I’m trying to find a motor for a project one of my grad student is doing. I need to rotate a cylindric metal sample at a speed of 20-25 rpm in an environment where it will be bombarded by small metallic pellets. The sample is about 5 cm in diameter and 30 in length. (See my very poor MSpaint skills for sample, motor M and the unmoving blue sample holder).
i initially tried using a # Nema 17 Closed Loop Stepper Motor 45Ncm/64oz.in with Magnetic Encoder 1000PPR(4000CPR) from stepperonline, as i worked with steppers before and knew how to program it. Turns out i wasn’t used to work with heavier loads and killed the stepper by demanding too much current.
What i’m looking for is a replacement motor with a diameter of maximum 45 mm and unspecified length with as high a torque as i can find since i cannot calculate how much the pellets will slow it down.
Question 1: should i be looking at DC motor, servos or steppers considering i need low speed high torque
Question 2: Is the “rated torque” on motors with gear reductors calculated before or after the gear
Question 3: I need the rotating speed to be consistent, which i think requires an encoder if i use a stepper, but is it necessary for other type of motors or will they consume more current and maintain their speed?
Thank you so much for any help you guys might provide, i’m still learning about robotics.
Hello @Jonathan_Rosa and welcome to the RobotShop community,
should i be looking at DC motor, servos or steppers considering i need low speed high torque?
For low speed, high torque you should be looking for a geared motor. If you simply need to rotate it at a certain speed a DC motor should be fine, if you need to position it at a specific angle you should look for a servo, and if you need to position it with a lot of precision you should look for a stepper.
You can find more information about the different types of motor here:
Is the “rated torque” on motors with gear reductors calculated before or after the gear
The torque calculated after the gear reduction is regularly called “output torque”, however, the specifications of high torque motors generally refer to the torque calculated after reduction as rated torque.
For example, the rated torque in the following products is the output torque:
I need the rotating speed to be consistent, which i think requires an encoder if i use a stepper, but is it necessary for other type of motors or will they consume more current and maintain their speed?
If you need to keep track of the speed then you should definitely add an encoder. Although, some motors already come with an encoder, for example, the motors I linked above already come with it.
