Why are more and more applications using coreless DC motors? Take humanoid robotic components for example. The finger joints in dexterous hands require a high degree of freedom and must be equipped with compact, high-power motors. Therefore, they mainly use coreless motors.
With global companies like Tesla, NVIDIA, and Huawei increasing their investments, the industry is rapidly gaining momentum.
Are you also curious about what a coreless motor is and how it’s made?
Coreless Electric Motor and Its Structure
The construction of coreless DC motors is different from traditional DC motors. It is a permanent magnet servo motor without a rotor core. It mainly consists of a shaft, bearings, brushes, commutator, cup-shaped winding, rotating shaft, coil, sliding bearings, housing, and magnets .
Based on the commutation method, coreless motors are divided into brushed and brushless types.
Coreless Brushed DC Motor
Brushed coreless motors have a simple structure and relatively low cost. The carbon brush and commutator on the rotor convert electrical energy into mechanical energy.
Their contact produces sparks and causes noise and vibration due to wear. This also affects performance and shortens motor lifespan.
Brushed coreless motors are suitable for areas with lower size and weight requirements, such as small household appliances.
Brushless DC Coreless Motor
Brushless coreless motors have a more complex structure and higher cost. Without brushes and commutators, they use electronic converters to convert electrical energy. They automatically adjust current direction based on rotor position, allowing spark-free operation and longer lifespan.
Brushless coreless motors are small and lightweight, yet efficient and durable. They are ideal for drones, robots, and precision equipment.
Brushed vs. Brushless Coreless Motors
| Brushed Coreless Motor | Brushless Coreless Motor | |
| Structure | Simple | Complex |
| Lifespan (hours) | 2,000 | 20000 |
| Efficiency | Limited speed | High speed |
| Noise | Has noise and sparks | Stable operation, less noise and vibration |
| Control Precision | Simple control | Requires drive controller |
| Size and Weight | Larger and heavier | Smaller and lighter |
| Cost | Low | High |
How Are Coreless Motors Manufactured?
Materials
Coreless motors use copper, steel, and permanent magnets as raw materials.
Coreless Stator Winding
The winding process is a core technical barrier. It directly affects the motor’s size, speed, power density, and yield rate.
Self-supporting windings without a core are made from enameled wire. During manufacturing, pressure and heat melt the varnish between wires to form a solid coil structure.
There are two main forming methods: coiled production and one-time forming.
Coiled Production: This method is complex. First, copper wire is wound into a hollow geometric shape. Then it’s pressed flat into a copper strip, and finally wound into a cylindrical coil.
One-Time Forming: The machine winds copper wire on a spindle in one go. It doesn’t need flattening or rounding steps.
The second method is simpler and more efficient.
Most Chinese manufacturers still use the coiled production method. It has lower efficiency, higher defect rates, and smaller coil diameters. Technology for high-performance large-diameter coils still needs improvement.
Winding Methods
There are three main winding shapes: straight winding, saddle winding, and skew winding.
Straight Winding
This method is complex and used for long winding structures. It often requires multiple rounds of winding.
The coil is arranged parallel to the rotor axis. The wires are stacked neatly, forming a rectangular or square cross-section.
The winding path is simple. It usually starts from one end and stacks layer by layer like a bookshelf.
Saddle Winding
The coil bends at both ends in an arc, with a straight middle section. The shape looks like a saddle. The path alternates between axial and radial directions.
The bent ends form a compact 3D structure, which shortens the coil ends effectively.
Skewed Winding
The wires are wound at an angle, typically between 30° and 60°, in a spiral. Layers are staggered to form a tight honeycomb-like structure.
The wires cross diagonally, filling the gaps efficiently. The cross-section looks circular or hexagonal.
Saddle and skew windings have simple processes. Their coils are light, with low inertia and time constants. They offer excellent dynamic performance and high torque output. These methods are common among advanced foreign manufacturers.
For example, Germany’s Faulhaber uses skew winding, and Switzerland’s Maxon uses saddle winding. Their motors have outstanding performance.
Coreless motors are small and allow less room for manufacturing error. Processing accuracy affects the stability of the magnetic field. Differences in wire thickness and coil turns can lead to large differences in resistance, startup current, and speed constants. So, improving precision and yield in production is crucial.
Applications of Coreless Motor
Coreless DC motors are used extensively in medical applications, including prosthetics, small pumps (such as insulin pumps), laboratory equipment, and X-ray machines. Their ability to handle fast, dynamic moves also makes them ideal for use in robotics, computer equipment, clocks, medical instruments, and ink-jet printer applications.
Coreless Motor & Lamination Stacks– Choose Lamnow
Lamnow is a leading motor lamination manufacturer in China. We design and produce slotless motor cores in various sizes and types. If you need a coreless motor or stator lamination, contact us today.
