Here is my setup and I am looking/suggestions to keep the heat at a minimum.
- 2 micro gear motors driving one shaft. They are 6V medium power, with 298:1 gear ratio. One has an encoder on it. They have small heat-sinks attached to them
- They are driven by MAX14870
They are driving a 3D printer extruder, controlled by adafruit feather m0-proto arduino.
They heat quite a bit which is not acceptable for my use case because the shaft temp above 60C can soften filament.
I’ve tried many things and verified many potential problems.
- Switched from single high power motor to double medium power motor
- Kept the min proportional PWM at 1/3. It is driven by only be proportional PID, Kp=something, the others 0.
- Verified that motors stop completely when they need to.
- Even tried r-sense resistor for current limiting.
Will try low power motors next, but they are coming close to the torque/speed requirements.
Any suggestions or is it something I might be doing wrong?
It sounds like you have very specific (and fixed) output power requirements, which is going to constrain your input power requirements, so your best bet for reducing heating would be to use the gearmotor version that offers the best efficiency for your desired operating conditions (i.e. pick the motor that can generate the output power you need with the least power wasted.) You can find the efficiency graphs for each micro metal gearmotor at their rated voltage in their datasheet.
If that is not enough, then external cooling like you are already trying could help, but probably it won’t have much of an impact. It is the rotor that is getting hot, and that is not well thermally coupled to the case.
The next best option would be to switch to a larger motor, since that will have more volume over which to dissipate the heat. Have you considered our 20D gearmotors?
By the way, I am a little concerned about your use of two gearmotors in parallel like that. If they are not well matched, they could be fighting each other in a way that reduces the efficiency a lot. However, this could be outweighed by spreading the power dissipation over multiple motors, so it might still be a net benefit over a single-motor approach.