Replacing Chinese screws/nuts with British bought gear.

[Wal]

I was thinking about my Z axis earlier, and why it would have seized when:

1. It's as lubed as the others
   
2. It's out of the way of debris
   
3. It moves less than the other axis
   

So what's different..? The spindle. It's mounted on the opposite side of the same plate that the ballnut bracket is mounted to. That has to be it... Have the vibrations/resonance of the spindle been transferred through to the ballnut and caused this? Hmm. That would suggest a new screw would suffer the same fate, eventually. Maybe the Z nut needs more grease, more frequently than the others..?

Any thoughts?

Wal.

[dazza]

hello wal
have you had the screw off?is it definatley the ballnut/bearings and not the end bearings on the screw causing the z to lock up...i had exact same trouble on my old routers z axis and thought/swore it was the ballnut at fault til I removed the screw.

[Wal]

Hi Deisel,

Yeah, the Z was definitely in a bit of a state - had to clamp one end of the screw in a vice and get a spanner around the flange of the nut to free it up..! What I thought was going to wind up unusable has actually been working fine ever since - well - it's not as smooth as it used to be, but accuracy remains good enough for my purposes. The click on the Y I'm assuming is the nut, but won't know for sure until I dismantle the stages and have a closer look. We'll see.

Cheers for the advice.

Wal.

[Wal]

I've had a closer look at my Y axis (with its .05mm of click) and in the spirit of finishing a story - it turns out that the problem lies with the FK12 ball-screw support bearings, which are rumbling a fair bit. Not great news, but a lot less hassle / expense to put right than replacing the screw and nut...

As for my musings on the Z - well, I posted a while back that I wasn't entirely satisfied that the screw was straight - but once it was installed and working without any noticeable issues I was happy to leave it at that. In retrospect (and ignoring my erroneous 'theories' above) it's very likely that the run-out in the screw is what contributed to it seizing. There, the penny dropped. It took a while...

New FK12's on order, will attempt to recondition the old as a spare set.

Wal.