News Column

Patent Issued for Material Removal Depth Measurement by Scribing

August 21, 2014



By a News Reporter-Staff News Editor at Computer Weekly News -- Apple Inc. (Cupertino, CA) has been issued patent number 8798782, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Lancaster-Larocque, Simon R. (Gloucester, CA); Whipple, Lucas Allen (Belmont, CA).

This patent was filed on June 24, 2012 and was published online on August 5, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "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 casing that provides an ergonomic shape and aesthetically pleasing visual appearance desirable to the user of the device. Surfaces of casings molded from thermoplastic compounds can be shaped and polished to a highly reflective finish; however, the polished reflective surface can reveal minor variations in the final surface geometry. Molded casings can include complex geometric shapes that are difficult to finish to a uniform surface appearance. Prior art techniques can result in a tactilely smooth finish with an undesirable variation in visual reflective appearance. Moreover, due to the soft nature of polishing media, it is difficult to provide a consistent polishing process over a surface of the housing resulting in visually obvious variations in the surface finish.

"Thus there exists a need for a method and an apparatus for polishing a three dimensional curved edge of an object resulting in a visually smooth and consistent reflective appearance."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "This paper describes many embodiments that relate to an apparatus, method and computer readable medium for enabling precise material removal as part of a polishing process.

"In a first embodiment a method is disclosed for refining polishing accuracy across a curved surface of a housing. The method includes at least the following steps: (1) providing a number of clustered scribe marks across at least a portion of the curved surface of the housing; (2) polishing the surface of the housing including the clustered scribe marks; and (3) optically checking a material removal amount around the plurality of clustered scribe marks by observing which of the plurality of indicia have been polished away during the polishing step. The clustered scribe marks include at least a number of indicia, each indicia having a different depth dimension, the deepest of the indicia having a depth no greater than a maximum material removal depth. The relative position of each indicia in relation to other indicia in that clustered scribe mark makes it optically discernible from the other indicia.

"In another embodiment an apparatus for scribing optically readable scribe marks into a curved surface of a housing is disclosed. The apparatus includes at least the following: (1) a laser having a wavelength small enough to etch scribe marks narrower than a minimum abrasive particle diameter of a polishing pad subsequently used to polish the housing; (2) a computer numerical control (CNC) system for orienting the laser along a desired scribe mark path as it cuts scribe marks across the curved surface of the housing; and (3) a housing support fixture able to maintain the housing at a desired orientation during a laser scribing operation. In this embodiment the laser scribes optically readable scribe marks by scribing a plurality of clustered scribe marks into the curved surface of the housing. The clustered scribe marks include a number of indicia, each indicia having a different depth dimension, the deepest of the indicia having a depth no greater than a maximum material removal depth. The relative position of each indicia in relation to other indicia in that clustered scribe mark makes it optically discernible from the other indicia.

"In yet another embodiment a non-transient computer readable medium for storing computer code executable by a processor in a computer aided manufacturing system for accurately polishing across a curved surface of a housing is disclosed. The non-transient computer readable medium includes at least the following: (1) computer code for providing a clustered scribe marks across the surface of the housing; (2) computer code for polishing the surface of the housing including the plurality of clustered scribe marks; and (3) computer code for optically checking a material removal amount around the plurality of clustered scribe marks by observing which of the plurality of indicia have been polished away during the polishing step. The clustered scribe marks include at least a number of indicia, each indicia having a different depth dimension, the deepest of the indicia having a depth no greater than a maximum material removal depth. The relative position of each indicia in relation to other indicia in that clustered scribe mark makes it optically discernible from the other indicia;

BRIEF DESCRIPTION OF THE DRAWINGS

"The described embodiments and the advantages thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings. These drawings in no way limit any changes in form and detail that may be made to the described embodiments by one skilled in the art without departing from the spirit and scope of the described embodiments.

"FIG. 1A illustrates a cross-sectional view of a workpiece having a number of scribe marks having different depths and shapes;

"FIG. 1B illustrates a cross-sectional view of a workpiece having a number of scribe marks, one of which extends past a maximum material removal depth;

"FIG. 2A illustrates a polishing pad conducting a polishing operation over two scribe marks with different sized openings;

"FIG. 2B illustrates how a polishing pad can have abrasive particles dislodge during a polishing operation and drop into a scribe mark with a sufficiently large opening;

"FIG. 2C illustrates how dislodged abrasive particles lying in a scribe mark can increase a depth dimension of that scribe mark;

"FIG. 3 illustrates a mechanical scribing fixture in accordance with the described embodiment;

"FIG. 4 illustrates a perspective view of a scribing bench suited for use with the mechanical scribing fixture illustrated in FIG. 3 in accordance with the described embodiment;

"FIG. 5A illustrates a top view of a metal casing inscribed with a number of different types of scribe marks;

"FIG. 5B illustrates a perspective close up view of a set of clustered scribe marks having multiple indicia useful for determining how much material has been removed in a polishing operation;

"FIG. 5C illustrates a top view of the set of clustered scribe marks illustrated in FIG. 5B;

"FIG. 5D illustrates a perspective view of a set of clustered scribe marks arranged in a chevron-shaped configuration along a curved edge portion of a metal casing;

"FIG. 6A illustrates a top view of a thermoplastic casing of a portable computing device having parting lines due to an injection molding process;

"FIG. 6B illustrates a front view of the thermoplastic casing illustrated in FIG. 6A;

"FIG. 7 illustrates a cross-section of the thermoplastic casing illustrated in FIG. 6A

"FIG. 8A illustrates a perspective view of a metal casing with a defect that may be able to be reworked into a usable part by a polishing operation;

"FIG. 8B illustrates a close up view and cross-sectional view of the defect illustrated in FIG. 8A with a rework scribe mark surrounding the defect;

"FIG. 8C illustrates a close up view and cross-sectional view of a partially removed defect and a the rework scribe mark a portion of which has been completely polished away;

"FIG. 9 shows a flow chart detailing a process for using scribe marks to accurately determine material removal amounts; and

"FIG. 10 shows a flow chart detailing a process for reworking a damaged component with a polishing operation in accordance with the described embodiment; and

"FIG. 11 shows a flow chart detailing a process for destructively testing a workpiece for establishing a repeatable polishing process for a manufacturing process.

"FIG. 12 shows a block diagram for an electronic device useful in controlling a manufacturing operation in accordance with the describe embodiments."

For the URL and additional information on this patent, see: Lancaster-Larocque, Simon R.; Whipple, Lucas Allen. Material Removal Depth Measurement by Scribing. U.S. Patent Number 8798782, filed June 24, 2012, and published online on August 5, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8798782.PN.&OS=PN/8798782RS=PN/8798782

Keywords for this news article include: Apple Inc.

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Source: Computer Weekly News


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