Abstract:
A device and method for transferring filtered molten metal to a die casting mold. The device and method include a casting filtration system that includes a funnel and a continuously replaceable filter placed fluidly between a molten metal source and a casting mold. Both the funnel and filter are automatically moved into cooperation with a molten metal receptacle such as a shot sleeve prior to each casting operation, and then automatically moved out of the way so that pressurization of the filtered molten metal may take place in the receptacle. In addition, the filter may be formed on a continuous strand such that indexed movement of the strand will advance the used portion of the filter out of the way to make room for a new unused filter portion that will be ready for a subsequent repeated casting operation.

Description:
BACKGROUND TO THE INVENTION 
     This invention relates generally to an improved way to pour molten metal used in a casting operation, and more particularly to filtering out inclusions from the molten metal during the filling of a horizontal high pressure die casting (HPDC) shot sleeve. 
     Low process cost, close dimensional tolerances (near-net-shape) and smooth surface finishes are all desirable attributes that make HPDC a widely used process for the mass production of metal components. By way of example, manufacturers in the automobile industry use HPDC to produce near-net-shape aluminum alloy castings for engine, transmission and structural components. In a typical HPDC process, molten metal is typically transferred to a casting mold through a series of channels, tubes and ladles that make up a filling system. This transfer typically takes place in two steps: a low pressure pour to a filler tube (called a shot sleeve), and a high pressure injection where movement of a piston or plunger in the tube forces the metal from the shot sleeve and into the casting cavity. 
     One transport system for HPDC shot sleeve filling is known as a dosing furnace trough system. In this system, a pressure or pump furnace is coupled to the shot sleeve with an inclined trough (which is also referred to as a dosing launder). The furnace bottom fills the required charge weight of molten metal to one end of the trough such that it then flows the length of the trough and drains into the shot sleeve. Devices to improve metal stream control by reducing the turbulence relative to a free-falling stream of molten metal as it impinges on the shot sleeve wall and pooling metal therein may also be used. Nevertheless, undesirable high metal velocities—and the resulting filling turbulence—may still be present in the shot sleeve. Furthermore, long trough lengths also create undesirably high metal surface areas and oxide films. Moreover, this system does not include a mechanism to clean the molten metal at the shot sleeve, as the generated oxides or furnace inclusions that reside in the metal at the entrance to the trough will be transported to the shot sleeve cavity. 
     Another metal transport system for HPDC shot sleeve filling is known as a tilt-pour ladle system. Typical designs of this type of system are similar to a pour basin in traditional sand casting molds, but without a sprue feature. In this system, a ladle is tilted to pour the molten metal through an external spout to the shot sleeve. Metal damage results from the turbulence of the impinging metal stream on the shot sleeve surface and the pooled melt within the shot sleeve. One method of reducing this filling turbulence is the use of a device placed above the sleeve entrance that collects the ladle metal stream and directs it into the shot sleeve. As with the trough-based system mentioned above, control of the metal stream location as it hits the shot sleeve wall and pooling metal may be its primary benefit in reducing metal damage. Nevertheless, neither this nor the trough-based system has a mechanism to clean the metal, instead leaving the generated oxides or furnace inclusions to remain in the pooled metal that is resident in the shot sleeve cavity. 
     Another method of eliminating this filling turbulence is described in U.S. patent application Ser. No. 14/159,866, filed Jan. 21, 2014 and entitled A METAL POURING METHOD FOR THE DIE CASTING PROCESS, the entirety of which is owned by the Assignee of the present invention and hereby incorporated by reference herein. In this approach, a special tilt pour ladle couples to a side orifice in the shot sleeve and rotates to introduce metal into the sleeve cavity, after which the assembly rotates to drain the ladle and place the shot sleeve orifice at the top. While the bottom filling of this approach is especially useful in eliminating turbulence and metal damage, it may add complexity. For example, the additional joints used to establish the relative rotation are exposed to molten metal for each casting; this may exacerbate maintenance and related foundry down-time concerns. Additionally, clearance constraints of the die casting machine may hamper the ladle motion, making implementation more difficult. 
     An additional method of reducing metal damage during the shot sleeve filling event is described in U.S. patent application Ser. No. 14/613,991, filed Feb. 4, 2015 and entitled METAL POURING METHOD FOR THE DIE CASTING PROCESS, the entirety of which is owned by the Assignee of the present invention and hereby incorporated by reference herein. This approach uses a tilt-pour ladle with a 360 degree nozzle that is fitted with a molten metal filter. A full ladle is rotated to place the nozzle and filter proximate to the shot sleeve such that in its final position, the filter is at or near the shot sleeve bottom surface for filling. The flow restriction of the filter reduces the metal velocity and turbulence of the incoming stream, while the physical capture of melt inclusions provides an additional benefit. The present inventors have recognized that a major hurdle to achieving such filtering is that the placement of the filter (in addition to its removal for periodic cleaning or servicing) may add significant time and expense to the process, and as such may make the use of a filter untenable, especially when used in conjunction with large-scale HPDC production (where hundreds or even thousands of castings may be produced each day in a single casting machine). Moreover, storage space for filters and their replacements in or around the shot sleeve is limited, while filter mishandling may cause significant damage to the shot sleeve or other parts of the filling system, further reducing the efficiency of the casting operation. 
     SUMMARY OF THE INVENTION 
     It is against the above background that embodiments of the present invention generally relate to the use of a continuously replaceable filter to improve the quality of the molten metal that is delivered to a horizontal die casting shot sleeve. In this way, casting quality is improved while not burdening the operation with complex filter storage, placement and disposal externalities. 
     According to a first aspect of the present invention, a continuously replaceable filter and a funnel cooperate as part of a system to deliver filtered molten metal from an upstream delivery vessel (such as a ladle or trough) to a downstream casting mold receptacle (such as the aforementioned shot sleeve or related runner). While the present disclosure focuses on HDPC equipment and ancillary processes, it will be appreciated by those skilled in the art that the moveable filter and funnel may also be coupled to other non-HPDC casting operations that may have a need for molten metal filtration. In these other configurations, a pouring basin, riser or other opening may be used in place of the shot sleeve; either variant is deemed to be within the scope of the present invention. 
     In the present context, a continuously replaceable filter is one that can be automatically placed in and removed from the molten metal flowpath without manual intervention between successive casting operations. In one particular form, the filter is delivered to and removed from the system as part of a continuous spool or roll-based mechanism. Such a configuration provides the benefits of a one-time use filter without having the disadvantage of manually placing a new discrete filter between the molten metal source and shot sleeve, runner or related receptacle for each casting operation. In optional forms, the system may include additional components, including a runner, sprue, fill cap, gates, cope, drag and other components associated with a horizontal HPDC system. 
     According to another aspect of the present invention, a high pressure die casting system includes a mold cavity, a filling system fluidly cooperative with the mold cavity to deliver molten metal to it, and a filtration system fluidly disposed between the molten metal source and a shot sleeve that makes up a part of the filling system. As discussed above, the filtration system includes a continuously replaceable filter and a funnel fluidly cooperative with the filter such that a quantity of molten metal being conveyed from the molten metal source passes through a flowpath defined by the funnel and the filter prior to receipt within the shot sleeve. A molten metal source may include a furnace, as well as a ladle that receives molten metal from the furnace. As will be discussed below, the discharge end of the ladle may be equipped with a nozzle-like extension that mimics features of the aforementioned funnel in order to perform a comparable molten metal delivery function to the shot sleeve. In a preferred form, the filter portions are stored as part of a continuous strand (which is more preferably delivered and taken up on rolls) to minimize storage; indexing or clocking movement of the rolls ensures accurate delivery of a used filter portion away from the casting system while simultaneously delivering a fresh unused filter portion into position between the molten metal source and the shot sleeve. Depending on the cleanliness of the metal being filtered, the roll can move during the metal delivery process, presenting clean filter area to the flowing metal. This reduces the risk of clogging the filter, stopping the flow of metal into the shot sleeve and interrupting the metal casting process 
     According to another aspect of the present invention, a method of delivering molten metal to a die casting mold is disclosed. The method includes providing a filling system fluidly between a molten metal source and the mold, introducing a quantity of molten metal from the molten metal source through a filtration flowpath defined by filling system components, moving at least some of the filling system components away from the shot sleeve to enable pressurizing of the filtered molten metal that has collected in a cavity that is formed in the shot sleeve. Once the filtered molten metal has been moved to a mold cavity or other destination via the pressurization, a new filter (along with the reusable funnel) may be moved into place near the entrance of the shot sleeve so that a new casting operation may be commenced. As before, both the filling system and filtration system may be thought of as either independent systems of continuous parts of the same system; in either view, they cooperate to filter and deliver molten metal to a mold cavity or related workpiece from a molten metal source. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description of the preferred embodiments of the present invention can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
         FIG. 1  shows a representative bi-film produced by turbulence of the prior art; 
         FIGS. 2A and 2B  show views of the cooperation of the filter and an HPDC shot sleeve according to an aspect of the present invention; and 
         FIGS. 3A and 3B  show sequential steps depicting the relative movement of the filter and a funnel relative to a shot sleeve, where in  FIG. 3A  the filter and funnel are in position to accept unfiltered molten metal, while in  FIG. 3B  the funnel and filter are moved upwardly out of engagement with the shot sleeve so that the next casting operation may be performed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring first to  FIG. 1 , multiple forms of defects in an aluminum alloy are shown. Upon heating into liquid (i.e., molten) form  100 , various streams of aluminum (for example, first stream  110  and second stream  120 , as well as droplets  130 ) interact in varied ways. When processed in an oxygen-containing environment, oxide films  140  may form on the outer surface of the liquid aluminum, including the first stream  110 , second stream  120  and droplets  130 . A bi-film  170  forms when the two oxide films  140  from respective first stream  110  and second stream  120  meet. Bi-films also form when turbulence-induced droplets land on the metal stream, as shown at  150 . While bi-films  150 ,  170  are an inherent part of almost every casting process, they are generally not detrimental to casting mechanical properties unless the oxide film  140  is entrained in the bulk of the alloy, as shown at location  160  due to the folding action when two separate streams, first stream  110  and second stream  120 , meet at large angles (typically more than 135 degrees, where the splashing action of one stream collapses onto another stream to form a cavity therebetween). Such a formation can have significant impacts on overall material integrity and subsequent casting scrap rates. Likewise, entrained gas  180  may form from the pouring action of liquid metal, creating additional entrained oxides. As mentioned above, when liquid metal is poured or forced into a mold or shot sleeve in a conventional manner, it is possible to trap large gas bubbles that result in one or more of the inclusions shown. 
     Referring next to  FIGS. 2A and 2B and 3A and 3B , portions of a horizontal HPDC system  200  that are configured to cooperate with a continuous tape-like strand  210  of the present invention are shown. These portions include shot sleeve  220  that defines a generally cylindrical cavity therein such that a plunger  230  introduced into the proximal end of shot sleeve  220  may move in a reciprocating translational motion along a substantially horizontal direction within the cavity in order to pressurize a quantity of poured molten metal  100  that is contained within the shot sleeve  220 . Although not shown, the distal end of the shot sleeve  220  may be fluidly connected to a network of gates or related channels to convey the molten material to the mold cavities; such a network is commonly referred to as a gating (or charging) system. A funnel  250  is also translationally moveable (such as by movement of an electric motor such as a stepper motor, not shown) along a substantially vertical direction within the proximal end of the shot sleeve  220 . The proximal end  260  of shot sleeve  220  defines a cavity or orifice  261  that helps provide a transition for the introduction of molten metal  100  into the shot sleeve  220 . A set of upstanding guide rails  265  may straddle the proximal end  260  of shot sleeve  220  for at least a portion of the travel path of the strand  210  in order to help keep it aligned as it moves toward the cavity  261 . In an alternate form (not shown), a fill cap may act as a cover that can be made rotatable as discussed in the co-pending U.S. patent application Ser. No. 14/159,866 discussed above. In yet another alternate form (not shown), the funnel  250  may be inserted in a rotary fashion into the proximal end  260  of shot sleeve  220 , as well as through a combination of translational and rotational movement; all such forms are deemed to be within the scope of the present invention. 
     As shown, the travel path for the strand  210  with its filters  211  defines a beginning and an end, such as through respective delivery  270  and take-up  280  mechanisms, where in one form the delivery may be made from a simple box-like container (as depicted with particularity in  FIG. 2B ) or a spooled reel (as depicted with particularity in  FIGS. 2A, 3A and 3B ). Similarly, take-up is preferably through an appropriate means where continuing tension may be maintained on the strand  210  and filters  211  to avoid bunching, as well as to provide ample force to pull the strand  210  and filters  211  through the relatively linear path depicted in  FIG. 3B  where the funnel  250  has been moved out of the way during a change of filters  211  between sequential casting operations. 
     In one preferred form, movement of the strand  210  with filters  211  only takes place in between successive casting operations; in that way, they are only exposed to significant tensioning loads during periods where their travel path adjacent the shot sleeve  220  defines a substantially straight, linear path as depicted in  FIG. 3B . Nevertheless, in an alternate embodiment (not shown), the strand  210  with filter  211  may be moved across the funnel  250  during a molten metal  100  pouring operation. This latter configuration is particularly useful when excessively dirty (i.e., oxide filled) molten metal  100  is contained in the furnace or ladle  105 . 
     In a preferred form, the strand  210  is formed with a porous, screen-like surface structure that is flexible enough to occupy a tortuous shape (or profile) defined by the cooperative action of the funnel  250  and the cavity  261  during at least the part of the casting operation where the funnel  250  and a filter  211  that is defined on the surface of strand  210  are inserted into the cavity  261 . In the present context, while a substantial entirety of the surface of strand  210  defines screen-like filter attributes, the filters  211  discussed herein are more easily understood as defining discrete portions that correspond in size and shape to the funnel exit face  251  with which it forms a selective filtration flowpath (also referred to herein as a filtration path); these discrete portions (shown in exemplary form in  FIG. 3B ) may be thought of as “used portions” (also called spent filters  211 B) and “unused portions” (also called fresh filters  211 A); related terms, such as “first portions” to designate a predecessor filter and “second portions” to designate a successor filter may also be used herein to distinguish respective places in line on the continuous strand  210 . All such indicia will be apparent from the context. Moreover (as discussed above), traversal of the strand  210  and filters  211  preferably only takes place once their travel path has been substantially straightened out so that sharp bends, edges and other undulations are avoided. 
     Significantly, the close-coupling of the bottom of the funnel  250  to the generally crescent-shaped lower surface of the cavity  261  helps promote a sealed passageway such that when a portion of strand  210  is present, the only way the molten metal  100  can enter the shot sleeve  220  is through the filter  211  that is present within the exit face  251  that is formed in the bottom of funnel  250 . In other words, the strand  210  is contoured to offset match the contour of the shot sleeve  220  bottom surface. This minimizes the metal drop after the filter  211  and reduces the time it takes for the strand  210  to be totally submerged and the metal surface area reduced. In one preferred form, an offset of between 5 and 12 millimeters (mm) is used; numbers higher than this tend to cause the quality of the molten metal  100  to suffer. By such positioning proximate the final pooling location within the shot sleeve  220 , in addition to reducing or removing inclusions, the short drop the filter  211  reduces the metal velocity entering the shot sleeve  220 , which helps to reduce the turbulence and oxide generation of the filtered molten metal stream  101  as it fills the shot sleeve  220  As mentioned above, in addition to reducing or removing inclusions, filter  211  reduces the metal velocity entering the shot sleeve  220 , which helps to reduce the turbulence and oxide generation of the filtered molten metal stream  101  as it fills the shot sleeve  220 . 
     Moreover, the shape of the cavity  261  (shown presently with a gently tapered geometry) permits the funnel  250  and filter  211  to be raised and lowered such that they are selectively placed into and removed from the fluid entrance at the proximal end of the shot sleeve  220 . In various embodiments, the filter  211  is made from fiberglass or some other material that is both chemically inert relative to molten metal  100  and flexible and strong enough to traverse the tight bends formed in cavity  261  without binding or breakage. Examples of such other material include steel wire mesh, carbon fiber mesh, tinplate, or combinations thereof. In addition, the mesh size of the filter  211  determines the minimum particle size of inclusions such as deleterious oxides transferred from the dip well bath which are captured. In various embodiments, the screen size of the filter  211  is made up of an approximately 9 to 17 mesh with approximately 1.8 to 0.9 mm width opening and an approximately 46 to 36% open area. A non-limiting exemplary filter  211  includes a 17 mesh screen with a width opening of 0.9 mm and an open area of approximately 36%. In any event, it will be appreciated by those skilled in the art that too small of a mesh size must be avoided to minimize the chance of unnecessarily constricting the flow of molten metal  100 , while too large of a mesh size also needs to be avoided in order to reduce the likelihood of deleterious inclusions passing through. In one exemplary form, the pore size selection of the filter  211  may be made to allow for an approximately 6 pound/sec flow rate of molten metal  100  into the horizontal shot sleeve  220  with no oxide films larger than 1×1 mm. 
     Significantly, the porous, screen-like construction of the strand  210  is such that a portion of it that corresponds to the two-dimensional projection of the funnel aperture  251  shape onto it permits it to function as a filter  211 . The delivery to and removal from the region immediately below the funnel aperture  251  of the strand  210  may be coupled to the casting operation of the remainder of the horizontal HPDC system  200  via controller (not shown) to enable automated, indexed movement of a fresh filter  211 A into fluid cooperation with the aperture  251  and related indexed movement of a spent filter  211 B away from such fluid cooperation. In one embodiment, the strand  210  may be in roll form  212  such that it can be mounted onto rotatable spindles  213  such that automated take-up and delivery may be effected. Furthermore, a motor or robotic manipulation device used to move the funnel  250  may also be operated by such a controller. 
     Referring with particularity to  FIGS. 3A and 3B , the sequential steps in filtering molten metal  100  are shown. In  FIG. 3A , the unfiltered molten metal  100  is introduced from a ladle  105  to the shot sleeve  220  by pouring into funnel  250  that defines a slightly tapered shape along the downwardly-directed flowpath. Significantly, there is very little taper in funnel  250 , as the cross section requirement to achieve the 6 lbs/sec molten metal  100  flow rate is too high to have it be form fitting to a falling metal stream; in this regard, its shape differs from that of a conventional sprue. Tautness in the strand  210  (such as that imparted to it by tensioning take-up rollers  290  that may act in a stand-alone manner such as shown in  FIGS. 3A and 3B , as well as part of a larger take-up structure  280  as shown in  FIG. 2B ) helps to ensure enough structural rigidity in the strand  210  such that the exit face  251  of the funnel  250  and the filter portion  211 A of strand  210  form a tight fit between them along bottom (or exit) face  251 . In this way, together they define a substantially sealed molten metal flowpath between the funnel  250  and the lower portion of the shot sleeve  220  where the filtered molten metal  102  as shown in  FIG. 3B ) pools. As such, flow velocity and impurities are reduced downstream of the filter while minimizing leakage around the sealed area defined by the funnel exit face  251  and filter  211 A.  FIG. 3B  shows withdrawal of the funnel  250 , as well as the indexed movement of the filter  211 A away from the fluid entrance of the sleeve  220  to permit subsequent pressurizing applications made possible by the reciprocating movement of the plunger  230  of  FIG. 2A . The relative linear and planar shape of the strand  210  in this raised position differs from the three-dimensional, tortuous shape depicted in  FIG. 3A ; in this way, indexing movement of the strand and the filters  211 A,  211 B is simplified in the manner discussed above. Moreover, the linear shape of the strand  210  during its indexing movement (shown presently along the direction indicated by the arrow) helps to keep the spent filter  211 A substantially flat so that the captured inclusions that have been filtered out of the molten metal  100  and are residing on the filter  211 A are less inclined to break off and fall back into the lower portion of the cavity  261  during movement. 
     In an alternate embodiment (not shown), the fluid-routing function of the funnel  250  may be achieved through a spout-type ladle with a similar downward-extending exit face formed at the discharge end of ladle  105  that is shown in  FIG. 3A . Because of possible clearance issues, the fluid entrance of the shot sleeve  220  may be modified to accommodate the ladle  105 . Regardless, either funnel variant is deemed to be a functional equivalent within the claimed and disclosed invention. For example, the trough formed in the ladle  105  can have an integral exit that penetrates in a vertically-downward direction into the shot sleeve cavity  261  to improve metal stream control by reducing the turbulence relative to a free-falling stream. Movement of such a device may be achieved in a manner similar to the funnel  250 . 
     Automated movement of both the filter  211  and funnel  250  within the cavity  261  formed in the shot sleeve&#39;s proximal end  260  shows how prior to the introduction of the molten metal  100 , the funnel  250  is lowered into the trough-like bottom of the cavity  261 . The generally arcuate shape of the cavity  261 , coupled with the generally planar (within the X-Z plane) shape of the exit face  251  creates a tight, sealing fit between the two around the peripheral edges of the filter  211  while leaving a crescent-shaped pooling region  262  within cavity  261 . Molten metal  100  that passes through the filter  211  at this location becomes filtered molten metal  101  that can collect within the cavity of the shot sleeve  220 . The structural cooperation between the exit face  251  and the adjacent arcuate surface of the cavity  261  imparts a sufficient pressure or contact load to the filter  211  to ensure that a substantial entirety of the molten metal  100  being delivered through the funnel  250  passes through the filter  211  without any leakage around the edges where the filter  211  and exit face  251  intersect. As shown with particularity in  FIG. 3B , withdrawal of the funnel  250  and indexed movement of the filter  211  permits subsequent pressurizing applications of the pool  102  of molten metal within the cavity of shot sleeve  220  by the action of the plunger  230  of  FIG. 2A , as well as setup for a subsequent repeat casting operation. Significantly, the use of rollers  212  and related tensioning equipment can help ensure that the strand  210  remains relatively taut during the substantial entirety of the filter  211  transport and placement operation. 
     Significantly, the roll-based approach depicted herein allows local storage of the filters  211  immediately adjacent the shot sleeve  220 . Importantly, the compact, automated filter  211  and funnel  250  movement structure is such that it can form a retrofit package that includes simple bolt-on connectivity to the shot sleeve  220  and horizontal HPDC system  200  support structure (not shown). This places a filter at bottom of the sleeve with low storage, placement and disposal costs. Importantly, the present invention may be retrofitted on existing shot sleeves, runners or related HPDC molten metal feed equipment. A die-casting charge filtration system that minimizes metal damage by bottom filling shot sleeve, all in a compact, bolt-on unit. Moreover, such an approach as discussed herein is compatible with the trough-funnel system and nozzled ladle systems discussed above. Depending on the size of the rolls  212  used to deliver and take up the strand  210  and filters  211 , it may be more convenient to have them located away from the die casting machinery. For example, if the roll  212  were larger (for example, with a roughly one meter diameter), it may be preferable to have a strand  210  delivery platform include additional spools, tensioners, guides and related conveying equipment such that the larger rolls  212  may be placed in a more suitable location; either variant is deemed to be within the scope of the present disclosure. 
     The two-stage cooperative movement of the filter  211  and funnel  250  relative to the introduction of the molten metal  100  into the shot sleeve  220  takes place each time a new component is being cast. The funnel  250  egress from the sleeve  220  allows the die casting cavity (not shown) to be injection filled via the translational movement of the plunger  230  into the shot sleeve  220  internal cavity. Upon upward movement of the funnel  250  out of the cavity  261 , the previous clamping pressure imparted by the portion of the funnel  250  that defines the exit face  251  is removed, thereby allowing the strand  210  to be indexed in order to present a fresh filter  211 A into the bottom of the cavity  261  for the next molten metal  100  pour. The used filter  211 B can then be conveyed toward a take-up reel or related spent filter  211 B collection device for subsequent disposal. Significantly, cooperative movement of the strand  210  relative to the portion of the funnel  250  defined by its exit face  251 —coupled with the shape and placement of the cavity  261  relative to the bottom of the shot sleeve  220 —ensures ample pressure to seal the filters  211  that are formed within the strand  210  such that upon receipt of molten metal  100  from a source (such as tilt pour ladle, a nozzled ladle or a trough system), the filtering takes place in such a way to remove inclusions while keeping critical fall heights of the molten metal  100  within limits. As will be understood by those skilled in the art, the critical fall height is the vertical distance above which a molten metal should not be exposed to in order to avoid the deleterious effects of bifolds and related inclusions that arise when a molten metal critical velocity (which for most metals is between about 3 mm and 15 mm) is exceeded. As such, the operation of the funnel  250  with and filter  211  (having a clean roll portion  211 A on one side of the funnel&#39;s exit face  251  and a used length  211 B on the other) promotes the delivery of a low velocity, filtered molten metal stream  101  to be delivered to the bottom of the shot sleeve  220  where inclusions (such as deleterious oxides mentioned above are trapped to remain behind on the filter  211 . 
     It will be appreciated by those skilled in the art that the feed direction of the strand  210  with filters  211  is shown going in one instance from right-to-left ( FIG. 2B ), and in the other from left-to-right ( FIGS. 3A and 3B ). In actuality, the proper feed direction will be dictated by the placement of the strand  210  relative to the shot sleeve  220 , as well as to other equipment that makes up the filling system; either feed direction variant is deemed to be within the scope of the present invention. 
     It is noted that terms like “preferably,” “commonly,” and “typically” are not utilized herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present invention. Moreover, the term “substantially” is utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. As such, it may represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     Having described the invention in detail and by reference to specific embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. More specifically, although some aspects of the present invention are identified herein as preferred or particularly advantageous, it is contemplated that the present invention is not necessarily limited to these preferred aspects of the invention.