 
     The die lips  82 ,  102  are fitted onto the deposition die head  32 . Die lips  82 ,  102  with tailored polymer melt channels  83 ,  104 , respectively, are selected to form the deposition opening  100  required for a particular application of the EDCM assembly  10 . The deposition opening  100  resulting from the interface of the tailored polymer melt channels  83 ,  104  may have any desired cross-sectional shape as required to form a specific fiber-reinforced polymer extruded section. FIGS. 6-8 depict exemplary deposition openings  100 . 
     The at least one fiber  40  is introduced into die channel  110  of the deposition die head  32  in such amount as required for the particular use of the reinforced polymer structural component and at such tension as to achieve adequate fiber wet-out. The at least one fiber  40  is heated to a pre-determined temperature by the fiber preheat die  42  prior to introduction into the die channel  110 . When desired, the polymer melt  30  is extruded into the die channel  110  by the extruder  22 . The wet-out process, as is commonly known and understood in the industry, occurs at this point within the die channel  110  of the deposition die head  32 . 
     The extrusion deposition compounding device  20  is movably mounted upon a positioning unit (not shown) which allows the device  20  to be moved, in a preferred embodiment, in three dimensions (x, y, and z coordinate planes) within the compression mold  12 . The extrusion deposition compounding device  20  may be brought proximate the contact surface  18  of the male half  16  of the compression mold  12  as shown in FIG.  1 . 
     When desired, by operator command or automatically by computer or robotic command, the extrusion deposition compounding device  20  deposits the fiber-reinforced polymer compound  25  through the deposition opening  100  onto the contact surface  18  of the male half  16  of the compression mold  12 . The extrusion deposition compounding device  20  deposits the fiber-reinforced polymer compound  25  on the contact surface  18  of the compression mold  12  in such concentration and in such a distribution as is required to form the desired reinforced polymer structural component. The percentage of fiber  40  within the fiber-reinforced polymer compound  25  may be varied by depositing additional fiber reinforced compound  25  on those portions of the structural member requiring greater reinforcement. Additionally, the fiber-reinforced polymer compound  25  may be deposited in one direction on a first pass of the extrusion deposition compounding device  20  and then in a second direction upon a second pass resulting in a cross-weaving of the at least one fibers  40  in those specific portions of the fiber-reinforced polymer structural component requiring such reinforcement. 
     Further, the percentage of reinforcing fibers in the resulting compound  25  may be varied by controlling the number of fibers  40  compounded with the melt  30 . The at least one reinforcing fiber  40  may be a plurality of reinforcing fibers  40  as shown in FIGS. 1 and 3. Thus, the percentage of reinforcing fibers  40  present in a polymer structural component formed in accordance with the present invention may be varied by increasing or decreasing the plurality of reinforcing fibers  40  compounded with the polymer melt  30  in the deposition die head  32  and deposited on the compression mold  12  as the fiber-reinforced polymer compound  25 . 
     Furthermore, the percentage of reinforcing fibers  40  present in the fiber-reinforced polymer compound  25  and, hence, the resulting fiber-reinforced polymer structural component may be varied by the selection of the die lips  82 ,  102 . Die lips  82 ,  102  which form a larger deposition opening  100  will allow the passage of a greater volume of polymer melt  30  thus reducing the percentage of reinforcing fibers  40  relative to the volume of the polymer melt  30  deposited from the extrusion deposition compounding device  20 . Die lips  82 ,  102  which form a smaller deposition opening  100  will allow passage of a lesser volume of the polymer melt  30  thus increasing the percentage of reinforcing fibers  40  relative to the deposited volume of polymer melt  30 . 
     The severing assembly  46  is used to terminate the deposition of the fiber-reinforced polymer compound  25  upon the compression mold  12 . The extrusion deposition compounding device  20  initiates the actuator  52  which moves the cutting member  50  into engagement with the fiber-reinforced polymer compound  25  thereby severing the compound  25  and terminating deposition. 
     After deposition of the fiber-reinforced polymer compound  25  upon the contact surface  18  of the compression mold  12 , the extrusion deposition compounding device  20  is withdrawn from the compression mold  12 . The compression mold  12  is closed, the female half  14 , generally located above the male half  16 , moves toward and is received by the male half  16 . The compound  25  is cooled within the compression mold  12 , thus forming the fiber-reinforced polymer structural component. 
     The type and the amount of the at least one fiber  40  introduced in the die channel  110  of the deposition die head  32  may be easily varied between uses of the EDCM assembly  10  by adjusting the fiber supply reel  38 . Additionally, the thickness and shape of the fiber-reinforced compound  25  may be varied between uses of the EDCM assembly  10  by switching between a variety of die lips  82 ,  102 . 
     The at least one reinforcing fiber  40  may be a plurality of individual reinforcing fibers  40 , as discussed above. It is understood that the amount of individual fibers  40  within the plurality of reinforcing fibers  40  may be varied during the production of the fiber-reinforced polymer structural component in accordance with the present invention. For example, the fiber assembly  34  may include a first plurality of reinforcing fibers (not shown) and a second plurality of reinforcing fibers (not shown). A controller (not shown) may, at a first predetermined time, introduce the first plurality of reinforcing fibers to the polymer melt  30  for compounding within the deposition die head  32 . The resulting fiber-reinforced polymer compound  25  then, for example, may include four ( 4 ) individual reinforcing fibers. The fiber-reinforced polymer compound  25  is deposited on the contact surface  18  of the compression mold  12  in those areas which correlate to the portions of the resulting fiber-reinforced polymer structural component which require less reinforcement. At a second predetermined time during the deposition of the fiber-reinforced polymer compound  25 , the controller may introduce the second plurality of reinforcing fibers to the polymer melt  30  within the die head  32 . The combination of the first and second pluralities of reinforcing fibers increases the concentration of the reinforcing fiber  40  within the resulting fiber-reinforced polymer compound  25 . The second plurality of reinforcing fibers may include, for example, two ( 2 ) additional individual fibers thus increasing the plurality of reinforcing fibers  40  to comprise six ( 6 ) individual reinforcing fibers. The fiber-reinforced polymer compound  25  comprising the combination of the first and second pluralities of reinforcing fibers is then deposited on the contact surface  18  of the compression mold  12  in those areas which correlate to portions of the resulting fiber-reinforced polymer structural component requiring greater reinforcement. 
     The EDCM assembly  10  described herein allows direct feed compounding of the fiber-reinforced polymer compound  25 , reducing the stress on fibers and minimizing fiber breakage during deposition. The EDCM assembly  10  introduces the at least one reinforcing fiber  40  directly into the deposition die head  32  instead of into the extruder  22  as in conventional compounding procedures. The EDCM assembly  10  does not subject the fibers to the shearing and heat of the extruder screw  28 , reducing damage and breakage of the fiber and eliminating wear on the screw  28  and on the extruder  22  in general. Thusly, the fiber-reinforced structural component produced will exhibit higher mechanical properties, particularly in impact strength, and the extruder  22  will require less maintenance. 
     The EDCM assembly  10  enables the variation of the fiber percentage within the fiber-reinforced polymer compound  25 , further enhancing the mechanical properties of the produced fiber-reinforced polymer structural component and allowing flexibility in the manufacture thereof. The EDCM assembly  10  also eliminates the complex mechanisms and processes required for conventional direct-feed and pultrusion compounding methods, reducing equipment capital and maintenance costs. The three-dimensional maneuvering capability of the extrusion deposition compounding device  20  enables the deposition of the fiber-reinforced polymer compound  25  directly on the compression mold  12  in any manner as desired, giving flexibility to the formation of the fiber-reinforced polymer structural component. 
     It will be understood that a person skilled in the art may make modifications to the preferred embodiment shown herein within the scope and intent of the claims. While the present invention has been described as carried out in a specific embodiment thereof, it is not intended to be limited thereby but is intended to cover the invention broadly within the scope and spirit of the claims.