Method for improving flatness and concentricity of lamination stack

Abstract

The invention relates to a method for improving the flatness and concentricity of a lamination stack. A method of forming a stack of laminations for a stator includes sequentially stamping a plurality of annular stator laminations from a continuous sheet metal. The annular stator laminations each comprise an inner surface with a plurality of winding teeth and an outer surface with a plurality of circumferentially spaced radially projecting lugs, the plurality of circumferentially spaced apart radially protruding lugs of each adjacently formed annular stator lamination are circumferentially offset from the circumferentially spaced apart radially protruding lugs of an immediately adjacent annular stator lamination. Each of the annular stator laminations is indexed with respect to an adjacent annular stator by a predetermined angular rotation, and the annular stator laminations are stacked such that circumferentially spaced apart radially protruding lug portions are aligned within the stack.

Description

[0001] introduction

[0002] The information provided in this section is for the purpose of generally presenting the context of the present disclosure. To the extent described in this section, the works of the presently named inventors and aspects of the description that may not constitute prior art at the time of filing are neither explicitly nor implicitly admitted to be prior art to the present disclosure. Technical Field

[0003] The present disclosure relates to stator lamination stacks for electric motors, and more particularly to methods of improving lamination stack flatness and concentricity. Background Art

[0004] Stator laminations are typically stamped from a continuous sheet of metal. Although it is formed to desired tolerances, the continuous sheet of metal will still include variations in thickness across the width of the sheet. The variations in thickness will result in stator laminations having varying thicknesses along the sides of the laminations. When stacked, the variations in steel lamination sheet thickness across the length and across the width of the coil affect the flatness of the lamination stack. For example, if the left side of the coil strip is consistently thicker than the right side, the stator stack produced will lose its verticality and flatness (and will tilt to the right). The present application is directed to improving lamination stack flatness and concentricity.

[0005] The stator stack is formed by stacking the laminations into packs. Progressive die stamping of stator and rotor laminations is a cost-effective method for medium to large volume production. Careful design of the die will ensure optimal performance. Progressive dies perform a series of operations in multiple stages in the die during each press stroke. These simultaneous operations produce parts from a strip of material moving through the die. Each working stage performs one or more die operations, but the strip must move from the first stage through each subsequent stage to produce a complete stator and / or rotor lamination.

[0006] Existing processes assemble individual stacks of laminations as sub-stacks. Therefore, the operator assembles four sub-stacks and rotates them simultaneously during stacking to produce 4 rotations.

[0007] Existing assembly methods have surfaces that are too flat (up to 0.36 mm) for both the stator core and the assembled stator.

[0008] The true position of the lamination stack ID (inside diameter) relative to the reference datum was too high by up to 1 / 4 mm.

[0009] The results of the data collected indicate that the top surface profile and the relationship of ID to OD are of concern. Therefore, it is desirable to reduce the variation in flatness and true position of the ID to improve the assembly of the stator in the housing. Summary of the invention

[0010] According to one aspect of the present disclosure, a method of forming a lamination stack for a stator includes sequentially stamping a plurality of primary annular stator laminations from a continuous sheet of metal. The primary annular stator laminations each include an inner surface having a plurality of winding teeth and an outer surface having a plurality of groups of circumferentially spaced radially protruding ears. All groups of equally spaced radially protruding ears except one group are cut from each annular stator lamination, and each primary annular stator lamination has a remaining group of equally spaced radially protruding ears that are circumferentially offset from the remaining group of equally spaced radially protruding ears of the immediately adjacent annular stator laminations. Each of the annular stator laminations is indexed by a predetermined angular rotation relative to an adjacent annular stator lamination, and the annular stator laminations are stacked so that the groups of equally spaced radially protruding ears are aligned within the stack.

[0011] According to another aspect, the plurality of groups of circumferentially spaced radially projecting ears includes at least two groups of circumferentially spaced radially projecting ears and at most four groups of circumferentially spaced radially projecting ears.

[0012] According to another aspect, the plurality of groups of circumferentially spaced radially projecting ears each include at least three circumferentially spaced radially projecting ears per group.

[0013] According to another aspect, indexing each of the annular stator laminations relative to an adjacent annular stator by a predetermined angular rotation includes indexing at least 22.5 degrees relative to the adjacent annular stator.

[0014] According to another aspect, indexing each of the annular stator laminations relative to an adjacent annular stator by a predetermined angular rotation includes indexing at least 30 degrees relative to the adjacent annular stator.

[0015] According to another aspect, indexing each of the annular stator laminations relative to an adjacent annular stator by a predetermined angular rotation includes indexing at least 45 degrees relative to the adjacent annular stator.

[0016] According to another aspect, each of the plurality of circumferentially spaced sets of radially projecting ears includes at least three ears.

[0017] The method of claim 7, wherein each of the plurality of circumferentially spaced apart groups of radially projecting ears comprises at least four ears.

[0018] According to another aspect, a method of forming a lamination stack for a stator includes sequentially stamping a plurality of annular stator laminations from a continuous sheet of metal, the annular stator laminations each including an inner surface with a plurality of winding teeth and an outer surface with a plurality of circumferentially spaced radially projecting ears, wherein the plurality of circumferentially spaced radially projecting ears of each adjacently formed annular stator lamination is circumferentially offset from the circumferentially spaced radially projecting ears of an immediately adjacent annular stator lamination. Each of the annular stator laminations is indexed a predetermined angular rotation relative to an adjacent annular stator, and the annular stator laminations are stacked such that the circumferentially spaced radially projecting ears are aligned within the stack.

[0019] According to another aspect, the plurality of circumferentially spaced radially projecting ears includes at least three ears.

[0020] According to another aspect, the plurality of circumferentially spaced radially projecting ears includes at least four ears.

[0021] According to another aspect, indexing each of the annular stator laminations relative to an adjacent annular stator by a predetermined angular rotation includes indexing at least 22.5 degrees relative to the adjacent annular stator.

[0022] According to another aspect, indexing each of the annular stator laminations relative to an adjacent annular stator by a predetermined angular rotation includes indexing at least 30 degrees relative to the adjacent annular stator.

[0023] According to another aspect, indexing each of the annular stator laminations relative to an adjacent annular stator by a predetermined angular rotation includes indexing at least 45 degrees relative to the adjacent annular stator.

[0024] According to another aspect, a segmented blank / punch is used to incrementally blank the ears at multiple locations around the perimeter of the lamination.

[0025] According to another aspect, the segmented blanker / punch includes at least two groups of a plurality of punches.

[0026] According to another aspect, the at least two groups of the plurality of punches each include at least three punches.

[0027] According to another aspect, at least three punches of a first group of at least two groups of the plurality of punches are spaced apart from each other at equal intervals.

[0028] According to another aspect, the at least three punches of a second group of the at least two groups of the plurality of punches are equally spaced apart from each other and from the first group of the at least two groups of the plurality of punches.

[0029] The present invention provides the following technical solutions.

[0030] Technical Solution 1. A method for forming a lamination stack for a stator, comprising:

[0031] sequentially stamping a plurality of primary annular stator laminations from a continuous sheet of metal, the primary annular stator laminations each comprising an inner surface with a plurality of winding teeth and an outer surface with a plurality of sets of circumferentially spaced radially projecting ears;

[0032] cutting away all but one set of equally spaced radially projecting ears from each annular stator lamination, with each primary annular stator lamination having a remaining set of equally spaced radially projecting ears that are circumferentially offset from the remaining set of equally spaced radially projecting ears of an immediately adjacent annular stator lamination; and

[0033] Each of the annular stator laminations is indexed a predetermined angular rotation relative to an adjacent annular stator lamination, and the annular stator laminations are stacked such that the sets of equally spaced radially projecting ears are aligned within the stack.

[0034] Technical Solution 2. A method according to Technical Solution 1, wherein the multiple groups of circumferentially spaced radially protruding ears include at least two groups of circumferentially spaced radially protruding ears and at most four groups of circumferentially spaced radially protruding ears.

[0035] Technical Solution 3. A method according to Technical Solution 2, wherein the multiple groups of circumferentially spaced radially protruding ears each include at least three circumferentially spaced radially protruding ears in each group.

[0036] Technical Solution 4. A method according to Technical Solution 1, wherein rotating each of the annular stator laminations relative to an adjacent annular stator by a predetermined angular rotation includes rotating each of the annular stator laminations by at least 22.5 degrees relative to an adjacent annular stator.

[0037] Technical Solution 5. A method according to Technical Solution 1, wherein rotating each of the annular stator laminations by a predetermined angular rotation relative to an adjacent annular stator includes rotating each of the annular stators by at least 30 degrees relative to the adjacent annular stator.

[0038] Technical Solution 6. A method according to Technical Solution 1, wherein rotating each of the annular stator laminations by a predetermined angular rotation relative to an adjacent annular stator includes rotating each of the annular stators by at least 45 degrees relative to the adjacent annular stator.

[0039] Technical Solution 7. A method according to Technical Solution 1, wherein each of the multiple groups of circumferentially spaced radially protruding ears includes at least three ears.

[0040] Technical Solution 8. A method according to Technical Solution 7, wherein each of the multiple groups of circumferentially spaced radially protruding ears includes at least four ears.

[0041] Technical solution 9. A method for forming a lamination stack for a stator, comprising:

[0042] stamping a plurality of annular stator laminations sequentially from a continuous sheet of metal, the annular stator laminations each including an inner surface with a plurality of winding teeth and an outer surface with a plurality of circumferentially spaced radially projecting ears, wherein the plurality of circumferentially spaced radially projecting ears of each adjacently formed annular stator lamination are circumferentially offset from the circumferentially spaced radially projecting ears of an immediately adjacent annular stator lamination; and

[0043] Each of the annular stator laminations is indexed a predetermined angular rotation relative to an adjacent annular stator lamination, and the annular stator laminations are stacked such that the circumferentially spaced radially projecting ears are aligned within the stack.

[0044] Technical Solution 10. The method according to Technical Solution 9, wherein the plurality of circumferentially spaced radially protruding ears include at least three ears.

[0045] Technical Solution 11. A method according to Technical Solution 9, wherein the plurality of circumferentially spaced radially protruding ears include at least four ears.

[0046] Technical Solution 12. A method according to Technical Solution 9, wherein rotating each of the annular stator laminations by a predetermined angular rotation relative to an adjacent annular stator includes rotating each of the annular stators by at least 22.5 degrees relative to an adjacent annular stator.

[0047] Technical Solution 13. A method according to Technical Solution 9, wherein rotating each of the annular stator laminations by a predetermined angular rotation relative to an adjacent annular stator includes rotating each of the annular stators by at least 30 degrees relative to the adjacent annular stator.

[0048] Technical Solution 14. A method according to Technical Solution 9, wherein rotating each of the annular stator laminations by a predetermined angular rotation relative to an adjacent annular stator includes rotating each of the annular stators by at least 45 degrees relative to the adjacent annular stator.

[0049] Technical Solution 15. A method according to Technical Solution 9, wherein a segmented blanker / punch is used to gradually blank ears at multiple locations on the periphery of the laminate.

[0050] Technical Solution 16. A method according to Technical Solution 15, wherein the segmented blanker / punch comprises at least two groups of multiple punches.

[0051] Technical Solution 17. The method according to Technical Solution 16, wherein the at least two groups of multiple punches each include at least three punches.

[0052] Technical Solution 18. The method according to Technical Solution 17, wherein the at least three punches of the first group of the at least two groups of multiple punches are spaced apart from each other at equal intervals.

[0053] Technical Solution 19. A method according to Technical Solution 18, wherein the at least three punches of the second group of the at least two groups of multiple punches are spaced apart from each other at equal intervals and are spaced apart from the first group of the at least two groups of multiple punches.

[0054] Technical Solution 20. A stator lamination stack manufactured according to the method described in Technical Solution 9.

[0055] Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the accompanying drawings.The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The present disclosure will be more fully understood from the detailed description and accompanying drawings, in which:

[0057] Figure 1 is a schematic diagram of a series of stamped stator laminations having ears taken from different lateral portions of a continuous sheet of sheet metal;

[0058] Figure 2 is a perspective view of a stack of stamped stator laminations;

[0059] Figure 3 is a schematic diagram of a series of stamped stator laminations having ears at different lateral portions taken from a continuous sheet of sheet metal according to an alternative method;

[0060] Figure 4 It is used to execute Figure 3 A schematic diagram of an example stamping apparatus for the method depicted in FIG. 1 ; and

[0061] Figure 5 An exemplary punching sequence for the method of the present disclosure is illustrated.

[0062] In the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0063] The present disclosure provides a method to minimize thickness variation and improve the flatness of a stator lamination stack. Figure 2, an exemplary stator lamination stack 10 for an electric motor is shown, which includes a plurality of stator laminations 12, each stator lamination 12 including an annular body 14 having an inner surface with a plurality of stator teeth 16 and an outer surface with a plurality of radially outwardly projecting locating ears 18. The locating ears 18 are configured to engage longitudinal locating slots in the housing of the electric motor so as to secure the stator lamination stack 10 within the motor housing. As shown, the stator lamination stack 10 is well known in the art. Typically, three or four locating ears 18 are used on each stator lamination 12. The total number of stator laminations 12 used in a particular motor application depends on the desired motor application.

[0064] Reference Figure 1 , a method of forming a stator lamination stack according to the principles of the present disclosure will now be described. Figure 1 , shows an exemplary primary stamped stator lamination 12' comprising an annular body 14 having an inner surface with a plurality of stator teeth 16 and an outer surface with a plurality of sets of radially outwardly projecting locating ears 18a, 18b, 18c and 18d. Figure 1 In the exemplary embodiment shown in FIG. 1 , each of the plurality of radially outwardly projecting locating ears 18 a, 18 b, 18 c and 18 d comprises four ears (thus, in FIG. Figure 1 In the embodiment shown in , sixteen (16) locating ears 18 are shown, but it should be understood that each group may include more or fewer locating ears. In the case of sixteen locating ears 18a, 18b, 18c, 18d, each locating ear is spaced 22.5 degrees from each other. During this forming method, a series of primary stamped stator laminations 12' (three of which are shown as 12'1, 12'2, 12'3) are formed. Primary stamped stator laminations 12'1, 12'2, 12'3, ..., 12' n The stator laminations 12a, 12b, 18c, and 18d are retained in their original rotational orientation and all but one set of radially outwardly projecting ears 18a, 18b, 18c, and 18d are removed to form the final stator lamination 12. For each successive stator lamination 121, 122, 123, ..., 12 n , a different set of the ears 18a, 18b, 18c and 18d is maintained for the final stator lamination 12. For example, a set of ears 18a is maintained for the first stator lamination 121, a set of ears 18b is maintained for the second stator lamination 122, a set of ears 18c is maintained for the third stator lamination 123, a set of ears 18d is maintained for the fourth stator lamination 124, and the cycle is repeated for each subsequent sub-set of four stator laminations. Stator laminations 121, 122, 123, ..., 12 n The stator laminations are then stacked in sequence with each successive stator lamination being rotationally "indexed" relative to the previous adjacent stator lamination 12. Figure 1In the embodiment shown in , each subsequent stator lamination 12 can be "indexed" 22.5 degrees (or multiples of 22.5 degrees) relative to the previous adjacent stator lamination in order to align the corresponding remaining sets of ears 18a, 18b, 18c, and 18d of the stator laminations. By successively indexing each successive stator lamination relative to the previous stator lamination, any thickness variations in the successive sheets of sheet metal used to make the stator stampings are rotationally evenly distributed around the circumference of the stator lamination stack 10 to provide a stator lamination stack 10 of more uniform thickness. In other words, blanking multiple ears during the shearing stage of the stator OD and then cutting off the excess ears allows for a smaller angle of rotation of the laminations within the stack to more evenly distribute thickness variations throughout the stack.

[0065] It will be appreciated that by using greater or fewer sets of ears 18a, 18b, 18c, and 18d that are removed in the manner discussed above, the amount by which each subsequent stator lamination 12 can be indexed can be varied. In particular, for a primary stator lamination having three sets of ears 18a, 18b, 18c having four ears each, a total of twelve ears 18 would be provided on the primary stator lamination, and each ear 18 would be separated by 30 degrees. Then, only two sets of the ears 18a, 18b, 18c would be removed from each successive primary stator lamination, and the process would be repeated for every three stator laminations. For this example, a rotational "index" distance of 30 degrees is achieved to allow the stack to evenly distribute thickness variations throughout the stack. Likewise, as Figure 3 As shown in FIG. , using two sets of ears 18a, 18b for a total of eight ears (spaced 45 degrees apart) on the primary stator lamination 12' would allow for the removal of one set of ears and a rotational "indexing" distance of 45 degrees.

[0066] In the process described above, the primary stator laminations are formed with redundant groups of ears. Selected groups of redundant ears are then removed from the primary stator laminations to allow sequential indexing of the stator laminations to evenly distribute thickness variations around the final stator lamination stack 10. Alternatively, as Figure 4As schematically shown in FIG. 1 , the segmented blanker / punch 30 can also be used to gradually punch out four ears 18 at multiple locations on the periphery of the lamination. In the example shown, the segmented blanker punch includes two groups of punches 32a-32d, 34a-34d of four punches each. The four punches 32a-32d of the first group can be used to form four ears 18 that are spaced apart at intervals of 90 degrees from each other. The four punches 34a-34d of the second group are spaced apart at intervals of 90 degrees from each other and are spaced apart at intervals of forty-five degrees from the four punches of the first group. Therefore, for every other stator lamination 12 formed, the ears 18 are circumferentially spaced apart at intervals of 45 degrees for the previously formed and subsequently formed stator laminations 12. The 45-degree interval allows each subsequent stator lamination 12 to be "shifted" 45 degrees or multiples of 45 degrees relative to the previous stator lamination 12 to more evenly distribute thickness variations throughout the stack.

[0067] According to yet another embodiment, the die that blanks / punches the ears 18 can rotate the blank to appropriately produce a lamination having a desired number of ears (typically 3 or 4) that are angularly oriented at a specified angular orientation of 30 degrees or 22.5 degrees, respectively, from the previous lamination. In this case, the outer section of the die that makes the ears 18 rotates about the lamination yoke (the outer cylindrical portion of the lamination) to reposition the ears at an angle of 30 or 22.5 degrees relative to the previous lamination. The system can use a gear or belt drive system to rotate the outer die section relative to the inner section to produce the lamination.

[0068] Thus, for the stator laminations 12 formed according to this example, with the first stator lamination 121 acting as a baseline, the second stator lamination 122 may be formed with the ears 18 offset by 45 degrees, so that the second stator lamination 122 may be indexed 45 degrees relative to the first stator lamination. The third stator lamination 123 may be sequentially formed in the same manner as the first stator lamination 121, but indexed 90 degrees relative to the first lamination 121 when it is added to the stack. The fourth lamination 124 may be sequentially formed in the same manner as the second stator lamination 122, but indexed 90 degrees relative to the second lamination 122 when it is added to the stack. The fifth stator lamination 125 may be sequentially formed in the same manner as the first stator lamination 121, but indexed 180 degrees relative to the first lamination 121 when it is added to the stack. The sixth lamination 126 may be sequentially formed in the same manner as the second stator lamination 122, but indexed 180 degrees relative to the second lamination 122 when it is added to the stack. The seventh stator lamination 127 may be sequentially formed in the same manner as the first stator lamination 121, but indexed 270 degrees relative to the first lamination 121 when it is added to the stack. The eighth lamination 128 may be sequentially formed in the same manner as the second stator lamination 122, but indexed 270 degrees relative to the second lamination 122 when it is added to the stack. The formation of the ears 18 from different rotational positions and the coordinated indexing of the sequence of stator laminations allow for less angular rotation of the laminations within the stack to more evenly distribute thickness variations throughout the stack. Instead of stamping out only 1 set of four ears 90 degrees apart in the prior art design, utilizing sets of ears from 2, 3, or 4 different circumferential positions in different stator laminations (i.e., 1 set of ears every 22.5, 30, 45, 60 degrees, etc.) allows for less angular rotation of the laminations within the stack to more evenly distribute the thickness variation of the stator laminations 12 throughout the stack 10.

[0069] Figure 5 An example progressive stamping operation is illustrated on a continuous lamination strip 40 to first produce a rotor component 42 and then a stator component 12. Existing progressive dies use round fixed cylindrical guides to position the sheets between die stages. However, using spring loaded conical guides to position the sheets between die stages will control and improve the quality of the stack by minimizing eccentricity and lamination offset between the ID and OD of the stator.

[0070] At the first stage A, a perf is used to punch a guide hole 44 in the sheet. Then, at the second stage B, a center perf will punch a rotor inner diameter hole 46. At the third stage C, four additional openings 48 are formed. At the fourth stage D, rotor slots 50 are punched on the outer diameter of the rotor, and the rotor laminations 42 are removed. In the fifth stage E, the stator inner diameter slots 52 are punched. In the sixth stage F, the outer diameter 54 of the primary stator lamination 12' is formed with two sets of ears 18a, 18b. As detailed above, the alternating ear sets 18a, 18b are then removed from each subsequent primary stator lamination 12' to allow for smaller incremental indexing as detailed above.

[0071] The previous description is merely illustrative in nature and is in no way intended to limit the present disclosure, its application or use. The broad teachings of the present disclosure can be implemented in many forms. Therefore, although the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, because after studying the drawings, the specification and the appended claims, other modifications will become apparent. It should be understood that one or more steps in the method can be performed in different orders (or simultaneously) without changing the principles of the present disclosure. In addition, although each embodiment is described above as having certain features, any one or more of those features described with respect to any embodiment of the present disclosure can be implemented in any other embodiment and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the arrangement of one or more embodiments to each other is still within the scope of the present disclosure.

[0072] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "engaged," "coupled," "adjacent," "immediately next to," "on top of," "above," "below," and "disposed on." Unless explicitly described as "directly," when describing a relationship between a first element and a second element in the above disclosure, the relationship may be a direct relationship in which no other intermediate elements exist between the first element and the second element, but may also be an indirect relationship in which one or more intermediate elements (spatially or functionally) exist between the first element and the second element. As used herein, the phrase "at least one of A, B, and C" should be interpreted as representing a logical (A or B or C) using a non-exclusive logical "or," and should not be interpreted as representing "at least one of A, at least one of B, and at least one of C."

Claims

1. A method of forming a lamination stack for a stator, comprising: sequentially stamping a plurality of primary annular stator laminations from a continuous sheet of metal, the primary annular stator laminations each comprising an inner surface with a plurality of winding teeth and an outer surface with a plurality of sets of circumferentially spaced radially projecting ears; cutting away all but one set of equally spaced radially projecting ears from each annular stator lamination, with each primary annular stator lamination having a remaining set of equally spaced radially projecting ears that are circumferentially offset from a remaining set of equally spaced radially projecting ears of an immediately adjacent annular stator lamination; and Each of the annular stator laminations is indexed a predetermined angular rotation relative to an adjacent annular stator lamination, and the annular stator laminations are stacked such that the sets of equally spaced radially projecting ears are aligned within the stack.

2. The method according to claim 1, wherein: The plurality of groups of circumferentially spaced radially projecting ears include at least two groups of circumferentially spaced radially projecting ears and at most four groups of circumferentially spaced radially projecting ears.

3. The method according to claim 2, wherein: The plurality of groups of circumferentially spaced radially projecting ears each include at least three circumferentially spaced radially projecting ears per group.

4. The method according to claim 1, wherein: Indexing each of the annular stator laminations relative to an adjacent annular stator by a predetermined angular rotation includes indexing at least 22.5 degrees relative to an adjacent annular stator.

5. The method according to claim 1, wherein: Indexing each of the annular stator laminations by a predetermined angular rotation relative to an adjacent annular stator includes indexing at least 30 degrees relative to an adjacent annular stator.

6. The method according to claim 1, wherein: Indexing each of the annular stator laminations relative to an adjacent annular stator by a predetermined angular rotation includes indexing at least 45 degrees relative to an adjacent annular stator.

7. The method according to claim 1, wherein: Each of the plurality of circumferentially spaced apart groups of radially projecting ears includes at least three ears.

8. The method according to claim 7, wherein: Each of the plurality of circumferentially spaced apart groups of radially projecting ears includes at least four ears.

9. A method of forming a lamination stack for a stator, comprising: stamping a plurality of annular stator laminations sequentially from a continuous sheet of metal, the annular stator laminations each including an inner surface with a plurality of winding teeth and an outer surface with a plurality of circumferentially spaced radially projecting ears, wherein the plurality of circumferentially spaced radially projecting ears of each adjacently formed annular stator lamination are circumferentially offset from the circumferentially spaced radially projecting ears of an immediately adjacent annular stator lamination; and Each of the annular stator laminations is indexed a predetermined angular rotation relative to an adjacent annular stator lamination, and the annular stator laminations are stacked such that the circumferentially spaced radially projecting ears are aligned within the stack.

10. A stator lamination stack manufactured according to the method of claim 9.

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