INCREASING STRENGTH IN A METAL SHEET

Abstract

Various aspects of the subject technology relate to methods and systems for strengthening a metallic alloy during machining. The method includes providing a metallic alloy. The method can include flattening a portion of the metallic alloy. The method can include forming a workpiece from the flattened portion of the metallic alloy, wherein the workpiece comprises a top surface and a bottom surface. The method can also include stamping a first dimple profile on a top surface of the workpiece, wherein a dimple profile comprises a plurality of dimple indentations into a surface of the workpiece. The method can also include stamping a second dimple profile on the bottom surface of the workpiece. The disclosure further comprises an apparatus configured to form a workpiece comprising a plurality of dimple profiles oriented in the workpiece to strengthen the workpiece.

Claims

1. A method for strengthening metallic alloys, comprising: providing a metallic alloy; flattening a portion of the metallic alloy; forming a workpiece from the flattened portion of the metallic alloy, wherein the workpiece comprises a top surface and a bottom surface, the workpiece defined by a thickness dimension between the top surface and bottom surface; and stamping a first dimple profile on a top surface of the workpiece, wherein a dimple profile comprises a plurality of dimple indentations into a surface of the workpiece.

2. The method of claim 1, further comprising stamping a second dimple profile to the bottom surface.

3. The method of claim 2, further comprising aligning the second dimple profile at an offset distance from a first tooling associated with the first dimple profile.

4. The method of claim 2, wherein the first dimple profile and the second dimple profile comprise a plurality of dimple indentation wherein the dimple indentation includes a depth dimension and the depth dimension associated with the first dimple profile is greater than the depth dimension associated with the second dimple profile.

5. The method of claim 1, further comprising flattening the workpiece to increase mechanical strength.

6. The method of claim 1, wherein forming the metallic alloy into a workpiece comprises trimming a portion of the workpiece from a peripheral region of the workpiece.

7. The method of claim 1, wherein a depth of the first dimple profile maintains a surface integrity of the bottom surface.

8. The method of claim 1, wherein a depth of a second dimple profile maintains a surface integrity of the top surface.

9. The method of claim 1, wherein the metallic alloy comprises an aluminum alloy including approximately 95.7-97.7 mass % Al, approximately 0.15-0.35 mass % Cr, approximately 0.1 mass % Cu and approximately 0.4 mass % Fe.

10. The method of claim 1, wherein a first dimple dimension ranges from approximately 0.1 mm to 0.4 mm.

11. An apparatus configured to generate a metallic alloy part configured for integration in a head mounted display, wherein the apparatus comprises: a feeder configured to provide the metallic alloy; a forming device configured to: flatten a portion of the metallic alloy; form a workpiece from the flattened portion of the metallic alloy, wherein the workpiece comprises a top surface and a bottom surface, the workpiece defined by a thickness dimension between the top surface and bottom surface; and stamp a first dimple profile on a top surface of the workpiece, wherein a dimple profile comprises a plurality of dimple indentations into a surface of the workpiece.

12. The apparatus of claim 11, wherein the forming device is further configured to stamp a second dimple profile to the bottom surface.

13. The apparatus of claim 12, wherein the forming device is further configured to align the second dimple profile at an offset distance from a first tooling associated with the first dimple profile.

14. The apparatus of claim 12, wherein the first dimple profile and the second dimple profile comprise a plurality of dimple indentations, wherein a dimple indentation includes a depth dimension and the depth dimension associated with the first dimple profile is greater than the depth dimension associated with the second dimple profile.

15. The apparatus of claim 12, wherein the forming device is further configured to flatten the workpiece to increase mechanical strength.

16. The apparatus of claim 12, wherein the forming device is further configured to trim a portion of the workpiece from a peripheral region of the workpiece.

17. The apparatus of claim 12, wherein the thickness dimension of a workpiece is greater than a depth dimension associated with the first dimple profile and the thickness dimension of the workpiece is greater than the depth dimension associated with the second dimple profile.

18. A metallic alloy part configured for integration in a head mounted display, wherein the metallic alloy part comprises: a substrate comprising a top surface and a bottom surface, defined by a thickness dimension between the top surface and bottom surface, wherein a first region associated with the top surface comprises a first dimple profile and a second region associated with the bottom surface comprises a second dimple profile, the second dimple profile oriented at an offset distance from the first dimple profile, wherein the first dimple profile and the second dimple profile comprise a plurality of dimple indentation wherein the dimple indentation includes a depth dimension and the depth dimension associated with the first dimple profile is greater than the depth dimension associated with the second dimple profile.

19. The metallic alloy part of claim 18, wherein the thickness dimension of the substrate is greater than the depth dimension associated with the first dimple profile and the thickness dimension of the substrate is greater than the depth dimension associated with the second dimple profile.

20. The metallic alloy of claim 19 comprises an aluminum alloy including approximately 95.7-97.7 mass % Al, approximately 0.15-0.35 mass % Cr, approximately 0.1 mass % Cu and approximately 0.4 mass % Fe.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0007] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0008] FIG. 1A is an isometric view of stipple tooling.

[0009] FIG. 1B is a block diagram of previous configurations to provide piercing stipples to a metallic sheet.

[0010] FIG. 2A is an isometric view of dimple tooling.

[0011] FIG. 2B is an isometric view of dimpling tooling to generate a dimpling profile.

[0012] FIG. 3 is a workpiece with a dimple profile

[0013] FIGS. 4A-C depict graphical testing results of dimple profile parameters.

[0014] FIGS. 5A-C depict graphical testing results of dimple profile parameters as percentage improvements.

[0015] FIG. 6 depicts graphical testing results displaying the rate of change by increasing dimpling profile parameter values.

[0016] FIG. 7 depicts statistical results of the overlay between profile parameters.

[0017] FIG. 8 depicts a flowchart process for strengthening metallic alloys.

[0018] In one or more implementations, not all of the depicted components in each figure may be required, and one or more implementations may include additional components not shown in a figure. Variations in the arrangement and type of the components may be made without departing from the scope of the subject disclosure. Additional components, different components, or fewer components may be utilized within the scope of the subject disclosure.

DETAILED DESCRIPTION

[0019] In the following detailed description, numerous specific details are set forth to provide a full understanding of the present disclosure. It will be apparent, however, to one ordinarily skilled in the art, that the embodiments of the present disclosure may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the disclosure.

[0020] In one aspect, unless otherwise stated, all measurements, values, ratings, positions, magnitudes, sizes, and other specifications that are set forth in this specification, including in the clauses/claims that follow, are approximate, not exact. In one aspect, they are intended to have a reasonable range, such that values modified with approximately are intended to include boundary values (e.g., +/10%) that is consistent with the functions to which they relate and with what is customary in the art to which they pertain. It is understood that some or all steps, operations, or processes may be performed automatically, without the intervention of a user. Method clauses may be provided to present elements of the various steps, operations, or processes in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

[0021] This disclosure addresses the mechanical strength of relatively ductile material to form the metallic components of head mounted devices (HMDs). The complex geometries impose limitations on metallic parts of an HMD. The geometric specification of certain metallic interior frame components of an HMD can require the use of softer metals, such as softer aluminum, to prevent cracking during stamping of the respective frame component. The choice of aluminum can affect the system's performance in the event of the HMD being dropped. In the context of mixed reality devices, the failure of the metallic component impacts other features. For example, failure of the metallic component can be based on the percentage in which a camera that is affixed to the metal component may change its direction (e.g., field of view). In a further aspect, failure can occur when the camera tilt angle is increases beyond a tilt threshold.

[0022] Embodiments of the disclosed technology may include or be implemented in conjunction with a mixed reality system. The term mixed reality or MR as used herein refers to a form of reality that has been adjusted in some manner before presentation to a user, which may include, e.g., virtual reality (VR), augmented reality (AR), extended reality (XR), hybrid reality, or some combination and/or derivatives thereof. Mixed reality content may include completely generated content or generated content combined with captured content (e.g., real-world photographs). The mixed reality content may include video, audio, haptic feedback, or some combination thereof, any of which may be presented in a single channel or in multiple channels (such as stereo video that produces a three-dimensional (3D) effect to the viewer). Additionally, in some embodiments, mixed reality may be associated with applications, products, accessories, services, or some combination thereof, that are, e.g., used to interact with content in an immersive application. The mixed reality system that provides the mixed reality content may be implemented on various platforms, including a head-mounted display (HMD) connected to a server, a host computer system, a standalone HMD, a mobile device or computing system, a cave environment or other projection system, or any other hardware platform capable of providing mixed reality content to one or more viewers. Mixed reality may be equivalently referred to herein as artificial reality.

[0023] Virtual reality or VR, as used herein, refers to an immersive experience where a user's visual input is controlled by a computing system. Augmented reality or AR as used herein refers to systems where a user views images of the real world after they have passed through a computing system. For example, a tablet with a camera on the back can capture images of the real world and then display the images on the screen on the opposite side of the tablet from the camera. The tablet can process and adjust or augment the images as they pass through the system, such as by adding virtual objects. AR also refers to systems where light entering a user's eye is partially generated by a computing system and partially composes light reflected off objects in the real world. For example, an AR headset could be shaped as a pair of glasses with a pass-through display, which allows light from the real world to pass through a waveguide that simultaneously emits light from a projector in the AR headset, allowing the AR headset to present virtual objects intermixed with the real objects the user can see. The AR headset may be a block-light headset with video pass-through. Mixed reality or MR, as used herein, refers to any of VR, AR, XR, or any combination or hybrid thereof.

[0024] In certain aspects, safety and privacy protocols are implemented so that the user understands user eye data is obtained by the system. The user is informed in advance of the purpose for obtaining the eye data, and may at any time opt out of the eye data being obtained. In certain aspects, the user may delete any past eye data stored by the system. Users who proceed with using the system may be notified that respective eye-movement data is being obtained for the purpose of determining pupil location as a representation of focusing direction of the user's eyes to more efficiently generate a foveated view in that respective direction.

[0025] Traditionally, after major forming is completed, stippling is used to improve part flatness. A stippling engagement surface 112 of a stippling forming device 100 can engage a metal sheet. Stippling functions flatten the metallic surface and also puncture through the thickness of the metal sheet via an arrangement of stipple protrusions 104 depicted in FIG. 1A, wherein the stipple protrusions 104 can be separated by a stipple pitch 106. In an alternative aspect the stipple protrusions 104 can comprise a flat surface at the apex of the stipple protrusion, wherein the flat surface has a dimension ranging approximately 0.050.05 to 0.2 mm0.2 mm. As depicted in FIG. 1B, the shape of the stipple protrusion 104 and the protrusions arrangement in a stipple pitch 106 can be configured to puncture through the thickness of the metal sheet 102, resulting in a plurality of apertures 108. In particular, puncturing of the metal sheet can occur by the sharp angular sides of the stipple protrusions. Stippling functions to cut the metal sheet 102 enable internal stresses to be relieved; also stippling does not introduce work hardening.

[0026] In contrast, the current disclosure implements a method of dimpling to change the mechanical properties of the metallic structures of a head mounted device (HMD). Dimpling is used to increase the tensile strength, the bending strength and the yield strength of the metallic piece in a particular region of the metallic part. In further contrast from stippling, dimpling does not puncture through the material like stippling. Instead, dimpling maintains the structural surface integrity of the opposing surface. A dimpling engagement surface 200 of a sampling forming device 200 can engage a metal sheet 102. For example, when the tooling for dimpling is applied to the top surface, the tooling does not puncture surface plane 215 on the bottom surface. Similarly, when the tooling for dimpling is applied to the bottom surface, the tooling does not puncture surface plane 217 of the top surface. In a further aspect, the tooling for dimpling introduces a dimple indentation defined by a depth dimension. The depth dimension is less than the thickness dimension of the part, maintaining the structural surface integrity and not piercing the surface planes 215, 217 of an opposing surface. Further, dimpling provides the ability to optimize machining parameters to enhance the mechanical properties of the materials. Optimizing the parameters of the density profile (e.g., shape of the indentation of the metallic surface, the depth of the indentation, and the density of indentations) yields a component part that structure to mitigate regions of the component previously susceptible during a fall. The dimpling profiles can be applied to both flat regions and regions that comprises curvature.

[0027] The system and method provides a manner for the metallic structure to have an increase in tensile strength and other strength while maintaining ductility. The system and method optimizes the application of dimples to the surface area of a metallic part. The application of dimples can be characterized as a dimple profile 200 as depicted in FIG. 2A, wherein the dimple profile comprises: 1) the indentation shape 202 of the metallic surface, 2) the height of the tooling 204 above the tooling surface 206 and 3) the spatial arrangement of the tooling. The spatial arrangement of the tooling defines the spatial arrangement of the dimples 208 can also be represented in considering a single dimension. Further, the spatial arrangement of the tooling can define the dimple pitch 210. The dimple pitch 210 comprises the spacing between two adjacent dimples 208. In one aspect, the dimple pitch 210 can comprise between approximately 2.0-3.0 mm, wherein the dimples are aligned in the same axial direction as depicted in FIGS. 2A and 2B. In a further aspect, the dimple profile can comprise a dimple density, wherein the dimple pitch is defined in two dimensions. The two dimensions define the area of the dimple tooling that can be stamped into a workpiece. For example, the dimple density can comprise ten (10) dimples in one (1) square centimeter (square inch). For example, in a Cartesian coordinate system, the spacing could comprise the distance in the x-direction as well as the distance in the y-direction.

[0028] The dimple shape 208 is defined by a protrusion shape 202 on dimpling forming device 200. In one aspect, the protrusion shape 202 can comprise a diameter of approximately 0.1 to 0.3 mm near the apex of protrusion and expand to a diameter of approximately 0.5 to 1.0 mm near the base of the protrusion. Other types of metal tooling can be used to create the dimples 208 in the metallic sheet 102. The indentation of the dimple 208 can be shaped as an ellipsoid, or hemisphere, with other shapes considered. The dimple 208 can be defined by a depth measurement 214; the depth measurement comprises a distance from the surface of the sheet to a maximum depth of the indentation.

[0029] As shown in FIG. 3, a workpiece 300 can comprise the dimple pattern which can be applied to the metallic sheet, in a predefined pattern. The dimple density can also be adjusted in different regions of the part. In the metallic component shown, the dimple density can comprise a predefined number of dimples in a certain square inch area (e.g., 20 dimples per square centimeters). Other regions of the workpiece can comprise either an increased or decreased density. For example, one region 302 can comprise an increased density such as 30 dimples per square centimeter, and the second region 304 can comprise an increased density such as 10 dimples per square centimeter. As depicted in the cross-sectional view of FIG. 2B, the dimple profile can be further tuned to stamp the dimple on both sides of the surface. The first dimple profile 216 applied to the top surface can be stamped into the worksheet such that the second dimple profile 218 can be oriented at an offset distance (OD) such that the tooling that forms the dimples does not have the same vertical alignment. Aligning the first dimple profile 216 and the second dimple profile 218 at the offset distance can also function to flatten the workpiece 300 providing additional mechanical strength. In yet a further aspect, the dimple pitch 210 and/or dimple density can be adjusted based on the size or shape of the dimple 208. For example, a large dimple 208 can necessitate the dimple pitch/density to be increased.

[0030] When optimizing the parameters for a dimple profile, dimple depth, second dimple depth, and spacing influence the strength of the parts. As shown in Table 1, a sample of Aluminum (e.g., Al CHN H36) can be tested wherein the dimple profile parameters are varied. The first dimple profile 216 and the reverse (second) dimple profile 218 represent the dimple depth 214 on two different sides of the metal sheet. Further as shown in Table 1, Aluminum sample 4 comprises a 2 mm pitch (distance between dimples), first dimple depth of 0.4 mm and second dimple depth of 0.1 mm yielded the highest yield strength (YS) 210 MPa, tensile strength (TS) 217 MPa, and bending force 45.0 N. As shown in Table 1, maximum values in each of the parameters do not yield the greatest strength. For example, Sample 4 and Sample 8 only differ by a dimple pitch of 1 mm; Sample 8 has a greater dimple pitch resulting in a lower yield strength, tensile strength and bending force. Further as exhibited by Sample 1 and Sample 3, dimple depth is directly proportional such that a deeper dimple depth can increase the mechanical strength. Similarly, when applying a second dimple pattern (reverse dimple) on the opposing side of the aluminum sheet, the second dimple depth increases the mechanical strength of the sheet, see Sample 1 vs. Sample 2 in Table 1.

TABLE-US-00001 TABLE 1 Mechanical Strength results in response to altering dimple profile parameters. Al CHN Dimple pitch 1st dimple 2nd dimple YS TS Max bending H36 mm depth mm mm (MPa) (MPa) Force N 1 2 0.1 0 108.7 143.4 40.5 2 2 0.1 0.1 193.7 219.4 44 3 2 0.4 0 185.9 202.1 40.7 4 2 0.4 0.1 210 217.8 45 5 3 0.1 0 173.2 211.3 40.4 6 3 0.1 0.1 186.2 223.3 43.5 7 3 0.4 0 182 208.6 39.9 8 3 0.4 0.1 197.1 210.7 42.9 POR 2 0.1 0 98 132.8 39.4

[0031] In validating, the claimed disclosure experiments to evaluate three different types of mechanical strength including: a compression test, a tensile test, and a bending test wherein the mechanical strengths in three different areas are evaluated including the yield strength, the tensile strength and the maximum bending force as shown in FIGS. 4A, 4B, and 4C. In viewing the graphs in FIGS. 4A, 4B, and 4C, the first column is a baseline workpiece without any applied forces comprising a plan-of-reference (POR) sample. The second column represents a workpiece that has undergone stamping of a dimple profile to the first side of a sheet and a second dimple profile to the bottom surface of that sheet. The third column represents machining the workpiece with both the first dimple profile and second dimple profile along with flattening the workpiece. As shown in FIG. 4A, yield strength (YS) was increased by 100 MPa to approximately 200 megapascals when the first and second dimpling profile was applied along with a slight increase when the part was also flattened. Similarly, the tensile strength, as depicted in FIG. 4B, exhibited the same pattern, wherein having the first and second dimple pattern applied along with the workpiece flattening increased the strength. Further, the evaluation of the maximum bending force exhibited a similar pattern in FIG. 4C, wherein having the first and second dimpling pattern be applied along with the flattening provided the most mechanical strength. Overall, machining the parts to include the dimpling patterns as well as the flattening increased the yield strength, the tensile strength, as well as the maximum bending force. As shown in FIGS. 5A-5C, applying the first and second dimpling profile along with flattening the workpiece increased the yield strength approximately 100%, the tensile strength approximately 60%, and the bending force approximately 15%.

[0032] The softer metallic alloys permit a workpiece to be formed with more complex geometries. The aggregation of the forming steps on a workpiece to increase the mechanical strength comprises the applying of the first dimple profile, the second dimple profile and flattening to increase the mechanical strength. In a further aspect, the maximum depth of the first dimple profile can be greater than the second dimple profile. As shown in FIG. 6, applying a second dimple profile increases the yield strength as the depth increases from 0.0 to 0.1 mm. In particular, the steep slope of the graph for the second dimple depth in FIG. 6 shows the rate of increase for the depth of the second dimple profile is greater than the rate of increase for the first dimple depth, which indicates that forming a workpiece with a second simple profile has an impact in increasing the yield strength. As depicted in FIG. 7, there is statistical significance shown between the combination of the first dimple profile depth and second dimple profile depth. In evaluating the relevance of these two factors, a statistical analysis was applied to workpieces with different variants of dimple profiles. A p-value less than 0.05 is typically considered to be statistically significant, in which case the null hypothesis should be rejected. A p-value greater than 0.05 means that deviation from the null hypothesis is not statistically significant, and the null hypothesis is not rejected. In the current disclosure, singular variables such as the first dimple profile depth and second dimple profile depth, in addition to combinations of variables were evaluated. These combinations were shown to have an impact on the yield strength (YS) resulting in P-values from 0.00095 to 0.05608. As a result, applying the first dimple profile and the second dimple profiles singularly and the dimple profiles in combination with flattening the workpiece were shown to be statistically significant in increasing the yield strength of a part.

[0033] As depicted in FIG. 8, a metallic workpiece for usage in a head mounted device can be formed from a workflow process 800. The process can be implemented to increase the mechanical strength of metallic alloys that are rated as softer alloys; the softer alloys provide greater formability and malleability when stamping parts with complex geometries. In step 802, the process can comprise uncoiling a metallic alloy. For example, the metallic alloy can comprise an aluminum alloy (e.g., Al CHN H36) including approximately 95.7-97.7 mass % of Aluminum (Al), approximately 0.15-0.35 mass % of Chromium (Cr), approximately 0.1 mass % of Copper (Cu), and approximately 0.4 mass % of Iron (Fc). In other embodiments, the metallic alloy can comprise other combinations of metals such as but not limited to: steel alloys, copper alloys, and titanium alloys. In one aspect, prior to undergoing any mechanical processing, the aluminum sheet can comprise a thickness ranging from approximately 0.3 mm to 2 mm. In alternative embodiments, additional ranges of metallic sheet thickness can be used. In a further aspect, uncoiling the metallic alloy can be provided by a feeder device.

[0034] At step 804, the process can comprise flattening the metallic sheet. The flattening can be performed by a hydraulic or mechanical forming device. In step 806, the workpiece can be formed from a portion of flattened metallic alloy, wherein forming can include trimming, stamping or embossing. In a further aspect, the metallic sheet can be trimmed to reduce the surface area of the workpiece. In one aspect, trimming the workpiece can comprise removing material from a peripheral region of the workpiece. In a further aspect, trimming can include cutting a metallic sheet into blanks. The blanks can comprise workpieces shaped approximately like the final workpiece. In certain aspects, the metallic sheet can be heated to reduce the force necessary to flatten the metallic sheet. In another embodiment, the press machine can be cold pressed wherein heat is not applied to the metallic machine before pressing. In another aspect, the trimming can be completed by laser cutting, shearing or with a blanking die. When the metallic alloy in the disclosure is aluminum or another softer metal, a lubricant can be used. A supplemental lubrication step may be implemented to reduce friction and prevent tearing or galling of the aluminum. A coating or lubrication can be applied to the dimple tooling to ensure the desired depth of the dimple and structural integrity of the dimple shape is maintained when the dimple tooling is removed from the workpiece. In particular, the dimple tooling may be harder than the metallic alloy of the workpiece; when the dimple tooling is removed, the dimple tooling may cause damage to the dimples in the absence of a friction-reducing coating or lubricant. In a further aspect, step 806 can include piercing the workpiece. Piercing the workpiece would add apertures in the workpiece to facilitate engagement and/or alignment with other components of the HMD. The pierced apertures can be used for grabbing and rotating the part for other operations. The piercing of the workpiece can be completed by specialized tooling oriented in predefined locations on a stamping machine. These holes/apertures can also be used as features for fasteners for coupling adjacent parts.

[0035] In a further aspect, forming the workpiece in step 806 can be completed by stamping or embossing the part to generate features such as divots, channels, ridges, curvatures, etc. In a further aspect, depending on the complexity of the part, a progressive die sub-process may be used or a transfer die sub-process may be used. In one embodiment, the progressive die sub-process can include implementing multiple stations in a single tool. A metallic strip can be fed continuously through the die, wherein at each station a specific operation such as piercing or bending can be done. In another embodiment, a transfer die sub-process can be used such that a series of separate dies including a robotic or mechanical transfer system moves a workpiece from one station to the next. At each separate station a different forming operation can be performed.

[0036] In step 808, the process 800 can include dimpling the workpiece. Dimpling the workpiece can comprise stamping a dimple profile into the workpiece. As discussed earlier, dimpling the workpiece does not puncture through the thickness of the workpiece like stippling, which uses a sharper tooling during stamping. In a further aspect, the stippling profile can be stamped on an opposing surface than the initial dimpled surface. For example, the top surface of the workpiece can be stamped with a dimple profile; and a secondary dimpling profile can be stamped on the bottom surface of the workpiece. The secondary dimpling profile can be used to mitigate the depth of the dimple stamped into the top surface because the dimpling in the second profile can reduce the thickness of the part. The dimpling profile can comprise three features that can be optimized: dimple pitch, size of the dimple protrusion, and dimple depth. In one aspect, the dimple pitch can be approximately 3 mm. The radius of the dimple can range from approximately 0.2 mm to 0.6 mm, with a preference for 0.4 mm, and the depth of dimple can range from approximately 0.1 mm to 0.4 mm. In a further aspect, to achieve the ranges of depth for the dimple, the dimple tooling can extend approximately 0.9 mm from the tooling base. Similarly, the dimple stamp applied to the bottom surface can comprise similar dimensions. As the dimpling has been applied in process 800, the workpiece 300 can be further modified. The process 800 can further comprise reforming the workpiece. In one aspect, reforming the workpiece can comprise flattening the workpiece. The flattening that occurs during the reforming step can further add strength. In yet another aspect, flattening the workpiece can occur when the secondary dimpling profile is applied to the workpiece. The process 800 can also include cutting out the workpiece.

[0037] As used herein, the phrase at least one of preceding a series of items, with the terms and or or to separate any of the items, modifies the list as a whole, rather than each member of the list (i.e., each item). The phrase at least one of does not require selection of at least one item; rather, the phrase allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. By way of example, the phrases at least one of A, B, and C or at least one of A, B, or C each refer to only A, only B, or only C; any combination of A, B, and C; and/or at least one of each of A, B, and C.

[0038] To the extent that the terms include, have, or the like is used in the description or the claims, such term is intended to be inclusive in a manner similar to the term comprise as comprise is interpreted when employed as a transitional word in a claim. The word exemplary is used herein to mean serving as an example, instance, or illustration. Any embodiment described herein as exemplary is not necessarily to be construed as preferred or advantageous over other embodiments.

[0039] A reference to an element in the singular is not intended to mean one and only one unless specifically stated, but rather one or more. All structural and functional equivalents to the elements of the various configurations described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by the subject technology. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the above description.

[0040] While this specification contains many specifics, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of particular implementations of the subject matter. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0041] The subject matter of this specification has been described in terms of particular aspects, but other aspects can be implemented and are within the scope of the following claims. For example, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed to achieve desirable results. The actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the aspects described above should not be understood as requiring such separation in all aspects, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Other variations are within the scope of the following claims.