# Running stepper motors fast

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1. May 23, 2017

### neoply

Hello all. Thanks for taking up your time to read my post.

I have ordered these stepper motors. I asked the seller how many revolutions the motor can achieve in a minute and they answered 43. I calculated (13 + 212/289) * 200 * 43 / 60 to determine how many steps I would need to step in a second to achieve 43 rpm. This results to roughly 1950 steps per second. However, when I try to run the stepper motor with 1950 steps per second, it stalls. It vibrates but doesn't turn. After reducing the steps per second to 1300, the stepper starts moving again.

I'm using MK70-1 drivers as the datasheet of http://www.kynix.com/uploadfiles/pdf2286/MK70-1.pdf, set to ignore microstepping and to supply 0,5 A current with 12 V. I'm controlling the driver with an Arduino Mega 2560 and AccelStepper library.

Why can't I run it with higher speeds? I've had this problem with other steppers, too.

2. May 23, 2017

### Asymptotic

What is providing power to the stepper motor? The above link is for Minebea stepper motors.
Can you provide a wiring sketch of what you've built?
How fast is the speed ramp?
Is the motor physically bolted to a structure, or is it freestanding?

3. May 23, 2017

### neoply

4. May 24, 2017

### Asymptotic

Jim Hardy linked out to this video tutorial in a previous stepper topic, "Stepper Motor Resistance".
. <iframe src="" </iframe>

Generally speaking, basic wiring problems are eliminated so long as a stepper motor operates correctly at lower speeds. If coil polarity was reversed on one of the phases, chances are the motor would sit and hum all the time, or rotate only after giving the shaft a nudge, or behave in a combination of the two, and rotate unpredictably.

As the video shows, a stepper rotor follows the sequencing of stator winding magnetic fields. The symptom you've described occurs when the rotor can't follow those fields. As speed increases beyond a certain point, typically the rotor (at first) misses commanded steps, then as speed command increases further it will fall out of step completely, and just sit there and buzz away.

As is the case for most physical devices, several phenomena conspire to yield this symptom, including,
• Mechanical resonance (which is why motor mounting is important, as well as driven equipment characteristics).
• Uneven mechanical loading. For instance, a ball bearing in early failure begins to "grab" at certain positions, and prevent the rotor from making it to the commanded position. Several other load-related reasons exist.
• Excessively rapid ramp rate. When a stepper is commanded to target speed too rapidly, the rotor will fall out of step with the commanded coil currents and magnetic fields they produce.
• Winding inductance. It takes x amount of time after coil current is turned on for the magnetic field to reach full strength, and develop rated torque. As speed increases, this effect becomes a limiting factor.
Section 4, "Motor Drive Topologies", in this STI application note goes into this in more detail. http://www.st.com/resource/en/application_note/cd00003774.pdf

http://www.motioncontroltips.com/fa...and-why-is-it-a-critical-stepper-motor-value/

5. May 25, 2017