I finally got to test the power out of my actuator. It’s 580g (1.25lbs) at a 100mm distance, which is awesome. That means 1160g (2.5lbs) at 50mm distance and 2300g at 25mm distance (5lbs). Considering the larger motors won’t be the problem, rather it’s the 3 small actuators at the end of the robot, I should be able to get at least 1lb of lifting force since the small actuators themselves weigh 176g (0.38lbs). Am I doing my math correctly?
In the video I’m running the stepper motor at 250mA. It’s rated at 150mA. The arm is 100mm long and the part pressing the scale is true to the center of the axis on the actuator.
One thing to be careful of when over-driving a motor, besides overheating, is demagnetizing the permanent magnets. Maximum rated stepper current can be close the demagnetization limit. I’ve seen hybrid steppers (NEMA style) that have a peak current limit (demagnetization limit) of only 110% of the steady state current limit (thermal limit), I don’t know if this is the same, though, for permanent magnet, tin-can style motors. To test if you’ve demagnetized the motor, you could compare the torque generated at the rated current of an over-driven motor to that of a fresh motor.
Also, are these the Moon’s motors, or are they the cheaper ones you found?
The test in this video is the Moon’s motor. It seems to still be as powerful as I recall it always being, but I could run a test on fresh Moon’s motors that I’ve barely used. I was going to test the other cheaper motor soon because it has a very different sound to it. My Moon’s motors have about a 90Ohm resistance per coil, and the other steppers have about a 12Ohm resistance.
These definitely heat up faster when I overdrive them, so hopefully it’s just heat creation which is manageable, rather than demagnetization, but your point does worry me I can’t push these too far.