anti backlash nuts

hi all,

I know with CNC anti backlash nuts are valued. The question is, is there a gain for them here?
I am building a mendelmax if it makes a difference.

Backlash in Z is largely irrelevant because it gets taken up by gravity, the Z only moves in one direction during the print and there is no dynamic load on the axis while printing.
Having them wouldn't hurt and people do sometimes sandwich a spring between two nuts to get the antibacklash effect.

Thanks for the information thats very useful.

I was reading about lift command and people getting good result from using it and was interested. Am I correct in saying it makes Z axis lift up then drop down to the same position? I assume problems with backlash are not an issue as long as the amount of backlash is equal for lifting as lowering back into position?

Hi Dave,
I'm running a Prusa Mendel style printer. From an axis perspective it's very similar to the MendelMax. I didn't ever fit the second nut or spring on the z-axis. Backlash has never been a concern for me and my print quality is very satisfactory. I sometimes enable the lift feature, and see not adverse effects. The total weight of the x-axis assembly is quite significant and serves to keep downward pressure on the z-nuts. Even if your rig is raising and lowering in the z direction very quickly I've never noticed the x-assembly fail to return to it's position before printing resumes.

Smoothly moving x-ends on the z-rods is essential. Once you have that I don't think z-backlash is a concern.
Regards,
NumberSix

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[numbersixreprap.blogspot.com]

edit: PRUSA mendel compensates for z height backlash using springs between the 2 nuts used on xbar assembly that has z axis rod go thru. for a rigid frame it would be a good idea to get a setup on z axis that is more precise, perhaps amce rods

Edited 2 time(s). Last edit at 08/28/2012 05:54AM by jamesdanielv.

The Sells Mendel uses no such backlash springs.
There is only one 8mm nut in the nut traps of the xbar assembly.
You are referring to the Prusa Mendel!

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
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