[turpija]

i've assembled most of machine, but can't get around this annoying problem

z axis while moving downwards makes huge vibrations, while moving upwards - nothing

so far i figured that pressing my hand against axis assembly removes vibration
and loosening bearings on the end also helps

x axis is assembled same as z, but it runs smoothly

to get an idea how it sounds, check the movie film



sta to drnda - YouTube

[PaulRowntree]

It is hard to tell from the vid, but are the two top jam-nuts locked up together? It looks like there might be some play there. If that is a thrust bearing just below them, it may not be under uniform load.

[DonFrambach]

Can't see your video (security restrictions on my computer at work) but I have some suggestions:

1) lubicate your leadscrew (I use pneumatic tool oil)
2) check the alignment of the leadscrew (mine made a horrible noise when misaligned)

hope this helps

Don

edit: see posts #27 and #30 of my build thread: http://www.cnczone.com/forums/diy-cn...r_build-3.html

[kevincnc]

If your bearings are binding, and there is any backlash in the leadscrew nut or play in the thrust bearing assembly, it will do that.

[dmalicky]

+1 on binding plus backlash/play. If an axis has binding while a loose nut drives it up, all is well since the weight keeps it on 1 side of the backlash. But when the nut tries to lower it down, the axis can go into stick-slip mode, falling to the other side of the backlash, then stopping and binding until the nut catches up, then falling again. Bam-bam-bam vibration, similar to climb cutting on a manual mill. Grease on the leadscrew helps dampen it temporarily, but eliminating the backlash (and binding) are the best fix.

[turpija]

thanks all for suggestions

i think the nut is tight enough, but will check it

that is exactly what i think is happening, dmalicky, it's like falling and catching the z assembly while moving down

btw screw is greased, and greasing it helped a bit, but not much

[turpija]

solved !

it appears that nut haven't been tight enough, now everything works much better

thanks all for help !