LOCALIZED SPOT LAPPING ON A LARGER WORK SURFACE AREA
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.
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This application claims priority to and benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent Application Ser. No. 61/603,177, filed Feb. 24, 2012, entitled LOCALIZED SPOT LAPPING ON A LARGER WORK SURFACE AREA, the entire disclosure of which is hereby incorporated by reference in its entirety and for all purposes.
BACKGROUND1. Technical Field
The present invention relates generally to the polishing of a three dimensional metal alloy object. More particularly, a method and an apparatus are described for polishing a portion of an exterior surface of a housing of a portable electronic device to form a visually continuous flat top edge surface.
2. Related Art
The proliferation of high volume manufactured, portable electronic devices has encouraged innovation in both functional and aesthetic design practices for enclosures that encase such devices. Manufactured devices can include a housing that provides an ergonomic shape and aesthetically pleasing visual appearance desirable to the user of the device. Exterior surfaces of housings of portable electronic devices can be shaped by computer numerically controlled machinery and can include combinations of flat regions and curved regions as well as accessory regions such as logos and the like. Irregularities in the surface of the surface between the accessory region and the remainder of the housing can result in an unacceptable appearance due to visual artifacts caused by physical transitions between the two regions. For example, if the accessory region and the remainder portion of the housing are separated by an abrupt change in surface finish, then this change can be visible rendering an unappealing transition between the accessory region and the rest of the housing.
Thus there exists a need for a method and an apparatus for polishing a surface of a housing resulting in a surface with a consistent surface variation within a tolerance required to achieve a desired surface appearance upon finishing.
SUMMARYThe embodiments relate to a system, method and apparatus for creating a gradual transition region between a polished accessory region and the remainder of a surface portion of a metal housing.
In one embodiment, an apparatus for creating a gradual transition region between an accessory region and a surrounding exterior surface region of a housing is disclosed. The apparatus includes a lapping tool. The lapping tool includes a lapping pad. The lapping pad includes at least the following: (1) a centerpoint surrounded by a central portion, and (2) a peripheral portion. During a lapping operation the centerpoint of the lapping pad is compelled to follow a lapping path, the lapping path includes a number of lapping segments. Each lapping segment substantially crosses the accessory region at an angle different than a preceding lapping segment and each lapping segment puts a peripheral portion of the lapping pad in tangential contact with a central area of the accessory region, thereby creating the gradual transition region.
In another embodiment a manufacturing method is disclosed. The manufacturing method includes at least the following steps: (1) mounting a housing to a stage, where the housing includes at least 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; (2) positioning a lapping tool in physical contact with a portion of the second region during a lapping operation, the lapping tool including a lapping pad having a central portion and a peripheral portion; and (3) finishing the transition region by causing the lapping pad to follow a lapping path, the lapping path comprising a number 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 the peripheral portion of the lapping pad in tangential contact with a central area of the second region.
In yet another embodiment a lapping assembly is disclosed. The lapping assembly includes at least the following: (1) a lapping tool comprising a rotating lapping plate coupled to a lapping pad; (2) a force sensor coupled to the lapping tool for regulating pressure exerted by the lapping tool; and (3) 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. During a lapping operation the lapping pad is compelled to follow a lapping path, the lapping path includes a number 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.
The embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which:
The present invention relates generally to the polishing of a three dimensional metal alloy object. More particularly, a method and an apparatus are described for polishing an exterior surface of a metal alloy housing of a portable electronic device to form a combination of a flat top edge surface, a curved edge surface and a flat bottom surface.
In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the present invention.
High volume manufactured portable electronics devices can include computer numerically controlled (CNC) machined metal alloy parts with various geometrically shaped surfaces. Representative portable electronic devices can include portable media players, portable communication devices, and portable computing devices, such as an iPod®, iPhone° and iPad® manufactured by Apple, Inc. of Cupertino, Calif. Both the tactile and visual appearance of a portable electronics device can enhance the desirability of the portable electronic device to the consumer. Housings can be used that include metal alloys which can provide a lightweight material that exhibits desirable properties, such as strength and heat conduction well suited for housings of portable electronic devices. A representative metal alloy can include an aluminum alloy. Both the tactile and visual appearance of a portable electronics device can enhance the desirability of the device to the consumer. A cosmetic outer layer machined from a metal alloy can be cut to a desired shape and polished to a desired reflective and/or matte appearance. In some embodiments, a continuously smooth shape having a uniformly visually smooth appearance is desired.
High volume manufacturing can benefit greatly from minimized processing time. Machining an aluminum billet to form the exterior surface of a housing of a portable electronic device using a single cutting tool can reduce the processing time required. Machining with a single continuous optimized path can result in a “rough” cut surface that can require minimal sanding and polishing to produce a visually smooth finish with no visually discernible breaks between regions having different cross sections. Curved regions can transition smoothly into flat regions including along corner areas without any visual change in surface appearance. In some cases specific regions along an exterior surface of the housing require additional polishing operations to achieve a desired polishing effect across that surface. Since polishing operations generally result in material removal, polishing operations targeting a discrete area for a smoother or shinier finish can cause a surface variation in the previously continuous surface of the housing. Unfortunately, in some cases the variation can cause an abrupt change between surface areas that can mar the overall look and feel of the housing.
In one embodiment a lapping process can be utilized to create a gradual transition region between the aforementioned accessory region and the less thoroughly polished remainder of the housing. The process can be referred to as spot lapping as the lapping operation is focused on a particular portion of the housing. A lapping tool associated with the lapping process is aligned parallel with the surface of the housing and maneuvered with respect to the surface of the housing during the lapping operation by a stage. The stage permits maneuvering of the housing in a number of degrees of freedom allowing movement in at least an X-Y plane. The lapping tool can be a rotary polishing tool configured to spin an abrasive pad across the surface of the housing. By maneuvering the lapping tool along a lapping path with respect to the housing such that efficient material removal portions of the lapping tool spends more time over a central portion of the depression than over peripheral portions of the depression a gradual transition region can be established, thereby smoothing an abrupt visual or tactile change between the accessory region and the remainder of the surface of the housing.
Various embodiments of lapping methods suitable for establishing a smooth transition region across a portion of a surface of a metal substrate are discussed below with reference to
It should be noted that in some embodiments multiple accessory regions 102 can be present on one surface of aluminum housing 100. Given such a configuration a single lapping operation can be designed to cover multiple accessory regions 102 when they are in close proximity to one another. For example, in one embodiment an aluminum housing 100 with a shiny corporate logo proximate to a shiny line of text can be desired. When the text is in proximity to the logo abrupt transition regions 104 of both the logo and the text can be removed in a single lapping operation. It should also be noted that in a more complex configuration an extra degree of freedom can be added to a lapping machine assembly allowing a lapping operation to be applied across a three dimensional surface. For example, a spline or curve shaped surface can also include accessory regions. As with a flat surface, abrupt changes between a surface finish of an accessory region and the remaining portions of a housing can result in visual and tactile distractions. The extra degree of freedom in the stage can allow blending across an abrupt transition region, thereby allowing aforementioned techniques such as the lapping path to be applied to a three dimensional surface.
The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. The described embodiments can also be embodied as computer readable code on a computer readable medium for controlling manufacturing operations or as computer readable code on a computer readable medium for controlling a manufacturing line used to fabricate thermoplastic molded parts. The computer readable medium is any data storage device that can store data which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, DVDs, magnetic tape, optical data storage devices, and carrier waves. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.
The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the invention. Thus, the foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.
The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.
Claims
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.
Type: Application
Filed: Sep 12, 2012
Publication Date: Aug 29, 2013
Applicant: Apple Inc. (Cupertino, CA)
Inventors: Collin Chan (San Jose, CA), Brian Miehm (Santa Clara, CA), Simon Lancaster-Larocque (Gloucester, CA), Ryan M. Satcher (San Jose, CA)
Application Number: 13/612,791
International Classification: B24B 37/00 (20120101); B24B 37/10 (20120101); B24B 37/20 (20120101);