Do you need a 2-nut & spring anti backlash arrangement on a vertical leadscrew?

Hello,

I appear to be getting z-banding on my prints (example attached to this post) on my Prusa i3 and I've been doing some reading on the various causes, and I've come across a few solutions, like the one at [www.thingiverse.com], that have the driven nut in a separate housing to the actual x-carriage. In the previous example, the author has placed two nuts with a spring in between them to eliminate backlash. Although I can appreciate the need for that in a horizontal leadscrew, why is such an arrangement necessary in a vertical leadscrew such as the z-axis? Surely the force of gravity will ensure that the z-nuts are always in contact with the leadscrew regardless of the direction it rotates.

Is it necessary or not?

Thanks,

Amr

I don't think the 'banding' in your picture is actually due to Z backlash, or at least not only.
To me, it appears to be rather X and Y backlash, hence different layers are offset on X and/or Y.

Anyway, the backlash on Z will affect homing the axis and also if you use Z lift during printing for some reasons.
As long as the axis is moving slow enough (as Z will do most of the time), the gravity could suffice.

"Do you need a 2-nut & spring anti backlash arrangement on a vertical leadscrew?"


Maybe, but in that video....that leadscrew needs straightening first.
Warped too much.

Do have a cheap dial indicator, that you can use to straighten that threaded rod?

Being that warped, it may screw up any other adjustments or improvements you make....with that much runout, gravity will not help you much at all.
Every rotation, affects how it mates with the nuts/holders.

Edited 1 time(s). Last edit at 02/24/2014 03:52PM by Metalmann.

Sorry, just noticed that it's not your video, or machine.