Six core manufacturing processes of flat wire motor stator

As one of the hottest technology trends at the moment, flat wire motors are the first to be affected. Since new energy vehicles began to adopt this technology, topics surrounding flat wire motors have become more and more intense. In actual production, flat wire motors will require higher stability and qualification rates than current round wire production. Below are the six core processes in the production process of flat wire motor stators.

The current basic process flow of the stator production line: slotting paper → making hairpins → threading hairpins → end ring shaping → end ring welding → star point connection → insulation treatment at the welding area, including center line forming and paper forming and paper insertion. These two processes Synchronization.

01-Paper insertion process

There is insulating paper between the stator slot and the conductor of the flat wire motor to ensure the insulation between out-of-phase conductors and between the conductor and the stator core. Generally speaking, the paper insertion process of flat wire motors mainly includes paper forming, paper cutting and paper insertion. Common groove paper forming processes include cold forming and hot forming. The paper shapes mainly include O-type, C-type, B-type, and S-type. The most common ones are O-type. B-type and S-type can significantly improve the insulation performance, but the manufacturing process is more complicated, and the pure copper tank full rate is low. Poor stability.

For some motors, due to process reasons, two adjacent out-of-phase conductors in the stator slot must be isolated by two pieces of insulating paper, which causes the insulating paper to occupy a large space and reduces the power density of the motor.

In addition, since the two insulating papers are not related to each other, it is currently inconvenient to use equipment to automatically insert them into the stator slot. This has also become a major pain point in the automated manufacturing and production process of flat wire motors.

02-PIN coil forming

The stator core part flat wire motor manufacturing mainly includes several process categories such as I-PIN, Hairpin, Wave Winding and so on. The PIN coil needs to go through a series of processes such as straightening, patent leather removal, cutting, and molding. Laser patent leather removal and traditional patent leather removal are generally used. Among them, although the traditional method is low in cost, it also has problems such as incomplete paint removal and damage to copper wires.

The main forming processes include stamping forming and spring machine technology forming. The latter is more expensive but causes less damage to the copper wire.

03-Coil insertion

Insert the card coil into the profiling tooling, then firmly insert all the card issuing coils into the iron core, and press them into the corresponding design size. In this part of the process, cross-layer automatic insertion has been upgraded from the previous 2-layer and 4-layer processes to the latest 6-layer and 8-layer processes. There are also some domestic companies that can complete the manufacturing of this product.

04-Enlarging & twisting & welding

Expansion process: Move the fixture positioning mechanism equipped with the stator to the expansion station to be layered. The expansion mechanism covers the upper ends of the flat wires of all layers except the innermost two layers, and pulls the flat wires to move outward, completing one after another. Flaring of all layers of flat wire.

Twisting process: Move the twisting mechanism and stator to the working position, and the expansion mechanism stretches out to resist the ends of the innermost two layers of flat wires, so that the ends of the innermost two layers of flat wires are aligned with the twisting mechanism, and then the expansion mechanism starts from the flat wire. The upper end of the wire is removed and shrunk back, and then the ends of the innermost two layers of flat wires are inserted into the twisting mechanism. The inner mold and the outer mold of the twisting mechanism rotate in opposite directions to complete the twisting process of the innermost two layers of flat wires and complete everything again. Flat wire twist.

Welding process: The existing welding methods mainly include laser welding or argon arc welding. Both methods melt copper through instantaneous high temperature to form solder joints, thereby realizing the electrical connection of windings. At the same time, there are also other companies using CMT cold welding or other welding methods.

There are two main shortcomings in existing laser welding or argon arc welding technology:

First, laser welding and argon arc welding require an instantaneous high temperature to melt the copper, which can easily damage the enameled wire film around the welding point and reduce the insulation reliability;

Second, there are a large number of hairpin coils or single-sided coils that constitute the stator winding of the flat wire motor, which requires a large number of solder joints. Laser welding or argon arc welding generally welds the solder joints one by one, which seriously affects the production efficiency of the flat wire stator.

05-Coating & Dipping

The detailed flow of this process is as follows: coating and loading → armature preheating → armature coating → armature curing → coating and unloading → weighing the armature before dripping paint → scanning the code before armature dripping paint → armature Paint dripping and loading → armature preheating → armature paint dripping → armature gel curing → armature unloading → armature dripping paint and weighing, etc. →

There are currently two main types of coating materials: powder and liquid; the dipping process mainly includes traditional dipping, vacuum dipping, vacuum pressure dipping, drip dipping, etc., as well as EUV dipping process.

06-Stator potting

For a long time, motor thermal management has been a major challenge faced by many car companies. The increasing cruising range and power density have put forward higher heat dissipation requirements for motors. Currently, motors have always relied on cooling systems to achieve thermal management. At present, motor manufacturing mainly uses the impregnation process, but there are problems such as poor heat dissipation performance, easy breakage, and intolerance to organic oil. In this case, the vacuum potting process came into being.

For vacuum potting, the required potting resin needs to have the following characteristics:

It should have good fluidity before curing. It can penetrate into the uneven gaps on the winding surface. After potting, the outer surface of the workpiece should be smooth and flat, so that the rotating part of the motor has basically the same moment of inertia when rotating, reducing the sudden mechanical stress caused by sudden changes in the speed and steering of the motor. Vibration caused by thermal changes reduces the resistance of the cooling medium to the rotating part of the motor.

It should have strong adhesion to the motor windings, strong resistance to hot and cold shock toughness, and sufficiently high mechanical strength.

It should have a high thermal conductivity to reduce the temperature difference between the inner and outer surfaces of the potting compound. On the one hand, it can quickly conduct the heat generated during the operation of the motor winding to the outer surface of the workpiece. On the other hand, it can reduce the internal stress caused by temperature difference.

It has good electrical insulation properties and oil resistance. After potting, the motor stator forms a whole, the heat dissipation and stator modal stiffness and damping performance are improved, the temperature rise and vibration noise are reduced, and the moisture resistance, shock resistance, and corona resistance are improved. promoted.

Ningbo Nide Mechanical Equipment Co., Ltd. focuses on motor manufacturing solutions, providing hairpin motor manufacturing equipment to customers in many countries around the world, and providing customers with large-scale hairpin motor production lines. By using open coil segments prefabricated with rectangular cross-section wires and a high degree of automation, motor hairpin technology produces high-quality stators with higher filling rates.