Milling machine - video

[tonyfoale]

I built similar working power feed for Z axis and I faced a problem which made me stuck.

Lead screw nut (made from bronze) when knee going down starts vibrating a lot. Very loud, whole machine starts shaking. I tried everything even welding in again flange for nut to remove any missaligment but nothing helped.

It worked well only two days...

Lead screw don't run dry, it's oiled.

Do you have any ideas what else I could try to remove those vibration?

IIRC you have linear ball slides on the Z axis, that is very low friction. I am guessing but I do not believe this is a good match to a normal lead screw. Maybe you need a ball screw. Like I said this is a guess, but the forces provided by the slide friction from normal dovetails will relieve load off the lead screw and nut on the way down.

I am currently building a CNC surface grinder which with a change of grinding head to a milling spindle will also be a 3 axes mill. I am using linear rails and ball screws on each axis. However as it is a work in progress it is too early to come to any conclusions about vibration. I have my fingers crossed.

Here is an idea. On my Bridgeport mill I have added 4 assist springs to the knee to relieve load off the stock screw and nut. Here is post that I made A knee helper
maybe something like that would work for you???????