Prusa i3 Z-axis noise when lowering

Hi all,

I've built my prusa i3 awhile back and have been using it for almost 6 months. Very happy with the printer's ability to print (as long as you know what settings to tweak). However, my machine keeps on making a constant noise when the Z-axis lowers (See video below). This doesn't happen to X-axis, Y-axis in either direction; only when Z-axis goes down. I've checked the belt tension, screws,Z-axis leveling, coupling spacing between motor and threaded rod, etc... I have exhausted with everything I can think of that may be the cause.

https://www.youtube.com/watch?v=GuD7HslTFsI

The last thing I tried is to put grease on the threaded rod to cut down the friction between threaded rod and the M5 nut on the X-end idler/motor printed part.

Any other suggestions??

Thank you for your help.

Edited 1 time(s). Last edit at 06/08/2016 04:43AM by loxua.

The noise is from the stepper motors. The printer's frame is helping to make them louder than the other motors. You could try something like this: [www.ebay.com] This one happened to be first one on an ebay search for "stepper motor isolator"