3D Printable Brushless Motor and Generator

Goal Statement:

The goal of this project is to design and build a brushless DC motor (BLDC) with as many 3D printable parts as possible. This project will provide a fundamental understanding of how brushless motors operate and will construct a usable BLDC motor that can be applied to a wide range of projects from RC cars to small scale wind turbines.

Background:

The applications of BLDC motors are endless in hobby and industry applications due to their efficiency, power and simplicity. BLDC motors are the powerhouse behind many modern electronics like drones, electric vehicles and power tools. They are superior to their simpler, brushed counterparts because they use electronic commutation verses the brushed motors mechanical commutation. This reduces the number of rubbing surfaces and thus increases efficiency, and power. The downside to these motors is they require an external circuit to power them called an Electronic Speed Controller (ESC) to generates a 3 Phase alternating current that powers the motor. The good news is that these are readily available and generally quite cheap.

Feature Specifications:

Motor Type: Inrunner BLDC

Slots/Poles: 9 Slots / 6 Poles

3D Print Material: PETG (recommended for heat resistance and strength) or PLA

Materials (prices as of 1/4/2026)

1. 8mm Alignment Shaft (https://amzn.to/4jm51jA) $6.59
2. 608 Ball Bearing (https://amzn.to/3Ljyazw) $6.29
3. Neodymium Bar Magnets 60 x 10 x 3 mm (https://amzn.to/4aJglEo) $18.99
4. 22AWG Enameled Copper Wire(https://amzn.to/4snPN1R) $9.99
5. 3D Printer Filament, PETG or PLA
6. Electronic Speed Controller (https://amzn.to/49nposo) $28.99
7. Note: I used an ESC that I had on hand, not this one, but I would recommend something like this.
8. Power Supply
9. PWM Controller (I used an Arduino)
10. Super Glue

Tools

1. 3D Printer (I printed with an Ender 3 S1)
2. Soldering Iron with Solder

Stator (Red): The stator holds the copper windings and is, as the name suggests, stationary. As current is pushed through the coils of wire, it creates a magnetic field that attracts and/or repels the magnets in the rotor which causes the motion in the rotor.

Rotor (Yellow Right): The rotor is the portion of motor that rotates to create mechanical work. This sits on an axel that is supported by a pair of bearings. The rotor holds the permanent magnets which the coils interact with in order to cause motion.

Housing(Blue): The housing is the base for this entire motor. It provides mechanical support for the stator slots, keeps radial alignment of the motor and provides a way to fix the motor to a part of a larger system.

Threaded Alignment Cap(Yellow Left): This cap contains a set of 3D printed threads and a recess for a bearing. The part allows for the insertion of the internal motor components. In addition there are vent holes to allow for airflow to cool the motor coils.

Material Selection & Sustainability

For my prototype, I chose PLA because it is easy to print and offers a more sustainable footprint during the iterative design phase. However, for the final assembly, I recommend PETG or ABS. These materials provide the superior tensile strength and heat resistance required to withstand the thermal energy generated by the copper windings and the centrifugal forces of high-RPM rotation.

Recommended Infill Settings

1. Rotor
2. Infill: 100%
3. Stator
4. Infill: 100%
5. Housing
6. Infill: 40%
7. Alignment Cap
8. Infill: 40%

Engineering for Tolerances in Fusion 360

One of the most important aspects of mechatronic design is management of tolerances. The provided files are modeled with clearances that work well for my specific printer. However, 3D printers vary significantly in their dimensional accuracy. If you find the bearings are too tight or the rotor rubs against the stator, you can easily adjust the parameters in the provided Fusion 360 file.

The Engineering Concept

For the motor to maintain continuous rotation, the magnetic polarity must alternate (North-South-North-South) around the circumference. This arrangement ensures that as the Electronic Speed Controller (ESC) switches the magnetic field in the stator, it is constantly "pushing" or "pulling" against the rotor magnets, creating consistent torque.

Assembly Instructions

1. Prepare the Slots: Inspect your 3D-printed rotor for any debris or printing artifacts. The magnets should sit flush against the walls to maintain a consistent air gap between the rotor and stator.
2. Apply Adhesive: Apply a small drop of high-strength superglue (cyanoacrylate) into the first magnet slot.
3. Polarity Check: One way to ensure your polarity is correct is to pay attention to how the magnets behave as you insert them:
4. Correct Polarity: If the magnet is oriented correctly relative to its neighbor, the magnetic flux will help pull it into the slot.
5. Incorrect Polarity: If the polarity is backward, the magnet will physically try to "jump" out of the slot or repel away from the adjacent magnet. Use this tactile feedback to double-check your N-S-N-S pattern before the glue sets.
6. Secure with Pressure: Because 3D-printed surfaces can be slightly uneven, apply constant pressure to ensure the magnets bond flat. A simple rubber band wrapped around the exterior of the rotor provides excellent, even clamping force.
7. Cure Time: Repeat this process for all poles. Once all magnets are installed, allow the assembly to sit undisturbed until the glue has fully cured.
8. Insert the Alignment Shaft: The alignment shaft should be inserted into the inner diameter for the rotor. This can be done by hand or may need to be forced in with a clamp depending on your printer and settings.

While the glue cures on your rotor assembly, it is time to move on to the most critical and skill-intensive part of the build: winding the stator. Because the performance and safety of your motor depend entirely on the quality of these coils, patience is key here.

1. Preparation & Quality Control

Before winding, it is important to remove any sharp points. Use a small file or sandpaper to smooth out any sharp edges on the stator teeth. Magnet wire is coated in a thin layer of enamel for insulation. If a sharp 3D-printed edge scratches this coating during winding, the copper could touch other wires, causing a short circuit that can destroy your ESC or battery.

2. The Winding Technique

1. The Count: Each of the 9 slots must have exactly the same number of revolutions of wire. For this motor I chose 14 revolutions of wire, however depending on the needs of your motor you may want to change this number.
2. Layering for Efficiency: To keep the motor compact and the magnetic field strong, wind your wire in two neat layers:
3. First Layer: Start at the base of the tooth and wind tight, side-by-side coils moving toward the tip.
4. Second Layer: Once you reach the tip, wind the coils back down toward the base, sitting them directly on top of the first layer.
5. Subsequent Layers: Repeat the instructions for the previous layers until you have reached the desired number of revolutions.
6. Avoid Overlap: Ensure the wire never crosses over itself unintentionally within a layer, as this creates bulk and reduces efficiency.

3. Following the Delta System

Using the Delta System diagram provided in the previous steps, you will wind three phases:

1. Phase A (Purple): Wind teeth 1, 4, and 7.
2. Phase B (Blue): Wind teeth 2, 5, and 8.
3. Phase C (Yellow): Wind teeth 3, 6, and 9.

4. Wire Termination

Once all 9 teeth are wound, you should have six wire ends (two for each phase). Refer back to the Delta System diagram to solder your starts and ends together.

With the rotor magnets cured and the stator wound, it is time to put everything together and use this motor.

1. Final Mechanical Assembly

Precision is everything in motor design. A small misalignment can lead to rubbing between the rotor and stator, which creates heat instead of motion.

1. Insert Bearings: Carefully insert your ball bearings into the 3D-printed recesses in the housing. They should be a snug "press-fit." If they are loose, a drop of glue on the outer race can secure them.
2. Insert Stator: Slide the wound stator into the housing. The slot arms will slightly recess into notches on the housing for a snug, sturdy fit.
3. Insert Shaft and Rotor: Slide the motor shaft with the rotor through the stator and the bearings.

2. Wiring and Electronics

To control the motor, we use an ESC, which powers the motor, and an Arduino, which tells the ESC how fast to spin the motor.

1. The Power Source: I utilized a 14V power supply for this build. While higher voltage increases the top speed (RPM), ensure your ESC is rated for that voltage to prevent hardware failure.
2. Control Logic: The Arduino sends a PWM signal to the ESC. Most hobby ESCs use a standard servo signal to determine speed.
3. Schematic: Connect the three phases of your motor to the three output wires of the ESC. If the motor spins in the wrong direction, simply swap any two of these three wires.

3. Testing and Operation

Before turning on the motor, ensure the motor base is secured to your work surface.

1. Initialization: Turn on your Arduino first, then the power supply. Most ESCs will emit a series of beeps to indicate they are armed and ready.
2. Gradual Throttle: Slowly increase the PWM signal to start the rotation. Listen for any grinding or unusual vibrations. If you do hear something unusual, power down the motor immediately to troubleshoot.

3. Use the Motor for Your Desired Application

This is a highly adjustable and practical motor design for use in a variety of hobby projects. Some examples of possible projects include:

1. RC Car: This motor could operate as a crucial part of the drive train for a beefy RC car.
2. RC Boat or Submersible: This project could be adjusted so that it could operate in wet conditions and be used to power a small scale boat or submarine.
3. Power Generator: One of the most exciting features of this design is its reversibility. Beyond just spinning, you can connect the three phases to a 3-phase rectifier circuit to turn this motor into a wind or water turbine to make your own small scale generator.
4. Further Motor Optimization: I constructed this simple BLDC motor with Fusion 360, and it is by no means the perfect motor. It could be further optimized for increased torque and top speed by applying modern motor theory to the Fusion file.