Patent Publication Number: US-2022234204-A1

Title: Method and system for assembling a rotor stack for an electric motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to copending applications filed concurrently herewith titled “ROTOR ASSEMBLY METHOD AND SYSTEM EMPLOYING CENTRAL MULTI-TASKING ROBOTIC SYSTEM,” “METHOD AND APPARATUS FOR TRANSFER MOLDING OF ELECTRIC MOTOR CORES AND MAGNETIZABLE INSERTS,” and “INTEGRATED ROBOTIC END EFFECTORS HAVING END OF ARM TOOL GRIPPERS,” which are commonly assigned with the present application and the contents of which are incorporated herein by reference in their entireties. 
     FIELD 
     The present disclosure relates to assembly of a rotor and more particularly to, assembly of a rotor formed of multiple rotor cores. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Recent advancements in electric converters such as electric motors and/or generators relate not only to performance, but also to manufacturing, as the need for electric converters has increased in various industries including automotive. More particularly, in the automotive industry, electric motors can vary across different platforms since powertrain requirements of a small vehicle is different from that of a truck. For example, with respect to the rotor of the electric motor, the overall size of the rotor (e.g., diameter, height, etc.) to the type of magnets installed, can vary platform-to-platform. Such variations can result in complex rigid assembly lines that impede dynamic flexible configurations. 
     These and other issues related to the assembly of a rotor are addressed by the present disclosure. 
     SUMMARY 
     This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features. 
     The present disclosure is directed toward a method of assembling a plurality of rotor cores for an electric converter. The method includes placing, by a core robotic system employing force control feedback, a rotor core on a mandrel, and for each of the plurality of rotor cores, placing, a plurality of magnetizable inserts into a plurality of cavities in the rotor core by an insert assembly robotic (IAR) system employing force control feedback. 
     The following provides one or more variations of this method, which may be implemented individually or in any combination: 
     In some variations, the IAR system includes a force control end-effector configured to hold one or more magnetizable inserts, and placing the plurality of magnetizable inserts further includes acquiring, by the force control end-effector, one or more magnetizable inserts from the plurality of magnetizable inserts, aligning the one or more magnetizable inserts with one or more cavities among the plurality of cavities, and releasing, by the force control end-effector, the one or more magnetizable inserts into the one or more cavities to have the one or more magnetizable inserts independently descend into the one or more of cavities. 
     In some variations, the IAR system includes a plurality of insert assembly robots to place the plurality of magnetizable inserts into the plurality of cavities and each of the plurality of insert assembly robots includes the force control end-effector. 
     In some variations, the method further includes rotating the mandrel to align empty cavities of the rotor core with the IAR system to receive the one or more magnetizable inserts from among the plurality of magnetizable inserts. 
     In some variations, the one or more magnetizable inserts are acquired at a first orientation of the end-effector and are aligned and released in the one or more cavities at a second orientation different from that of the first orientation, and 
     In some variations, the method further includes changing orientation of the end-effector from the first orientation to the second orientation after the magnetizable inserts are acquired. 
     In some variations, two or more magnetizable inserts are acquired and aligning the two or more magnetizable inserts further includes aligning and positioning, by the force control end-effector, a first magnetizable insert of the two or more magnetizable inserts with a first cavity of two or more cavities among the plurality of cavities based on a force feedback detected a load cell of the force control end-effector, and aligning and positioning, by the force control end-effector, a second magnetizable insert of the two or more magnetizable inserts with a second cavity of the two or more cavities in response to the first magnetizable insert being aligned with the first cavity. 
     In some variations, to align and position the second magnetizable insert, the method further includes moving a portion of the force control end-effector having the second magnetizable insert a set offset to align with the second cavity. 
     In some variations, placing the magnetizable inserts further includes gripping, at a first orientation, one or more magnetizable inserts from the plurality of magnetizable inserts by the IAR system, and aligning and positioning, at a second orientation different from the first orientation, the one or more magnetizable inserts at one or more cavities among the plurality of cavities based on a force feedback detected by the IAR system. 
     In some variations, placing the magnetizable inserts further includes releasing, by the IAR system, the one or more magnetizable inserts into the one or more cavities, wherein the one or more magnetizable independently descend into the one or more cavities. 
     In some variations, the plurality of magnetizable inserts includes a first set of magnetizable inserts and a second set of magnetizable inserts, where the first set of magnetizable inserts is of a different size than that of the second set of magnetizable inserts. 
     In some variations, placing the magnetizable inserts further comprises sequentially placing N magnetizable inserts at a time into N cavities among the plurality of cavities, where N is a number that is less than a total number of magnetizable inserts to be placed. 
     In some variations, sequentially placing the magnetizable inserts further includes rotating the mandrel to align N empty cavities of the rotor core with the IAR system to receive the N magnetizable inserts. 
     In some variations, placing the rotor core on the mandrel further includes aligning, by the core robotic system, an alignment feature at an inner diameter of the rotor core with an alignment feature at an outer diameter of the mandrel based on a force feedback detected by the core robotic system, and translationally moving, by the core robotic system, the rotor core along the mandrel based on the force feedback detected by the core robotic system. 
     In some variations, after the plurality of magnetizable inserts are placed in a first rotor core from among the plurality of rotor cores, the method further includes aligning, by the core robotic system, a second rotor core from among the plurality of rotor cores on the mandrel and the first rotor core based on the force feedback. 
     In some variations, the method further includes controlling, by a control system, movement of the core robotic system and the IAR system to have the core robotic system acquire the second rotor core prior to the IAR system completing placement of the plurality of magnetizable inserts into the plurality of cavities. 
     In some variations, the method further includes transferring, by the core robotic system, the plurality of rotor cores with the mandrel in response to completion of the assembly, and placing, by the core robotic system, a second mandrel for subsequent assembly of rotor cores. 
     In some variations, the method further includes monitoring force control feedback from the core robotic system, the IAR system or a combination thereof; and determining an abnormal installation operation in response to the monitored force control feedback exceeding a desired parameter. 
     In one form, the present disclosure is directed toward, a method of assembling a plurality of rotor cores for an electric converter. The method includes placing, by a core robotic system employing force control feedback, a rotor core on a mandrel. For each of the plurality of rotor cores, the method further includes acquiring, by an insert assembly robotic (IAR) system, N magnetizable inserts among a plurality of magnetizable inserts at a time into N cavities among a plurality of cavities employing force control feedback, where N is a number that is less than a total number of magnetizable inserts to be placed, aligning, by the IAR system, the N magnetizable inserts with the N cavities among the plurality of cavities by employing force control feedback, and releasing by the IAR system, the N magnetizable inserts into the N cavities to have the N magnetizable inserts independently descend into the N cavities. 
     The following provides one or more variations of this method, which may be implemented individually or in any combination: 
     In some variations, the IAR system includes at least one force control end-effector configured to hold one or more magnetizable inserts. 
     In some variations, the method further includes controlling movement of the core robotic system and the IAR system to have the core robotic system acquire a subsequent rotor core from among the plurality of rotor cores prior to the IAR system completing placement of the plurality of magnetizable inserts into the plurality of cavities. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a rotor in accordance with the present disclosure; 
         FIGS. 2A and 2B  are exploded views of a mandrel having rotor core and magnets in accordance with the present disclosure; 
         FIG. 3  illustrates a rotor assembly cell in accordance with the present disclosure; 
         FIGS. 4A, 4B, and 4C  illustrate movement of an end-effector tool of an insert assembly robot; and 
         FIG. 5  is a flowchart of an exemplary assembly routine of the rotor cores in accordance with the present disclosure. 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     In an exemplary application, a rotor for an electric converter, such as an electric motor or a generator, comprises a plurality of rotor cores fixedly secured to one another and a plurality of magnets disposed within the rotor cores, where the rotor cores and the plurality of magnets are fixedly secured to one another. The present disclosure provides a method of assembling the rotor cores using force control feedback robotic systems that employ force control technology to monitor and adjust automated processes to, for example, position rotor cores on a mandrel and place magnetizable inserts into cavities defined within the rotor cores. In one form, the tolerance range associated with the size of the cavity and the magnetizable inserts is typically tight (e.g., less than a millimeter) making it difficult to use other monitoring techniques such as a vision system to control operation of a robotic system. The assembly method described herein can be employed for different size rotor cores and/or magnetizable inserts and using the same or substantially the same robotic systems. While the rotor assembly method is described in association with an electric motor, the same method can be employed with other suitable electric converters, such as a generator. 
     Referring to  FIGS. 1, 2A, and 2B , a rotor assembly  100  of an electric motor includes a plurality of rotor cores  102 A to  102 D (collectively “rotor cores  102 ”) and a plurality of magnetizable inserts  104  that are disposed in the rotor cores  102 . The rotor cores  102  are stackingly and coaxially arranged with one another about a mandrel  106 . Each rotor core  102  defines a plurality of cavities  108  for receiving the plurality of magnetizable inserts  104 . In one application, the plurality of cavities  108  may be of different sizes to accommodate different size magnetizable inserts  104 . For example, as illustrated, the plurality of cavities  108  includes a first set of cavities  108 A and a second set of cavities  108 B, where the first set of cavities  108 A are smaller in size than that of the second set of cavities  108 B. In one form, the first set of cavities  108 A and the second set of cavities  108 B are arranged in pairs to form first set pairs and second set pairs that are circumferentially distributed about the rotor core  102  and are arranged such that a pair of the first set of cavities  108 A is disposed between a pair of the second set of cavities  108 B and an outer perimeter  110  of the rotor core  102 . 
     The magnetizable inserts  104  include a material(s) having ferromagnetic properties such as, but not limited to, iron, neodymium, and nickel. Accordingly, the magnetizable inserts do not exhibit magnetic properties during the rotor assembly, and only become magnets after undergoing a magnetizing process performed after the rotor is assembled. In one form, the plurality of magnetizable inserts  104  may be of different sizes. For example, as illustrated, the inserts  104  includes a first set of magnetizable inserts  104 A to be disposed within the first set of cavities  108 A and a second set of magnetizable inserts  104 B to be disposed within the second set of cavities  108 B, where the size of the first set of magnetizable inserts  104 A is smaller than that of the second set of magnetizable inserts  104 B. In one form, the first set of magnetizable inserts  104 A form an outer magnetizable insert ring and the second set of magnetizable inserts  104 B form an inner ring magnetizable insert ring. 
     While the rotor cores  102  are provided as having different size cavities  108  for different size magnetizable inserts  104 , the rotor cores may be configured in other suitable ways. For example, the rotor core may only include one size of magnetizable inserts and thus, only have one size cavities. In addition, the cavities do not have to be arranged in pairs as described and illustrated in the figures, and can be configured in various suitable ways. In another example, the rotor core is configured to have one or more magnetizable insert rings disposed circumferentially along the rotor core. Accordingly, the present disclosure is applicable to other types of rotor cores having different cavities and/or magnetizable inserts. 
     In one form, to assist in the assembly process, the rotor cores  102  includes one or more alignment features at an inner diameter  120  to correspond with one or more alignment features provided at an outer diameter  122  of the mandrel  106 . For example, referring to  FIG. 2B , the rotor core  102 C has, as an alignment feature, tabs  124  extending radially inward at the inner diameter  120  of the rotor core  102 C, and the mandrel  106  has, as an alignment feature, slots  126  defined longitudinally along the outer diameter  122  of the mandrel  106 . The tabs  124  of the rotor core  120  and the slots  126  are configured such that the tabs  124  extend into or mate with the slots  126  and the tabs  124  may travel along the slot  126  during assembly. While specific example of the alignment features for the rotor core  102  and the mandrel  106  are shown, other suitable alignment features may also be used. 
     With reference to  FIG. 3 , in one form, a rotor assembly cell  200  is a manufacturing cell to assemble and stack a plurality of rotor cores with a plurality of magnetizable inserts. The rotor assembly cell  200  includes a core robotic system  202 , an insert assembly robotic (IAR) system  204  having a first insert assembly (IA) robot  206 A and a second IA robot  206 B (collectively “IA robot  206 ”), and a central controller  208 . As described further herein, the core robotic system  202  is configured to assemble rotor cores  210 A to  210 D (collectively “rotor cores  210 ”) on to a mandrel  212  and the IAR system  204  is configured to place the magnetizable inserts in cavities of the rotor cores  212 . In one form, the central controller  208  is configured to control the operation of the core robotic system  202  and the IAR system  204  to coordinate movement therebetween and thus, assembly of the rotor cores  210 . In the following, the core robotic system  202  and the IAR system  204  may collectively be referred to as robotic systems  202  and  204 . In one form, the rotor cores  210  and the mandrel  212  are provided as the rotor cores  102  and the mandrel  106 , respectively, and thus, the rotor cores  210  are assembled with magnetizable inserts that are similar to magnetizable inserts  104 . 
     The core robotic system  202  is a multi-axal industrial robotic arm  214  with an end-of-arm tool  216  having a rotor core end effector  218  with an integrated load cell  220  to provide force feedback. Specifically, the load cell  220  is configured to detect a force and torque having multiple degree of freedom (e.g., 6-degrees freedom) and output the detected force and torque as an electrical signal, which can then be analyzed. The load cell  220  may be strain gauge and/or other suitable force detecting device and is configured to detect along multiple axis. 
     In one form, the rotor core end effector  218  includes two opposing elongated members  222  having a dual V shaped portion or any number of geometries configured to interface with the outer perimeter of the rotor core  210 . Specifically, the end-of-arm tool  216  is configured to pick-up the rotor core  210  from a core staging area  224  and align and assemble the rotor core  210  on the mandrel  212 . While a specific rotor core end-effector  218  is illustrated, the rotor core end effector  218  having the integrated load cell  220  may be configured in other suitable ways. 
     The core robotic system  202  further includes a controller  226  (i.e., a core controller  226 ) for controlling movement of the robotic arm  214 . In one form, the core controller  226  is configured to employ force control based positioning in which the core robotic system  202  automatically adjusts movement of the robotic arm  214  having end-of-arm tool  216  from a programmed path based on force feedback detected by the load cell  220 . For example, if the force feedback is greater than a defined value or profile for the particular operation being performed, which may also be provided as a desired parameter, the core controller  226  adjusts the position of the end-of-arm tool  216  until the force feedback coincides with the defined value/profile. Alternatively, if the force feedback does not coincide with the desired parameter, the core controller  226  determines the occurrence of an abnormal installation operation and notifies the central controller  208 . 
     In one form, the IAR system  204  includes two IA robots, where the first IA robot  206 A is configured to place a first set of magnetizable inserts into a first set of cavities of the rotor core  210  and the second IA robot  206 B is configured to place a second set of magnetizable inserts into a second set of cavities. In one form, the IA robots  206  are multi-axial (e.g., six axis) industrial robotic arms  228 A and  228 B with end-of-arm tools  230 A and  230 B having gripper end-effectors  232 A and  232 B with integrated load cells  234 A and  234 B to provide force feedback similar to the load cell  220 . In the following the industrial robotic arms  228 A and  228 B are collectively referred to as “industrial robotic arms  228 ,” the end-of-arm tools  230 A and  230 B are collectively referred to as “end-of-arm tools  230 ,” the gripper end-effectors  232 A and  232 B are collectively referred to as “gripper end-effectors  232 ,” and load cells  234 A and  234 B are collectively referred to as “load cells  234 .” The end-of-arm tools  230  may also be referred to as force control end-effector(s). 
     In one form, each of the gripper end-effectors  232  is provided as a two-finger grippers configured to retrieve and grip a magnetizable insert. In one form, the end-of-arm tools  230  are further configured to acquire the magnetizable inserts at a first orientation and to align and release the inserts in respective cavities at a second orientation different from that of the first orientation. For example, with reference to  FIG. 4A to 4C , the end-of-arm tool  230  is configured to retrieve magnetizable inserts  231 A and  231 B at a first orientation provided along an X-Y plane ( FIG. 4A ) and then change orientation to align the inserts  231 A and  231 B above a core  233  along the Y-Z plane. In addition, in one form, at least one of the finger grippers of the gripper end-effector  232  is pivotable about an insert installation axis (e.g., axis Z) to position the inserts  231 A and  231 B in the cavities (not shown) that are skewed or slanted from one another (e.g., cavities in  FIGS. 2A and 2B ). An example of such an end-of-arm tool for the IA robot is disclosed in Applicant&#39;s co-pending application titled “INTEGRATED ROBOTIC END EFFECTORS HAVING END OF ARM TOOL GRIPPERS” which is commonly owned with the present application and the contents of which are incorporated herein by reference in its entirety. While the gripper end-effectors  232  are illustrated as having a pair of two-finger grippers, the gripper end-effector  232  may include one or more two-finger grippers to retrieve one or more magnetizable inserts. 
     The IAR system  204  further includes one or more controllers  238  (i.e., IAR controllers  238 A and  238 B in  FIG. 3 ) for controlling movement of the robotic arms  228 . In one form, similar to the core controller  226 , the IAR controllers  238  are configured to employ force control based positioning in which the IA robots  206  automatically adjusts from a programmed path based on force feedback detected by the load cells  234 . For example, if the force feedback is greater than a defined value or profile (i.e., desired parameter) for the particular operation being performed such as, aligning and positioning magnetizable inserts with respective cavities, the IAR controllers  238  adjust the position of the end-of-arm tools  230  until the force feedback resistance coincides with the defined valued/profile. Alternatively, similar to the core controller  226 , if the force feedback does not coincide with the desired parameter, the IAR controllers  238  determines the occurrence of an abnormal installation operation and notifies the central controller  208 . 
     While the IAR system  204  includes two IA robots  206 , the IAR system  204  may include one or more IA robots  206  based on, for example, the configuration of the rotor cores, the manufacturing parameters (e.g., cycle time, part assembly quota, etc.), among other considerations. In addition, an IA robot may be configured to install different size magnetizable inserts, and thus, the IAR system  204  is not required to have different IA robot for different sized magnetizable inserts. 
     By employing force control feedback, the robotic systems  202  and  204  are able to learn and adapt to the assembly process allowing flexibility. Accordingly, the core robotic system  202  is able to adapt to the assembly process allowing flexibility with respect to, for example, placement and positioning of rotor cores  210  irrespective of the size of the rotor core. In addition, the IAR system  204  can adapt to manufacturing tolerances associated with the cavities of the rotor cores  210 . 
     In one form, the central controller  208  is configured to synchronously control the robotic systems  202  and  204  to assemble the rotor cores  210  and is communicably coupled to the robotic systems  202  and  204  and more specifically, the core controller  226  and the IARs controller  238 , as illustrated by dash lines  225 ,  227  and  229  in  FIG. 3 . The central controller  208  may include a controller and/or a programmed logical controller (PLC) to execute computer readable instructions for performing the operations described herein and a user interface (not shown), such as a touchscreen display, a speaker, a microphone, among others. In particular, in one form, the central controller  208  is configured to centrally control the motion of the robotic system  202  and  204  to improve overall assembly process efficiency and achieve manufacturing metrics such as cycle time and jobs per hour. 
     In one form, the central controller  208  is configured to monitor operations of the robotic systems  202  and  204 , and/or coordinate movement of the robotic systems  202  and  204 , among other functions such as issue a notification if an abnormal operation has occurred. More particularly, the robotic systems  202  and  204  may transmit data to the central controller  208  regarding whether a rotor core is positioned on the mandrel, whether the IAR system  204  has placed magnetizable inserts into cavities, and/or an occurrence of an abnormal operation, among other information regarding the processes performed by respective robotic systems  202  and  204 . Based on these determinations, the central controller  208  is configured to instruct the robotic systems  202  and  204  on performing subsequent steps such as having the IAR system  204  place next set of magnetizable inserts, have the core robotic system  202  position the next rotor core onto the mandrel, have the core robotic system  202  transfer the assembled rotor cores, and/or stop the rotor assembly and issue a notification to the user regarding the abnormal operation. 
     Furthermore, in one form, the central controller  208  is configured to obtain data regarding the force control feedback performed by the robotic systems  202  and  204  and analyze the data to determine trends associated with the rotor assembly process. For example, the central controller  208  is configured to associate the force feedback with abnormal operations to track number of occurrences which can then be used to detect quality issues in the rotor cores and/or the magnetizable inserts. In another example, the central controller  208  is further configured to include machine learning logic to improve automation of the tasks by recognizing patterns in force feedback and positional adjustments made to perform an installation. 
     In one form, the central controller  208 , the core controller  226 , and the IARs controller  238  form a control system for controlling the operations the described herein. In one variation, the central controller  208  may be omitted and thus, the control system includes the core controller  226  and the IARs controller  238  for performing the operations described herein. For example, the core controller  226  and the IARs controllers  238  are communicably coupled to one another via wired and/or wireless communication links to coordinate operations and transmit notifications. In addition, the core controller  226  and/or the IARs controllers  238  are configured to detect abnormal operations of the robotic system  202  and  204 , determine trends associated with the rotor assembly process, and/or employ learning logic to improve automation of the tasks, as described above with the central controller  208 . 
     In one form, the rotor assembly cell  200  also include a worktable  240  and magnetizable insert cartridge feeders  242 A and  242 B (collectively “insert cartridge feeders  242 ”). The worktable  240  supports the rotor core(s)  210  and the mandrel  212  and, in one form, is rotatable. More particularly, in one form, the worktable  240  is operable by the central controller  208 , as represented by dashed line  241  in  FIG. 3 , to automatically rotate an incremental amount to align the IAR system  204  with cavities of the rotor core  210 . If the central controller  208  is not employed, the worktable  240  may be operable by the core controller  226  and/or the IARs controllers  238 . It should be readily understood that rotatable worktable  240  is not required for aligning the cavities with the IAR system  204 . For example, the IAR system  204  may employ multiple IA robots  206  that are configured to sequential place the inserts in the cavities. 
     The insert cartridge feeders  242  are configured to hold and dispense the magnetizable inserts to be assembled in the rotor core, and one or more cartridge feeders  242  may be provided for each of the IA robots  206 . In the example application, the insert cartridge feeders  242 A for the first IA robot  206 A holds the first set of magnetizable inserts and the insert cartridge feeders  242 B for the second IAR hold the second set of magnetizable inserts. In an example application, an insert cartridge feeder  242  includes a cartridge  244  holding multiple magnetizable inserts from the plurality of magnetizable inserts and a pneumatic slide  246  to dispense a single magnetizable insert at a time from the cartridge  244 . In the example application, the cartridge  244  is arranged as a vertical tower. While four cartridge feeders  242  are illustrated, one or more cartridge feeders  242  may be employed based on the number of IA robots, the type of magnetizable inserts, among other considerations. In addition, while specific cartridge feeders are illustrated other suitable dispensers may be used for automatically dispensing the magnetizable inserts. 
     Referring to  FIG. 5 , an example assembly routine  400  performed with the rotor assembly cell  200  is provided. At  402 , the core robotic system  202  places a first rotor  210 A on the worktable with the mandrel  212 . That is, in one form, the first rotor core  210  from among the plurality of rotor cores is preassembled with the mandrel  212  and provided at the pallet area  224  with the other rotor cores  210 B,  210 C,  210 D. As such, at  402 , the core robotic system  202  picks up and transfers the first rotor core with the mandrel to the worktable  240  and in one form, transmits a signal indicating completion of placement to the central controller  208  to trigger placement of magnetizable inserts. 
     At  404 , the IAR system  204  places a plurality of magnetizable inserts into a plurality of cavities in the rotor core (i.e., the first rotor core). Specifically, the first IA robot  206 A obtains and grips one or more magnetizable inserts from the first set of magnetizable inserts provided at the insert cartridge feeders  242 A. The first IA robot  206 A then aligns and positions the magnetizable inserts from the first set of magnetizable inserts into one or more cavities from the first set of cavities based on a force feedback detected by the load cell of the first IA robot  206 . In one form, the one or more cavities from the first set of cavities are directly adjacent to one another. In another form, one or more cavities are separated from another by at least one other cavity. 
     In one form, in aligning the magnetizable inserts, the first IA robot  206 A is configured to position and align a first magnetizable insert into a first cavity, and once aligned, position and align the other magnetizable insert(s) based on a set offset. Accordingly, the magnetizable inserts are staggeredly placed in the cavities. In one form, in positioning the magnetizable inserts, the first IA robot  206 A is configured to release the one or more of magnetizable inserts from the first set of magnetizable inserts into the one or more of cavities, such that the one or more of magnetizable inserts from the first set of magnetizable inserts independently descend into the one or more of cavities. That is, the magnetizable inserts fall into respective cavities via gravity. In another application, the first IA robot  206 A may apply some force to the one or more of magnetizable inserts to position them within the cavity. 
     The second IA robot  206 B obtains and grips one or more magnetizable inserts from the second set of magnetizable inserts provided at the insert cartridge feeders  242 B, and performs in a similar manner as that of the first IA robot  206 A to align and position of the magnetizable inserts with one or more cavities from the second set of cavities. Thus, details regarding such operation is omitted for brevity. 
     At  404 , the central controller  208  coordinates movement of the IA robots  206 A and  206 B such that the magnetizable inserts from the first set of magnetizable inserts and the second set of magnetizable inserts are positioned at about the same time. Once the magnetizable inserts are placed, the IAR system  204  notifies the central controller  208  and the central controller  208  automatically rotates the mandrel  212  having the rotor core  210 A to align empty cavities of the rotor core  210 A with the IAR system  204  to place the next set of magnetizable inserts into respective cavities. For example, the central controller  208  rotates the worktable  240  supporting the mandrel  212  and the rotor core(s)  210  to align the empty cavities. In one form, at  404 , the central controller  208  is configured to track the placement of the magnetizable inserts based on, for example, the number of rotations, the number of completion notifications from the IAR system  204 , and/or the number of magnetizable inserts retrieved from the insert cartridge feeders  242 , among other methods. 
     At  406 , after the plurality of magnetizable inserts are assembled in the plurality of cavities, the central controller  208  determines if additional rotor cores  210  are to be assembled. For example, the central controller  208  may maintain a counter for determining the number of rotor cores  210  assembled. If all the rotor cores  210  are assembled, the central controller  208  instructs the core robotic system  202  to transfer the stacked rotor cores. Specifically, the core robotic system  202 , at  408 , transfers the rotor cores  210  with the mandrel  212  from the worktable  240  to a second area such as a mold-press operation. 
     If additional rotor cores  210  are to be assembled, the core robotic system  202 , at  408 , acquires the next rotor core  210  from the pallet  224  and assembles it onto the mandrel  212 . In one form, with the rotor core  210  and mandrel  212  having alignment features as described above, the core robotic system  202 , using force feedback detected by the load cell, aligns the tabs of the rotor core  210  with the slots of the mandrel  212  and then translationally moves the rotor core  210  along the mandrel  212  until the rotor core  210  abuts against the preceding rotor core  210 . Once the new rotor core  210  is positioned the routine proceeds to placing the magnetizable inserts, at  404 . 
     It should be readily understood that the routine  400  is for exemplary purposes and that other routines may be provided. For example, in lieu of a first rotor core preassembled with the mandrel, the routine may place a mandrel stand onto the worktable and then place the first rotor core onto the mandrel. In another example, a vision system may be provided within the rotor assembly system to monitor macro motions such as movement of rotor cores, retrieval of magnetizable inserts, transfer of rotor core, among other processes. 
     Furthermore, the routine  400  may also vary based on the configuration of the rotor assembly cell and more particularly, the number of insert assembly robots of the IAR system. In one form, the rotor assembly cell may sequentially place N magnetizable inserts at a time into N cavities among the plurality of cavities, wherein N is a number that is less than a total number of magnetizable inserts to be placed. For example, in the application provided herein, N is 4 since there are two insert assembly robots. In another example, additional insert assembly robots may be provided such that all the magnetizable inserts are placed into the cavities at once and/or without rotating the mandrel having the rotor cores. 
     Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word “about” or “approximately” in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability. 
     As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” 
     The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure. 
     In this application, the term “controller” and/or “module” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality, such as, but not limited to, movement drivers and systems, transceivers, routers, input/output interface hardware, among others; or a combination of some or all of the above, such as in a system-on-chip. 
     The term memory is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).