loose Z-axis drive nut

[tsp42 0]

Hello all,

I'm currently assembling my Ultimaker, however the drive nut on the Z-axis is not fixed very well. It appears like the laser cut holes are to wide. Not sure that to do other than use epoxy if it starts to cause trouble when I finish the machine (still waiting for a replacement for the brass pipe I broke...)

https://www.youtube.com/watch?v=http://www.youtube.com/watch?v=HXp20DXWwOA&feature=youtu.be

 

[joergen 2]

The nut needs freedom in the XY direction, since the ACME rod is never perfectly straight. if you restrict the XY movement, the lead screw will scrunch the table around, shifting your print badly.

 

[calinb 11]

My nut was extremely tight in the wood holder, with no discernible movement. However, my rods are very straight (no discernible wobble when rolled on glass) and I'd rate my lead screw as fair (some wobble). The lead screw wobble is, no doubt, why it is not anchored (bushed) at the top.

My rods are straight and firmly mounted in the frame. My lead screw nut has no play. Thus, my wobbly lead screw is forced to track to center by the other, dimensionally correct and well-fitted components. No biggie, really.

Crappy lead screws are a problem with cheap Chinese hobby mills and lathes too, but a good machine will have very straight lead screws. I had to upgrade one of my Chinese machines for this reason too.

 

[jhertzberg 19]

When I first assembled my Ultimaker, I got very noticeable banding at a 3mm interval from a lead screw imperfection pulling the platform back and forth to the limit that the smooth rods allowed. I reduced the banding somewhat by disassembling the nut box and sanding it to hold the nut more loosely. The banding is greatly reduced, but not always eliminated. I'm thinking of taking it all apart again, sanding a bit more, and putting some teflon tape on the rubbing surfaces to allow the nut to float more freely. Has anyone tried any lubrication to allow the nut to laterally move more freely?

 

[nick-foley 5]

I have this same problem on a second Ultimaker I'm building. Is it still the prevailing wisdom that some of this wiggle is actually a good thing?

 

[Nicolinux 288]

I'd say it is. Daid (the developer of Cura) and Simon (Iluminarti) are both very experienced users and they both reinforce this statement.

http://umforum.ultimaker.com/index.php?/topic/2294-z-axis-drive-nut-assembly-loose/?p=16193

But it doesn't seem to apply to anybody. George (gr5), another experienced user does not have wiggle at all in his build. So I guess it depends. If your threaded rod doesn't wobble a bit with the z-nut extremely tight, then don't touch it. If not, loosen it.