Method of controlling electric motor resin transfer molding process

Abstract

The present disclosure provides a method of controlling an electric motor resin transfer molding process. A method of transfer molding a rotor core stack includes assembling a mandrel and a runner plate between a jig press and a plunger; determining a final clamp press position, a nominal clamp press position, and a nominal plunger position; calculating height deviation; and calculating a standardized position of the plunger. The plunger is moved at a first speed until the plunger contacts liquid polymer within a reservoir between the runner plate and the plunger. The plunger is moved at a second speed until the plunger reaches the standardized position to extrude the liquid polymer in the reservoir through the runner plate and into the rotor core stack. The plunger speed is controlled to maintain a constant pressure between the plunger and the liquid polymer until transfer of the liquid polymer is completed and the plunger is stopped at a final plunger position.

Description

Technical Field

[0001] The present disclosure relates to a method for transfer molding a rotor core for an electric traction motor. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] Electric traction motors are used to provide propulsion in electric vehicles and hybrid electric vehicles. Electric traction motors conventionally include a stationary component or stator and a rotating component or rotor. The rotor includes a rotor core stack and magnets inserted into cavities of the rotor core stack. The magnets are sealed in the rotor core stack with a thermosetting resin during a resin transfer molding pressing process.

[0004] During the resin transfer molding process, a press clamps the rotor core stack between a mandrel and a runner plate via the bottom of the press and the top of the press. Raw resin is placed in a reservoir located above the runner plate and heated to a liquid state. A plunger moves at a set speed and presses the liquid resin through the runner plate to fill most of the cavities around the magnets in the rotor core stack. Once the plunger reaches a predetermined position, the plunger moves at a variable speed to maintain a set pressure, thereby filling the remaining cavities in the rotor core stack with liquid resin over a set period of time. Then, the plunger stops and remains in a final position so that the liquid resin can cure. Once the resin cures into a solid state, the magnets are permanently sealed within the rotor core stack.

[0005] The point at which the plunger switches from moving at a constant speed to moving at a variable speed directly affects the quality of the rotor core stack. If the switch occurs too early, the liquid resin may not completely fill all the cavities in the rotor core stack. If the switch occurs too late, the pressure may peak, causing the liquid resin to be extruded from the rotor core stack. Having a fixed position for the plunger to switch from moving at a constant speed to moving at a variable speed does not account for variations between the volumes of the cavities in the rotor core stack. For this reason, for some rotor core stacks, the switch may occur too early, while for other rotor core stacks, the switch may occur too late, resulting in an increase in quality problems during the transfer molding process.

[0006] The present disclosure addresses challenges related to variations in the molding process in an electric motor rotor stack. Summary of the Invention

[0007] This section provides an overview of the present disclosure and is not a full disclosure of its entire scope or all of its features.

[0008] In one form of the present disclosure, a method for polymer transfer molding a rotor core includes: stacking and assembling the rotor core between a mandrel and a runner plate, the runner plate being between a clamp press and a plunger; determining a final clamp press position of the clamp press, a nominal clamp press position of the clamp press, and a nominal plunger position; calculating a height offset; calculating a normalized position of the plunger by adding the nominal plunger position and the height offset; moving the plunger at a first speed until the plunger reaches an initial position; adjusting the speed of the plunger to a second speed until the plunger reaches the normalized position, wherein the plunger extrudes liquid polymer in a reservoir between the runner plate and the plunger through the runner plate and into the rotor core stack; and controlling the speed of the plunger to maintain a constant pressure between the plunger and the liquid polymer until the liquid polymer transfer is complete and the plunger stops at a final plunger position.

[0009] In variants of the method that can be implemented individually or in combination: calculating the height offset of the rotor core stack further includes calculating the difference between the final clamp press position and the nominal clamp press position of the clamp press to determine a position difference; calculating the height offset of the rotor core stack further includes normalizing the plunger cross-sectional area of the bore of the plunger by the cross-sectional area of the rotor core stack to determine a normalized area; the cross-sectional area of the rotor core stack is the cross-sectional area of a plurality of cavities of the rotor core stack; the final clamp press position of the clamp press is the distance between the top surface of the clamp press and the top surface of the runner plate located on the top surface of the rotor core stack; the nominal plunger position is the distance between the bottom surface of the plunger and the top surface of the runner plate located on the top surface of the rotor core stack; determining the nominal clamp press position of the clamp press further includes adding the height of the rotor core stack, the height of the mandrel, and the height of the runner plate; determining the nominal plunger position further includes averaging a plurality of final plunger positions from a data set; the nominal plunger position is at a predetermined distance above the average final plunger position; and holding the plunger at the final plunger position for a specified time to cure the liquid polymer.

[0010] In another form, a method of polymer transfer molding a rotor core stack includes: assembling the rotor core stack between a mandrel and a runner plate, the runner plate being between a clamp press and a plunger; determining a final clamp press position of the clamp press, a nominal clamp press position of the clamp press, and a nominal plunger position of the plunger; calculating a difference between the final clamp press position and the nominal clamp press position of the clamp press to determine a position difference; normalizing a plunger cross-sectional area of a bore of the plunger with a cross-sectional area of a plurality of cavities of the rotor core stack; calculating a height offset by multiplying the normalized area and the position difference; calculating a normalized position of the plunger by adding the nominal plunger position and the height offset; moving the plunger at a first speed until the plunger reaches an initial position; adjusting the speed of the plunger to a second speed until the plunger reaches the normalized position, wherein the plunger extrudes a liquid polymer in a reservoir between the runner plate and the plunger through the runner plate and into the rotor core stack; controlling the speed of the plunger to maintain a constant pressure between the plunger and the liquid polymer until the liquid polymer transfer is complete and the plunger stops at a final plunger position; and holding the plunger at the final plunger position for a specified time to cure the liquid polymer.

[0011] In variations of the method that can be implemented individually or in combination: the final clamp press position of the clamp press is the distance between the top surface of the clamp press and the top surface of the runner plate located on the top surface of the rotor core stack; the nominal plunger position is the distance between the bottom surface of the plunger and the top surface of the runner plate located on the top surface of the rotor core stack; determining the nominal clamp press position further includes adding the height of the rotor core stack, the height of the mandrel, and the height of the runner plate; determining the nominal plunger position further includes averaging a plurality of final plunger positions from a data set; and the nominal plunger position is at a predetermined distance above the average final plunger position.

[0012] In yet another form of the present disclosure, a system for polymer transfer molding a rotor core stack includes: a rotor core stack; a clamp press disposed below a bottom surface of the rotor core stack; a runner plate disposed above a top surface of the rotor core stack; a plunger disposed above the runner plate; at least one sensor for determining a final clamp press position of the clamp press and a final plunger position of the plunger; and a controller for determining a nominal clamp press position and a nominal plunger position, calculating a height offset of the rotor core stack, and calculating a normalized position of the plunger by adding the nominal plunger position and the height offset, wherein the controller controls movement of the plunger.

[0013] In a variant of the system that can be implemented individually or in combination: the height offset is the position difference multiplied by a normalized area, wherein the position difference is the difference between the final clamp press position of the clamp press and the nominal clamp press position, and wherein the normalized area is the cross-sectional area of the rotor core stack divided by the plunger cross-sectional area of the bore of the plunger; the cross-sectional area of the rotor core stack is the cross-sectional area of a plurality of cavities of the rotor core stack; and the nominal plunger position is the average of a plurality of final plunger positions from a sample data set offset by a predetermined distance.

[0014] Based on the description provided herein, additional applicable fields will become apparent. It should be understood that the description and specific examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] To better understand the present disclosure, various forms of the present disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0016] Figure 1 A schematic view of a rotor core stack in a transfer molding press according to the present disclosure is depicted;

[0017] Figure 2 A locator for a rotor core stack according to the present disclosure is depicted;

[0018] Figure 3A A schematic view of a nominal clamp press position and a nominal plunger position of a rotor core stack in a transfer molding press according to the present disclosure is depicted;

[0019] Figure 3B A schematic view of a normalized plunger position of a rotor core stack in a transfer molding press according to the present disclosure is depicted;

[0020] Figure 3CDepicts a schematic view of the final fixture press position and the final plunger position of the rotor core stack in a transfer molding press according to the present disclosure;

[0021] Figure 4 Depicts a method of transfer molding a rotor core stack; and

[0022] Figure 5 Depicts a method for calculating the height offset of the core stack of the rotor core according to FIG. 3.

[0023] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. Detailed Description

[0024] 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 the same or corresponding parts and features.

[0025] Referring to Figure 1 and Figure 2 , the transfer molding system 100 includes a rotor core stack 102. The rotor core stack 102 includes a series of rotor cores 200 stacked one on top of the other along a vertical direction. The rotor core stack 102 also includes a plurality of cavities 201 provided in each of the rotor cores 200 of the rotor core stack 102. The cavities 201 include a plurality of magnet slots 202 in which a plurality of magnets 205 are provided. In one form, the cavities 201 of the rotor core stack 102 may also include structural holes 204.

[0026] The transfer molding system 100 further includes a runner plate 104, a mandrel 106, a fixture press 108, and a support member 110. The rotor core stack 102 is disposed between the runner plate 104 and the mandrel 106. The mandrel 106 is disposed on the top surface of the fixture press 108, and the rotor core stack 102 is disposed on the top surface of the mandrel 106. Then, the runner plate is disposed above the rotor core stack 102 and below the support member 110. During the transfer molding pressing process, the fixture press 108 moves toward the support member 110 to clamp the rotor core stack 102 between the runner plate 104 and the mandrel 106 with a predetermined force.

[0027] The transfer molding system 100 further includes a plunger 114 disposed in a hole of the support member 110. The hole and the runner plate 104 define a reservoir 112. The reservoir 112 is located between the runner plate 104 and the plunger 114. A solid polymer is placed in the reservoir 112 and heated until it reaches a liquid state and becomes a liquid polymer 116. In one form, the liquid polymer 116 is an epoxy resin.

[0028] During a transfer molding press process, a plunger 114 presses a liquid polymer 116 through holes in a runner plate 104 to fill cavities within a rotor core stack 102. The liquid polymer 116 fills the space between a plurality of magnet slots 202 and a plurality of magnets 205. Once the liquid polymer 116 cures and reaches a solid state, the plurality of magnets 205 are permanently retained within the plurality of magnet slots 202. In one form, the cavities can also include structural holes 204 that are filled with the liquid polymer 116 to provide structural support for the rotor core stack 102 after the liquid polymer 116 cures.

[0029] The transfer molding system 100 also includes at least one sensor 120 and a controller 122. The at least one sensor 120 determines a clamp press position 126 of the clamp press 108 and a plunger position 124 of the plunger 114. The clamp press position 126 provides the position of the clamp press relative to the remainder of the transfer molding system 100. In one form, the clamp press position 126 is the distance between the top surface of the clamp press 108 and the top surface of the runner plate 104. In various forms, the clamp press position 126 is the case when the clamp press 108 is in a final position that clamps the mandrel 106, the rotor core stack 102, and the runner plate 104 between the clamp press 108 and the support member 110 with a predetermined force. The plunger position 124 provides the position of the plunger relative to the remainder of the transfer molding system 100. In a particular form, the plunger position 124 is the distance between the bottom surface of the plunger 114 and the top surface of the runner plate 104. In one form, the plunger position 124 is the case when the plunger 114 is in a final position and has completed extruding the liquid polymer 116 into the rotor core stack 102. The sensor 120 communicates the clamp press position 126 and the plunger position 124 to the controller 122.

[0030] Reference Figure 3A , the clamp press position 126 includes a nominal clamp press position 126a. In one form, the nominal clamp press position 126a is the sum of the heights of the rotor core stack 102, the runner plate 104, and the mandrel 106. In another form, the nominal clamp press position 126a can be the average or mean of a plurality of final positions from a sample data set of the previous rotor core stack 102 transfer molding system 100 of the clamp press 108.

[0031] The plunger position 124 includes a nominal plunger position 124a. The nominal plunger position 124a is determined by averaging a plurality of final positions of the plunger 114 from a sample data set of a previous rotor core transfer molding assembly. In one form, the nominal plunger position 124a is offset from the average final position by a predetermined value. In one form, the nominal plunger position 124a is between one millimeter and three millimeters higher than the average of the plurality of final positions of the plunger 114. In one form, the nominal plunger position 124a is two millimeters higher than the average of the plurality of final plunger positions of the plunger 114.

[0032] Reference Figure 3B , the plunger position 124 includes a normalized plunger position 124a. The normalized plunger position 124b of the plunger 114 is calculated by adding the nominal plunger position 124a and a height offset.

[0033] Reference Figure 3C , the fixture press position 126 includes a final fixture press position. The final fixture press position 126c is the situation when the fixture press 108 is in the final position, which clamps the mandrel 106, the rotor core stack 102, and the runner plate 104 between the fixture press 108 and the support member 110 with a predetermined force. In one form, the final fixture press position 126c is the nominal fixture press position 126a. In other forms, the final fixture press position 126c may vary from the nominal fixture press position 126a by a tolerance within a predetermined tolerance range.

[0034] The plunger position 124 includes a final plunger position 124c, as Figure 3C shown. The final plunger position 124c is the situation when the plunger 114 is in the final position and has completed extruding the liquid polymer 116 into the rotor core stack 102. In one form, the final plunger position 124c is variable and is determined based on the transfer molding process of each rotor core stack 102. During the final stage of the transfer molding process, the plunger 114 extrudes the liquid polymer 116 through a hole in the runner plate 104 at a predetermined pressure for a first predetermined duration. Then, the plunger 114 stops and holds for a second predetermined duration while the liquid polymer 116 cures into a solid. In one form, the position where the plunger 114 stops is the final plunger position 124c.

[0035] Reference Figure 4, which shows a method 300 for transfer molding a rotor core stack. In step 302, the rotor core stack 102 is assembled between the mandrel 106 and the runner plate 104, and the runner plate is between the clamp press 108 and the plunger 114. In one form, the mandrel 106 is disposed on the top surface of the clamp press 108, and the rotor core stack 102 is disposed on the top surface of the mandrel 106. Then, the runner plate is disposed above the rotor core stack 102 and below the support member 110 and the plunger 114.

[0036] In step 304, at least one sensor 120 determines the final clamp press position 126c. The controller 122 records the final clamp press position 126c and determines the nominal clamp press position 126a of the clamp press 108 and the nominal plunger position 124a of the plunger 114. In one form, determining the nominal clamp press position 126a includes adding the heights of the rotor core stack 102, the runner plate 104, and the mandrel 106. In another form, determining the nominal clamp press position 126a determines the average or mean of multiple final positions from a sample data set of the previous rotor core stack 102 transfer molding system 100 of the clamp press 108. In one form, the nominal clamp press position 126a is the final clamp press position 126c of the clamp press 108. Determining the nominal plunger position 124a includes averaging multiple final plunger positions from a sample data set of the plunger 114 from a previous rotor transfer molding assembly. The nominal plunger position 124a is between one millimeter and three millimeters higher than the average of the multiple final plunger positions of the plunger 114. In one form, the nominal plunger position 124a is two millimeters higher than the average of the multiple final plunger positions of the plunger 114.

[0037] In step 306, the controller 122 calculates the height offset. Refer to Figure 5 , which provides more details of step 306. In step 402, the position difference is determined by subtracting the nominal clamp press position 124a from the final clamp press position 126c. Then, in step 404, the controller determines the normalized area. The normalized area is the cross-sectional area of the rotor core stack 102 divided by the cross-sectional area of the bore of the plunger 114. In one form, the cross-sectional area of the rotor core stack 102 is the total cross-sectional area of the cavity 201 of the rotor core stack 102. In one form, the total cross-sectional area of the cavity 201 includes at least one of the total cross-sectional area of the plurality of magnet slots 202 and the total cross-sectional area of the structural holes 204. In step 406, the normalized area of step 404 is multiplied by the position difference of step 402 to provide the height offset of the rotor core stack 102. The height offset is determined by the following equation:

[0038]

[0039] where X2 is the final fixture press position 126c, is the nominal fixture press position 126a, A1 is the cross-sectional area of the bore of the plunger 114, and A2 is the cross-sectional area of the rotor core stack 102.

[0040] In step 308, the normalized plunger position 124b of the plunger 114 is calculated. The normalized plunger position 124b is the sum of the nominal plunger position 124a and the height offset calculated in step 306. The normalized plunger position 124b depends on the geometry of the rotor core stack 102 because it takes into account the height and cross-sectional area of the cavity 201 of the rotor core stack 102. Step 308 can be completed before, after, or simultaneously with step 310.

[0041] In step 310, the controller 122 controls the movement of the plunger 114. The plunger 114 moves at a first speed until the plunger 114 reaches an initial position. In one form, the initial position is just before the plunger 114 contacts the liquid polymer 116 within the reservoir 112. In another form, the initial position is the position where the plunger 114 first contacts the liquid polymer 116 within the reservoir 112. In yet another form, the initial position can be a predetermined position of the plunger 114. In one form, the first speed is constant, but in other forms it can vary. Then the speed of the plunger 114 is adjusted to a second speed in step 312. The second speed is a constant speed. In one form, the second speed is less than the first speed. In another form, the second speed is the same as the first speed. As the plunger 114 moves at the second speed, the liquid polymer 116 in the reservoir 112 is extruded through the holes in the flow plate 104 into the cavity 201 of the rotor core stack 102. The plunger 114 moves at the second speed until the plunger 114 reaches the normalized plunger position 126b. In one form, once the plunger 114 reaches the normalized plunger position 124b, most of the volume of the cavity 201 is filled with the liquid polymer 116. In one form, most of the volume of the filled cavity 201 is between 90% and 95% of the volume of the cavity 201 filled with the liquid polymer 116.

[0042] Once the plunger 114 reaches the standardized plunger position 124b, the speed of the plunger 114 is controlled in step 314 to maintain a constant pressure between the plunger 114 and the liquid polymer 116. In one form, the speed of the plunger can be varied to maintain a constant pressure. In one form, the constant pressure is set to a value between 10 bar and 50 bar. The point at which the plunger 114 switches from moving at a constant speed to maintaining a constant pressure affects the quality of the rotor core stack. If the switch occurs too early, the liquid polymer 116 may not completely fill all of the cavities 201 in the rotor core stack 102. If the switch occurs too late, the pressure may peak, causing the liquid polymer 116 to be extruded from the rotor core stack 102. As the plunger 114 moves while maintaining a constant pressure, the liquid polymer 116 in the reservoir 112 is extruded through the holes in the flow channel plate 104 into the cavities 201 of the rotor core stack 102. The plunger 114 moves while maintaining a constant pressure until the transfer of the liquid polymer 116 is complete and the plunger 114 stops at the final plunger position 124c. The final plunger position 124c can vary between each rotor core stack 102.

[0043] In step 316, the plunger 114 remains at the final plunger position 124c for a specified time while the liquid polymer 116 cures. The specified time for the liquid polymer 116 to cure depends on the chemical structure of the liquid polymer 116. In one form, the specified time can be between 60 seconds and 240 seconds. Once the liquid polymer 116 cures into a solid state, the magnet 205 is permanently sealed within the rotor core stack.

[0044] Unless expressly indicated otherwise herein, all numerical values indicating mechanical / thermal properties, percentage compositions, dimensions, and / or tolerances or other characteristics should be understood to be modified by the word "about" or "approximately" when describing the scope of the present disclosure. This modification is desired for various reasons, including: industrial practice; material, manufacturing, and assembly tolerances; and testing capabilities.

[0045] As used herein, the phrase "at least one of A, B, and C" should be construed to represent the logical (A or B or C) using non-exclusive logic "or", and should not be construed to mean "at least one of A, at least one of B, and at least one of C".

[0046] In the present application, the terms "controller" and / or "module" may refer to, be part of, or include the following: an application specific integrated circuit (ASIC); digital, analog, or mixed analog / digital discrete circuits; digital, analog, or mixed analog / digital integrated circuits; combinational logic circuits; a field programmable gate array (FPGA); processor circuitry (shared, dedicated, or grouped) that executes code; memory circuitry (shared, dedicated, or grouped) that stores code executed by the processor circuitry; other suitable hardware components that provide the described functionality (e.g., operational amplifier circuit integrators as part of a heat flux data module); or a combination of some or all of the above, such as in a system on a chip.

[0047] The term memory is a subset of the term computer-readable medium. As used herein, the term computer-readable medium does not cover transitory electrical or electromagnetic signals propagated through a medium (such as on a carrier wave); thus, the term computer-readable medium can be considered tangible and non-transitory. Non-limiting examples of non-transitory tangible computer-readable media are non-volatile memory circuits (such as flash memory circuits, erasable programmable read-only memory circuits, or mask read-only circuits), volatile memory circuits (such as static random access memory circuits or dynamic random access memory circuits), magnetic storage media (such as analog or digital magnetic tape or hard disk drives), and optical storage media (such as CDs, DVDs, or Blu-ray discs).

[0048] The devices and methods described in the present application can be implemented, in part or in whole, by a special purpose computer created by configuring a general purpose computer to execute one or more specific functions embodied in a computer program. Functional blocks, flowchart components, and other elements described above serve as software specifications that can be translated into a computer program by routine work of a technician or programmer.

[0049] The description of the present disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the present disclosure are intended to be within the scope of the present disclosure. Such variations should not be regarded as departing from the spirit and scope of the present disclosure.

[0050] According to the present invention, a method for transfer molding a rotor core stack includes: assembling the rotor core stack between a mandrel and a runner plate, the runner plate being between a clamp press and a plunger; determining a final clamp press position of the clamp press, a nominal clamp press position of the clamp press, and a nominal plunger position of the plunger; calculating a difference between the final clamp press position and the nominal clamp press position of the clamp press to determine a position difference; normalizing a plunger cross-sectional area of a bore of the plunger with a cross-sectional area of a plurality of cavities of the rotor core stack; calculating a height offset by multiplying the normalized area and the position difference; calculating a normalized position of the plunger by adding the nominal plunger position and the height offset; moving the plunger at a first speed until the plunger reaches an initial position; adjusting the speed of the plunger to a second speed until the plunger reaches the normalized position, wherein the plunger extrudes a liquid polymer in a reservoir between the runner plate and the plunger through the runner plate and into the rotor core stack; controlling the speed of the plunger to maintain a constant pressure between the plunger and the liquid polymer until the plunger stops at a final plunger position; and holding the plunger at the final plunger position for a specified time to cure the liquid polymer.

[0051] In one aspect of the present invention, the final clamp press position of the clamp press is a distance between a top surface of the clamp press and a top surface of the runner plate located on a top surface of the rotor core stack.

[0052] In one aspect of the present invention, the nominal plunger position is a distance between a bottom surface of the plunger and a top surface of the runner plate located on a top surface of the rotor core stack.

[0053] In one aspect of the present invention, determining the nominal clamp press position further includes adding the height of the rotor core stack, the height of the mandrel, and the height of the runner plate.

[0054] In one aspect of the present invention, determining the nominal plunger position further includes averaging a plurality of final plunger positions from a data set.

[0055] In one aspect of the present invention, the nominal plunger position is at a predetermined distance above the average final plunger position.

Claims

1. A method for transfer molding a rotor core stack, the method comprising: Assembling the rotor core stack between the mandrel and the flow channel plate, wherein the flow channel plate is between the clamp press and the plunger; determining a final clamp press position of the clamp press, a nominal clamp press position and a nominal plunger position of the clamp press; Calculate height offset; calculating a normalized position of the plunger by adding the nominal plunger position and the height offset; moving the plunger at a first speed until the plunger reaches an initial position; adjusting the speed of the plunger to a second speed until the plunger reaches the standardized position, wherein the plunger squeezes liquid polymer in a reservoir between the flow channel plate and the plunger through the flow channel plate and into the rotor core stack; as well as The velocity of the plunger is controlled to maintain a constant pressure between the plunger and the liquid polymer until the plunger stops at a final plunger position. 2 . The method of claim 1 , wherein calculating the height offset of the rotor core stack further comprises calculating a difference between the final jig press position of the jig press and the nominal jig press position to determine a position difference. 3 . The method of claim 2 , wherein calculating the height offset of the rotor core stack further comprises normalizing a plunger cross-sectional area of ​​a bore of the plunger with a cross-sectional area of ​​the rotor core stack to determine a normalized area. 4 . The method of claim 3 , wherein the cross-sectional area of ​​the rotor core stack is a cross-sectional area of ​​a plurality of cavities of the rotor core stack. 5 . The method of claim 1 , wherein the final jig press position of the jig press is a distance between a top surface of a jig press and a top surface of the runner plate located on a top surface of the rotor core stack. 6 . The method of claim 1 , wherein the nominal plunger position is the distance between a bottom surface of the plunger and a top surface of the flow channel plate located on a top surface of the rotor core stack.

7. The method of claim 1 wherein said determining said nominal jig press position of said jig press further comprises adding said height of said rotor core stack, said height of said mandrel, and said height of said runner plate.

8. The method of claim 1, wherein said determining said nominal plunger position further comprises averaging a plurality of final plunger positions from a data set.

9. The method of claim 8, wherein the nominal plunger position is a predetermined distance above the average final plunger position.

10. The method of claim 1, further comprising maintaining the plunger in the final plunger position for a specified time to allow the liquid polymer to solidify.

11. A system for transfer molding a rotor core stack, the system comprising: Rotor core stacking; a jig press disposed below a bottom surface of the rotor core stack; a flow channel plate disposed above a top surface of the rotor core stack; A plunger, the plunger being arranged above the flow channel plate; at least one sensor for determining a final clamp press position of the clamp press and a final plunger position of the plunger; as well as a controller for determining a nominal clamp press position and a nominal plunger position, calculating a height offset of the rotor core stack, and calculating a normalized position of the plunger by adding the nominal plunger position and the height offset, Wherein the controller controls the movement of the plunger.

12. The system of claim 11 wherein the height offset is a position difference multiplied by a normalized area, wherein the position difference is a difference between the final clamp press position and the nominal clamp press position of the clamp press, and wherein the normalized area is a cross-sectional area of ​​the rotor core stack divided by a plunger cross-sectional area of ​​the plunger bore.

13. The system of claim 12, wherein the cross-sectional area of ​​the rotor core stack is a cross-sectional area of ​​a plurality of cavities of the rotor core stack.

14. The system of claim 11, wherein the nominal plunger position is an average of a plurality of final plunger positions from a sample data set offset by a predetermined distance.

Images