A high-speed high-precision numerical control machine tool permanent magnet synchronous motor machining method

Abstract

The application provides a machining method of a high-speed high-precision permanent magnet synchronous electric spindle motor for a numerical control machine tool, and optimizes design of machining processes of four aspects of a stator core, an armature winding, a wound stator core grinding and a rotor core. The stator core is designed by a five-in-one lamination process, the armature winding is designed by a dynamic dip paint process, the wound stator core is designed by a non-cooling liquid intermittent air cooling dry grinding process, and the non-uniform segmented herringbone skew pole rotor core is designed by a seven-step lamination forming process. The application is helpful to improve the electrical performance of the electric spindle motor and is also beneficial to improve the overall accuracy of the electric spindle.

Description

Technical Field

[0001] The present application relates to the field of permanent magnet synchronous electric spindle motors, and in particular to a method for machining permanent magnet synchronous electric spindle motors for high-speed and high-precision CNC machine tools. Background Art

[0002] Motor manufacturing involves the machining of multiple key components. Different materials require different processing techniques, and machining accuracy and process approaches directly impact the motor's overall performance and reliability. Spindle motors have consistently developed toward higher power density and higher speeds. Precision machining and process design are key core technologies in motor manufacturing. However, current electric spindle motor manufacturing errors are relatively large, which can lead to rotor eccentricity and thus cause vibration in the electric spindle shaft system. This, in turn, can cause unequal air gap lengths between the stator and rotor, generating unilateral electromagnetic pull and causing electromagnetic oscillation, ultimately impacting the motor's electrical and dynamic performance. As the core drive component of the electric spindle unit, the manufacturing accuracy and process of the permanent magnet synchronous electric spindle motor directly impact the stability of the electric spindle's operation and various key performance indicators. Therefore, it is imperative to design appropriate machining methods and process parameters to maximize the motor's designed performance. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a method for processing permanent magnet synchronous electric spindle motors for high-speed and high-precision CNC machine tools. The process optimization design is carried out from four aspects: stator core processing, armature winding processing, winding stator core processing, and rotor core processing. This helps to improve the electrical performance of the electric spindle motor and also helps to improve the overall accuracy of the electric spindle.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for machining a permanent magnet synchronous electric spindle motor for high-speed and high-precision CNC machine tools, comprising machining a stator core, machining an armature winding, grinding a stator core with windings, and machining a non-uniform segmented herringbone skewed-pole rotor core.

[0006] A five-in-one lamination process is designed during the stator core processing process, including: first, high-precision laser cutting of the stator electrical steel under argon protection, then aligning the cleat slots and bonding them piece by piece, the stator end plates acting as axial fixation, inserting cleats into the cleat slots, which act as circumferential fixation, pressing the cleats to the designed dimensions using a press, bending the cleats, and performing segmented staggered laser welding under locking, pressure maintenance, and argon protection. Finally, high-temperature annealing is performed after welding to remove residual stress.

[0007] The dynamic varnishing process is designed during the armature winding processing to optimize the preheating, varnishing and drying processes during the armature winding processing, including preheating the armature winding as a whole and locally heating it, reciprocating stirring and vacuum varnishing, slow rotation baking and local UV curing.

[0008] During the grinding process of the winding stator core, a coolant-free intermittent air-cooled dry grinding process is designed, which sequentially performs rough grinding of the outer circle to remove residual paint, fine grinding of the inner circle to meet the air gap requirement, and fine grinding of the outer circle to meet the interference requirement. During the grinding process of the winding stator core, no coolant is used, and compressed air is used for cooling and blowing away iron chips.

[0009] During the processing of the non-uniform segmented herringbone skew-pole rotor core, a seven-step lamination forming process is designed. First, the rotor electrical steel is laser cut with high precision under argon protection. Then, multiple W-shaped welding grooves are aligned and bonded piece by piece. The rotor core is laminated to the designed size by a press. Each section of the rotor core is laser welded under locking, pressure maintenance and argon protection. A non-magnetic plug-in plate is made and inserted into the magnet slot for trial installation. Each plate is tested one by one to ensure that the magnet can be inserted smoothly. Then, the permanent magnet is coated with adhesive to install the magnet. After the magnets in each section of the rotor core are installed in order, the stainless steel rods are perforated and staggered for circumferential fixation, and the stainless steel end plates are fixed axially. The stainless steel rods and the stainless steel end plates are laser welded into one under locking, pressure maintenance and argon protection. Finally, the inner and outer circles of the rotor core are ground to remove the multiple W-shaped welding grooves.

[0010] Furthermore, during the processing of the stator core, a first cleat slot, a second cleat slot, a third cleat slot, a fourth cleat slot, a fifth cleat slot, and a sixth cleat slot are provided on the outer circumference of the stator electrical steel, which are evenly distributed on the circumference. Clasps are respectively inserted into the cleat slots to fix the stator core circumferentially. During the five-in-one lamination process of the stator core, the number and position of the welding slots are optimized, and the number of welding slots is not an integer multiple of the number of motor poles. The centerline of the welding slot is aligned with the centerline of the stator tooth and cannot be located on the centerline of the stator slot. The first stator end plate and the second stator end plate are located at the outermost side of the stator electrical steel to play an axial fixing role. The multiple pieces of stator electrical steel are connected by adhesive to increase the friction in the circumferential direction. The stator core is laser welded in sections and staggered under locking, pressure maintenance, and argon gas protection. The two sides of each cleat are welded in sections.

[0011] Furthermore, in the processing of the non-uniform segmented herringbone skewed pole rotor core, the outer circle of the rotor core is symmetrically distributed with a first W-shaped welding groove, a second W-shaped welding groove, a third W-shaped welding groove, and a fourth W-shaped welding groove. Each W-shaped welding groove is set at the center line position between permanent magnets of the same polarity. After bonding, it is pressed to the designed size by a press and then locked. Then, each section of the rotor core is welded together.

[0012] Furthermore, the stainless steel rods and stainless steel end plates are made of 1Cr18Ni9Ti non-magnetic material for axial fixation of the rotor core, which has minimal impact on the magnetic field. The first stator end plate, the second stator end plate and the buckle are made of Q235-A material, which has good plasticity and weldability.

[0013] The present invention maximizes the motor design performance through a five-in-one lamination process for stator core design, a dynamic varnishing process for armature winding design, an intermittent air-cooled dry grinding process without coolant for stator core design with windings, and a seven-step lamination forming process for non-uniform segmented herringbone skewed pole rotor core design.

[0014] Beneficial effects:

[0015] 1. The traditional stator core lamination process is carried out by selecting one or two of the three methods: bonding, clip-on slot fixation, and welding. Unlike the traditional method, the present invention designs a five-in-one stator core lamination process, which combines the advantages of bonding, axial fixation of the stator end plate, circumferential fixation of the clip-on slot, segmented staggered laser welding, and high-temperature annealing into one. Adhesive can increase the friction between the stator electrical steel sheets in the circumferential direction, but relying solely on friction is not suitable for high-speed and high-power electric spindle motors; the clip slots can play an alignment and positioning role during stacking, which is sufficient when the stacking coefficient is not high, but for electric spindle motors with high power density and high stacking coefficient, only using clip slots to fix the stator core may cause the stator core to be non-circular after stacking, resulting in a horseshoe phenomenon; the electrical steel sheet is generally between 0.15mm and 0.5mm, and the thinner it is, the smaller the eddy current loss. The thinner the stator core is, the easier it is for the outermost electrical steel sheet to partially bounce off after stacking, resulting in surface Bow-shaped protrusions appear, and the present invention adds a 5mm thick stator end plate for axial fixation to solve this problem; the biggest disadvantage of welding is that the melting of local areas will destroy the insulating coating of the connection area, which will increase eddy current losses and introduce residual stress, causing the hysteresis properties of the material to deteriorate. Traditional arc welding is upgraded to segmented staggered laser welding. Laser welding has more concentrated heat input, faster welding speed, and smaller welding deformation, which minimizes the impact on the electromagnetic properties of the stator core; very few people pay attention to the residual stress after welding. In the present invention, a high-temperature annealing process is added after welding to remove the residual stress.

[0016] 2. In the present invention, argon protection is added during the high-precision laser cutting of stator and rotor electrical steel and the laser welding of stator core and rotor core. When the electrical steel is rapidly melted by the high-power laser beam, the alloy elements silicon and aluminum in the electrical steel easily undergo high-temperature oxidation reaction with oxygen in the air to form a silicon-aluminum oxide layer. The argon protection can isolate oxygen and prevent the formation of high-temperature oxides.

[0017] 3. In traditional stator core welding processes, little attention is paid to the number and location of welding slots, and most designs are based on experience. This invention explicitly emphasizes that to reduce three-phase electromotive force imbalance, the number of stator core welding slots should not be an integer multiple of the number of motor poles, and the welding slot centerline must be aligned with the stator tooth centerline, and is strictly prohibited from being located on the stator slot centerline. This process is beneficial for improving the balance of three-phase voltage and current in high-speed, high-precision electric spindle motors.

[0018] 4. The traditional stator core varnishing process includes preheating, varnishing, and drying. Preheating is generally performed as a whole in an oven or drying room. Varnishing is generally performed statically in a vacuum. Drying is generally performed statically in an oven or drying room. The present invention designs a dynamic varnishing process. During the preheating process, overall preheating and local ultraviolet heating are used to try to make the temperature inside the winding higher. During the varnishing process, reciprocating stirring vacuum varnishing is used. By continuously stirring the paint solution, the permeability of the insulating paint into the stator winding can be increased. The paint film of the stator winding after varnishing is uniform, and the amount of paint applied can be more than doubled compared to static varnishing. During the drying process, slow rotation drying and local ultraviolet curing are used. During static drying, the unsolidified insulating paint will flow down. During the slow rotation drying process, the stator is In the state of uniform rotation around the axis, the flow trajectory of the paint is circular, so the loss of the impregnating paint is not only greatly reduced, but also with the rotation of the motor stator or rotor, it will continue to penetrate into the nearby gaps or defective parts, so that the quality of the impregnation is improved; in the static drying process, the temperature outside the winding is high, the external insulating paint is cured first, and the internal insulating paint is cured later, which makes it easy for gaps to exist, and the external insulating paint is cured first, which also prevents the insulating paint from entering again during the second impregnation. Local UV curing is used to heat the inside of the winding to speed up the curing progress inside the winding.

[0019] 5. The present invention adopts a scheme of first embedding wires, connecting wires, and dipping in paint before processing the inner and outer circles of the stator, so as to avoid first processing and then embedding wires, which may cause bumps and scratches on the outer surface of the core during the winding production process. It also avoids first processing and then dipping in paint, which may cause the insulating paint in the winding to flow out and adhere to the inner and outer circular surfaces of the stator core, affecting the surface quality.

[0020] 6. During the machining of the inner and outer circles of the stator of the present invention, a coolant-free intermittent air-cooled dry grinding process is designed to prevent coolant from entering the windings, and compressed air is used for cooling and blowing away iron chips.

[0021] 7. The non-uniform segmented herringbone skew-pole rotor core of the present invention adopts a seven-step lamination forming process to weld the stainless steel rods and stainless steel end plates together to ensure that there are no welding marks after processing. 1Cr18Ni9Ti stainless steel non-magnetic material is used for axial fixation of the rotor core, which has minimal impact on the magnetic field. The first stator end plate, the second stator end plate and the buckle are made of Q235-A material, which has good plasticity and weldability. It is easier to bend into a right angle to fasten and fix the stator electrical steel, and it is also easier to weld with the electrical steel. When machining the outer circle of the rotor core, the grinding amount is greater than the designed W-shaped welding groove to ensure that the outer circle of the rotor core is smooth and the air gap between the stator core and the rotor core is uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of the method for machining a permanent magnet synchronous electric spindle motor for a high-speed and high-precision CNC machine tool according to the present invention;

[0023] Figure 2 is a schematic diagram of the stator core;

[0024] Figure 3 is a schematic diagram of the rotor core;

[0025] Figure 4 Schematic diagram of the axial fixation of the non-uniform segmented herringbone skew pole rotor core.

[0026] Among them, the figure marks are: first clip slot 1, second clip slot 2, third clip slot 3, fourth clip slot 4, fifth clip slot 5, sixth clip slot 6, stator tooth center line 7, stator slot center line 8, first stator end plate 9, second stator end plate 10, clip 11, stator electrical steel 12, segmented staggered laser welding 13, first W-shaped welding groove 14, second W-shaped welding groove 15, third W-shaped welding groove 16, fourth W-shaped welding groove 17, first stainless steel end plate 18, second stainless steel end plate 19, stainless steel rod 20, chamfered groove 21. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Figure 1 As shown, a method for machining a permanent magnet synchronous electric spindle motor for a high-speed and high-precision CNC machine tool of the present invention includes stator core machining, armature winding machining, winding stator core grinding machining, and non-uniform segmented herringbone skewed pole rotor core machining.

[0028] A five-in-one lamination process is designed during the stator core processing process, including: first, high-precision laser cutting of the stator electrical steel under argon protection, then aligning the cleat slots and bonding them piece by piece, the stator end plates play an axial fixing role, and the cleats are respectively inserted into the cleat slots to play a circumferential fixing role, and the cleats are bent after being laminated to the designed size by a press, and then segmented staggered laser welding is performed under locking, pressure maintenance and argon protection. Finally, high-temperature annealing is performed after welding to remove residual stress.

[0029] Specifically, if Figure 2 As shown, the outer circumference of the stator electrical steel 12 is provided with six cleat slots: first cleat slot 1, second cleat slot 2, third cleat slot 3, fourth cleat slot 4, fifth cleat slot 5, and sixth cleat slot 6. These slots are evenly distributed around the circumference and serve to secure the stator core circumferentially. During the five-in-one lamination process of the stator core, the number and position of the welding slots are optimized. To minimize three-phase electromotive force imbalance, the number of stator core welding slots should not be an integer multiple of the number of motor poles. Figure 2 In the figure, the welding slot is also the clip slot. The center line of the welding slot must be aligned with the center line 7 of the stator tooth. It is strictly forbidden to be located on the center line 8 of the stator slot. The first stator end plate 9 and the second stator end plate 10 are located on the outermost side of the stator electrical steel 12, and play an axial fixing role. The first stator end plate, the second stator end plate and the clip are made of Q235-A material, which has good plasticity and weldability. It is easier to bend into a right angle to fasten and fix the stator electrical steel, and it is also easier to weld with the electrical steel. The friction force in the circumferential direction is increased by adhesive between multiple pieces of stator electrical steel 12. Clips 11 are inserted into the first clip slot 1, the second clip slot 2, the third clip slot 3, the fourth clip slot 4, the fifth clip slot 5, and the sixth clip slot 6 respectively. The clip slot plays a circumferential fixing role. Segmented staggered laser welding 13 is performed under locking, pressure maintenance and argon protection. The two sides of each clip 11 are segmented and welded. Figure 2 The division into three sections is for illustration only. The specific number of sections and the length of each section can be determined according to the axial length of the stator core, but it must be ensured that there is staggering between adjacent sections.

[0030] The armature winding process includes armature winding coil fabrication, followed by wire embedding, wiring, preheating, varnish dipping, and finally drying. The present invention optimizes and transforms the preheating, varnish dipping, and drying processes, specifically designing a dynamic varnish dipping process that includes overall preheating and local heating of the armature winding, reciprocating agitation, vacuum varnish dipping, slow rotation baking, and local UV curing.

[0031] During the grinding process of the stator core with windings, a coolant-free intermittent air-cooled dry grinding process is designed. First, the stator core shaft is ground, and then the stator core shaft is inserted into the inner circle of the stator. The coolant-free intermittent air-cooled dry grinding process is designed, that is, the outer circle is coarsely ground to remove residual paint, the inner circle is finely ground to meet the air gap requirement, and the outer circle is finely ground to meet the interference requirement. No coolant is used throughout the grinding process of the stator core with windings to prevent coolant from entering the windings, and compressed air is used to cool down and blow away iron chips.

[0032] During the processing of the non-uniform segmented herringbone skew-pole rotor core, a seven-step lamination forming process is designed. First, the rotor electrical steel is laser cut with high precision under argon protection. Then, multiple W-shaped welding grooves are aligned and bonded piece by piece. The press is laminated to the designed size. Each section of the rotor core is laser welded under the conditions of locking, pressure maintenance and argon protection. A non-magnetic plug-in plate is made and inserted into the magnet slot for trial installation. Each test is conducted one by one to ensure that the magnet can be inserted smoothly. Then, the permanent magnet is coated with adhesive to install the magnet. After the magnets in each section of the rotor core are installed in order, the stainless steel rods are perforated and staggered for circumferential fixation. The stainless steel end plates are fixed axially. The stainless steel rods and the stainless steel end plates are laser welded into one piece under the conditions of locking, pressure maintenance and argon protection. Finally, the inner and outer circumferences of the rotor core are ground to remove the multiple W-shaped welding grooves.

[0033] like Figure 3 As shown, four W-shaped welding grooves are symmetrically distributed on the outer circle of the rotor core, namely a first W-shaped welding groove 14, a second W-shaped welding groove 15, a third W-shaped welding groove 16, and a fourth W-shaped welding groove 17. The W-shaped welding grooves are located on the center line between permanent magnets N and N, or S and S of the same polarity, so as to have the least impact on the electromagnetic properties of the rotor core. After bonding, a press is used to stack the rotor core to the designed size and then locked. Then, each section of the rotor core is welded together. Figure 3 middle, The reference diameter size to be processed by the outer cylindrical grinding of the rotor core must be greater than the designed W-shaped welding groove to ensure that the final outer cylindrical diameter of the rotor core is less than , ensuring uniform air gap between the stator core and the rotor core.

[0034] like Figure 4 As shown, L1, L2, L3, L4, L5, and L6 are the axial lengths of each section of the rotor core, respectively. The lengths L1=L6>L2=L5>L3=L4. Unequal lengths indicate non-uniform segmentation. After each section of the rotor core is welded together, the stainless steel rod 20 is laser welded to the first stainless steel end plate 18, the second stainless steel end plate 19, and the chamfered grooves 21 on the stainless steel rod 20, and the outer surfaces are polished.

[0035] Preferably, to ensure that there are no welding marks on the surface after processing, the stainless steel rod 20 and the first stainless steel end plate 18 and the second stainless steel end plate 19 are made of 1Cr18Ni9Ti non-magnetic material for axial fixation of the rotor core, which minimizes the impact on the magnetic field.

Claims

1. A method for machining a permanent magnet synchronous electric spindle motor for a high-speed and high-precision CNC machine tool, characterized in that: Including stator core processing, armature winding processing, winding stator core grinding processing, non-uniform segmented herringbone skew pole rotor core processing; The stator core is manufactured using a five-in-one lamination process, including: first, high-precision laser cutting of the stator electrical steel under argon protection, then aligning the cleat slots and bonding them piece by piece; the stator end plates act as axial fixation, inserting cleats into the cleat slots, which act as circumferential fixation; lamination by a press to bend the cleats; and then laser welding in sections and staggered sections under locking, pressure maintenance, and argon protection. Finally, high-temperature annealing is performed after welding to remove residual stress. The armature winding processing includes designing a dynamic varnishing process, including preheating the armature winding as a whole and locally heating it, reciprocating stirring and vacuum varnishing, slow rotation baking and local UV curing; During the grinding process of the winding stator core, a coolant-free intermittent air-cooled dry grinding process is designed, which sequentially performs rough grinding of the outer circle to remove residual paint, fine grinding of the inner circle to meet the air gap requirement, and fine grinding of the outer circle to meet the interference requirement. No coolant is used during the entire grinding process of the winding stator core. During the processing of the non-uniform segmented herringbone skew-pole rotor core, a seven-step lamination forming process is designed. First, the rotor electrical steel is laser cut with high precision under argon protection. Then, multiple W-shaped welding grooves are aligned and bonded piece by piece. The press is laminated and locked to maintain pressure. Each section of the rotor core is laser welded under argon protection. A non-magnetic plug-in plate is made and inserted into the magnet slot for trial installation. Each plate is tested one by one to ensure that the magnet can be inserted smoothly. Then, the permanent magnet is coated with adhesive to install the magnet. After the magnets in each section of the rotor core are installed in order, the stainless steel rods are perforated and installed with staggered poles circumferentially, and the stainless steel end plates are fixed axially. The stainless steel rods and the stainless steel end plates are laser welded into one piece under locking, pressure maintenance and argon protection. Finally, the inner and outer circles of the rotor core are ground to remove the multiple W-shaped welding grooves.

2. The method for machining a permanent magnet synchronous electric spindle motor for a high-speed and high-precision CNC machine tool according to claim 1, characterized in that: The armature winding processing includes armature winding coil production, followed by wire embedding, wiring, preheating, varnish dipping, and finally drying. The coolant-free intermittent air-cooled dry grinding process is an optimized transformation of the preheating, varnish dipping, and drying processes.

3. The method for machining a permanent magnet synchronous electric spindle motor for a high-speed and high-precision CNC machine tool according to claim 1, characterized in that: The process of grinding the winding stator core, before the intermittent air-cooled dry grinding process without coolant, also includes: first grinding the stator core shaft, and then inserting the stator core shaft into the stator inner circle.

4. The method for machining a permanent magnet synchronous electric spindle motor for a high-speed and high-precision CNC machine tool according to claim 1, characterized in that: During the processing of the stator core, a first clip slot, a second clip slot, a third clip slot, a fourth clip slot, a fifth clip slot, and a sixth clip slot are evenly distributed on the outer circumference of the stator electrical steel to circumferentially fix the stator core. During the five-in-one lamination process of the stator core, the number and position of the welding slots are optimized, and the number of welding slots is not an integer multiple of the number of motor poles. The center lines of the welding slots are aligned with the center lines of the stator teeth and cannot be located on the center lines of the stator slots. The first and second stator end plates are located on the outermost sides of the stator electrical steel to provide axial fixation. Adhesive is used to increase circumferential friction between the multiple pieces of stator electrical steel. Clips are respectively inserted into the first, second, third, fourth, fifth, and sixth clip slots to provide circumferential fixation. Segmented staggered laser welding is performed under locking, pressure maintenance, and argon gas protection, with each clip welded in sections.

5. The method for machining a permanent magnet synchronous electric spindle motor for a high-speed and high-precision CNC machine tool according to claim 1, characterized in that: In the processing of the non-uniform segmented herringbone skewed pole rotor core, a first W-shaped welding groove, a second W-shaped welding groove, a third W-shaped welding groove, and a fourth W-shaped welding groove are symmetrically distributed on the outer circle of the rotor core. Each W-shaped welding groove is set at the center line position between permanent magnets of the same polarity. After bonding, a press is used to stack to the designed size and then locked. Then, each segment of the rotor core is welded together.

6. The method for machining a permanent magnet synchronous electric spindle motor for a high-speed and high-precision CNC machine tool according to claim 4, characterized in that: The stainless steel rods and stainless steel end plates are made of 1Cr18Ni9Ti non-magnetic material and are used for axial fixation of the rotor core. The first stator end plate, the second stator end plate and the buckle are made of Q235-A material.

Images