Troubleshooting NEMA 17 Motor Issues (Possibly current related)

I am having some issues with the motor control on my y-axis, please see: [www.youtube.com]

This issue began about halfway through my first print, the failure happening in the moment can be seen here: [justin.tv] starting @ 3:15ish.

I am using RAMPS v1.4 with marlin firmware. I replaced the pololu stepper and played with the pot settings on them as well, increasing the pot only increases the intensity of the jittering motor. I also replaced the NEMA 17 with another brand (?) with same issues.

I would appreciate any speculation you guys may have regarding this issue. My first print was going so well until this point.

Please let me know if you have any questions that may help deduce the problem.

My next step: I am going to try and monitor the current to the motor and compare to X-axis with a multimeter, but I can almost guess the result will be a sporadic current. Could it be a bad ground/neutral or something.

(By the way, I am a materials/plastics guy, so sorry for the ignorance but I will be glad to answer any material related questions, CHEERS!

What does it do if you remove the belt and run the motor under no load?

In the justin.tv video, the Y axis is is still moving, it just skipped a lot of steps, maybe multiple times. That happened to mine when the Pololu driver over-heated and the fail-safe cut out until it cooled down enough. Feeding too much current to the motor can do that. I ended up putting a small fan on my controller board to avoid the possibility of that happening again.

Same thing happens with no load (belt). Is there a way to change the temp cut off in the firmware, or is this built into the pololu driver?
Cheers, thanks for the feedback. I will try a fan or other cooling method today, but it did not happen before and now happens every time, even from cool.

The problem must be in the driver, board, or firmware. I have ruled out everything else.

Hi there,

I am having a similar problem. Using Sanguinololu 1.4 and StepStick drivers, Marlin firmware running with Pronterface., NEMA 17 motors.

When I give the motors a move command, they just asit and judder back and forth, or make a high-pitched whine and don't turn at all. I thought that I wired the motors incorrectly, but when wired correctly they do turn, just juddering and skipping. Then VREF value from the trimpot dial to ground when logic power is connected is approx 1.26V, and increasing the value doesn't have much effect, though I am wary to increase it too high lest the stalled motors draw too much current and blow the driver chips. If it matters I am using a computer PSU to supply motor and logic power. Under full load the voltage across the input drops no lower than 11.98V, from 12V nominal no load. When testing, the motors are not connected to the printer. IE: spinning (or not) freely.

I am lost as to why this is happening. Does anyone have any suggestions?

I had the same issue on my X axis... Turns out my pololu was bad...

switch out the plugs for your X/Y motors
(so the X axis is now Y, and Y is now X)
and see if the problem follows the axis.

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LVyali Wrote:
-------------------------------------------------------
> Hi there,
>
> I am having a similar problem. Using Sanguinololu
> 1.4 and StepStick drivers, Marlin firmware running
> with Pronterface., NEMA 17 motors.
>
> When I give the motors a move command, they just
> asit and judder back and forth, or make a
> high-pitched whine and don't turn at all. I
> thought that I wired the motors incorrectly, but
> when wired correctly they do turn, just juddering
> and skipping. Then VREF value from the trimpot
> dial to ground when logic power is connected is
> approx 1.26V, and increasing the value doesn't
> have much effect, though I am wary to increase it
> too high lest the stalled motors draw too much
> current and blow the driver chips. If it matters I
> am using a computer PSU to supply motor and logic
> power. Under full load the voltage across the
> input drops no lower than 11.98V, from 12V nominal
> no load. When testing, the motors are not
> connected to the printer. IE: spinning (or not)
> freely.
>
> I am lost as to why this is happening. Does anyone
> have any suggestions?


Did you solve your problem, i have about the same...