Abstract:
A method for controlling a temperature of a portion of a die casting system having a shot tube plunger, according to an exemplary aspect of the present disclosure includes, among other things, communicating a fluid through a fluid inlet of a fluid passageway of a thermal control scheme of the shot tube plunger. The fluid circulates through the fluid passageway of the thermal control scheme to selectively adjust a temperature of the shot tube plunger. The fluid is discharged through a fluid outlet of the fluid passageway.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 13/023,607 which was filed Feb. 9, 2011 and issued on Jan. 22, 2013 as U.S. Pat. No. 8,356,655. 
    
    
     BACKGROUND 
     This disclosure relates generally to die casting systems, and more particularly to a shot tube plunger for a die casting system that includes a thermal control scheme for maintaining a temperature of the shot tube plunger. 
     Casting is a known technique used to yield near net-shaped components. For example, investment casting is often used in the gas turbine engine industry to manufacture near net-shaped components, such as blades and vanes having relatively complex geometries. A component is investment cast by pouring molten metal into a ceramic shell having a cavity in the shape of the component to be cast. Generally, the shape of the component to be produced is derived from a wax pattern or SLA pattern that defines the shape of the component. The investment casting process is capital intensive, requires significant manual labor and can be time intensive to produce the final component. 
     Die casting offers another known casting technique. Die casting involves injecting molten metal directly into a reusable die to yield a near net-shaped component. The components of the die casting system, including the shot tube and the shot tube plunger, are subjected to relatively high thermal loads and stresses during the die casting process. 
     SUMMARY 
     A method for controlling a temperature of a portion of a die casting system having a shot tube plunger, according to an exemplary aspect of the present disclosure includes, among other things, communicating a fluid through a fluid inlet of a fluid passageway of a thermal control scheme of the shot tube plunger. The fluid circulates through the fluid passageway of the thermal control scheme to selectively adjust a temperature of the shot tube plunger. The fluid is discharged through a fluid outlet of the fluid passageway. 
     In a further non-limiting embodiment of the foregoing method, the method includes monitoring a temperature of at least a portion of the shot tube plunger. 
     In a further non-limiting embodiment of either of the foregoing methods, the fluid passageway includes a coiled portion and the step of circulating the fluid includes circulating the fluid through the coiled portion of the fluid passageway. 
     In a further non-limiting embodiment of any of the foregoing methods, the coiled portion is disposed entirely inside of a tip portion of the shot tube plunger. 
     In a further non-limiting embodiment of any of the foregoing methods, the fluid heats the fluid passageway. 
     In a further non-limiting embodiment of any of the foregoing methods, the fluid cools the fluid passageway. 
     In a further non-limiting embodiment of any of the foregoing methods, discharging the fluid through a fluid outlet of the fluid passageway includes discharging the fluid through a shot rod of the die casting system. 
     In a further non-limiting embodiment of any of the foregoing methods, the fluid inlet and the fluid outlet extend in parallel in a direction of a longitudinal axis of the shot tube plunger and the thermal control scheme includes multiple coiled portions each having an inlet and an outlet. Each of the inlets of the multiple coiled portions are connected to the fluid inlet and each of the outlets of the multiple coiled portions are connected to the fluid outlet. 
     In a further non-limiting embodiment of any of the foregoing methods, the fluid outlet surrounds the fluid inlet. 
     In a further non-limiting embodiment of any of the foregoing methods, the fluid passageway includes a coiled portion that is cast or machined into the shot tube plunger. 
     In a further non-limiting embodiment of any of the foregoing methods, the fluid passageway includes a coiled portion that includes tubing sections separate from, and disposed internally to, the shot tube plunger. 
     A method for controlling a temperature of a shot tube plunger of a die casting system, according to another exemplary aspect of the present disclosure includes, among other things, circulating a fluid through a thermal control scheme disposed inside of the shot tube plunger to selectively adjust a temperature of the shot tube plunger. The shot tube plunger includes a plunger body and a separate tip portion attached only at a first face of the plunger body. 
     In a further non-limiting embodiment of the foregoing method, the fluid adds heat to the shot tube plunger. 
     In a further non-limiting embodiment of either of the foregoing methods, the fluid removes heat from the shot tube plunger. 
     In a further non-limiting embodiment of any of the foregoing methods, the first face faces toward a charge of material within the die casting system. 
     The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example die casting system. 
         FIG. 2A  illustrates an example shot tube plunger for use with a die casting system. 
         FIG. 2B  illustrates a portion of an example shot tube plunger. 
         FIG. 3  illustrates a tip portion of an example shot tube plunger. 
         FIGS. 4A-4D  illustrate features of an example shot tube plunger. 
         FIG. 5  illustrates another example shot tube plunger for use with a die casting system. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a die casting system  10  including a reusable die  12  having a plurality of die elements  14 ,  16  that function to cast a component  15 . The component  15  could include aeronautical components, such as gas turbine engine blades or vanes, or non-aeronautical components. Although two die elements  14 ,  16  are depicted by  FIG. 1 , it should be understood that the die  12  could include more or fewer die elements, as well as other parts and other configurations. 
     The die  12  is assembled by positioning the die elements  14 ,  16  together and holding the die elements  14 ,  16  at a desired position via a mechanism  18 . The mechanism  18  could include a clamping mechanism powered by a hydraulic system, pneumatic system, electromechanical system and/or other systems. The mechanism  18  also separates the die elements  14 ,  16  subsequent to casting. 
     The die elements  14 ,  16  include internal surfaces that cooperate to define a die cavity  20 . A shot tube  24  is in fluid communication with the die cavity  20  via one or more ports  26  that extend into the die element  14 , the die element  16  or both. A shut tube plunger  28  is received within the shot tube  24  and is moveable between a retracted and injected position (in the direction of arrow A) within the shot tube  24  by a mechanism  30 . A shot rod  31  extends between the mechanism  30  and the shot tube plunger  28 . The mechanism  30  could include a hydraulic assembly or other suitable system, including, but not limited to, pneumatic, electromechanical, hydraulic or any combination of the systems. 
     The shot tube  24  is positioned to receive a charge of material from a melting unit  32 , such as a crucible, for example. The melting unit  32  may utilize any known technique for melting an ingot of metallic material to prepare molten metal for delivery to the shot tube  24 . In this example, the charge of material is melted into molten metal by the melting unit  32  at a location that is separate from the shot tube  24  and the die  12 . However, other melting configurations are contemplated as within the scope of this disclosure. The example melting unit  32  is positioned in relative close proximity to the die casting system  10  to reduce the transfer distance of the charge of material between the melting unit  32  and the die casting system  10 . 
     Materials used to die cast a component  15  with the die casting system  10  include, but are not limited to, nickel-based super alloys, cobalt-based super alloys, titanium alloys, high temperature aluminum alloys, copper-based alloys, iron alloys, molybdenum, tungsten, niobium or other refractory metals. This disclosure is not limited to the disclosed alloys, and other high melting temperature materials may be utilized to die cast a component  15 . As used in this disclosure, the term “high melting temperature material” is intended to include materials having a melting temperature of approximately 1500° F./815° C. and higher. 
     The charge of material is transferred from the melting unit  32  to the die casting system  10 . For example, the charge of material may be poured into a pour hole  33  of the shot tube  24 . A sufficient amount of molten metal is communicated to the shot tube  24  to fill the die cavity  20 . The shot tube plunger  28  is actuated to inject the charge of material under pressure from the shot tube  24  into the die cavity  20  to cast a component  15 . Although the casting of a single component  15  is depicted, the die casting system  10  could be configured to cast multiple components in a single shot. 
     Although not necessary, at least a portion of the die casting system  10  can be positioned within a vacuum chamber  34  that includes a vacuum source  35 . A vacuum is applied in the vacuum chamber  34  via the vacuum source  35  to render a vacuum die casting process. The vacuum chamber  34  provides a non-reactive environment for the die casting system  10 . The vacuum chamber  34  therefore reduces reaction, contamination or other conditions that could detrimentally affect the quality of the die cast component, such as excess porosity of the die cast component from exposure to air. In one example, the vacuum chamber  34  is maintained at a pressure between 5×10 −3  Torr (0.666 Pascal) and 1×10 −6  Torr (0.000133 Pascal), although other pressures are contemplated. The actual pressure of the vacuum chamber  34  will vary based on the type of component  15  or alloy being cast, among other conditions and factors. In the illustrated example, each of the melting unit  32 , the shot tube  24  and the die  12  are positioned within the vacuum chamber  34  during the die casting process such that the melting, injecting and solidifying of the high melting temperature material are all performed under vacuum. In another example, the vacuum chamber  34  is backfilled with an inert gas, such as argon, for example. 
     The example die casting system  10  of  FIG. 1  is illustrative only and could include more or fewer sections, parts and/or components. This disclosure extends to all forms of die casting, including but not limited to, horizontal, inclined or vertical die casting systems and other die casting configurations. 
       FIG. 2A  illustrates an example shot tube plunger  128  for use with a die casting system, such as the die casting system  10 . In this disclosure, like reference numerals signify like features, and reference numerals identified in multiples of 100 signify slightly modified features. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments within the scope of this disclosure. In addition, it should be understood that the shot tube plunger  128  is not shown to the scale it would be in practice. Rather, the shot tube plunger  128  is shown enlarged to better illustrate its features. 
     The shot tube plunger  128  includes a first face  40 , a second face  42  and a plunger body  44  that extends between the first face  40  and the second face  42 . The first face  40  faces toward a charge of material M within the shot tube  24 , while the second face  42  faces toward and receives a portion of the shot rod  31 . In this example, the plunger body  44  of the shot tube plunger  128  includes a cylindrical shape disposed about a longitudinal axis A of the shot tube plunger  128 , although other shapes are contemplated as within the scope of this disclosure. The example shot tube plunger  128  could be made from copper, copper alloys or other suitable materials. 
     The shot tube plunger  128  also includes a tip portion  46  and a thermal control scheme  48  for controlling a temperature of the shot tube plunger  128  during the die casting of a component made from a high melting temperature material. In particular, the thermal control scheme  48  controls the temperature of the tip portion  46  of the shot tube plunger  128 , which is the portion of the shot tube plunger  128  that is in direct contact with molten metal M during the die casting process. The tip portion  46  is attached to the first face  40  of the shot tube plunger  128  such that the tip portion  46  is positioned axially forward (in this case, toward the charge of material M) of the first face  40 . In this example, the tip portion  46  is attached to the first face  40  of the shot tube plunger  128  with fasteners  50 . Other attachment methods are contemplated as within the scope of this disclosure. 
     The thermal control scheme  48  includes a fluid inlet  52 , a fluid outlet  54  and a coiled portion  56 . The fluid inlet  52 , the fluid outlet  54  and the coiled portion  56  define a fluid passageway  58  (shown schematically with arrows) of the thermal control scheme  48 . The fluid passageway  58  receives a fluid, such as water, that is circulated through the thermal control scheme  48  to either add or remove heat from the shot tube plunger  128 , and in particular, from the tip portion  46 . In other words, the thermal control scheme  48  can either heat or cool the fluid passageway  58  and in turn adjust a temperature of the shot tube plunger  128 . 
     The fluid passageway  58  of the thermal control scheme  48  is disposed internally to the shot rod  31  and the shot tube plunger  128 . The thermal control scheme  48  can be cast or machined into the shot rod  31  and the shot tube plunger  128 . For example, portions  60 ,  61  of the fluid inlet  52  and the fluid outlet  54 , respectively, are disposed inside the shot rod  31 . The shot tube plunger  128  also receives portions  62 ,  63  of the fluid inlet  52  and the fluid outlet  54 , respectively. The coiled portion  56  is disposed within the tip portion  46  of the shot tube plunger  128 , and is connected at an inlet  64  of the coiled portion  56  to receive fluid from the fluid inlet  52 . The fluid is circulated through the coiled portion  56  and exits through an outlet  66  of the coiled portion  56 . The fluid is then communicated through the fluid outlet  54  and exits the shot rod  31  for disposal or recirculation. A fluid source  68  provides a fluid, such as water, for circulation through the fluid passageway  58  of the thermal control scheme  48  to heat or cool the tip portion  46  of the shot tube plunger  128 . 
     Alternatively, the thermal control scheme  48  can include multiple tubing sections that are separate from and positioned within the internal passageways formed in the shot rod  31  and the shot tube plunger  128 . In this way, the thermal control scheme would provide a “closed-loop fluid passageway” in which the fluid that is circulated through the thermal control scheme  48  does not come into contact with the external surfaces of the shot rod  31  and shot tube plunger  128 . 
       FIG. 2B  illustrates a slightly modified fluid passageway  158 . In this example, a fluid outlet  154  surrounds the fluid inlet  52 . In other words, the fluid inlet  52  extends through the fluid outlet  154  to communicate the fluid into and out of the fluid passageway  158 . 
       FIG. 3  illustrates an end view of the tip portion  46  of the shot tube plunger  128 . In this example, the coiled portion  56  is helix-shaped. Other shapes are contemplated, including spiral shaped portions or other non-linear portions. 
     The thermal control scheme  48  could further include one or more thermocouples  70  embedded within a surface  47  of the tip portion  46 . The thermocouples  70  may be embedded at any location of the tip portion  46 . In this example, the thermocouple  70  is embedded at a location directly adjacent to the coiled portion  56  of the thermal control scheme  48 . The embedded thermocouple  70  monitors a temperature of the tip portion  46  and indicates whether the temperature of the fluid circulated through the thermal control scheme  48  should be increased or decreased to either heat or cool the shot tube plunger  128  as desired. 
     The thermocouples  70  could include type K, type J or type T thermocouples. Other thermocouples are also contemplated as within the scope of this disclosure and could be chosen depending upon design specific parameters, including but not limited to, atmospheric temperatures and the alloy used to cast a component. 
       FIGS. 4A-4D  depict other example features of the thermal control scheme  48 . For example, the coiled portions  56  of the fluid passageway  58  can include internal passageways  72  having geometric features  74  designed to create a turbulent fluid flow F within the internal passageway  72  and increase the amount of heat transfer that occurs between the fluid and the shot tube plunger  128 . As shown in  FIG. 4A , for example, the geometric features  74  include knurled textures  76  that protrude from a wall  80  of the internal passageway. 
     Alternatively, as shown in  FIG. 4B , the geometric features  74  include alternating trip strips  78  that protrude from the wall  80  of the internal passageway  72 .  FIG. 4C  illustrates that the geometric features  74  could include pedestals  82 . In addition, as depicted in  FIG. 4D , the geometric feature  74  of the internal passageway  72  could include a combination of features, such as pedestals  82  in combination with trip strips  78 . Other geometric features and combinations of features for increasing heat transfer are contemplated as within the scope of this disclosure. 
       FIG. 5  illustrates another example shot tube plunger  228  for use with a die casting system. The shot tube plunger  228  is similar to the shot tube plunger  128  described above, except that the shot tube plunger  228  includes a modified tip portion  246 .  FIG. 5  is not to scale, but is shown enlarged to better detail the features of the tip portion  246 . 
     In this example, the tip portion  246  includes a plurality of tip layers  90 A- 90   n  that are axially stacked upon one another (from the left to the right of  FIG. 5 ) to provide a tip portion  246  having a desired thermal control scheme  248 . In other words, the tip layers  90 A- 90   n  are coaxially disposed relative to the shot tube plunger  128 . The actual number of tip layers  90  used will vary depending upon the cooling requirements of the shot tube plunger  128 , among other factors. The stacked tip layers  90 A- 90   n  are attached relative to one another in a known manner, such as with a fastener  92 . The tip portion  246  may then be attached to a first face  240  of the shot tube plunger  228 . 
     The thermal control scheme  248  defines a fluid passageway  258 . In one example, each tip layer  90 A- 90   n  includes a coiled portion  256 A- 256   n  of the fluid passageway  258 . In this manner, a multiple layered thermal control scheme  248  is provided within the tip portion  246 . 
     Each coiled portion  256 A- 256   n  includes an inlet  264 A- 264   n  and an outlet  266 A- 266   n  for receiving and discharging a fluid, respectively. The inlets  264 A- 264   n  of the coiled portions  256 A- 256   n  are connected to the inlet(s) of adjacent coiled portions via passages  96  such that fluid from a fluid source  268  is communicated through a fluid inlet  252  and is circulated through each coiled portion  256 A- 256   n  of the thermal control scheme  248 . In other words, the inlet  264 A of the coiled portion  256 A is connected to the inlet  264 B of the coiled portion  256 B and so on. The outlets  266 A- 266   n  are in fluid communication with a fluid outlet  254  to discharge the circulated fluid. 
     Although not shown, the shot tube plunger  228  can also include other features such as those shown in  FIG. 3  and  FIG. 4 . For example, the shot tube plunger  228  could include an embedded thermocouple or geometric features disposed within the internal passageways of the coiled portions  256 . 
     The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.