Localized spot lapping on a larger work surface area

Abstract

An apparatus for lapping a portion of an exterior surface of a housing is described. The apparatus includes at least a lapping tool arranged to execute a lapping operation. The lapping tool takes the form of a lapping pad which includes a conduit through which slurry can be transported for local deposition on the housing during a lapping operation. The apparatus also includes a stage on which a workpiece in the form of a housing is mounted. During the lapping operation, slurry is passed through the slurry conduit in the lapping tool, the lapping tool and the housing are moved in various motions. In this way, a gradual transition region is created between an accessory region and the remainder of the housing.

What is claimed is: 
     
         1 . An apparatus for creating a gradual transition region between an accessory region and a surrounding exterior surface region of a housing, the apparatus comprising:
 a lapping tool, the lapping tool comprising:
 a lapping pad, comprising:
 a centerpoint surrounded by a central portion, and 
 a peripheral portion, 
 
   wherein during a lapping operation the centerpoint of the lapping pad is compelled to follow a lapping path, the lapping path comprising a plurality of lapping segments, each lapping segment substantially crossing the accessory region at an angle different than a preceding lapping segment and each lapping segment putting the peripheral portion of the lapping pad in tangential contact with a central area of the accessory region, thereby creating the gradual transition region.   
     
     
         2 . The apparatus as recited in  claim 1 , wherein the created gradual transition region provides a gradual transition between a fine finish associated with the accessory region and a coarser finish associated with the surrounding exterior surface region. 
     
     
         3 . The apparatus as recited in  claim 2 , wherein a geometric configuration of the polishing path causes the peripheral portion of the lapping pad to come in more frequent contact with the central area of the finished accessory region than with any other portion of the surrounding exterior surface region. 
     
     
         4 . The apparatus as recited in  claim 3 , wherein the lapping tool further comprises a lapping plate mechanically coupled to the lapping pad, the lapping plate comprising:
 a rigid central portion; and   a flexible peripheral portion mechanically coupled to the rigid central portion,   wherein the flexible peripheral portion allows a greater force to be applied across the central portion of the lapping pad and smaller force towards the peripheral portion of the lapping pad during a lapping operation.   
     
     
         5 . The apparatus as recited in  claim 3 , wherein the lapping tool further comprises a lapping plate mechanically coupled to the lapping pad, the lapping plate comprising:
 a composite plate having a rigid central portion and a more flexible periphery, the change in rigidity occurring gradually between the rigid central portion and the periphery.   
     
     
         6 . The apparatus as recited in  claim 3 , wherein the housing is mechanically coupled to a stage having at least four degrees of freedom, the stage configured to maneuver the housing substantially parallel with respect to the lapping pad, the maneuvering of the stage compelling the lapping pad to follow the lapping path with respect to the housing. 
     
     
         7 . The apparatus as recited in  claim 6 , wherein the stage is configured to rotate around a first axis offset from a second axis of rotation associated with the lapping plate as it continues to compel the lapping tool to follow the lapping path by translation in X and Y axes,
 wherein the offset between the first and second axes randomizes the lapping path.   
     
     
         8 . The apparatus as recited in  claim 7 , wherein the lapping path has a star shaped geometry. 
     
     
         9 . The apparatus as recited in  claim 7 , wherein the housing includes a plurality of accessory regions and the polishing path causes the lapping pad to create a gradual transition region covering the plurality of accessory regions. 
     
     
         10 . The manufacturing method as recited in  claim 6 , wherein a diameter dimension of the lapping pad is between about 35 and 45 mm. 
     
     
         11 . A manufacturing method, comprising:
 mounting a housing to a stage, the housing comprising:
 a first region, 
 a second region surrounded and defined by the first region, and 
 a transition region disposed between the first region and the second region; 
   positioning a lapping tool in physical contact with a portion of the second region during a lapping operation, the lapping tool comprising a lapping pad having a central portion and a peripheral portion; and   finishing the transition region by causing the lapping pad to follow a lapping path, the lapping path comprising a plurality of lapping segments, each lapping segment substantially crossing the second region at an angle different than a preceding lapping segment and each lapping segment putting a peripheral portion of the lapping pad in tangential contact with a central area of the second region.   
     
     
         12 . The manufacturing method as recited in  claim 11 , wherein the finished transition region provides a gradual surface texture transition between the second region and the first region. 
     
     
         13 . The manufacturing method as recited in  claim 12 , further comprising:
 performing a three dimensional scan of the housing prior to beginning a lapping operation,   wherein the lapping path can be adjusted to target the transition region.   
     
     
         14 . The manufacturing method as recited in  claim 12 , wherein after a lapping operation a subsequent lapping operation is performed if the transition region is not completely finished. 
     
     
         15 . The manufacturing method as recited in  claim 12 , wherein the finishing the transition region comprises rotating the housing in an axis of rotation offset from the lapping tool axis of rotation while the lapping path is being followed. 
     
     
         16 . A lapping assembly, comprising:
 a lapping tool comprising a rotating lapping plate coupled to a lapping pad;   a force sensor coupled to the lapping tool for regulating pressure exerted by the lapping tool; and   a stage configured to maneuver a housing in a plane substantially parallel with the lapping pad during a lapping operation, the housing having an exterior surface with an accessory region and a surrounding surface region,   wherein during a lapping operation the lapping pad is compelled to follow a lapping path, the lapping path comprising a plurality of lapping segments, each lapping segment substantially crossing the accessory region at an angle different than a preceding lapping segment and each lapping segment putting a peripheral portion of the lapping pad in tangential contact with a central area of the accessory region, thereby creating a gradual transition region between the accessory region and the surrounding surface region.   
     
     
         17 . The lapping assembly as recited in  claim 16 , wherein the stage has at least 6 degrees of freedom, and wherein the degrees of freedom of the stage allow the lapping tool to establish the gradual transition region across a three dimensional curved surface portion of the housing. 
     
     
         18 . The lapping assembly as recited in  claim 16 , wherein the lapping tool has a chamfered edge portion configured to prevent scratching of the metal housing when a misalignment between the lapping tool and the metal housing takes place. 
     
     
         19 . The lapping assembly as recited in  claim 16 , wherein the lapping tool further comprises a slurry delivery conduit having a plurality of slurry delivery branches configured within the lapping plate,
 wherein the rotational motion of the lapping tool draws slurry down through the slurry conduit as a result of a geometrical configuration of the plurality of slurry delivery branches.   
     
     
         20 . The spot lapping assembly as recited in  claim 16 , wherein the housing is an aluminum housing and the accessory region has a mirror finish prior to the lapping operation.