Patent Publication Number: US-2020298309-A1

Title: Shrouded rotor and a hybrid additive manufacturing process for a shrouded rotor

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. application Ser. No. 15/864,599 filed Jan. 8, 2018 for “A SHROUDED ROTOR AND A HYBRID ADDITIVE MANUFACTURING PROCESS FOR A SHROUDED ROTOR” by D. E. Army, D. Giulietti and A. Madinger. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates to the manufacture of a shrouded rotor and, in particular, to a hybrid additive manufacturing process utilized in the manufacture of a shrouded rotor. 
     BACKGROUND 
     Rotating airfoils, such as rotors of an air cycle machine (hereinafter “ACM”) on an aircraft, lose efficiency due to the need to have clearance between the rotor tips and a nonrotating shroud radially outward from the rotors. To increase efficiency, the shroud can be fastened to the rotors so as to rotate with the rotors and a hub radially inward from the rotors. Prior art processes utilized to create this shrouded rotor fasten the shroud to the rotors through brazing, welding, bolts and nuts, rivets, or other fasteners. Other prior art methods utilize a process that constructs the shrouded rotor such that space within the shrouded rotor is limited and prevents the access of tools to machine (i.e., smooth) the flow surfaces adjacent the flow path within the shrouded rotor. 
     SUMMARY 
     A hybrid additive manufacturing process is utilized for creating a shrouded rotor with the shrouded rotor having a hub at a radial center, a shroud at a radial outer side, and vanes extending therebetween. The hybrid additive manufacturing process includes forming the shrouded rotor in stages, with a first stage being formed by depositing material in an axial direction through a first stage of the hub, machining an outer surface of the first stage of the hub to smooth the outer surface, depositing material on the first stage of the hub in a radial direction through a first stage of the vanes and the shroud, and machining all functional surfaces of the first stage of the vanes and an inner surface of the first stage of the shroud to smooth the surfaces. A second stage of the shrouded rotor is formed by depositing material on the first stage of the hub in the axial direction through a second stage of the hub, machining an outer surface of the second stage of the hub to smooth the outer surface, depositing material on the second stage of the hub in the radial direction through a second stage of the vanes and the shroud, and machining all functional surfaces of the second stage of the vanes and an inner surface of the second stage of the shroud to smooth the surfaces. The hybrid manufacturing process can form the shrouded rotor through any number of stages similar to the process of forming the first stage and/or the second stage. 
     A shrouded rotor includes a hub at a radial center having an outer surface forming an inner wall of a flow path, a shroud at a radial outer side having an inner surface forming an outer wall of the flow path, and vanes extending within the flow path between the hub and the shroud with the outer surface of the hub, the inner surface of the shroud, and all surfaces of the vanes having a surface roughness of less than 32R a  (also referred to as “roughness average” with this parameter/measurement being known to someone of skill in the art). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of an ACM shrouded rotor. 
         FIG. 1B  is a cross-sectional view of the ACM shrouded rotor. 
         FIG. 1C  is a perspective view of the ACM shrouded rotor with inserts in place. 
         FIG. 2  is a flow diagram of a hybrid additive manufacturing process. 
     
    
    
     DETAILED DESCRIPTION 
     A hybrid manufacturing process for creating a shrouded rotor is disclosed herein that includes forming the shrouded rotor in a number of stages to ensure that machining tools have sufficient clearance to machine/smooth the flow surfaces adjacent the flow path within the shrouded rotor. The hybrid manufacturing process includes forming each stage before proceeding on to forming a subsequent stage of the shrouded rotor. Forming a first stage (and most subsequent stages) includes depositing material in an axial direction through a first stage/portion of the hub at a radial center, machining a radially outer surface (i.e., a flow surface) of the first stage of the hub to smooth the outer surface, depositing material on the first stage of the hub in a radial direction through a first stage of vanes (i.e., rotors) and a shroud, and machining all surfaces of the first stage of the vanes and an inner surface of the first stage of the shroud (i.e., flow surfaces) to smooth the surfaces. Because the flow surfaces are machined/smoothed after the first stage of the hub is formed (and then after the first stage of the vanes and shroud are formed), the machining tools are easily able to access the flow surfaces to machine/smooth those surfaces, which would not be possible if the entire shrouded rotor was additively manufactured all in one step/stage. After the first stage is formed, the second stage is formed through a similar process building upon the first stage of the hub, vanes, and shroud. A subsequent stage (or multiple subsequent stages) can utilize at least one insert that is placed into at least one void within the soon-to-be-created flow path to provide support to the soon-to-be-created vanes and the soon-to-be-created shroud. After depositing material to create that stage&#39;s vanes and shroud, the at least one insert is removed through machining, chemically, or through other means. Forming each stage of the shrouded rotor can include additional steps, such as rotating the partially created shrouded rotor before depositing material to create that stage&#39;s vanes and shroud, rotating the partially created shroud rotor back before depositing material to create a subsequent stage&#39;s hub, and depositing material on an outer surface of the shroud to create a labyrinth seal. The hybrid additive manufacturing process can include other steps as set out in the description below. 
     As stated above, the hybrid additive manufacturing process constructs the shrouded rotor in stages that allow for machining/smoothing tools to access the flow surfaces adjacent the flow path within the shrouded rotor. With the hybrid additive manufacturing process allowing for the flow surfaces to be machined/smoothed, the efficiency of the resulting shrouded rotor is increased because of the smoothness of the flow surfaces. Because the vanes/rotors of the shrouded rotor are supported at both ends (i.e., supported at a radially inner end by the hub and at a radially outer end by the shroud), the vanes can have a reduced thickness, which also increases efficiency by reducing the mass of the shrouded rotor and by requiring a less robust containment structure that is needed to prevent damage if/when the vanes/rotors become detached from the hub. With the shroud being integral with the vanes and hub, the manufacturing process is simplified because a separate shroud does not need to be fastened to the vanes and hub through brazing, welding or other means. Further, because the shroud in integral with the vanes and hub, the vanes and hub do not need to be axially shimmed to adjust the clearance between the rotating vanes and hub and the nonrotating shroud, thus further simplifying the manufacturing process. 
     This disclosure will first describe the structure of the ACM shrouded rotor and then describe the hybrid additive manufacturing process utilized in construction of the ACM shrouded rotor. While this disclosure describes the hybrid additive manufacturing process with regards to an ACM shrouded rotor, the process can be utilized with the construction of other components that require machining/smoothing. 
       FIG. 1A  is a perspective view of an ACM shrouded rotor,  FIG. 1B  is a cross-sectional view of the ACM shrouded rotor, and  FIG. 1C  is a perspective view of the ACM shrouded rotor with inserts in place. Shrouded rotor  10  includes hub  12 , vanes (also referred to as rotors)  14 , shroud  16 , and flow path  18 . Hub  12  includes bore  20  at radial center  22 , ribs  24 , and outer surface  26 . Vanes  14  include partial vanes  28   a , full vanes  28   b , and surfaces  30 . Shroud  16  includes radial outer side  32  and inner surface  34 . Shrouded rotor  10  also includes first axial end  36 , second axial end  38 , and labyrinth seal  40 . Inserts  42  that can be located within voids  44  in flow path  18  during manufacture of shrouded rotor  10 . Also shown is axial build direction A, radial build direction R, first stage  51 , second stage S 2 , and third stage S 3  of shrouded rotor  10  with first stage  51 , second stage S 2 , and third stage S 3  dividing shrouded rotor  10  into “slices” (i.e., discrete portions). 
     Shrouded rotor  10  is a rotating component (about centerline C) within an ACM that provides flow path  18  through which air that is conditioned flows to eventually be provided to a fuselage of an aircraft. Shrouded rotor  10  can be radially outward from and centered about a shaft (which extends through bore  20  of hub  12 ) that extends along centerline C. Shrouded rotor  10  is shown as having a substantially frustoconical shape with flow path  18  providing a path for air to enter at an inlet adjacent second axial end  38  by flowing radially inward, change direction while flowing through flow path  18  formed within shrouded rotor  10 , and exit flow path  18  at an outlet adjacent first axial end  36  by flowing in an axial direction parallel to centerline C. While shrouded rotor  10  is shown as being substantially frustoconical, shrouded rotor  10  can have other configurations, such as a cylindrical configuration in which flow path  18  is parallel to centerline C. Shrouded rotor  10  can be constructed from a variety of materials, such as steel and/or titanium alloys or aluminum silicone alloys, but the material should be suitable to be used in an additive manufacturing process while also being able to be machined to provide a smooth surface to the flow surfaces of flow path  18 . 
     Hub  12  is annular in shape extending axially along centerline C. Hub  12  is centered about centerline C at radial center  22 . Hub  12  includes bore  20  at radial center  22  that provides an aperture through which a shaft of the ACM can extend. Hub  12  also includes outer surface  26  forming the radially outward most part of hub  12 , with outer surface  26  being a flow surface that forms the innermost surface of flow path  18 . During manufacture of shrouded rotor  10 , outer surface  26  of hub  12  is machined to a surface roughness of less than 32R a  to provide less drag on the air flowing through flow path  18 . In this disclosure, the surface roughness of various surfaces, including outer surface  26  of hub  12 , is measured using the roughness average, R a , which is the arithmetic average of the absolute values of the profile height deviations from the mean line that is recorded within the evaluation length. While the roughness average parameter/measurement is used, other parameters/measurements can be utilized to determine the roughness of the surfaces of interest of shrouded rotor  10 . 
     Extending axially within hub  12  can be ribs  24 , which are radially extending internal support structures. Hub  12  can have one or multiple ribs  24  circumferentially spaced within hub  12 . Ribs  24  can decrease a thickness of walls that form hub  12  because ribs  24  provide additional support to shrouded rotor  10 . Hub  12  can be frustoconical (as shown in the disclosed embodiment) with first axial end  36  having a cross section with a smaller diameter than a diameter of a cross section at second axial end  38 . Thus, the diameter of hub  12  formed during first stage  51  can be smaller than a diameter of a cross section of hub  12  formed doing second stage S 2 . During construction of shrouded rotor  10 , first stage  51  will be adjacent first axial end  36  with first stage  51  of hub  12  being constructed in axial build direction A. At second axial end  38 , hub  12  extends radially outward to form the axial side of shrouded rotor  10 . Hub  12  can have other features and configurations to provide support to flow path  18  and shrouded rotor  10 . 
     Vanes  14  are outward from hub  12  and extend between the hub  12  and shroud  16 . Vanes  14  are substantially radially outward from hub  12 , but near second axial end  38  vanes  14  are axially forward of hub  12  (with forward being a direction downward in  FIGS. 1A-1C ) due to the changing direction of flow path  18 . Vanes  14  can also be classified as rotors because vanes  16  rotate along with the other components of shrouded rotor  10 . Vanes  16  include two configurations of vanes: partial vanes  28   a  and full vanes  28   b . Partial vanes  28   a  extend only a portion of a length of flow path  18 , beginning at the inlet adjacent second axial end  38  and extending along flow path  18  towards first axial end  36  but not extending the entire length of flow path  18  to first axial end  36 . Full vanes  28   b  extend the entire length of flow path  18 , beginning at the inlet adjacent second axial end  38  and ending at the outlet at first axial end  36 . Both partial vanes  28   a  and full vanes  28   b  can be angled and/or bowed (or have other features) such that the vanes extend at least partially in a circumferential direction. As is known to someone of ordinary skill in the art, partial vanes  28   a  and full vanes  28   b  can have a variety of configurations to guide the flow of air through flow path  18 . Additionally, other configurations of vanes  14  do not have to include partial vanes  28   a  and/or full vanes  28   b . Vanes  14  includes surface  30 , which are exposed to air flowing through flow path  30 . During manufacture of shrouded rotor  10 , surfaces  30  of vanes  14  are machined to a surface roughness of less than 32R a  to provide less drag on the air flowing through flow path  18 . With vanes  14  being supported at both radial ends by hub  12  and shroud  16 , vanes can be thinner (i.e., have a thin wall) than if supported only at one end. 
     Shroud  16  is annular in shape and the radially outermost component of shrouded rotor  10 . Shroud  16  includes radial outer side  32  on the radially outermost side and inner surface  34  forming the radially outer boundary/wall of flow path  18 . Shroud  16  extends axially from first axial side  36  to the inlet of flow path  18  such that shroud  16  does not extend an entire axial length of shrouded rotor  10 . Shroud  16  can have a frustoconical shape that is similar to the shape of outer surface  26  of hub  12  with a diameter of shroud  16  adjacent first axial end  36  being smaller than a diameter of shroud  16  adjacent the inlet of flow path  18  closer to second axial end  38 . Radial outer side  32  can include other features that interact with structures radially outward from shroud  16 , such as labyrinth seal  40 . 
     Labyrinth seal  40  is a radially outward extending seal located on radial outer side  32  of shroud  16  adjacent first axial end  36 . Labyrinth seal  40  seals a gap radially outward from shroud  16  between shrouded rotor  10  and structures outward from shrouded rotor  10 . During manufacture of shrouded rotor  10 , labyrinth seal  40  can be constructed in conjunction with shroud  16  such that the two are one continuous component (i.e., labyrinth seal  40  can be one continuous component with shrouded rotor  10 ). While this disclosure describes the seal as being labyrinth seal  40 , other embodiments can include other types of seals. 
     Inner surface  34  of shroud  16  is a flow surface that forms the outermost surface of flow path  18 . During manufacture of shrouded rotor  10 , inner surface  34  of shroud  16  is machined to a surface roughness of 32R a  (also referred to as “roughness average” with this parameter/measurement being known to someone of skill in the art) to provide less drag on the air flowing through flow path  18 . Shroud  16  is one of the last components to be constructed during manufacture of each stage of shrouded rotor  10 . 
     As shown in  FIG. 1C , inserts  42  can be located within voids  44  (shown in  FIG. 1B ) of flow path  18  at the inlet of flow path  18  near second axial end  38  of shrouded rotor  10 . Inserts  42  are blocks that can have any shape and/or configuration to fit within voids  44  during manufacture of vanes  14  and shroud  16 . During manufacture of shrouded rotor  10 , inserts  42  can be placed within voids  44  to support soon-to-be-created vanes  14  and shroud  16 . Support for shroud  16  may be necessary during construction (i.e., depositing of material) of shroud  16  due to shroud  16  having a large overhang at a location near the inlet of flow path  18 . As will be described with regards to  FIG. 2 , inserts  42  can be inserted into voids  44  during manufacture of shrouded rotor  10  during construction of one of the final stages of vanes  14  and shroud  16  (with a later stage being referred to as an Nth stage). After the corresponding vanes  14  and shroud  16  are constructed and have hardened such that no support is needed, inserts  42  are removed from voids  44  so that flow path  18  is unobstructed. Inserts  42  can be constructed from a variety of materials that allow for inserts  42  to be easily removed from voids  44 , such as a material that is machined away (i.e., inserts  42  are ground, drilled, or otherwise removed using a machine) or a material that can be removed through chemical means (i.e., a chemical is used to dissolve inserts  42  while not dissolving or otherwise affecting shrouded rotor  10 ). Thus, insert  42  can be constructed from a different material than the material that makes up the components of shrouded rotor  10  (i.e., hub  12 , vanes  14 , and shroud  16 ). 
     Shrouded rotor  10  is manufactured in multiple stages, with first stage  51 , second stage S 2 , and third stage S 3  being set out in  FIG. 1B . While  FIG. 1B  shows the entirety of shrouded rotor  10  being divided into three stages, the manufacture of shrouded rotor  10  can be performed in any number of stages. Thus, when describing the hybrid additive manufacturing process in  FIG. 2 , stages after first stage  51  and second stage S 2  are denoted as being the Nth stage with hub  12 , vanes  14 , and shroud  16  in those stages being constructed very similarly to the construction of hub  12 , vanes  14 , and shroud  16  of second stage S 2  (other than the placement and removal of inserts  42 ). 
     When describing first stage S 1 , second stage S 2 , and third stage S 3 , each stage represents the portion of hub  12 , vanes  14 , and shroud  16  (as set out in  FIG. 1B ) constructed during that particular manufacturing subprocess/stage. Thus, for example, during first stage S 1 , a portion of hub  12 , vanes  14 , and shroud  16  closest to first axial end  36  is constructed. Then, during second stage S 2 , a portion of hub  12 , vanes  14 , and shroud  16  adjacent the first stage S 1  is constructed. Finally, because shrouded rotor  10  is shown as being manufactured in three stages, during third stage S 3 , a final portion of hub  12 , vanes  14 , and shroud  16  closest to second axial end  38  is constructed. If more stages were utilized during the hybrid additive manufacturing process to construct shrouded rotor  10 , a smaller axial portion of hub  12 , vanes  14 , and shroud  16  would be constructed during each of the stages (thus dividing shrouded rotor  10  into thinner axial “slices”). This hybrid additive manufacturing process is described in  FIG. 2 . 
       FIG. 2  is a flow diagram of hybrid additive manufacturing process  50 . The steps of hybrid additive manufacturing process  50  will be described in conjunction with  FIG. 1B  and the stages outlined therein. Hybrid additive manufacturing process  50  is divided into multiple stages, each of which includes multiple manufacturing steps. Hybrid manufacturing process  50  includes forming the first stage  52 , forming the second stage  54 , and forming the Nth stage  56  (which can be third stage S 3  or another later stage if the process includes more than three stages). Forming first stage  52  includes depositing material through the first stage of the hub  58 , rotating the hub  60 , machining the first stage of the hub  62 , depositing material through the first stage of the vanes and shroud  64 , machining the first stage of the vanes and shroud  66 , and rotating the shrouded rotor back  68 . Forming second stage  54  includes depositing material through the second stage of the hub  70 , rotating the shrouded rotor  72 , machining the second stage of the hub  74 , depositing material through the second stage of the vanes and shroud  76 , machining the second stage of the vanes and shroud  78 , and rotating the shrouded rotor back  80 . Forming Nth stage  56  includes depositing material through the Nth stage of the hub  82 , rotating the shrouded rotor  84 , machining the Nth stage of the hub  86 , placing the inserts into the voids  88 , depositing material through the Nth stage of the vanes and shroud  90 , and removing the inserts  92 . Hybrid additive manufacturing process  50  can additionally include the step of depositing material to create the labyrinth seal  94 , which can be performed at a variety of times through hybrid additive manufacturing process  50 . 
     Before forming first stage  52 , an additive manufacturing system is provided that is configured to deposit material and machine surfaces to form shrouded rotor  10 . Forming first stage  52  begins by depositing material to construct the first stage of the hub  58 . The material is deposited to construct first stage S 1  of hub  12  in axial build direction A by depositing material layer by layer in an additive manufacturing process building axially upon the prior layer. By depositing material in axial build direction A, all features of first stage S 1  of hub  12  can be constructed, including bore  22 , ribs  24 , and outer surface  26  of hub  12 . 
     Next, the first stage of the hub can be rotated  60  from axial build direction A to radial build direction R. The rotation of hub  12  is approximately ninety degrees so that hub  12  can be machined and material can be deposited layer by layer the same way as in step  58  but in radial build direction R. Hybrid additive manufacturing process  50  does not need to include step  60  (rotating hub  12 ) if the additive manufacturing system is configured to deposit material in radial build direction R without the need to rotate hub  12 . 
     Step  62  is machining outer surface  26  of first stage S 1  of hub  12  to smooth outer surface  26 . As mentioned above, outer surface  26  of first stage S 1  of hubs  12  is machined to have a low surface roughness to provide less drag on the air flowing through flow path  18 . This machining can be done by a buffer system or another configuration/machine designed to smooth outer surface  26 . 
     After machining outer surface  26 , material is deposited through the first stage of the vanes and shroud  64 . Step  64  entails depositing material layer by layer in an additive manufacturing process to construct first stage S 1  of vanes  14  and shroud  16 . The material is deposited in radial build direction R (i.e., depositing layer by layer in a radially outward direction). First stage S 1  of hub  12  and the soon-to-be and/or partially constructed vanes  14  and shroud  16  can be rotated circumferentially about centerline C as material is deposited to create first stage S 1  of vanes  14  and shroud  16  during step  64  so that one entire radial layer of first stage S 1  of vanes  14  and shroud  16  is completely constructed before beginning construction/deposition of the next radial layer radially outward from the prior radial layer (or the apparatus depositing material can rotate about centerline C to deposit material circumferentially). Thus, the entire radially inward layer is completed before beginning construction of a radially outward layer upon that radially inward layer. Alternatively, material can be deposited in another order to construct first stage S 1  of vanes  14  and shroud  16 . 
     After radial outer side  32  of first stage S 1  of shroud  16  is constructed (with the rest of first stage S 1  of vanes  14  and shroud  16  radially inward from radial outer side  32  also being constructed), the first stage of the surfaces of the vanes and the inner surface of the shroud is machined to smooth those flow surfaces  66 . As mentioned above, surfaces  30  of first stage S 1  of vanes  14  and inner surface  34  of first stage S 1  of shroud  16  are machined to have a low surface roughness to provide less drag on the air flowing through flow path  18 . As with the machining of outer surface  26  of hub  12 , this machining can be done by a buffer system or another configuration/machine designed to smooth surfaces  30  of vanes  14  and inner surface  34  of shroud  16 . 
     The final stage of forming the first stage of the shrouded rotor  52  includes step  68 , which is rotating the newly created first stage S 1  of shrouded rotor  10  (which includes first stage S 1  of hub  12 , vanes  14 , and shroud  16 ) back to axial build direction A. The rotation places first stage S 1  of shrouded rotor  10  in the orientation that the component was in prior to forming the first stage  52  and ensures the partial shrouded rotor  10  (i.e., first stage S 1  of shrouded rotor  10 ) is properly oriented for the forming of the second stage of the shrouded rotor  54 . The rotation of first stage S 1  of shrouded rotor  10  back to axial build direction A is approximately ninety degrees so that second stage S 2  of hub  12  can be deposited in axial build direction A. As with step  60 , hybrid additive manufacturing process  50  does not need to include step  68  (rotating first stage S 1  of shrouded rotor  10 ) if the additive manufacturing system is configured to deposit material in radial build direction R without the need to rotate shrouded rotor  10  (thus, there would be no need to rotate shrouded rotor  10  back). 
     After the first stage is formed  52 , the second stage is formed  54  in a similar process except that the geometry of second stage S 2  of hub  12 , vanes  14 , and shroud  16  is different than the geometry of those components of first stage S 1 . 
     Forming second stage  54  begins by depositing material to construct the second stage of hub  70 . Different than step  58  (depositing material to construct first stage S 1  of hub  12 ), however, is that the material is deposited on first stage S 1  of hub  12  such that second stage S 2  of hub  12  is built/constructed upon the already created first stage S 1  of hub  12  to form a shrouded rotor  10  that is one continuous component. The material bonds to first stage S 1  of hub  12  so that first stage S 1  and second stage S 2  of hub  12  is one continuous component. As with step  58 , the material is deposited to construct second stage S 2  of hub  12  in axial build direction A by depositing material layer by layer in an additive manufacturing process. Second stage S 2  of hub  12  can have the same, different, or additional features than those of first stage S 1  of hub  12 . For example, second stage S 2  of hub  12  can include a radial diameter that is larger than a radial diameter at any axial cross section of first stage S 1  of hub  12  (i.e., forming hub  12  as a frustoconical shape). Additionally, second stage S 2  of hub  12  can continue the construction of ribs  24  within hub  12 . 
     The next steps of forming second stage  54  are identical to those of forming first stage  52 , except that the geometry of second stage S 2  of vanes  14  and shroud  16  (and hub  12 ) is different than the geometry of those components in first stage S 1 . After depositing material to construct the second stage of hub  70 , the shrouded rotor (which includes first stage S 1  of hub  12 , vanes  14 , and shroud  16  and also second stage S 2  of hub  12 ) can be rotated  72 . The rotation can be from axial build direction A to radial build direction R (approximately ninety degrees). Next, step  74  is machining second stage S 2  of outer surface  26  of hub  12  to have a low surface roughness to provide less drag on the air flowing through flow path  18 . After that, material is deposited through the second stage of the vanes and shroud  76 . As with step  64  in the forming of the first stage  52 , the material is deposited in radial build direction R layer by layer to form second stage S 2  of vanes  14  and shroud  16 . Next, the second stage of the surfaces of the vanes and the inner surface of the shroud is machined to smooth those flow surfaces  78 . Surfaces  30  of second stage S 2  of vanes  14  and inner surface  34  of second stage S 2  of shroud  16  are machined to have a low surface roughness to provide less drag on the air flowing through flow path  18 . Finally, the newly created second stage of the shrouded rotor and the previously created first stage of the shrouded rotor are rotated back  80  from radial build direction R to axial build direction A. The rotation of first stage S 1  and second stage S 2  of shrouded rotor  10  is approximately ninety degrees so that the next stage of hub  12  can be deposited in axial build direction A. As with steps  60 ,  68 , and  72 , hybrid manufacturing process  50  does not need to include step  80  (rotating first stage S 1  and second stage S 2  of shrouded rotor  10 ) if the additive manufacturing system is configured to deposit material in radial build direction R without the need to rotate shrouded rotor  10 . 
     After forming the second stage of the shrouded rotor  54 , third stage S 3  through [N−1]th stage are performed in a similar process to forming second stage S 2 . As described above, the manufacture of shrouded rotor  10  can be divided into any number of stages necessary to allow access of a buffering/machining system to smooth the flow surfaces of shrouded rotor  10 . With shrouded rotor  10  in  FIG. 1B , the manufacture process includes three stages so third stage S 1  would be the same as the Nth stage described below. However, if more stages were used, the process used to create the portion of shrouded rotor  10  constructed during each of those stages would be similar to the process utilized to construct the portion of shrouded rotor  10  formed during second stage S 2 . Thus, one of the last stages in hybrid additive manufacturing process  50  is the Nth stage as described below because inserts  44  are utilized during the Nth stage. However, other embodiments of hybrid additive manufacturing process  50  do not need to utilize inserts  42 , so the Nth stage would the same as second stage S 2  described above. 
     Forming the Nth stage of the shrouded rotor  56  is similar to forming the second stage of the shrouded rotor  54  except that forming the Nth stage  56  includes incorporating inserts  42  shown in  FIG. 1C  into the manufacturing process. Also, the geometry of second stage S 2  of hub  12 , vanes  14 , and shroud  16  is different than the geometry of subsequent stages, including the Nth stage. As with forming second stage  54 , forming Nth stage  56  begins by depositing material through the Nth stage of the hub  82  by depositing material to create the Nth stage of hub  12  upon the already created second stage S 2  of hub  12  to form a shrouded rotor  10  that is one continuous component. Next, the shrouded rotor (which includes hub  12 , vanes  14 , and shroud  16  constructed by previous stages) can be rotated  84 . The rotation can be from axial build direction A to radial build direction R (approximately ninety degrees). Next, step  86  is machining outer surface  26  of the Nth stage of hub  12  to have a low surface roughness to provide less drag on the air flowing through flow path  18 . 
     After that, inserts are placed into the voids in the flow path  88 . Inserts  42  are placed into voids  44  in flow path  18  to provide support to the soon-to-be-created Nth stage of vanes  14  and shroud  16  when support is necessary due to the Nth stage of shroud  16  having a large overhang that may not be able to be supported by vanes  14  until the Nth stage of shroud  16  hardens. Inserts  42  can have any shape and/or configuration able to fit within voids  44  in flow path  18  and then allow for removal of inserts  44  at the end of the forming of the Nth stage  56 . 
     With inserts  42  in place within voids  44 , material is deposited through the Nth stage of the vanes and shroud  90 . As with step  78  in the forming of the second stage  54 , the material is deposited in radial build direction R layer by layer to form the Nth stage of vanes  14  and shroud  16 . However, with inserts  42  in place, the material forming the Nth stage of shroud  16  may also be deposited upon inserts  42  with inserts  42  providing support to the Nth stage of vanes  14  and shroud  16  until vanes  14  and shroud  16  cool and harden. 
     Next, the inserts are removed  92  after the Nth stage of vanes  14  and shroud  16  has hardened such that no support is needed. Inserts  42  are removed from voids  44  so that flow path  18  is unobstructed (aside from vanes  14 , which function to guide air flowing through flow path  18 ). Inserts  42  can be removed through machining (i.e., inserts  42  are ground, buffed, drilled, or otherwise removed using a machine) or through chemical means (i.e., a chemical is used to dissolve inserts  42  while not dissolving the material used to construct shrouded rotor  10 ). After inserts  42  are removed, forming the Nth stage  56  can optionally include machining surface  30  of the Nth stage of vanes  14  and inner surface  34  of the Nth stage of shroud  16  to smooth those flow surfaces to have a low surface roughness to provide less drag on the air flowing through flow path  18 . However, this step may not be needed if inserts  42  are constructed from a material that does not bond with the material used to contract shrouded rotor  10  so that when inserts  42  are removed, surface  30  of vane  14  and inner surface  34  of shroud  16  are already smooth. Additionally, the removal of the inserts (step  92 ) could also include machining surfaces  30  and inner surface  34 . 
     If the Nth stage is not the final stage to be formed during hybrid additive manufacturing process  50 , then forming the Nth stage  56  may include rotating the partially created shrouded rotor  10  back from radial build direction R to axial build direction A to prepare for the deposition of material to form the next stage of hub  12 . 
     While shown as the final step in hybrid additive manufacturing process  50 , depositing material to create the labyrinth seal  94  can be performed during or after the construction of the stage of shroud  16  upon which labyrinth seal  40  is located (or another time during hybrid additive manufacturing process  50 ). Material is deposited on radial outer side  32  of shroud  16  layer by layer in an additive manufacturing process to create labyrinth seal  40 , and the process utilized to deposit material to create labyrinth seal  40  is similar to the process utilized to deposit material to create shroud  16 . The material is deposited in radial build direction R and can be deposited such that labyrinth seal  40  is one continuous component with shrouded rotor  10 . Shrouded rotor  10  can be rotated circumferentially about centerline C as material is deposited during step  94  so that one entire radial layer of labyrinth seal  50  is completely constructed before beginning construction/deposition of the next radial layer upon the prior radial layer (or the apparatus depositing material can rotate about centerline C to deposit material circumferentially). Alternatively, material can be deposited in another order to construct labyrinth seal  40 . Once all material necessary to construct labyrinth seal  40  is deposited, labyrinth seal  40  can be machined and/or other components of labyrinth seal  40  not continuous with shrouded rotor  10  can be fastened to labyrinth seal  40 . 
     As stated above, hybrid additive manufacturing process  50  manufactures shrouded rotor  10  in stages (first stage  51 , second stage S 2 , third stage S 3 , the Nth stage described in subprocess  56 , etc.) that allow for machining/smoothing tools to access the flow surfaces (outer surface  26  of hub  12 , surfaces  30  of vanes  14 , and inner surface  34  of shroud  16 ) adjacent flow path  18  within shrouded rotor  10 . With hybrid additive manufacturing process  50  allowing for the flow surfaces to be machined/smoothed, the efficiency of the resulting shrouded rotor  10  is increased because of the smoothness of the flow surfaces. Because vanes  14  of shrouded rotor  10  are supported at both ends (i.e., supported at a radially inner end by hub  12  and at a radially outer end by shroud  16 ), vanes  14  can have a reduced thickness, which also increases efficiency by reducing the mass of shrouded rotor  10  and by requiring a less robust containment structure that is needed to prevent damage if/when vanes  14  become detached from hub  12 . With shroud  16  being integral with vanes  14  and hub  12 , the manufacturing process is simplified because a separate shroud does not need to be fastened to vanes  14  and hub  12  through welding or other means. Further, because shroud  16  in integral with vanes  14  and hub  12 , vanes  14  and hub  12  do not need to be axially shimmed to adjust the clearance between rotating vanes  14  and hub  12  and the nonrotating shroud, thus further simplifying the manufacturing process. 
     DISCUSSION OF POSSIBLE EMBODIMENTS 
     The following are non-exclusive descriptions of possible embodiments of the present invention. 
     A hybrid additive manufacturing process is utilized for creating a shrouded rotor with the shrouded rotor having a hub at a radial center, a shroud at a radial outer side, and vanes extending therebetween. The hybrid additive manufacturing process includes forming the shrouded rotor in stages, with a first stage being formed by depositing material in an axial direction through a first stage of the hub, machining an outer surface of the first stage of the hub to smooth the outer surface, depositing material on the first stage of the hub in a radial direction through a first stage of the vanes and the shroud, and machining all surfaces of the first stage of the vanes and an inner surface of the first stage of the shroud to smooth the surfaces. A second stage of the shrouded rotor is formed by depositing material on the first stage of the hub in the axial direction through a second stage of the hub, machining an outer surface of the second stage of the hub to smooth the outer surface, depositing material on the second stage of the hub in the radial direction through a second stage of the vanes and the shroud, and machining all surfaces of the second stage of the vanes and an inner surface of the second stage of the shroud to smooth the surfaces. The hybrid manufacturing process can form the shrouded rotor through any number of stages similar to the process of forming the first stage and/or the second stage. 
     The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations, steps, and/or additional components: 
     During the forming of the first stage of the shrouded rotor after depositing material in the axial direction through the first stage of the hub, rotating the first stage of the hub from an axial build direction to a radial build direction before machining the outer surface of the first stage of the hub. 
     During the forming of the first stage of the shrouded rotor after machining all surfaces of the first stage of the vanes and the inner surface of the first stage of the shroud, rotating the newly created first stage of the shrouded rotor back to the axial build direction. 
     During the forming of the first stage of the shrouded rotor and during the depositing of material on the first stage of the hub in the radial direction through the first stage of the vanes and the shroud, rotating the first stage of the hub in a circumferential direction as the material is being deposited to create the first stage of the vanes and the shroud. 
     Forming a third through Nth stage of the shrouded rotor using the same steps performed to form the second stage of the shrouded rotor. 
     During an Nth stage after machining an outer surface of the Nth stage of the hub, placing at least one insert into at least one void between a soon-to-be-created Nth stage of vanes to provide support to the soon-to-be-created Nth stage of vanes and a soon-to-be-created Nth stage of the shroud, depositing material in the radial direction though the Nth stage of the vanes and the Nth stage of the shroud, and removing the at least one insert. 
     The removal of the at least one insert is accomplished by machining the at least one insert. 
     The removal of the at least one insert is accomplished by using a chemical to dissolve the at least one insert. 
     The at least one insert is constructed from a different material than the material deposited to create the hub, vanes, and shroud. 
     The material that the at least one insert is constructed from does not bond to the material deposited to create the Nth stage of the hub, vanes, and shroud such that all surfaces of the Nth stage of the vanes and the inner surface of the Nth stage of the shroud adjacent to the at least one insert have a surface roughness of less than 32R a . 
     The shrouded rotor is one continuous component. 
     Depositing material on an outer surface of the shroud to create a labyrinth seal. 
     Depositing material in an axial direction through a first stage of the hub and depositing material through the second stage of the hub includes depositing material to create an internal structure of the hub. 
     The internal structure of the hub includes radially extending ribs. 
     The vanes are a thin wall supported at a radially inner end by the hub and at a radially outer end by the shroud. 
     The hub is a hollow frustoconical shape such that a first axial end of the hub formed during the forming of the first stage has a cross section with a smaller diameter than a diameter of a cross section of the hub formed during the forming of the second stage of the hub. 
     A shrouded rotor includes a hub at a radial center having an outer surface forming an inner wall of a flow path, a shroud at a radial outer side having an inner surface forming an outer wall of the flow path, and vanes extending within the flow path between the hub and the shroud with the outer surface of the hub, the inner surface of the shroud, and all surfaces of the vanes having a surface roughness average of less than 32R a . 
     The shrouded rotor of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations, steps, and/or additional components: 
     A diameter of the hub at a first axial end is less than a diameter of the hub at a second axial end. 
     The hub includes a bore at the radial center configured to allow a shaft to extend through. 
     A labyrinth seal that is on an outer surface of the shroud. 
     While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.