So I have been playing with a fairly large Nema 23 stepper motor but I cannot really exceed 300 RPM under any load.
Currently, I seem to be experiencing a very sharp drop off in torque. As such it seems to me that at 200RPM the motor seems to have plenty of torque (I'm using a linear rod actuator which is not stoppable by hand @ 200rpm) whereas at 300rpm it seems to have virtually no torque.
As such, I was wondering why I don't seem to see people gear UP stepper motors. It seems to me that there is no way I could drive my actuator at 800rmp but it feels like the motor has enough torque at 200rmp that is it was 4:1 Geared up it would be able to turn?
I'm prepared for my logic to be ripped to shreds, but it was just a thought I had.
krishpants:
I'm prepared for my logic to be ripped to shreds, but it was just a thought I had.
Some stepper motor manufacturers publish graphs showing how the torque varies with speed. You could use the graph (for your motor or one like it) to see if the torque at 200 RPM is significantly more than 1.5 times the torque at 300 RPM.
Also keep in mind that gearing introduces friction losses. It may also introduce backlash which would not be acceptable if precision control is required.
Driving a stepper motor with a higher voltage should give more high-speed torque - subject to the voltage limit of the stepper driver.
If you tell us what you are trying to drive someone might be able to give you useful advice.
I am trying to drive a ball screw captive rod type actuator with a 10mm pitch thread, ie, I rotation = 1cm actuation. It has about 10kg of vertical load on it.
I was hoping to move it at around 200mm per second but it looks like achieving 1200 rpm at load from a stepper is unrealistic.
That said I am not able to get much above 300rpm either. I am limited to Nema 23 due to the size of the motor flange on this Festo Actuator.
I'm wondering if a closed loop motor might perform any better. Failing that I might have to see if I can find an actuator with a larger thread pitch.
You are asking for advice without sharing any facts.
Post a link to the datasheet for your stepper motor
Post a link to the datasheet for your stepper driver
Tell us what motor power supply you have - volts and amps.
If you have a snort test program to demonstrate the behaviour of the motor please post that.