PATENT DOCUMENT

Publication Number: US-9713865-B2
Application Number: US-201514728882-A
Country: US
Kind Code: B2

Title: Electromechanical surface texturing

Abstract:
Magnetic apparatuses and systems for shaping parts are described. One or more magnets can be used to direct a magnetically responsive fluid having magnetically responsive particles around surfaces of a part. The magnetically responsive fluid can include abrasive particles that follow movement of the magnetically responsive fluid across surfaces of the part and remove material from the part until the part takes on a desired shape. The magnetic apparatuses can be configured to provide a rough cut, similar to machining process, and/or a fine cut, similar to polishing or buffing process, to the part.

Claims:
What is claimed is: 
     
       1. A method of shaping a workpiece, the method comprising:
 positioning a fixture such that walls of the fixture cooperate with a portion of a workpiece surface to define a channel for holding a magnetically responsive fluid having magnetically attractable particles and abrasive particles, wherein only the portion of the workpiece surface is immersed within the magnetically responsive fluid; and 
 causing a magnetic field of a magnet arranged with respect to the workpiece to move the magnetically responsive fluid in a path across the portion of the workpiece surface, wherein movement of the magnetically responsive fluid provides a cutting action sufficient for the abrasive particles to remove material from the portion of the workpiece surface resulting in the workpiece taking on a predefined shape. 
 
     
     
       2. The method of  claim 1 , further comprising filling the channel with the magnetically responsive fluid via an inlet of the fixture. 
     
     
       3. The method of  claim 1 , further comprising emptying the channel of the magnetically responsive fluid via an outlet of the fixture. 
     
     
       4. The method of  claim 1 , wherein the magnetically attractable particles and the abrasive particles both provide the cutting action that removes the material from the workpiece. 
     
     
       5. The method of  claim 1 , wherein the magnetically responsive fluid includes carrier fluid that includes organic fluid, aqueous fluid, or a combination thereof. 
     
     
       6. The method of  claim 1 , wherein the workpiece is fixed with respect to the fixture during a shaping operation. 
     
     
       7. The method of  claim 1 , wherein more than one magnet is used to move the magnetically responsive fluid. 
     
     
       8. The method of  claim 1 , wherein the abrasive particles are characterized as having a first diameter, the method further comprising:
 moving a second magnetically responsive fluid comprising a second type of abrasive particles across the portion of the workpiece surface, the second type of abrasive particles characterized as having a second diameter smaller than the first diameter. 
 
     
     
       9. A magnetic shaping apparatus, comprising:
 a fixture including walls that cooperate with a portion of a workpiece surface to define a channel configured to hold a magnetically responsive fluid having magnetically attractable particles and abrasive particles suspended in a carrier fluid, wherein the fixture is configured to immerse only the portion of the workpiece surface within the magnetically responsive fluid; and 
 a magnet arranged with respect to the workpiece such that the magnet directs movement of the magnetically responsive fluid in a path across the immersed portion the workpiece surface, wherein movement of the magnetically responsive fluid provides a cutting action sufficient for the abrasive particles to remove material from the immersed portion of the workpiece surface resulting in the immersed portion of the workpiece surface taking on a predefined shape. 
 
     
     
       10. The magnetic shaping apparatus of  claim 9 , wherein the magnet includes a permanent magnet, an electromagnet and/or a superconducting magnet. 
     
     
       11. The magnetic shaping apparatus of  claim 9 , wherein the magnet is an electromagnet that is supplied electric current by a power supply. 
     
     
       12. The magnetic shaping apparatus of  claim 11 , wherein a magnetic flux of the electromagnet is varied during a shaping operation. 
     
     
       13. The magnetic shaping apparatus of  claim 9 , wherein the magnetic shaping apparatus includes two or more magnets, wherein polarities of the two or more magnets are switched during a shaping operation. 
     
     
       14. The magnetic shaping apparatus of  claim 9 , wherein the fixture is fixed with respect the workpiece during a shaping operation the magnetically responsive fluid. 
     
     
       15. The magnetic shaping apparatus of  claim 9 , wherein the fixture includes an inlet and an outlet for the magnetically responsive fluid. 
     
     
       16. A magnetic shaping apparatus for shaping a workpiece, comprising:
 a fixture including walls that cooperate with a portion of a workpiece surface to define a channel for holding a magnetically responsive fluid having magnetically attractable particles and abrasive particles, wherein the fixture is configured to immerse only the portion of the workpiece surface within the magnetically responsive fluid; 
 an electromagnet arranged with respect to the workpiece such that a magnetic field of the electromagnet directs movement of the magnetically responsive fluid in a path across the portion of the workpiece surface, wherein movement of the magnetically responsive fluid provides a cutting action sufficient for the abrasive particles to remove material from the workpiece; and 
 a power supply configured to supply varying amounts of electric current to the electromagnet, wherein an amount of electric current supplied to the electromagnet is associated with a strength of the magnetic field. 
 
     
     
       17. The magnetic shaping apparatus of  claim 16 , wherein the magnetically attractable particles are comprised of a ferromagnetic material. 
     
     
       18. The magnetic shaping apparatus of  claim 16 , wherein the abrasive particles are comprised of a non-metallic material. 
     
     
       19. The magnetic shaping apparatus of  claim 18 , wherein the abrasive particles are comprised of one or more of zirconia, titania, and alumina. 
     
     
       20. The magnetic shaping apparatus of  claim 16 , wherein the magnetic shaping apparatus additionally includes a permanent magnet and/or a superconducting magnet.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of International Application PCT/US15/33669, with an international filing date of Jun. 2, 2015, entitled “ELECTROMECHANICAL SURFACE TEXTURING”, which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The described embodiments relate generally to methods of shaping a workpiece using a magnetically responsive fluid, such as a ferrofluid, that includes abrasive particles. Magnets can be positioned with respect to a surface of the workpiece in a way that directs the magnetically responsive fluid with abrasive particles in a path across the surface, creating a cutting action that shapes the workpiece. 
     BACKGROUND 
     Many consumer electronic devices have outer enclosures and coverings that give the enclosures and coverings an aesthetically pleasing look and feel. Some enclosures and coverings have curved surfaces that add to the aesthetic appeal of the device. Often, the enclosures and coverings undergo finishing operations in order to impart distinctive characteristics to the enclosures and coverings. For example, surfaces can be texturized to give the enclosures and coverings a matte look and feel. Other times, the surfaces are polished to a mirror shine. The finishing process can also remove surface defects that would otherwise be visible and detract from the aesthetic appeal of the enclosure or covering. 
     One challenge associated with finishing curved surfaces is that it can be difficult to follow a contour of a curved surface using conventional finishing techniques. For example, it can be difficult to control fine movement of a flat sanding belt or round abrasive wheel over curved edges and corners of a part. The resultant part can have an uneven finish at the curved edges and corners. It can be especially difficult to control the finishing process if the curved surface has a complex three-dimensional shape, such as a spline shape. 
     SUMMARY 
     This paper describes various embodiments that relate to shaping parts using electromechanical techniques. In particular embodiments, the parts are shaped using magnets to move a magnetically responsive fluid having abrasive particles over surfaces of the parts. 
     According to some embodiments, a method of shaping a workpiece is descried. The method includes moving a magnetically responsive fluid in a path across a surface of the workpiece. The magnetically responsive fluid has magnetically attractable particles and abrasive particles suspended in a carrier fluid. The path is defined by one or more magnets positioned with respect to the surface of the workpiece such that movement of the magnetically responsive fluid provides a cutting action sufficient to remove material from the workpiece resulting in the workpiece taking on a predefined shape. 
     According to another embodiment, a magnetic shaping apparatus is described. The magnetic shaping system includes a container configured to hold a magnetically responsive fluid and a workpiece immersed in the magnetically responsive fluid. The magnetically responsive fluid has magnetically attractable particles and abrasive particles suspended in a carrier fluid. The magnetic shaping system also includes a magnet arranged with respect to the workpiece such that the magnet directs movement of the magnetically responsive fluid in a path across a surface of the workpiece. Movement of the magnetically responsive fluid provides a cutting action sufficient for the abrasive particles to remove material from the workpiece resulting in the workpiece taking on a predefined shape. 
     According to a further embodiment, a magnetic shaping apparatus is described. The magnetic shaping system includes a container configured to hold a magnetically responsive fluid and a workpiece immersed in the ferrofluid, the ferrofluid having abrasive particles. The magnetic shaping system also includes an electromagnet arranged with respect to the workpiece such that a magnetic field of the electromagnet directs movement of the ferrofluid in a path across a surface of the workpiece. Movement of the ferrofluid provides a cutting action sufficient for the abrasive particles to remove material from the workpiece. The magnetic shaping apparatus further includes a power supply configured to supply varying amounts of electric current to the electromagnet. An amount of electric current supplied to the electromagnet is associated with a strength of the magnetic field. 
     These and other embodiments will be described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements. 
         FIG. 1  shows a magnetic shaping apparatus used to shape a surface of a workpiece, in accordance with some embodiments. 
         FIG. 2  shows another magnetic shaping apparatus used to shape a surface of a workpiece, in accordance with some embodiments. 
         FIGS. 3A-3C  show a workpiece undergoing a chamfering operation using a magnetic shaping apparatus in accordance with some embodiments. 
         FIGS. 4A-4C  show a workpiece undergoing a chamfering operation using a magnetic shaping apparatus in accordance with other embodiments. 
         FIG. 5  shows a magnetic finishing apparatus configured to provide a texture surface on a workpiece. 
         FIG. 6  shows a flowchart indicating a magnetic shaping or finishing process in accordance with some embodiments. 
         FIG. 7  shows a block diagram of an electronic system suitable for controlling the magnetic shaping and finishing processes according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     The following disclosure relates to use of magnetic systems to mechanically shape and/or finish a surface of a workpiece. In some embodiments, the magnetic systems include electromagnets, and therefore can be referred to as electromechanical systems. In particular embodiments, the shaping and/or surface finishing methods include the use of magnetically responsive fluids, such as ferrofluids. Magnets can be used to guide the magnetically responsive fluids in paths across surfaces of the workpiece. The magnetically responsive fluids can include abrasive particles that abrade or otherwise cut into surfaces of the workpiece such that some material is removed from the workpiece, resulting in the workpiece taking on a final desired shape. 
     The magnetically responsive fluid can have magnetically responsive particles that respond to a magnetic field produced by a nearby magnet or system of magnets. The magnet(s) can be arranged to define a path in which the magnetically responsive fluid moves with respect to the workpiece. In some cases, the magnetically responsive particles are harder than the workpiece. Thus, the relative movement of the magnetically responsive particles can abrade the surface of the workpiece. In some cases, separate abrasive particles are added to the magnetically responsive fluid to provide the abrasive action. The methods can be used to provide precise removal of material in predefined areas of the workpiece and achieve a final workpiece shape that can be difficult to achieve using conventional machining, abrading, polishing and buffing techniques. 
     The systems and methods described herein can be use to form complex geometries, such as spline-shaped surfaces, within a workpiece that are difficult to achieve using traditional machining and polishing techniques. This is, in part, because the magnetically responsive fluid can move in a fluid and well-controlled manner over surfaces of the workpiece. In addition, it can be possible to finish hard to reach places of the workpiece, such as small grooves or undercut areas of the workpiece. 
     The methods and systems can be used to shape a workpiece on a macro-scale, similar to conventional machining processes, and/or on a micro-scale, similar to conventional polishing and buffing processes. These can be referred to as rough cutting and fine cutting techniques, respectively. In some embodiments, the same system can be used to perform rough cutting and fine cutting of the workpiece. For example, a first magnetically responsive fluid having aggressively abrasive particles can be used to perform the rough cutting. Then, the system can be replaced with a second magnetically responsive fluid having less abrasive particles to perform the fine cutting. In some embodiments, chamfers are formed and polished within a workpiece using the methods described herein. 
     Since the magnetically responsive fluid is in liquid form instead of powder form, the methods described herein can be safer that traditional polishing and abrasive texturing techniques that use dry powdered abrasive materials. In particular, use of dry powdered materials can be an explosive hazard, especially when heat from friction is generated. In contrast, the magnetically responsive fluid can remain in liquid form through the shaping process, reducing the risk of explosion related to powdered materials. 
     In some embodiments, the magnetic shaping methods are combined with other types of shaping processes. For example, the methods can be combined with a forging process, whereby the workpiece is intentionally heated to a predetermined temperature sufficient to place the workpiece in a more malleable and forgeable state. The magnetically induced shaping process can then exert a force on the workpiece that forges the workpiece in addition to finishing the workpiece surface. 
     In some embodiments, the workpiece is mapped in three-dimensions such that the shaping process can be adjusted in real time. One advantage of using the magnetic-based shaping methods compared to conventional shaping techniques such as machining and traditional polishing operations is that it may be possible to accomplish a pre-determined final shape of the workpiece without the use of traditional computerized numerical code (CNC). For example, it may be possible to create the final shape based on a three-dimensional representation, such as a computer-aided design (CAD) drawing. 
     Methods described herein are well suited for providing cosmetically appealing and/or functional parts of consumer products. For example, the methods described herein can be used to form enclosures or portions of enclosures for electronic devices, such as computers, portable electronic devices, wearable electronic devices and electronic device accessories, such as those manufactured by Apple Inc., based in Cupertino, Calif. 
     These and other embodiments are discussed below with reference to  FIGS. 1-7 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these Figures is for explanatory purposes only and should not be construed as limiting. 
       FIG. 1  shows magnetic shaping apparatus  100  used to shape a surface of workpiece  102  in accordance with some embodiments. Apparatus  100  includes container  106  that is configured to contain magnetically responsive fluid  108  and magnet  104 . It should be noted that although  FIG. 1  shows magnet  104  outside of container and magnetically responsive fluid  108 , in other embodiments magnet  104  is positioned within of magnetically responsive fluid  108  and container  106 . Workpiece  102  can be supported by first fixture  103  and magnet  104  can be supported by second fixture  105 . 
     Magnetically responsive fluid  108  can be any suitable fluid that responds to the presence of a magnetic field. Magnetically responsive fluid  108  can be in colloidal form with magnetically responsive particles  110  suspended within the carrier fluid  111 , or a non-colloidal form, such as when magnetically responsive particles  110  are very small and/or soluble within carrier fluid  111 . In some embodiments, magnetically responsive fluid  108  is a ferrofluid that becomes magnetized in the presence of a magnetic field. In general, a ferrofluid is a colloidal liquid that includes magnetically responsive particles  110 , which are ferromagnetic in nature, suspended within carrier fluid  111 . Magnetically responsive particles  110  are made of a material that responds to the presence of a magnetic field, such as one or more of iron, nickel, cobalt, rare earth metals (e.g., neodymium) and certain minerals. In some embodiments, magnetically responsive particles  110  are magnetized such that they are permanent magnets. In other embodiments, magnetically responsive particles  110  are not permanent magnets but are responsive to magnets. Container  106  can be made of any material suitable for containing magnetically responsive fluid  108 . In some embodiments, container  106  is made of plastic, glass, ceramic, or metal that does not substantially magnetically interact with magnet  104  and/or magnetically responsive fluid  108 . 
     Workpiece  102  can be made of any suitable metal material and or non-metal material, such as plastic, glass and/or ceramic. In some embodiments, workpiece  102  is made of a combination of metal and non-metal materials. In one embodiment, workpiece  102  is made of aluminum or aluminum alloy. In another embodiment, workpiece  102  is made of a molded plastic material. Magnetically responsive fluid  108  can include abrasive particles  114 , which are made of one or more materials that are abrasive in nature such that abrasive particles  114  can abrade and remove some material from workpiece  102 . Thus, the material of abrasive particles  114  can depend, in part, on the hardness of the material of workpiece  102 . In some embodiments, abrasive particles  114  are made of one or more non-metallic materials, such as zirconia, alumina, titania, and/or iron oxide, or one or more metallic materials. In some embodiments, abrasive particles  114  include one or more non-metallic materials and one or more metallic materials. 
     Magnet  104  is situated with respect to workpiece  102  such that magnetic fields  112  of magnet  104  influence magnetically responsive fluid  108  near surfaces of workpiece  102 . Apparatus  100  is arranged to provide relative motion between workpiece  102  and magnetically responsive fluid  108 . For example, workpiece  102  can be rotated about first axis  118  using first fixture  103 . Alternatively, magnet  104  can be rotated about second axis  116  using second fixture  105 . This can be accomplished by arranging first fixture  103  and/or second fixture  105  to respective motors (not shown). In some embodiments, both workpiece  102  and magnet  104  are rotated. 
     The relative movement of workpiece  102  with respect to magnetically responsive fluid  108  can cause abrasive particles  114  within magnetically responsive fluid  108  to provide a cutting action on surfaces of workpiece  102 , such as at curved surface  120  of workpiece  102 . That is, the relative motion between workpiece  102  and magnetically responsive fluid  108  changes the magnetic field  112  at curved surface  120 , which causes movement of magnetically responsive particles  110  near curved surface  120 . Abrasive particles  114  become entrained with the movement of magnetically responsive particles  110 , which cases abrasive particles  114  to contact and rub up against curved surface  120 . In this way, abrasive particles  114  can remove material form workpiece  102  at surface  120  and shape curved surface  120 . In some embodiments where the cutting action is strong enough, abrasive particles  114  can remove larger portions of material from workpiece  102  similar to a cutting or machining operation. These types of shaping operations can be referred to as rough cutting. In other embodiments, the cutting action is lessened so as to provide a polishing effect to curved surface  120 . These types of shaping operations can be referred to as fine cutting. 
     In some embodiments, magnetically responsive particles  110  are also made of an abrasive material that can also abrade and remove material from workpiece  102 . In some embodiments where magnetically responsive particles  110  are made of sufficiently abrasive material for shaping and/or finishing workpiece, separate abrasive particles  114  are not used. Note that if workpiece  102  includes an electrically conductive metal, it may be necessary to ground workpiece  102  so as to prevent interaction of workpiece  102  with electric currents (if any) generated by relative movement of magnetically responsive fluid  108  with respect to workpiece  102 . 
     The size and shape of abrasive particles  114  can vary depending on design requirements and desired outcome. For example, abrasive particles  114  can be sized and shaped to provide relatively fast cutting of workpiece  102 . In these cases, abrasive particles  114  can have sharp edges. In addition, abrasive particles  114  can have a relatively large average size, such as having average diameters in hundreds of nanometers or even in millimeters, which can provide relatively aggressive cutting action. In other embodiments, abrasive particles  114  have relatively smooth and rounded (e.g., spherical) shapes that provide more gentle abrasive action for finer polishing action. It may be desirable for abrasive particles  114  to be relatively small, such as having an average diameter in the scale of nanometers, to provide a relatively gentle cutting action. Any suitable combination of shape (spherical and/or sharp edged) and average size (nanometer and/or millimeter scale diameters) can be used depending on desired outcome. 
     The constitution of carrier fluid  111  can vary depending on the type of magnetically responsive particles  110  and/or abrasive particles  114 , as well as desired properties magnetically responsive fluid  108 . For example, the material of carrier fluid can be chosen based on its lubrication, cooling, viscosity and solvation properties. In some cases, carrier fluid  111  dissipates heat from friction generated by movement of magnetically responsive particles  110  with respect to workpiece  102 . Carrier fluid  111  can also act as a lubricant that reduces friction between magnetically responsive particles  110  and/or abrasive particles  114  against workpiece  102 . In some embodiments, carrier fluid  111  includes an aqueous solution. In other embodiments, carrier fluid  111  includes an organic solvent. In some embodiments, carrier fluid  111  includes a combination of aqueous and organic solutions. In some embodiments, carrier fluid  111  has one or more surfactants that can inhibit clumping of magnetically responsive particles  110  and/or abrasive particles  114 . 
     One important factor to consider in choosing process parameters of a shaping operation can be the viscosity of magnetically responsive fluid  108 . The viscosity of magnetically responsive fluid  108  is related to the ease of movement of magnetically responsive fluid  108 . That is, the higher the viscosity of magnetically responsive fluid  108 , the more force required to move magnetically responsive fluid  108  around workpiece  102 . The viscosity of magnetically responsive fluid  108  can depend on the viscosity of carrier fluid  111 , as well as the density of magnetically responsive particles  110  and abrasive particles  114  within carrier fluid  111 . In addition, the temperature of magnetically responsive fluid  108  can affect the viscosity of magnetically responsive fluid. For example, magnetically responsive fluid  108  at higher temperatures can make it less viscous. Therefore, it may be desirable to heat magnetically responsive fluid  108  using an external heat source, such as a hot plate or heat lamp (not shown). In addition, friction of magnetically responsive fluid  108  against workpiece  102  can also generate heat, which can also affect the viscosity of magnetically responsive fluid  108 . In some cases, magnetically responsive fluid  108  is maintained at a predetermined viscosity to reduce the occurrence of agglomeration of magnetically responsive particles  110  and/or abrasive particles  114 . This can be important if such agglomeration can lead to pitting or denting of workpiece  102  during the shaping operation. However, it may be also important to assure that workpiece  102  does not reach a high enough temperature to cause deformation of workpiece  102 . 
     Magnet  104  should be strong enough such that magnetic field  112  can control movement of magnetically responsive fluid  108  with respect to curved surface  120  of workpiece  102  of keep magnetically responsive fluid  108  stable with respect to curved surface  120  if workpiece  102  is moved (e.g., rotated). The strength of the magnetic field  112  can depend on the type of magnet  104 . In some embodiments, magnet  104  includes a permanent magnetic material, such as magnetized iron, nickel, cobalt and/or rare earth magnetic material. In some embodiments, magnet  104  is an electromagnet, which is magnetized by an electric current provided by one or more power supplies (not shown). For example, a power supply can be electrically coupled to magnet  104  via second fixture  105 . In some embodiments, magnet  104  is a superconducting magnet. In some embodiments, magnet  104  includes a combination of permanent magnet(s), electromagnet(s) and superconducting magnet(s). 
     One advantage of using an electromagnet is that the amount of current supplied to magnet  104  can be controlled, thereby controlling the strength of magnetic field  112 . In some embodiments, magnetic field  112  is changed over time, such as by increasing and decreasing an amount of electric current to magnet  104 . This can create a pulsing action where magnetically responsive particles  110  are pull toward and away from magnet  104 . For example, a current can be applied to magnet  104  for a first period of time, and then the current can be removed (turned off) for a second period of time. This can be repeated such that a pulsing action is created across magnetically responsive fluid  108  that pulls and pushes abrasive particles  114  across surface  120  of workpiece  102 . In some embodiments, the amount of current is gradually changed such that movement of magnetically responsive fluid  108  is correspondingly smooth. In other embodiments, the amount of current is abruptly changed such that the movement of magnetically responsive fluid  108  is correspondingly abrupt. 
     In some embodiments, the polarity of magnet  104  is switched during the shaping operation. For example, a first electric current can be applied to magnet  104  that makes magnet  104  have a positive polarity for a first period of time. Then a second electric current can be applied to magnet  104  that makes magnet  104  have a negative polarity for a second period of time. This polarity switching can be repeated creating another type of pulsing effect, which can be similar to or different than the pulsing effect caused by increasing and decreasing the strength of magnetic field  112 . In some embodiments, a combination of increasing/decreasing the electric current and switching the polarity of magnet  104  is used to create particular movements of magnetically responsive fluid  108  around workpiece  102 . 
     In some embodiments, apparatus  100  is configured to interact with a computerized mapping system. The computerized mapping system can determine the three-dimensional position of workpiece  102  within apparatus  100  and/or the shape of workpiece  102 . For example, an imaging system, such as those including sensors and/or a charge-coupled device (CCD), can collect image data of workpiece  102 . The image data can be then be entered into a computer that calculates the position and/or shape of workpiece  102  in three-dimensional space (x, y, z). This three-dimensional position data can then be used to make decisions as to changing magnetic field  112  in real time during the shaping operation. Features of a suitable electronic system for accomplishing computerized mapping are described below with respect to  FIG. 7 . 
     In particular embodiments, a replica fixture (not shown) is used to mimic hand motions of an operator such that precise control over the shaping of workpiece  102  can be achieved. The replica fixture can be computationally mapped similar to apparatus  100  in order to collect and store another set of positional data in three-dimensional space (x 1 , y 1 , z 1 ) related to the replica fixture in the computer. The replica fixture can have a corresponding sensors and/or CCD imaging system that is configured to detect in real time the location in three-dimensional space of an object, such as a operator&#39;s hand, that is within the replica fixture. The computer can then be used to adjust magnetic field  112  and direct magnetically responsive fluid  108  in apparatus  100  in accordance with movement of the operator&#39;s hand within the replica fixture during a shaping operation. In this way, the shaping operation can be performed in a manner precisely in accordance with a user&#39;s directive. This application can be useful for artistic purposes since a user can observe the shaping of workpiece  102  during the shaping operation and adjust further shaping based on how workpiece  102  appears to change. 
     In some embodiments, apparatus  100  can be used to rework workpiece  102 . For example, prior to the shaping operation is performed, an operator can identify areas of workpiece  102  that need rework. The operator can then apply a substance, such as adhesive having some abrasive particles  114  therein, on these rework areas. When workpiece  102  undergoes the shaping process, the rework areas of workpiece  102  having the substance with some abrasive particles  114  adhered thereon can become abraded faster than areas of workpiece  102  without abrasive particles  114  adhered thereon. In this way, localized machining at identified rework regions can be preferentially abraded. 
       FIG. 2  shows another magnetic shaping apparatus  200  used to shape workpiece  202  in accordance with some embodiments. Apparatus  200  includes magnets  204   a  and  204   b  radially arranged around container  206 , which holds magnetically responsive fluid  208  and workpiece  202 . Fixture  210  can support workpiece  202  within magnetically responsive fluid  208 . In some embodiments, fixture  210  is configured to rotate workpiece  202  about axis  212 . In some embodiments, magnets  204   a  and  204   b  are supported by a fixture or multiple fixtures (not shown) that are configured to rotate magnets  204   a  and  204   b  around container  206 . Such fixture(s) are not shown for simplicity. Note that in other embodiments, magnets  204   a  and  204   b  are positioned within container  206  and magnetically responsive fluid  208 . 
     Magnetically responsive fluid  208  includes magnetically responsive particles  214  suspended within carrier fluid  218 . Magnetically responsive fluid  208  can also include abrasive particles  216  that are made of material(s) sufficiently hard to abrade workpiece  202 . In some embodiments, magnetically responsive particles  214  are sufficiently hard to abrade workpiece  202  such that abrasive particles  216  are not added to magnetically responsive fluid  208 . Magnets  204   a  and  204   b  are positioned such that their magnetic fields  205   a  and  205   b , respectively, affect magnetically responsive fluid  208  near surface  207  of workpiece  202 . For example, magnets  204   a  and  204   b  can be configured to provide magnetic fields  205   a  and  205   b  having stronger magnetic flux at regions A of magnetically responsive fluid  208  compared to regions B. Since magnetically responsive particles  214  are more strongly attracted to regions of greater magnetic flux, regions A can have greater densities of magnetically responsive particles  214  than regions B. The density of abrasive particles  216 , which are suspended within magnetically responsive fluid  208 , can also be greater at regions A compared to regions B. Put another way, the viscosity of magnetically responsive fluid  208  at regions A can be higher than at regions B. In some embodiments, the density of magnetically responsive particles  214  and abrasive particles  216  is high enough at concentrated regions A that magnetically responsive fluid  208  substantially solidifies at or near regions A. 
     If workpiece  202  is rotated, magnetic fields  205   a  and  205   b  that retain magnetically responsive particles  214  (and by proxy abrasive particles  216 ) at regions A and B can provide a resistance force that workpiece  202  moves relative to. This relative movement can create a cutting action where abrasive particles  216  cut into surface  207 . Since the density of abrasive particles  216  can be higher at regions A, the rate of abrasion can be higher at portions of surface  207  proximate to regions A compared to portions of surface  207  proximate to regions B. This can result in the more material removal at surface  207  near regions A compare to regions B and the symmetrically shaped workpiece  202  shown in  FIG. 2 . 
     If magnets  204   a  and  204   b  are rotated, magnetic fields  205   a  and  205   b  can force the movement of magnetically responsive particles  214  relative to surface  207 . Abrasive particles  216  can become entrained with the relative movement of magnetically responsive particles  214 . This relative movement can create a cutting action where abrasive particles  216  cut into surface  207 . As described above, the higher density of abrasive particles  216  at regions A can create more abrasion at regions A compared to regions B, resulting in the symmetrically shape workpiece  202  along surface  207  shown in  FIG. 2 . 
     In some embodiments, both workpiece  202  and magnets  204   a  and  204   b  are rotated. For example, workpiece  202  can be rotated in a first direction and magnets  204   a  and  204   b  can be rotated in an opposite direction. This can create more relative motion between workpiece  202  and workpiece  202 , providing a faster abrasion process. It should be noted that it might be necessary to change the magnitudes of magnetic fields  205   a  and  205   b  during the shaping process in order to account for the change in shape of workpiece  202  during the shaping process. For example, it may be necessary to increase the magnitudes of magnetic fields  205   a  and  205   b . This can be accomplished, for example, by increasing the electric current to magnets  204   a  and  204   b  if they include electromagnets. In some embodiments, the positions of magnets  204   a  and  204   b  are changed. For example, magnets  204   a  and  204   b  can be moved closer to workpiece  202  during the shaping process such that the magnetic flux of their respective magnetic fields  205   a  and  205   b  becomes greater near surface  207 . 
     Although  FIG. 2  shows two magnets  204   a  and  204   b , in other embodiments more than two magnets are radially positioned around container  206 . In some embodiments, an array of magnets, such as a Halbach array of magnets, are be used to create uniquely shaped magnetic fields within magnetically responsive fluid  208 . If magnets  204   a  and  204   b  are electromagnets, the electrical current provided to magnets  204   a  and  204   b  can be changed during the shaping operation providing a pulsing action of magnetically responsive fluid  208 , as described above with reference to  FIG. 1 . 
     In some embodiments, the frictional heat generated during the shaping operation is used to aid the shaping process. For example, heat generated between magnetically responsive fluid  208  and workpiece  202  can heat up workpiece  202  such that workpiece  202  is more malleable and responsive to applied pressures. Thus, in some cases the pressures applied to surface  207  of workpiece  202  by magnetically responsive particles  214  and abrasive particles  216 , provided by the force of magnetic fields  205   a  and  205   b , can be strong enough to forge workpiece  202  while in this heated and more malleable state. This can further shape workpiece  202  along surface  207 . That is, the shaping operation can be a hybrid of an abrasive finishing operation and a forging operation. Heat can additionally or alternatively be supplied to workpiece  202  in other ways. For example, workpiece  202  can be heated prior to or during the shaping operation. Alternatively or additionally, magnetically responsive fluid  208  can be heated using a separate heat source (not shown), such as a hot plate. The temperature of magnetically responsive fluid  208  and/or workpiece  202  can be heated to predetermined temperature as measured using a temperature sensor, such as thermocouple (not shown). 
       FIGS. 3A-3C  show workpiece  302  undergoing a shaping operation using magnetic shaping apparatus  300 , in accordance with some embodiments.  FIG. 3A  shows a perspective view of apparatus  300 , and  FIGS. 3B and 3C  show cross section views A-A of apparatus  300 . In  FIGS. 3A-3C , magnetic shaping apparatus  300  is used to chamfer an edge of workpiece  302 .  FIG. 3A  shows apparatus  300 , which includes magnets  304   a  and  304   b  and container  306 . Workpiece  302  is positioned within container  306 . In some embodiments, fixture  305  positions and supports workpiece  302  within container  306 . In some embodiments, fixture  305  is configured to rotate. Portions of workpiece  302  can be masked using mask  307  such that portion  309  of workpiece  302  is exposed. Mask  307  can be made of any suitable material sufficient for masking portions of workpiece  302  from exposure to a magnetically responsive fluid. For example, mask  307  can be made of a polymer material, such as a photoresist material. 
     At  FIG. 3B , first magnetically responsive fluid  311  is added to container  306 . First magnetically responsive fluid  311  includes first magnetically responsive particles  310  and first abrasive particles  312  dispersed within first carrier fluid  313 . First abrasive particles  312  can be characterized have having a first average diameter configured to aggressively abrading exposed portion  309  of workpiece  302  when magnets  304   a  and  304   b  apply respective magnetic fields. Note that the magnetic fields of magnets  304   a  and  304   b  are not shown in  FIGS. 3B and 3C  for simplicity. 
     Relative movement of workpiece  302  and first abrasive particles  312  can be created using any of the techniques described above. For example, the magnitudes of the magnetic fields of magnets  304   a  and  304   b  can be changed by increasing/decreasing electric current supplied to magnets  304   a  and  304   b . Alternatively or additionally, the polarity of magnets  304   a  and  304   b  can be repetitively switched to create a pulsing action of first magnetically responsive particles  310  and, in turn, first abrasive particles  312  with respect to workpiece  302 . Additionally or alternatively, fixture  305  and/or magnets  304   a  and  304   b  can be rotated. These motions can give first abrasive particles  312  a cutting action that cuts and removes material from exposed portion  309  of workpiece  302 . As shown, exposed portion  309  has a rough surface since first abrasive particles  312  are configured to provide an aggressive rough cut. Other parameters that can affect the roughness of exposed portion  309  can include the magnitudes of the magnetic fields of magnets  304   a  and  304   b , the amount of abrasive particles  312  within magnetically responsive fluid  311 , and the rotational speeds of fixture  305  and/or magnets  304   a  and  304   b.    
     At  FIG. 3C , first magnetically responsive fluid  311  is replaced with second magnetically responsive fluid  315  within container  306 . Second magnetically responsive fluid  315  includes second magnetically responsive particles  314  and second abrasive particles  316  dispersed within second carrier fluid  318 . Second abrasive particles  316  can be characterized have having a second average diameter configured to gently abrade exposed portion  309  of workpiece  302  when magnets  304   a  and  304   b  apply respective magnetic fields. In some embodiments, the second average diameter of second abrasive particles  316  is smaller than first average diameter of first abrasive particles  312 . In some embodiments, the shapes of first abrasive particles  312  and second abrasive particles  316  are different. For example, first abrasive particles  312  can have more irregular shapes and have sharper edges that are capable of more efficient cutting compared to second abrasive particles  316 . First magnetically responsive particles  310  can be different or the same type or material as second magnetically responsive particles  314 . First carrier fluid  313  can be different or the same type as second carrier fluid  318 . 
     The relatively gentle abrasive action of second abrasive particles  316  can polish exposed portion  309 . The magnitudes of the magnetic fields of magnets  304   a  and  304   b , the amount of abrasive particles  316  within magnetically responsive fluid  315 , and the rotational speeds of fixture  305  and/or magnets  304   a  and  304   b  can also be adjusted to provide a desired amount of polishing and removal. After the polishing process is complete, mask  307  can be removed from workpiece  302 , revealing portions of workpiece  302  substantially unaffected by the shaping process and resulting in chamfered workpiece  302 . 
       FIGS. 4A-4C  show an alternative chamfering operation, in accordance with some embodiments.  FIG. 4A  shows a perspective view of apparatus  400 , and  FIGS. 4B and 4C  show cross section views A-A of apparatus  400 .  FIG. 4A  shows apparatus  400 , which includes fixture  404  that is configured to create a chamfer along an edge of workpiece  402 . Fixture  404  includes inlet  406  and outlet  408  configured to provide entry and exit, respectively, of a magnetically responsive fluid within a channel of fixture  404 . 
       FIG. 4B  shows a cross section view of apparatus  400  after channel  413  is filled with first magnetically responsive fluid  412  via inlet  406 . First magnetically responsive fluid  412  includes first magnetically responsive particles  415  and first abrasive particles  414  suspended within first carrier fluid  417 . Magnets  410   a  and  410   b  are positioned around channel  413  and configured to direct first magnetically responsive fluid  412 . Magnetic fields of magnets  410   a  and  410   b  control movement of first magnetically responsive particles  415  with respect to exposed portion  416  of workpiece  402 . 
     Relative movement of first abrasive particles  414  and workpiece  402  can be created using any of the techniques described above. For example, magnet  410   a  can have a polarity that is opposite of the polarity of magnet  410   b . This can create a strong magnetic flux near exposed portion  416 , causing first magnetically responsive particles  415  and first abrasive particles  414  to be concentrated near exposed portion  416  of workpiece  402 . In some embodiments, the polarities of magnets  410   a  and  410   b  are repeatedly switched during the operation, causing the magnetic fields of magnets  410   a  and  410   b  to change. This can provide motion that allows first abrasive particles  414  to cut and abrade exposed portion  416 . In some embodiments, further motion is provided by the physical flow of first magnetically responsive fluid  412  across exposed portion  416  within channel  413 . For example, a pump (not shown) can pump magnetically responsive fluid  412  through channel  413 . First magnetically responsive fluid  412  can be configured to provide a rough cut to exposed portion  416 . First abrasive particles  414  are characterized as having a first average diameter that can be chosen to provide aggressive abrasion of workpiece  402 . 
     At  FIG. 4C , first magnetically responsive fluid  412  is replaced with second magnetically responsive fluid  418 , which includes second magnetically responsive particles  419  and second abrasive particles  420  dispersed within second carrier fluid  421 . Second abrasive particles  420  can be characterized have having a second average diameter configured to gently abrade exposed portion  416  of workpiece  302  when magnets  410   a  and  410   b  apply respective magnetic fields. In some embodiments, the second average diameter of second abrasive particles  420  is smaller than the first average diameter of first abrasive particles  414 , and the shapes of first abrasive particles  414  and second abrasive particles  420  are different. First magnetically responsive particles  415  can include different or the same material as second magnetically responsive particles  419 . First carrier fluid  417  can be different or the same type as second carrier fluid  421 . After exposed portion  416  of workpiece  302  is abraded to a desired finish, workpiece  402  is removed from fixture  404  with a chamfered and polished edge. 
       FIG. 5  shows a perspective view of magnetic finishing apparatus  500  configured to provide a textured to surface  503  of workpiece  502 . Apparatus  500  includes container  506  and magnets  504   a  and  504   b . Workpiece  502  can be supported by fixture  505  within container  506 . Container is configured to hold magnetically responsive fluid  512 , which includes magnetically responsive particles  508  and abrasive particles  510  within carrier liquid  509 . Magnets  504   a  and  504   b  can each include one or more electromagnets and permanent magnets. Magnetic fields from magnets  504   a  and  504   b  combine to create a combined magnetic field  514  that preferentially directs magnetically responsive particles  508  toward surface  503 . Abrasive particles  510  become entrained with the movement of magnetically responsive particles  508  toward surface  503  and impinge upon surface  503 , creating corresponding indentations  515 . The force at which abrasive particles  510  impact surface  503  will, in part, depend on the force of combined magnetic field  514 , which can be adjusted by adjusting the strength of each of magnets  504   a  and  504   b . In some cases, magnets  504   a  and  504   b  have opposing polarities, which are repeatedly switched. As described above, other process parameters such as the size and shape of abrasive particles  510 , can be chosen to create a predefined texture to surface  503 . 
     In some embodiments, portions of workpiece  502  are masked using mask  516  such that a portion of workpiece  502  is exposed. Mask  516  can be made of any suitable material sufficient for masking portions of workpiece  502  from exposure to magnetically responsive fluid  512 . For example, mask  516  can be made of a polymer material, such as a photoresist material. After the texturing operation is complete, mask  516  can be removed such that the portion of workpiece  502  covered by mask  516  having a pre-texturing surface finish is exposed. In some embodiments, the portion of workpiece  502  covered by mask  516  has a shiny reflective surface. Thus, surface  503  of workpiece  502  can have a textured portion and an untextured portion. 
       FIG. 6  shows flowchart  600  indicating a process for shaping and/or finishing a workpiece using a magnetic shaping apparatus according to some embodiments. At  602 , a workpiece is placed within a magnetically responsive fluid. The magnetically responsive fluid includes magnetically responsive particles within a carrier fluid. In some embodiments, the magnetically responsive fluid is a ferrofluid. In some embodiments, the magnetically responsive particles can act as abrasive particles during a shaping or finishing operation. In some embodiments, separate abrasive particles are added to the magnetically responsive fluid. In some embodiments, the abrasive particles include one or more of zirconia, titania, and alumina. 
     At  604 , a magnetic field is applied to the magnetically responsive fluid such that magnetically responsive particles and/or abrasive particles remove material from the workpiece. The apparatus can be configured to provide a rough cut, similar to a machining process or a fine cut, similar to a polishing or buffing process. In some embodiments, the same apparatus can be used to rough cut (e.g., similar to machining) the workpiece and fine cut (e.g., polish) the workpiece. For example, a first magnetic fluid having abrasive particles with relatively sharp edges and/or large average diameter can be used with a strong magnetic force to provide the rough cutting. A second magnetic fluid having abrasive particles with rounded edges (e.g., spherical shapes) and/or small average diameter can be used with a weaker magnetic force to provide the fine cutting. 
     The magnetic fields can be created by one or more magnets placed in proximity to the magnetically responsive fluid and positioned to direct movement of the magnetically responsive particles along predefined paths across the surface of the workpiece. Abrasive particles can become entrained with the movement of the magnetically responsive particles and abrade surfaces of the workpiece in accordance with the predefined paths until the workpiece takes on a desired shape. One advantage of the magnetic techniques provided herein over conventional machining operations is that tool wear can be an issue with conventional machining techniques. In magnetic-based shaping operations described herein, the magnetically responsive fluid can take place of tools, thereby eliminating tool wear issues. The magnetically responsive fluid can be replaced with new magnetically responsive fluid having new abrasive particles. 
       FIG. 7  is a block diagram of electronic system  700  suitable for controlling some of the magnetic and/or finishing processes described above. Electronic system  700  can represent a computing system in conjunction with a magnetic shaping and/or finishing apparatus such as a magnetic shaping and/or finishing apparatus described above. Electronic system  700  includes a processor  702  that pertains to a microprocessor or controller for controlling the overall operation of electronic system  700 . Electronic system  700  contains instruction data pertaining to manufacturing instructions in a file system  704  and a cache  706 . The file system  704  is, typically, a storage disk or multiple disks. The file system  704  typically provides high capacity storage capability for the electronic system  700 . However, since the access time to the file system  704  can be relatively slow, electronic system  700  can also include a cache  706 . Cache  706  can be, for example, Random-Access Memory (RAM) provided by semiconductor memory. The relative access time to the cache  706  can be substantially shorter than for the file system  704 . However, cache  706  may not have the large storage capacity of the file system  704 . Further, file system  704 , when active, can consume more power than cache  706 . The power consumption is often a concern when the electronic system  700  is a portable device that is powered by a battery  724 . The electronic system  700  can also include a RAM  720  and a Read-Only Memory (ROM)  722 . ROM  722  can store programs, utilities or processes to be executed in a non-volatile manner. RAM  720  can provide volatile data storage, such as for cache  706 . 
     Electronic system  700  can also include a user input device  708  that allows a user of the electronic system  700  to interact with the electronic system  700 . For example, a user input device  708  can take a variety of forms, such as a button, keypad, dial, touch screen, audio input interface, visual/image capture input interface, input in the form of sensor data, etc. Still further, the electronic system  700  can include a display  710  (screen display) that can be controlled by the processor  702  to display information to the user. As described above, in some embodiments, display  710  provides images collected from an imaging tool. Data bus  716  can facilitate data transfer between at least the file system  704 , the cache  706 , the processor  702 , and a coder/decoder (CODEC)  713 . CODEC  713  can be used to decode and play multiple media items from file system  704  that can correspond to certain activities taking place during a particular manufacturing process. Processor  702 , upon a certain manufacturing event occurring, supplies the media data (e.g., audio file) for the particular media item to a CODEC  713 . CODEC  713  can then produce analog output signals for a speaker  714 . Speaker  714  can be a speaker internal to electronic system  700  or external to electronic system  700 . For example, headphones or earphones that connect to the electronic system  700  would be considered an external speaker. 
     Electronic system  700  can also include a network/bus interface  711  that couples to a data link  712 . Data link  712  can allow electronic system  700  to couple to a host computer or to accessory devices. Data link  712  can be provided over a wired connection or a wireless connection. In the case of a wireless connection, network/bus interface  711  can include a wireless transceiver. The media items (media assets) can pertain to one or more different types of media content. In one embodiment, the media items are audio tracks (e.g., songs, audio books, and podcasts). In another embodiment, the media items are images (e.g., photos). However, in other embodiments, the media items can be any combination of audio, graphical or visual content. Sensor  726  can take the form of circuitry for detecting any number of stimuli. For example, sensor  726  can include any number of sensors for monitoring a manufacturing operation such as for example a Hall Effect sensor responsive to external magnetic field, an audio sensor, a light sensor such as a photometer, and so on. 
     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 non-transitory computer readable medium for controlling manufacturing operations or as computer readable code on a non-transitory computer readable medium for controlling a manufacturing line. The non-transitory computer readable medium is any data storage device that can store data, which can thereafter be read by a computer system. Examples of the non-transitory computer readable medium include read-only memory, random-access memory, CD-ROMs, DVDs, magnetic tape, optical data storage devices, and carrier waves. The non-transitory 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. 
     It should be noted that the embodiments described above with reference to  FIGS. 1-7  are provided for illustrative purposes and not meant to limit the scope of inventive aspects of the instant disclosure. That is, other suitable embodiments having similar features can fall within the scope of the disclosure described herein. In addition, any suitable combinations of features of  FIGS. 1-7  can be used within the scope of the present disclosure. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not meant to be exhaustive or to limit the embodiments 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.

Metadata:
Filing Date: 20150602
Publication Date: 20170725
Grant Date: 20170725
Priority Date: 20150602
Inventors: CASTILLO ALFREDO
RAGHAVAN ADITHYA
MULLER PETER R.
Assignee: APPLE INC
CPC Classifications: [{"code": "B24B31/102", "inventive": true, "first": false, "tree": "[]"}, {"code": "B24B31/003", "inventive": true, "first": false, "tree": "[]"}, {"code": "B24B1/005", "inventive": true, "first": true, "tree": "[]"}, {"code": "B24B1/005", "inventive": true, "first": true, "tree": "[]"}, {"code": "B24B31/102", "inventive": true, "first": false, "tree": "[]"}, {"code": "B24B31/003", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 57441435