Finding Torque Without An Angular Acceleration (stepper motor)

In summary, my friend is trying to find out what torque and angular acceleration he needs to use an electric stepper motor to turn a thin disk. He is looking at datasheets for different motors and trying to choose one that will provide the necessary torque and angular acceleration.
  • #1
Tyler
3
0
A friend of mine posed a question to me the other day and I can't seem to wrap my head around it.

He's working with an electric stepper motor to turn a large thin disk, but he can't be sure of the torque required because to find the torque he needs the moment of inertia and the angular acceleration. The moment of inertia is easy to find since he has all of the disk's dimensions, but the electric stepper motor is taking the thin disk from 0 to a near constant velocity and back down to zero almost instantaneously.

Is there some other way to find the torque/angular acceleration that I'm just not thinking of?
 
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  • #2
Tyler said:
A friend of mine posed a question to me the other day and I can't seem to wrap my head around it.

He's working with an electric stepper motor to turn a large thin disk, but he can't be sure of the torque required because to find the torque he needs the moment of inertia and the angular acceleration. The moment of inertia is easy to find since he has all of the disk's dimensions, but the electric stepper motor is taking the thin disk from 0 to a near constant velocity and back down to zero almost instantaneously.

Is there some other way to find the torque/angular acceleration that I'm just not thinking of?
What does the datasheet for the stepper motor say for the available torque per step? How many degrees is each step? The steps are not "instantaneous" -- the datasheet should give some idea of the time per step that is advised (depends on drive voltage and current)...
 
  • #3
berkeman said:
What does the datasheet for the stepper motor say for the available torque per step? How many degrees is each step? The steps are not "instantaneous" -- the datasheet should give some idea of the time per step that is advised (depends on drive voltage and current)...
Well, therein lies the catch. He's trying to pick a motor based on the amount of torque he needs, or at the very least trying to verify that the motor he is looking at is more than enough for the task.
 
  • #4
Tyler said:
Well, therein lies the catch. He's trying to pick a motor based on the amount of torque he needs, or at the very least trying to verify that the motor he is looking at is more than enough for the task.
Well, post links to a few of the datasheets he is considering, and we'll see if we can help. :smile:
 
  • #5
berkeman said:
Well, post links to a few of the datasheets he is considering, and we'll see if we can help. :smile:
Sorry, could've sworn I put the link in the last post. My mistake.

http://www.newmarksystems.com/rotary-positioners/rm-8-motorized-rotary-stage/
Also, the thin disk being rotated is 6061 aluminum, 1/4" thick, 15" radius, and he wants it to turn 40 degrees over a period of 3.5 seconds.
 

1. What is torque and why is it important in a stepper motor?

Torque is a measure of the rotational force exerted on an object. In a stepper motor, torque is important because it determines the motor's ability to produce movement and maintain control over its position.

2. How can I find the torque of a stepper motor without knowing its angular acceleration?

There are a few different methods for finding torque without measuring angular acceleration. One approach is to measure the motor's current and voltage while it is running, and use these values to calculate torque using the motor's torque constant. Another method is to use a dynamometer to physically measure the torque output of the motor.

3. Can I determine the torque of a stepper motor using its specifications?

Yes, most stepper motors will have a listed torque value in their specifications. This value is typically measured at a specific speed and current, so it may not be an accurate representation of the motor's torque in all operating conditions.

4. Does the load on a stepper motor affect its torque output?

Yes, the load on a stepper motor can significantly impact its torque output. A heavier load will require more torque to move and maintain control over the motor's position, while a lighter load will require less torque.

5. How does the step angle of a stepper motor relate to its torque?

The step angle of a stepper motor is the angle that the motor rotates with each step. In general, a smaller step angle will result in a higher torque output, as the motor is able to make more precise movements. However, this also depends on other factors such as the motor's size and construction.

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