How to Make UAV Motor Stator Lamination Stacks?

author: Zove

2025-12-25

How to Make UAV Motor Stator Lamination Stacks?

Introduction
Understanding Stator Lamination Stacks
The Manufacturing Process: A Step-by-Step Guide
Key Design and Material Considerations
UAV Motor Stator Core: Typical Parameters Table
UAV Inrunner vs. Outrunner Lamination Stacks
Expert Insights
Frequently Asked Questions (FAQs)

1. Introduction

At the heart of every efficient and powerful UAV brushless motor lies a critical component: the stator lamination stack. This core element is responsible for converting electrical energy into precise magnetic fields that drive the rotor, directly impacting the motor's performance, efficiency, and thermal management. For engineers, manufacturers, and DIY enthusiasts in the UAV industry, understanding how these lamination stacks are made is key to optimizing motor design. This blog provides a comprehensive guide to the manufacturing process, design nuances, and industry insights.

2. Understanding Stator Lamination Stacks

The stator core is not a solid block of metal. Instead, it is constructed from hundreds of thin, insulated steel sheets pressed together—a lamination stack. This design is fundamental to fighting eddy current losses. If the core were solid, circulating currents induced by the alternating magnetic field would generate significant heat, drastically reducing efficiency. By using insulated laminations, these paths are broken, minimizing energy loss and heat generation.

3. The Manufacturing Process: A Step-by-Step Guide

Creating a high-performance stator stack is a multi-stage process requiring precision at every step.

H3: 3.1 Material Selection

The journey begins with choosing the right electrical steel, often silicon steel. The grade (e.g., 35JN230, 50JN400) dictates properties like core loss and permeability. Thinner laminations (typically 0.1mm to 0.35mm) reduce eddy currents further but increase manufacturing complexity and cost.

H3: 3.2 Stamping/Punching

The selected steel coil is fed into a high-precision progressive die. This die stamps out the intricate stator lamination shape, including the central bore, stator teeth, and winding slots in a single press. Die design and maintenance are critical for achieving clean, burr-free edges, as burrs can create short circuits between layers.

H3: 3.3 Heat Treatment (Annealing)

After stamping, the laminations undergo stress relief annealing. This process removes internal stresses caused by punching, restoring the steel's magnetic properties and improving its permeability, which is crucial for performance.

H3: 3.4 Insulation Coating

Each lamination is coated with an insulating layer. This can be an organic coating (like enamel or varnish) or an inorganic one (like phosphate or oxide). This thin, durable layer is essential for preventing interlamination shorts.

H3: 3.5 Stacking and Bonding

The insulated laminations are precisely stacked to the required height. They must be aligned perfectly to ensure smooth magnetic flux paths. The stack is then bonded using:

Interlocking: Small tabs are stamped and bent to hold layers.
Welding: Spot welds at the stack's outer edge.
Adhesives: Epoxy or other bonding agents.
Riveting: Using small rivets through the stack.

H3: 3.6 Final Machining and Quality Control

The bonded stack may undergo final machining for a precise OD and ID. Rigorous QC checks follow, measuring stack height, parallelism, slot dimensions, and insulation resistance. Advanced methods like core loss testing ensure the stack meets electrical specifications.

For a deeper dive into core assembly and winding preparation, you can refer to our previous blog: How to make drone motor stator core?.

4. Key Design and Material Considerations

Slot-Pole Combination: The choice (e.g., 12N14P, 9N12P) affects torque ripple, cogging, and efficiency. It's a fundamental trade-off in motor design.
Slot Design: The shape and size of the stator slots influence winding ease, copper fill factor, and magnetic saturation.
Lamination Profile: The geometry of the teeth and yoke is optimized for magnetic flux path and heat dissipation.
Material Grade: Higher-grade, thinner silicon steel with lower core loss is preferred for high-end, high-RPM UAV motors where efficiency is paramount.

5. UAV Motor Stator Core: Typical Parameters Table

Parameter	Typical Range/Value for UAV Motors	Notes
Lamination Material	Silicon Steel (Non-Grain Oriented)	Grades like 35JN230 are common.
Lamination Thickness	0.1mm - 0.35mm	Thinner for higher RPM/efficiency.
Stack Height	3mm - 20mm	Depends on motor size (e.g., 2207, 4014).
Number of Slots (N)	9, 12, 15, 18, 24	Standard options for 3-phase motors.
Outer Diameter (OD)	15mm - 80mm	Scales with motor stator size.
Inner Diameter (ID)	5mm - 60mm	Defines the air gap with the rotor.
Insulation Coating	Organic (C5, C6) or Inorganic	C5/C6 offers excellent corrosion resistance.
Tolerance (Stack Height)	±0.05mm	Critical for consistent performance.

6. UAV Inrunner vs. Outrunner Lamination Stacks

UAV motors primarily use Outrunner configurations, where the stator is inside and the magnet bell rotates externally. However, Inrunner designs are used in specific applications like turbojet starters or some FPV drone systems.

Feature	Outrunner Stator Lamination Stack	Inrunner Stator Lamination Stack
Location	Inside, stationary.	Outside, stationary (housing).
Diameter	Smaller OD for a given motor size.	Larger OD for a given power.
Cooling	Good, as windings are exposed to airflow.	Can be more challenging; often requires forced air or liquid cooling.
Torque & RPM	High torque, lower RPM direct drive.	Lower torque, very high RPM (often geared).
Lamination Design	Focus on maximizing tooth surface area for torque.	Yoke design is more critical for magnetic flux return.
UAV Application	Overwhelmingly standard for multirotor propulsion.	Less common; used in special applications requiring high RPM.
Manufacturing Complexity	Generally standard.	Often requires more complex housing integration.

7. Expert Insights

Dr. Elena Rodriguez, Senior Electromechanical Engineer at AeroDynamic Labs, notes: "The trend in high-performance racing and cinematic UAVs is pushing toward ultra-thin laminations (0.1mm-0.15mm) and higher-silicon-content steel. While costlier, the reduction in high-frequency core loss at 40,000+ RPM is non-negotiable for peak efficiency. Furthermore, we are seeing more sophisticated asymmetric slot designs to optimize torque density while managing cogging."

8. Frequently Asked Questions (FAQs)

Q1: Why can't we use a solid steel block for the stator?
A: A solid block would create massive eddy current losses, causing extreme inefficiency and overheating. Laminations with insulation break these current paths.

Q2: What is the impact of poor lamination insulation?
A: Poor insulation leads to interlamination shorts, effectively making the stack act thicker. This significantly increases eddy current losses, reduces efficiency, and causes localized hot spots.

Q3: How does the number of stator slots affect performance?
A: More slots generally provide a smoother torque output and lower cogging torque but can reduce slot area for windings and increase manufacturing cost. It's a key design trade-off.

Q4: Can I use the same lamination stack for different KV motors?
A: Yes, primarily. The KV rating is mainly determined by the number of winding turns. The same physical stack can be wound with different turn counts to achieve different KV values, though the optimal slot-pole combination remains constant.

Q5: What's the main takeaway in choosing laminations for a UAV motor?
A: Prioritize low core loss material and precision manufacturing. For most UAV applications, an outrunner stator stack with thin-gauge, high-grade silicon steel, clean stamping, and reliable insulation will deliver the best performance-to-weight ratio.