Patent Publication Number: US-8967078-B2

Title: Abrasive finish mask and method of polishing a component

Description:
BACKGROUND 
     This disclosure relates to an abrasive finish mask. The disclosure also relates to a method of abrasively polishing a component. 
     Abrasive finishing or polishing is used to round off sharp edges and remove material from components. Various engine components in the aerospace industry, such as stator clusters, utilize abrasive polishing to improve the surface finish of the component. Typically, portions of the component must be masked to prevent undesired polishing or material removal on those portions to maintain desired dimensions. One method of component polishing includes depositing the masked component into a slurry containing abrasive media. The slurry is agitated in a manner that causes the abrasive media to remove material from unmasked areas of the component. Masked areas of the component are protected from the abrasive media and remain dimensionally unchanged. 
     Current masking techniques are labor and time intensive and, for example, apply a masking material that is adhered to the component. Quite often other processes are needed to clean the polished component to remove remnants left from the masking process, which is undesirable. Occasionally, process incidental damage may result when the masking is removed from the component. 
     SUMMARY 
     A mask for a component is disclosed that includes a flexible gasket having a first cavity with a shape configured to generally correspond to at least a portion of a contour of a component masking area. The flexible gasket has an outer surface. A backer, which is more rigid than the flexible gasket, includes a second cavity having an inner surface that generally corresponds to the outer surface. The inner surface is configured to be engageable with the outer surface in an installed condition and deflect the outer surface away from the inner surface to compress the flexible gasket between the inner surface and the portion. 
     A method of masking a component includes installing a flexible gasket over a portion of a component masking area leaving an unmasked area exposed. A backer is installed over the flexible gasket to compress the flexible gasket between the backer and the portion. The flexible gasket and the backer are secured to the component to provide an assembly. The assembly is deposited into a slurry with an abrasive media to polish the unmasked area, in one example. The flexible gasket and backer prevent abrasive media from reaching the masked area. The flexible gasket and backer can be removed from the component and reused on other similarly shaped components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of an assembly including a mask according to the disclosure and a component to be polished. 
         FIG. 2A  is a partial cross-sectional view of an example gasket. 
         FIG. 2B  is a partial cross-sectional view of the mask installed and retained onto the component. 
         FIG. 3  is a schematic view of the assembly in a polishing machine. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts a component in need of polishing. In the illustrated example, the component  10  is a stator cluster. The component  10  includes a masking area  12  and an unmasked area  14 . The masking area  12  is a portion of the component  10  that is in need of masking or covering to prevent undesired material removal during an abrasive polishing process. The unmasked area  14  is a portion of the component in need of abrasive polishing to round-off sharp edges and remove material to improve surface finish in the unmasked area  14 . 
     The example component  10  includes inner and outer ends  18 ,  20  in the masking area  12 . Radially extending vanes  16  interconnect the inner and outer ends  18 ,  20  in the unmasked area  14 . The vanes  16  are polished during the abrasive polishing process to improve the aerodynamic surface finish of the vane  16 , which are arranged in the flow path of a gas turbine engine. 
     A reusable mask  13  is removably installed onto each of the inner and outer ends  18 ,  20  to cover the masking area  12 . The masks  13  are secured about the component  10  to provide an assembly  15  that can be deposited into a polishing machine  48  having abrasive media  52  ( FIG. 3 ). In the disclosed example, the mask  13  includes a flexible gasket  22  and a backer  24  that is more rigid than the flexible gasket  22 . In one example, the flexible gasket  22  is constructed from a silicone material, for example, using a mold. The backer  24  is constructed from a relatively rigid nylon, for example, using a selective laser sintering process. In the example, the flexible gasket  22  and backer  24  are constructed from different materials, although they may be constructed from generally the same material with different rigidities. 
     The flexible gasket  22  includes a cavity  26  that receives the inner end  18 . The cavity  26  includes a locating feature  28  that cooperates with a complementary feature on the inner end  18 , such as a slot  30  in an installed position. An opening  31  adjoins the cavity  26 . 
     Referring to  FIGS. 2A and 2B , the flexible gasket  22  includes a wall  32  having inner and outer surfaces  34 ,  36  spaced from one another. The cavity  38  is of a slightly smaller dimension than the inner end  18  to ensure an interference fit between the flexible gasket  22  and the inner end  18  so that abrasive media  52  does not penetrate the masking area  12 . 
     In one example, the inner and outer surfaces  34 ,  36  are canted at an approximately 10° angle toward the opening  31  in an uninstalled position ( FIG. 2A ) relative to an adjoining surface  33  of the inner end  18  with the component  10  installed into the flexible gasket  22 . In the example, the inner end  18  is inserted through the opening  31  into the cavity  26 . Thus, the opening  31  to the cavity  26  is smaller than a perimeter  35  of the inner end  18  where the flexible gasket  22  seals against the inner end  18  in the installed position ( FIG. 2B ). The backer  24  includes a cavity  38  that is sized slightly smaller than the outer surface  36  of the flexible gasket  22  to ensure that the flexible gasket  22  firmly engages and deflects the perimeter of the inner end  18 . In the example, the backer  24  includes a wall  40  having an inner surface  42  that engages the outer surface  36  of the flexible gasket  22  away from the inner surface  42  in the installed position. In this manner, the backer  24  compresses the flexible gasket  22 , between the backer  24  and component  10  and applies uniform pressure to the flexible gasket  22  around at least the perimeter  35  to prevent abrasive media from reaching the masked area  12 . 
     Another backer  25  and flexible gasket is installed onto the outer end  20  in a manner similar to that described above relative to the inner end  18 . 
     Referring to  FIGS. 2B and 3 , the backers  24 ,  25  include one or more notches  46  on a side opposite the cavity  38  for locating retainers  44  that maintain the masks  13  tightly about the component  10  during polishing. In one example, the retainers  44  are zip or cable ties. The retainers  44  are tightened until the masking area  12  is fully received within the cavities  26  of the flexible gaskets  22  so that abrasive media  52  will not penetrate the masking area  12 . 
     The assembly  15  is deposited into a polishing machine  48 . The polishing machine  48  includes a tank  49  filled with a slurry  50  having abrasive media  52 . A vibratory device  54  agitates the slurry  50  causing the abrasive media  52  to remove and polish material from the unmasked area  14 . The masks  13  at the ends  18 ,  20  of the component  10  seal out the abrasive media  52  from the masking area  12  on the component  10 . The zip ties are cut to remove the flexible gaskets  22  and backers  24 ,  25  from the component  10 . The flexible gaskets  22  and backers  24 ,  25  can be reused with other similarly shaped components. 
     Although example embodiments have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.