Patent Publication Number: US-2015061438-A1

Title: Magnet co-formed to back iron

Description:
BACKGROUND 
     An electric motor may use stators, magnets, and/or coils to rotate an object. For example, a motor may rotate data storage disks used in a disk drive storage device. The data storage disks may be rotated at high speeds during operation using the stators, magnets, and/or coils. For example, magnets and coils may interact with a stator to cause rotation of the disks relative to the stator. 
     In some cases, electric motors are manufactured with increasingly reduced sizes. For example, in order to reduce the size of a disk drive storage device, the size of various components of the disk drive storage device may be reduced. Such components may include the electric motor, stator, magnets, and/or coils. The precision at which the stators, magnets, and coils are manufactured can affect the acoustical properties and performance of the electric motor. 
     SUMMARY 
     An apparatus includes a hub. The apparatus also includes a back iron that is coupled to the hub. In addition, a magnetic annulus is co-formed to the back iron. 
     These and other aspects and features of embodiments may be better understood with reference to the following drawings, description, and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements. 
         FIG. 1  provides a top perspective of a number of stator teeth, magnetic annulus, and a back iron, according to one aspect of the present embodiments. 
         FIG. 2  provides a cross-sectional perspective of an exemplary back iron and hub, according to one aspect of the present embodiments. 
         FIG. 3  provides a cross-sectional perspective of a stator tooth, a back iron, a magnetic annulus co-formed to the back iron, and a hub, according to one aspect of the present embodiments. 
         FIG. 4  provides a cross-sectional perspective of a back iron, a magnetic annulus co-formed to the back iron and a hub, according to one aspect of the present embodiments. 
         FIGS. 5A and 5B  provide a cross-sectional perspective of co-forming a magnet to a back iron, using a mold, according to one aspect of the present embodiments. 
         FIGS. 6A and 6B  provide a cross-sectional perspective of a first magnet and a second magnet, both co-formed to a back iron, according to one aspect of the present embodiments. 
         FIG. 6C  provides a cross-sectional perspective of a magnet, a back iron, and a clamshell tool, according to one aspect of the present embodiments. 
         FIG. 6D  provides a cross-sectional perspective of a hub, a first back iron with a first magnet, and a second back iron with a second magnet, according to one aspect of the present embodiments. 
         FIG. 7  shows an exemplary flow diagram for co-forming a magnet to a back iron, according to one aspect of the present embodiments. 
         FIG. 8  provides a plan view of a conventional hard disk drive in which embodiments of one or more magnets co-formed to a back iron may be used. 
     
    
    
     DETAILED DESCRIPTION 
     Before various embodiments are described in greater detail, it should be understood that the embodiments are not limited to the particular embodiments described and/or illustrated herein, as elements in such embodiments may vary. It should likewise be understood that a particular embodiment described and/or illustrated herein has elements which may be readily separated from the particular embodiment and optionally combined with any of several other embodiments or substituted for elements in any of several other embodiments described herein. 
     It should also be understood that the terminology used herein is for the purpose of describing embodiments, and the terminology is not intended to be limiting. Unless indicated otherwise, ordinal numbers (e.g., first, second, third, etc.) are used to distinguish or identify different elements or steps in a group of elements or steps, and do not supply a serial or numerical limitation on the elements or steps of the embodiments thereof. For example, “first,” “second,” and “third” elements or steps need not necessarily appear in that order, and the embodiments thereof need not necessarily be limited to three elements or steps. It should also be understood that, unless indicated otherwise, any labels such as “left,” “right,” “front,” “back,” “top,” “bottom,” “forward,” “reverse,” “clockwise,” “counter clockwise,” “up,” “down,” or other similar terms such as “upper,” “lower,” “aft,” “fore,” “vertical,” “horizontal,” “proximal,” “distal,” and the like are used for convenience and are not intended to imply, for example, any particular fixed location, orientation, or direction. Instead, such labels are used to reflect, for example, relative location, orientation, or directions. It should also be understood that the singular forms of “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. 
     Disks of a hard disk drive (“HDD”), such as that of  FIG. 8  described herein below, may be rotated at high speeds by means of an electric motor including a spindle assembly mounted on a base of a housing. Such electric motors include a stator assembly including a number of stator teeth, each extending from a yoke. Each stator tooth of the number of stator teeth supports a field coil that may be energized to polarize the field coil. Such electric motors further include one or more permanent magnets disposed adjacent to the number of stator teeth. As the number of field coils disposed on the number of stator teeth are energized in alternating polarity, the magnetic attraction or repulsion of a field coil to an adjacent permanent magnet causes the spindle of the spindle motor assembly to rotate, thereby rotating the disks for read/write operations by one or more read-write heads. 
     Various means may be used to attach a permanent magnet to a motor part (e.g., base, back iron, etc.). Glue may be used thereby introducing a constructive “gap” (e.g., the space filled by the glue) between the magnet and the motor part. This gap thus wastes space thereby adding to the dimensions of the device. 
     If a magnet is formed separate from a motor part, the magnet may not be as round as the motor part to which the magnet is attached (e.g. back iron, hub). Another variance may be created by a variation in the gap going around the circumference created by the magnetic. For example, the magnetic nature of the magnet may cause the magnet to unevenly attach to a motor part, thereby being off center. In other words, the magnetic nature of the magnet causes the magnet to lock to one side of the motor part. These variances between the motor part and magnet cause the magnet to be eccentric, thereby causing non-uniform electromagnetic forces during operation and/or resulting in acoustical issues. As a result, the magnet and motor part manufacture may be restricted to a tolerance range in order to limit eccentricities and/or acoustical issues. 
     A protective coating may be applied after assembly of the magnet and motor part. The protective coating may prevent a portion of the magnet or other motor parts from separating and damaging a magnetic storage disk. For example, if magnetic material comes into contact with a magnetic disk, a catastrophic error on the magnetic disk may result. This coating adds thickness, and the thickness may not be even from part to part. The variances in the coating can cause problems (e.g. vibration, acoustic, etc.) during the rotation of electric motor components. Additionally, this coating further consumes space thereby adding to the dimensions of the device. 
     On the other hand, co-forming the magnet onto a motor part (e.g., back iron) allows a substantially rounder magnet, thereby reducing variances and associated tolerances. In addition, co-forming the magnet to one or more motor parts while reducing the gap, allows a reduction in the size of the device and recovery of usable space. Further, the magnet may be reduced in thickness, while maintaining loop strength and reducing the gap between the magnet and the motor part. Thus, co-forming of the magnet to another motor component substantially eliminates the distance (e.g., caused by glue) between the magnet and the motor component and allows reducing the magnet thickness. The co-forming of the magnet to another motor component (e.g., back iron) further allows for elimination of a coating layer where the magnet is in contact with the motor component (e.g., on a surface of the magnet in contact with a portion of a surface of the back iron). 
       FIG. 1  provides a top perspective of a number of stator teeth, magnetic annulus, and a back iron, according to one aspect of the present embodiments. Portion of electric motor  100  includes base  101 , back iron  102 , magnetic annulus  104 , stator teeth  106 , yoke  108 , field coils  110 , and shaft  112 . Stator teeth  106  may be part of a stator assembly which is supported by the base  101  (e.g., base deck of  FIG. 8 ). In one embodiment, magnetic annulus  104  is co-formed on back iron  102  thereby removing gaps and variances between magnetic annulus  104  and back iron  102 . Magnetic annulus  104  includes magnetic material, for example, neodymium, boron, iron, or a combination thereof. 
     Field coils  110  are coupled to the yoke  108 . Stator teeth  106  are coupled to (e.g., mounted on) yokes  108 . Field coils  110  cause stator teeth  106  to output a magnetic field. The magnetic field causes magnetic annulus  104  to be pushed and pulled relative to stator teeth  106 , thereby causing magnetic annulus  104  to rotate. The rotation of magnetic annulus  104  causes back iron  102  to rotate and motor components coupled to back iron  102  (e.g., a hub) to rotate. For example, the rotation of magnetic annulus  104  may cause a hub to rotate about an axis normal to the base (e.g., rotate about shaft  112 ). Back iron  102  closes magnetic flux from the stator teeth, thereby preventing a magnetic field generated by field coils  110  from extending to a magnetic data storage area (e.g., magnetic disk). 
     In one embodiment, a stator assembly including stator teeth  106  may have a diameter of 16 mm, for example. The gap between stator teeth  106  and magnetic annulus  104  may be approximately 250 microns or ⅓ of a millimeter, for example. The outer diameter of a hub coupled to back iron  102  may be 20 mm, for example. 
       FIG. 2  provides a cross-sectional perspective of an exemplary back iron and hub, according to one aspect of the present embodiments. Portion of electric motor  200  includes hub  202  and back iron  204 . Back iron  204  is coupled to hub  202 . Back iron  204  may be pressed, slipped, or adhered (e.g. glue or adhesive) onto hub  202 . In some embodiments, the back iron  204  is separate from the hub  202  until after co-forming a magnet (e.g. magnetic annulus  104 ) to the back iron  204 . Thus, the back iron  204  includes the magnet when it is coupled to the hub  202 . In one exemplary embodiment, back iron  204  includes an annular channel or cavity  206  for a magnet to be co-formed into. 
     Back iron  204  may thereby provide structural strength to a magnet co-formed to back iron  204 . In one embodiment, the material (e.g., steel) used for back iron  204  is stronger and cheaper than magnetic material, thereby providing support to the magnetic material. For example, the magnetic material may be magnetized by exposing the magnetic material to a strong magnetic field. This strong magnetic field can create forces that may distort or pull apart a magnet with insufficient strength. Thus, forming of the magnet on back iron allows the back iron to provide structural support to the magnet, thereby allowing the magnet to be thinner while being strong enough to withstand the forces created during the magnetization process. In one embodiment, higher grade magnetic material (e.g., grades of 12 and above) is used to provide sufficient magnetic properties while using less magnetic material. In various embodiments, the reduction in space occupied by the magnet may be used for the back iron, thereby allowing a structurally stronger back iron. In some embodiments, the reduction in space occupied by the magnet may also be used to change the size of the gap (e.g., air gap) between stator teeth and a magnetic annulus. In various embodiments, the reduced size of the magnet may allow for smaller overall motor design, or larger and/or smaller motor components (e.g. stator, sleeve, hub, limiter, etc.). 
       FIG. 3  provides a cross-sectional perspective of a stator tooth, a back iron, a magnetic annulus co-formed to the back iron and a hub, according to one aspect of the present embodiments. Portion of electric motor  300  includes hub  302 , back iron  304 , magnet  306 , and stator tooth  308 . 
     Back iron  304  is coupled to hub  302 . Magnet  306  is co-formed to back iron  304 . Magnet  306  is formed into an annular channel or annular cavity of back iron  304 . In some embodiments, back iron  304  is coupled to three sides of magnet  306  (e.g. top, bottom, and outer diameter). However, in various embodiments the back iron  304  may couple to any number of sides, portions of one or more sides, or combinations of sides and/or portions of sides of the magnet  306 . Furthermore, in several embodiments the magnet  306  and/or back iron  304  may include various shapes. For example, the top and/or bottom and/or sides of the magnet  306  and/or cavity  206  ( FIG. 2 ) of the back iron  304  may be rounded, include protrusions, and/or include indentations. 
     Magnet  306  is separated from stator tooth  308  by gap  310 . Stator tooth  308  creates a magnetic field that causes magnet  306  to rotate thereby rotating hub  302 . In one embodiment, stator tooth  308  may have different dimensions (e.g., height) than dimensions of magnet  306 . In further embodiments, the stator tooth  308  and the magnet  306  may be axially offset from one another. For example, the center of the magnet  306  may be higher than the center of the stator, thereby providing a magnetic bias to the electric motor  300 . 
     In various embodiments, gap  310  between the stator tooth and the magnet may be between, for example, 150-300 microns. Some embodiments reduce the variance on the gap between the stator teeth and the magnet by having a co-formed magnet that is substantially uniform in shape with respect to back iron  304 . For example, the gap between the stator teeth and magnet may vary less than 5%, thereby substantially reducing or substantially eliminating acoustic tones during operation of the electric motor. 
       FIG. 4  provides a cross-sectional perspective of a back iron, a magnetic annulus co-formed to the back iron and a hub, according to one aspect of the present embodiments. Electric motor portion  400  includes hub  402 , back iron  404 , and magnet  406 . Magnet  406  is co-formed on back iron  404 . In one embodiment, magnet  406  may not be co-formed into a channel or cavity of back iron  404 . For example, magnet  406  may be co-formed onto a side of back iron  404 . 
       FIGS. 5A and 5B  provide a cross-sectional perspective of co-forming a magnet  502  to a back iron  504 , using a mold  506 , according to one aspect of the present embodiments. In various embodiments, the magnet  502  may be co-formed to the back iron  504  before the back iron  504  is attached to the hub  302  ( FIG. 3 ). 
     In various embodiments, magnet  502  may be co-formed by using back iron  504  as a molding component (e.g., clamshell mold). Back iron  504  (e.g. 4/16″ or 4/30″ steel) may be half of a clamshell mold, thereby supporting the top and bottom of the magnet  502 . The other half may be mold  506 . Back iron  504  and mold  506  may be moved together, forming mold cavity  508 . The magnet  502  may then be co-formed to the back iron  504 , and the mold  506  is removed, thereby leaving the magnet  502  co-formed to the back iron  504 . For example, material may be injected into the cavity  508 , through a channel  510 . The material may be co-formed to the back iron  504 , the mold  506  removed, and the material magnetized in further processes, thereby forming the magnet  502 . After the material has been formed into magnet  502 , the co-formed magnet  502  and back iron  504  are secured (e.g. glued, press fitted, welded, etc.) to the hub  302  ( FIG. 3 ). 
       FIGS. 6A and 6B  provide a cross-sectional perspective of a first magnet  602  and a second magnet  614 , both co-formed to back iron  604 , according to one aspect of the present embodiments. First magnet  602  is co-formed into first mold cavity  608 , and second magnet  614  is co-formed into second mold cavity  616  of back iron  604  by tool  610 . Tool  610  may be a tool or machine operable to apply, inject, extrude, or attach magnetic material to back iron  604 . Back iron  604  provides structural support and strength to first magnet  602  and second magnet  614  during the magnetization process and the co-forming process, thereby allowing first magnet  602  and second magnet  614  to be thinner. 
     First magnet  602  and second magnet  614  are annular in shape. First magnet  602  is operable to cause rotation of a motor part (e.g., caused by stator teeth  106 ,  FIG. 1 ). Second magnet  614  is formed in a bottom portion (e.g. second mold cavity  616 ) of back iron  604 . Thus, second magnet  614  is configured for axial biasing of a motor part (e.g., hub  302 ,  FIG. 3 ). First magnet  602 , second magnet  614 , and back iron  604  may be surrounded by a protective coating after being magnetized. 
       FIG. 6C  provides a cross-sectional perspective of a magnet  602 , a back iron  604 , and a clamshell tool  610 , according to one aspect of the present embodiments. In the present embodiment, tool  610  is clamshell shaped, instead of the back iron  604 . Thus, the clamshell shaped tool  610  is combined with the back iron  604  to form a cavity in which the magnet  602  is co-formed onto the back iron  604 . As a result, the clamshell shaped tool  610  supports the magnet  602  on the top and bottom during co-forming, instead of the back iron supporting the top and bottom of the magnet (see  FIGS. 5A and 5B ). 
       FIG. 6D  provides a cross-sectional perspective of a hub  652 , a first back iron  654  with a first magnet  656 , and a second back iron  660  with a second magnet  662 , according to one aspect of the present embodiments. Back irons  654  and  660  are coupled to hub  652 . First magnet  656  has been co-formed onto first back iron  654 , and second magnet  662  has been co-formed onto second back iron  660 . First magnet  656  and second magnet  662  may be co-formed onto first back iron  654  and second back iron  660  by a tool or machine (e.g., tool  610 ). First magnet  656  may be operable to cause rotation of a motor part (e.g., caused by stator teeth  106 ,  FIG. 1 ). Second magnet  662  may be operable for axial biasing of a motor part (e.g., hub  652 ). 
       FIG. 7  shows an exemplary flow diagram for co-forming a magnet to a back iron, according to one aspect of the present embodiments. Flow diagram  700  depicts various processes in accordance with forming various embodiments for co-forming one or more magnets onto one or more back irons. 
     At block  702 , a first back iron is formed. The first back iron may be formed of steel. 
     At block  704 , a magnetic material is applied to a portion of the first back iron. The magnetic material may be applied, injected, or extruded (e.g., directly) into an annular cavity or channel of the back iron. In one embodiment, the magnetic material is applied to the back iron with a mold (e.g.,  FIGS. 5A and 5B ). 
     At block  706 , the magnetic material is magnetized to produce a magnet. In one embodiment, the magnetic material is magnetized by exposing the magnetic material to a magnetic field while heating the magnetic material and the back iron. 
     At block  708 , the first back iron is coupled to an electric motor component (e.g., a hub). The first back iron may be adhered/glued onto, pressed onto, or slipped onto a hub. 
     At block  710 , a magnetic material is applied to a first portion of the first back iron and a second portion of the back iron. In one embodiment, the back iron includes a second cavity (e.g., on a bottom portion of the back iron) and the magnetic material is applied into the second cavity (e.g.,  FIGS. 6A and 6B ). 
     At block  712 , the magnetic material is magnetized to produce a first magnet and a second magnet (e.g., magnets  602  and  614 ). 
     At block  720 , a second back iron is formed. The second back iron may be formed of steel. 
     At block  722 , a magnetic material is applied to a first portion of the first back iron and a second portion of the second back iron (e.g.,  FIGS. 6A and 6B ). 
     At block  724 , the magnetic material is magnetized to produce a first magnet and a second magnet. 
     At block  726 , the first back iron and the second back iron are attached to a electric motor component (e.g., hub). In one embodiment, the second back iron is coupled to a bottom portion of a motor component (e.g., hub as in  FIG. 6B ). 
     At block  728 , a coating is applied to the one or more magnets and an electric motor component (e.g., one or more back irons). The coating may be applied around and/or surround the one or more back irons and the one or more magnets thereby acting as a protective coating during operation of the electric motor. 
       FIG. 8  provides a plan view of a hard disk drive  800 , which hard disk drive may use the co-formed magnet(s) described herein. Hard disk drive  800  may include a housing assembly including a cover  802  that mates with a base deck having a frame  803  and a floor  804 , which housing assembly provides a protective space for various hard disk drive components. The hard disk drive  800  includes one or more data storage disks  806  of computer-readable data storage media. Typically, both of the major surfaces of each data storage disk  806  include a number of concentrically disposed tracks for data storage purposes. Each data storage disk  806  is mounted on a hub  808 , which in turn is rotatably interconnected with the base deck and/or cover  802 . The hub  808  may include one or more magnets that have been co-formed onto a back iron (as described above). Multiple data storage disks  806  are typically mounted in vertically spaced and parallel relation on the hub  808 . A spindle motor assembly  810  rotates the data storage disks  806 . 
     The hard disk drive  800  also includes an actuator arm assembly  812  that pivots about a pivot bearing  814 , which in turn is rotatably supported by the base deck and/or cover  802 . The actuator arm assembly  812  includes one or more individual rigid actuator arms  816  that extend out from near the pivot bearing  814 . Multiple actuator arms  816  are typically disposed in vertically spaced relation, with one actuator arm  816  being provided for each major data storage surface of each data storage disk  806  of the hard disk drive  800 . Other types of actuator arm assembly configurations could be utilized as well, an example being an “E” block having one or more rigid actuator arm tips, or the like, that cantilever from a common structure. Movement of the actuator arm assembly  812  is provided by an actuator arm drive assembly, such as a voice coil motor  818  or the like. The voice coil motor  818  is a magnetic assembly that controls the operation of the actuator arm assembly  812  under the direction of control electronics  820 . The control electronics  820  may include a number of integrated circuits  822  coupled to a printed circuit board  824 . The control electronics  820  may be coupled to the voice coil motor assembly  818 , a slider  826 , or the spindle motor assembly  810  using interconnects that can include pins, cables, or wires (not shown). 
     A load beam or suspension  828  is attached to the free end of each actuator arm  816  and cantilevers therefrom. Typically, the suspension  828  is biased generally toward its corresponding data storage disk  806  by a spring-like force. The slider  826  is disposed at or near the free end of each suspension  828 . What is commonly referred to as the read-write head (e.g., transducer) is appropriately mounted as a head unit (not shown) under the slider  826  and is used in hard disk drive read/write operations. The head unit under the slider  826  may utilize various types of read sensor technologies such as anisotropic magnetoresistive (AMR), giant magnetoresistive (GMR), tunneling magnetoresistive (TuMR), other magnetoresistive technologies, or other suitable technologies. 
     The head unit under the slider  826  is connected to a preamplifier  830 , which is interconnected with the control electronics  820  of the hard disk drive  800  by a flex cable  832  that is typically mounted on the actuator arm assembly  812 . Signals are exchanged between the head unit and its corresponding data storage disk  806  for hard disk drive read/write operations. In this regard, the voice coil motor  818  is utilized to pivot the actuator arm assembly  812  to simultaneously move the slider  826  along a path  834  and across the corresponding data storage disk  806  to position the head unit at the appropriate position on the data storage disk  806  for hard disk drive read/write operations. 
     When the hard disk drive  800  is not in operation, the actuator arm assembly  812  is pivoted to a “parked position” to dispose each slider  826  generally at or beyond a perimeter of its corresponding data storage disk  806 , but in any case in vertically spaced relation to its corresponding data storage disk  806 . In this regard, the hard disk drive  800  includes a ramp assembly (not shown) that is disposed beyond a perimeter of the data storage disk  806  to both move the corresponding slider  826  vertically away from its corresponding data storage disk  806  and to also exert somewhat of a retaining force on the actuator arm assembly  812 . 
     Exposed contacts  836  of a drive connector  838  along a side end of the hard disk drive  800  may be used to provide connectivity between circuitry of the hard disk drive  800  and a next level of integration such as an interposer, a circuit board, a cable connector, or an electronic assembly. The drive connector  838  may include jumpers (not shown) or switches (not shown) that may be used to configure the hard disk drive  800  for user specific features or configurations. The jumpers or switches may be recessed and exposed from within the drive connector  838 . 
     As such, provided herein is an apparatus, including a stator assembly including a number of stator teeth; a number of field coils singly disposed on the number of stator teeth; a base configured to support the stator assembly; and a back iron coupled to a hub, wherein the hub is configured to rotate about an axis normal to the base. The apparatus further includes a magnet in the form of a magnetic annulus proximate to each of the number of stator teeth, wherein the number of field coils are operable to cause the hub to rotate via the magnetic annulus. Thus, the stator assembly is operable to cause the magnet to rotate. The magnet is co-formed on the back iron. In some embodiments, a coating surrounds the back iron and the magnetic annulus (e.g. the magnet) thereby acting as a protective coating. 
     In some embodiments, the back iron includes a first cavity and the magnet is a magnetic annulus is in the first cavity. In some embodiments, the apparatus further includes a second magnetic annulus, wherein the back iron includes a second cavity and the second magnetic annulus is in the second cavity of the back iron. In some embodiments, the second magnetic annulus is in a bottom portion of the back iron. In some embodiments, the second magnetic annulus is operable for axial biasing of the hub. In some embodiments, the back iron is operable to provide structural strength to the magnetic annulus (e.g. the magnet). In some embodiments, the magnetic annulus is in contact with a vertical portion of the back iron. In some embodiments the magnet is co-formed to a vertical portion of the back iron. 
     Also provided is an apparatus, including a stator assembly including a number of stator teeth; a number of field coils singly disposed on the number of stator teeth; and a base operable to support the stator assembly. The apparatus further includes a back iron coupled to a hub, wherein the hub is operable to rotate about an axis normal to the base, and wherein the back iron includes a first annular channel; and a first magnetic ring proximate to each of the number of stator teeth, wherein the magnet is formed in the first annular channel of the back iron. In some embodiments, the magnet is a magnetic annulus that is co-formed to the back iron. 
     In some embodiments, the back iron is coupled to three sides of the magnetic annulus. In some embodiments, a portion of the first magnetic ring extends outside of the first annular channel. In some embodiments, the first annular channel is in a vertical portion of the back iron. In some embodiments, the apparatus further includes a second annular channel in the back iron; and a second magnetic ring, wherein the second magnetic ring is formed in the second annular channel. In some embodiments, the second magnetic ring is formed in a bottom portion of the back iron and the second magnetic ring is operable for axial biasing of the hub. In some embodiments, an inner surface of the first magnetic ring is vertically flush with a vertical portion of the back iron. In some embodiments, the top and bottom of the magnetic annulus are not surrounded by the back iron and are therefore substantially free from the back iron. 
     Also is provided is a method, including forming a back iron; applying magnetic material to a portion of the back iron; magnetizing the magnetic material to produce a magnet; and coupling the back iron to a hub of an electric motor. In some embodiments, a mold cavity is formed and defined with the back iron and a mold. In some embodiments, the magnetic material is injected into the cavity and co-formed onto the back iron. In some embodiments, the back iron defines three sides of the mold cavity. 
     In some embodiments, the magnetic material is applied directly to the back iron. In some embodiments, the method further includes applying a coating around the back iron and the magnet. In some embodiments, the magnetic material is applied to the back iron with a mold. In some embodiments, the back iron includes another mold cavity (e.g. a second mold) on a bottom portion of the back iron, and the magnetic material is applied into the second cavity. In some embodiments, another mold cavity is formed with the back iron and the mold. In some embodiments, the magnetic material is co-formed to another mold cavity in the back iron. 
     While embodiments have been described and/or illustrated by means of examples, and while these embodiments and/or examples have been described in considerable detail, it is not the intention of the applicant(s) to restrict or in any way limit the scope of the embodiments to such detail. Additional adaptations and/or modifications of the embodiments may readily appear in light of the described embodiments, and, in its broader aspects, the embodiments may encompass these adaptations and/or modifications. Accordingly, departures may be made from the foregoing embodiments and/or examples without departing from the scope of the embodiments. The implementations described above and other implementations are within the scope of the following claims.