Introduction: 3D Printed Brushless Motor
I designed this motor using Fusion 360 for a demonstration on the topic of motors, so I wanted to make a fast yet coherent motor. It clearly shows the parts of the motor, so it can be used as a model of the basic working principles present in a brushless motor.
I found that when powering the motor with a standard AA, it works best with only one bearing because to the decreased friction. When using higher voltage, the top bearing helps to center the rotor and allow it to reach higher speeds.
I powered my motor using a DC power supply set to 1-12V and a current limit of 6A. The 6.0A pictured on the power supply's screen is not a measure of the current draw, but rather a current limit. Because of the resistance present in the thin gauge motor windings, the actual current draw is much lower than the set limit. If you wanted a more useful motor, with more torque, you could try using thicker gauge windings.
Here is the link to the files for this project:
How it works: When energized, the coil creates a magnetic field that pushes or pulls a magnet. When the coil is energized at just the right time, the magnet is pushed or pulled, and the rotor rotates. The coil is timed by using a reed switch: When one magnet is near the reed switch, the other is at just the right position to be pushed or pulled by the coil, which in turn causes the rotor to spin.
It might seem improper to call this a brushless motor because of the reed switch, but the reed switch could be replaced by a latching Hall Effect sensor and even some control electronics. In order to drive the motor without current limitations, this sensor should connect to the base of a Darlington Pair of transistors. I opted for a reed switch because I had a few around and didn't want to overcomplicate the motor, as I was using it for a demo on the principles of a brushless motor.
File Names Breakdown:
'rotor': This is the rotor that will need supports to print.
'base': Well, the base!
'sensorMount': Mounts the reed switch or hall effect sensor to the base. This part requires supports to print.
'spool1' and 'spool2': Print one of each; These collectively form the spool to make a coil.
'switchMount': This optional part goes over the switch to hold it in place.
**The motor can be configured in two ways: With a AA or other low voltage source, the motor works well without the upper bearing mount. In fact, even when spinning quickly, the motor doesn't need the upper and lower bearing mount.
'lowerBearingMountONLY': This is the mount you should use if you only want to use one bearing for decreased friction.
'lowerBearingMount' and 'upperBearingMount': These are the mounts you should use if you choose to use two bearings for increased stability and balance.
*I am not responsible for any injuries or damage to property that may result from following this Instructable. If not secured properly, the spinning magnets may pose a risk to you and your surroundings.
1. 3d printer or access to a 3d printer (no special magnetic filament required)
2. 2x 12⌀ x 5mm circular neodymium magnet
3. Enabled copper wire. I used ~26 gauge, but I suggest experimenting with different gauges to get different amounts of torque and speed; Thicker wire should allow for more current to flow and often results in a motor with more torque and a higher current draw, but a lower kV. Thinner wire should result in the opposite of the aforementioned properties. Remember: The higher the wire gauge number, the thinner the wire.
4. ~14 gauge silicone wire
5. 1or2x Ungreased/ unsealed 608 ball bearing(s) (same size as found in fidget spinners)
6. Reed switch or threshold hall sensor
Step 1: Making the Coil
Glue the 'spool1' and 'spool2' together to create a spool. Using the enameled copper wire, make a coil on the spool until it is ~3mm below the edges. Keep the two ends of the wire a few inches long for later use.
Step 2: Assembling the Rotor
Press the 12mm⌀ by 5mm circular magnets into the rotor and use copious amounts of glue. Upon further inspection of my motor post-explosion (see the intro video), I found out that the high centrifugal forces caused one magnet to fly off and imbalanced the rotor. Wrapping electrical tape around the rotor to secure the magnets wouldn't be a bad idea. Once securing the magnets, test the fit of the rotor's shafts in the bearings. If the fit is too loose, wrap electrical tape around the shafts until the fit is snug.
If you need to balance the rotor, I would suggest using adding small amounts of clay to the lighter side, or sanding away some plastic from the heavier side.
Step 3: Mounting the Switch
The 'switchMount' simply goes around the top of the switch and is secured with glue. The switch is optional but useful.
Step 4: Mounting the Coil
Slide the coil into the two slots in the base and secure with glue. The orientation does not matter, as we can change the polarity when we wire it.
Step 5: Mounting the Rotor
Test the fit of the 608 bearings in the 'lowerBearingMount'. If it is too loose, wrap some tape around it until it is snug.
The 'lowerBearingMount' or 'lowerBearingMountONLY' should be glued 4mm to the right of the coil (from the perspective of facing the switch). The side of the part that was printed facing the print bed should be glued touching the base. Make sure to use high strength adhesive as mine flew apart when I loosely glued it (see the video at the intro).
If you have not already done so, press the bearing into its mount and then press the rotor into the bearing:
If you are using one bearing press the side of the rotor that faced up during printing into the bearing (flip it over) as shown above
If you are using two bearings press the second bearing into the 'upperBearingMount', and glue it to the 'lowerBearingMount'. Make sure to do this AFTER you have installed the rotor with the side that faced down during printing, down (don't flip it over).
Step 6: Mounting the Sensor
You can use a threshold hall effect sensor that turns on when a magnet is near or a reed switch. I used a reed switch because I had a few, but a hall effect sensor should also work (possibly requiring a transistor).
I taped the reed switch to the 'sensorMount' and glued the mount 45° to the coil. If you want to advance the timing to optimize the motor's performance in a particular direction, you can do so by making the position of the sensor slightly greater or less than 45°. It should be spaced away from the rotor just enough to allow clearance for the magnets. See the above images.
Step 7: Wiring It Up!
Reed Switch: Connect one wire from the coil to the black wire from the switch, and then attach the other wire from the coil to the top of the reed switch. Next, wire the bottom of the reed switch to a 12 AWG wire that will go to your power source. The red wire from the switch will also go to your power source.
Polarity does not matter as the motor will simply spin in the opposite direction if the polarity is reversed.
You could instead use a hall sensor and Arduino to drive the motor rather than using a reed switch, but I had a few reed switches lying around, and didn't want to overcomplicate the motor as I was using it for a demo.
Participated in the
3D Printed Contest