Solved z axis homing issue

when I try to move the z axis it works perfectly fine but, when I try to home the z axis is makes a loud buzzing noise and dosent move at all

 

That's strange. Look underneath the printer and verify the fan that cools the ramps board is running.

Also try lubricating the Z threaded rods if you haven't.

Barring that, it might be a defective stepper driver or some loose connections.

 

Sounds about like what was happening to my z-axis. I ended up having to adjust the potentiometer on the stepper driver to give the steppers more current. Steppers can be in an under voltage state where they work, but get confused and start twitching or just buzz like in my case, or an over voltage state where the steppers and drivers get hot and shut down.

I would highly recommend using a volt meter (you can pick up a cheap one for 10 bucks if you don't already have one) to see what the voltage is at the pot, and only adjusting it around .05v at a time (its not easy to be precise because it is very sensitive). You can check the voltage by putting the positive lead on the pot and the negative on the ground on the ramp board.

Also, watch the videos I found that was posted toward the bottom of the thread below (they helped me a lot!)...

http://community.robo3d.com/index.php?threads/z-axis-doesnt-always-work.6392/#post-53720