New Prusa i3 - X and Y motors 'hammering'. Z axis working fine. Help?

Hi all,

Just completing my first ever Reprap, a Prusa i3 (based on the 'Improved' version here: [www.thingiverse.com]) and am using a RAMPS 1.4 electronics kit from RepRapDiscount (included motors, heatbed, LCD screen, etc). However I'm having a hell of a time getting the motors working correctly.

Basically the Z Axis works fine, as does the extruder motor. These work without any problems at all.

However both the X and Y axis dont want to work. If I turn the screw on the pololu drivers anti-clockwise to the lowest setting, they vibrate lightly with an audible whine. IF I start turning them up, the motors shudder like crazy. I thought it may be a torque issue, so disconnected the timing belt, which seemed to have zero effect.

I've been reading up on it now for over a day and the only issue I can see that others have had is that there wasn't enough power. However surely that isn't the case here given that I can have the Z axis working (Which is 2 motors) along with the extruder motor and the heating element without it being an issue.

Any ideas here? I'm completely lost as to what the heck could be causing this.

Many thanks.

when I've had "shudder", it's been a wiring problem (broken header crimp pin in stepper socket, broken solder joint on my motor extension wire etc). maybe check your wiring, make sure it's all connected right ?

Thanks for the reply Masnachu. I managed to find the culprit. It's the heatsinks on the pololu drivers. Its slightly larger than the actual chip it sticks to. I noticed it was touching the pins on one side, causing them to short. I realigned it ever so slightly and the drivers now work perfectly fine (shocked I didn't blow them up to be honest!)

I'm not sure if RepRapDiscount sent me the wrong heatsinks, or maybe you just cant get them any smaller, they are a bit to big for the chip though I think.