Stepper Motor Jittering

We are in the testing phase for the electronics before final assembly, and we've run into a problem. When we try to step our motors they don't spin, just sort of jitter. The only definate indication it is doing anything is the noise and the vibration.

Not knowing enough about stepper motors, we were looking for ideas as to:
How to diagnose the issue,
What could cause this,
Any possible fixes.

FYI: Running Gen 7 v1.2 electronics with pololus on a Prusa.

Thanks in advance.

If they jitter with no load then most likely they are wired incorrectly.

If they spin OK with no load, but jitter in the machine then most likely the current is set too low, or the speed or acceleration is too high.

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[www.hydraraptor.blogspot.com]

If the coils are wired incorrectly, you will see it turn one way then back again when single stepping.
You'll have to re-arrange the wiring, there are tutorials online on how to do this.

Secondly, if you have them wired correctly but have the speed set too high, they will also jitter and not rotate continuously.
Lower the speed and/or initial speed in your firmware.
Try this first (I initially had to lower the speed of stepping b/c the default firmwares sometimes have it set too high)

Hey nophead, aplavins - thanks for the feedback.

I've thrown together every combination of wiring, so can rule that out (hopefull)

Im using pronterface and Marlin firmware, would you have an idea how to adjust the speed or acceleration in these tools?

You change these lines in configuration.h and then reload the firmware.

#define DEFAULT_MAX_FEEDRATE          {500, 500, 5, 45}    // (mm/sec)    
#define DEFAULT_MAX_ACCELERATION      {9000,9000,100,10000}    // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for skeinforge 40+, for older versions raise them a lot.

#define DEFAULT_ACCELERATION          3000    // X, Y, Z and E max acceleration in mm/s^2 for printing moves 
#define DEFAULT_RETRACT_ACCELERATION  3000   // X, Y, Z and E max acceleration in mm/s^2 for r retracts

// 
#define DEFAULT_XYJERK                20.0    // (mm/sec)
#define DEFAULT_ZJERK                 0.4     // (mm/sec)
#define DEFAULT_EJERK                 5.0    // (mm/sec)

Edited 1 time(s). Last edit at 06/11/2012 03:29AM by nophead.

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[www.hydraraptor.blogspot.com]