What are the product barriers for coreless motors?

Currently, the coreless motor industry has high product barriers, making entry difficult. The core challenge lies in winding technology, specifically encompassing three dimensions: winding design, winding process, and winding equipment. Even after overcoming technical bottlenecks and achieving mass production, the product yield remains difficult to maintain at a consistently high level due to factors such as tension fluctuations and wire fit during the winding process, further raising the barrier to large-scale implementation. 1. Winding Design: Winding design is the core of the coreless motor's technological barriers. It is a typical deep integrated optimization process involving multiple physical fields (electromagnetism, thermodynamics) and multiple disciplines (electromagnetism, materials science, mechanical engineering). This process specifically covers three core tasks: Electromagnetic and Structural Parameter Optimization: Precise matching of parameters such as the number of turns and wire diameter is required to achieve the optimal magnetic field distribution and magnetomotive force without core constraints. This directly determines the motor's power density, efficiency, and output torque. Winding Topology Design: For irregular cup-shaped structures (such as cylinders and discs), the spatial arrangement path, end turning, and fixing method of the conductors must be precisely designed to ensure the mechanical stability of the windings and avoid deformation or vibration caused by electromagnetic or centrifugal forces. Material Selection and Thermal Management Co-design: The conductors need to have both high conductivity and high strength; simultaneously, due to the lack of a core, the heat dissipation path changes, requiring optimization of the winding gap and matching of the thermal conductivity of the insulation material to construct an efficient heat dissipation path and control operating temperature rise. The core challenge for designers lies in balancing conflicting goals such as high power density, low torque fluctuation, small size, and high reliability. An excellent winding design not only defines the upper limit of motor performance but also lays the foundation for process feasibility and equipment selection, making it the primary and most critical link in forming industry barriers. 2. Winding Process: The winding process is the core barrier to building the performance and mass production feasibility of coreless motors. This process aims to transform individual enameled wires into a self-supporting coil with sufficient mechanical strength. The key lies in the precise control of temperature, pressure, and time, allowing the insulation varnish (such as polyurethane or polyamide-imide) of the enameled wires to thermally melt and solidify, forming a strong insulating bond between adjacent conductors to withstand the enormous centrifugal force generated by the high-speed rotation of the motor. The level of this process directly determines the coil's precision, consistency, and final structural strength, thus affecting the motor's torque output, efficiency, NVH (noise, vibration, and harshness), and mass production yield. Based on the winding method, the mainstream processes mainly include three types: straight winding, saddle winding, and oblique winding. Their technical characteristics and applicable scenarios differ significantly: Straight winding: A coil winding method suitable for long winding structures in coreless motors. Its core feature is that, using the axis direction of the motor stator or rotor (i.e., the length direction of the motor) as a reference, the wire tension and arrangement trajectory are precisely controlled to tightly wind the wire along this direction, forming a columnar or layered regular winding. Because it needs to meet the production requirements of longer windings, it usually requires multiple windings, resulting in relatively high process complexity. The final finished winding has good insulation performance and stable output torque. Saddle winding: One of the mainstream coil winding schemes in the field of coreless motors, and also a commonly used winding method in advanced coreless motor technology abroad. Based on the arc-shaped contour of the motor stator slots, the wire is wound in one continuous motion along the arc-shaped trajectory within the slots, resulting in a symmetrical "saddle-shaped" overall winding profile-the main body of the winding perfectly matches the stator slots, with gently sloping and symmetrical extensions at both ends. This winding method is simple and efficient, requiring no multiple rewindings. The finished winding boasts core advantages such as light weight, low moment of inertia, high electromagnetic utilization, high output torque, and a small time constant. Inclined winding: A key coil winding method in high-end applications of coreless motors, representing an advanced international technology. During winding, the wire is kept at a 5°-15° angle to the motor axis. The inclination angle and helix spacing are precisely controlled by the winding machine, continuously winding along the stator slots to form a helical winding. This winding exhibits a smooth and uniform magnetic field distribution. The manufacturing difficulty falls between that of straight winding and saddle-shaped winding. The finished product possesses significant characteristics such as minimal moment of inertia, low electromagnetic noise, small time constant, and high lightweight, making it suitable for scenarios with stringent requirements for rapid response and low noise.

3. Winding Equipment for Hollow Cup Motors: Based on their forming path, winding equipment for hollow cup motors is mainly divided into two categories: sheet winding and direct winding. Sheet Winding: This process is long and complex. First, copper wire is wound into a two-dimensional diamond-shaped or wavy coil on a flat mold. Then, the coil is pressed into a flat wire strip using a precision mold. Finally, this wire strip is wound and cured to form the final cylindrical coil. Characteristics of this forming method: The technology is mature, but the steps are numerous, and the requirements for materials (enamel film ductility) and mold precision are extremely high. During the pressing and winding process, enamel film damage, wire deformation, or internal stress can easily occur, leading to poor consistency and a high scrap rate. Its main advantage is the ability to produce coils with very short axial lengths, but it has significant disadvantages in the production of large-diameter, high-power coils. Direct Winding: Using a multi-axis linkage precision winding machine, the enameled wire is directly wound in three dimensions on a cylindrical mold (mandrel) in one step, eliminating the need for subsequent flattening and rolling processes. The characteristics of this forming method are: short path, high degree of automation, and low risk of material damage, resulting in high efficiency and good consistency. Advanced direct winding technology can produce high-performance coils with larger dimensions, higher slot fill factor, and superior geometry. Its technological barriers mainly lie in the complexity of the winding machine and the precision of the control algorithm. It is currently the mainstream process for high-end coreless motors.