Everything had been going excellently, but A little while ago my Z seized (the mess suggested that the BB's might've been made of clay...) and over the weekend I noticed a click in my Y - I fixed the Z and as yet the Y isn't causing me any issues, but wanting to do things properly I've decided to replace my Chinese bought screws with gear that I'll buy here in the UK. Expensive, I know - but hey, I love my little mill and now can't imagine weekends without it..!
I suppose I could have a go at fixing up the Y by popping some new ball-bearings in etc, but my fear is that perhaps I'm not starting from a great baseline anyway and cutting my losses and starting afresh will save me the time and hassle in the long run.
My question is - not wanting to mess around with getting ball-nut brackets etc. remade, does anyone know a UK supplier that supplies their gear in a spec that closely matches the the stuff that we buy in from China (ie. ball-nuts have mounting holes in the same place, flanges are similar etc.)
I was thinking about my Z axis earlier, and why it would have seized when:
- It's as lubed as the others
- It's out of the way of debris
- 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..?
- It's as lubed as the others
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.
Last edited by deisel; 12-11-2014 at 04:21 PM.
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.
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.
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