Is there a reason for the z-axis M5 drive nut to be super loose on the lead screw? (3 Solutions!)
Channel: Roel Van de Paar
Date: 26/06/2019

3D Printing: Is there a reason for the z-axis M5 drive nut to be super loose on the lead screw?


The Question: So I bought a prusa i3 kit from a company called folger tech off of ebay. I've
built it and even printed out a few parts, but I noticed that a lot of noise
seemed to be happening only while the x-axis motor was moving the extruder.
Then I noticed if I put my finger lightly on the plastic part of the x-carriage
I could dampen the vibrations and pretty much eliminate the noise I noticed.
Then I took apart that part of the printer and examined everything and all I
could notice that seemed to be loose was that nut that allows the z motor to
push up the x carriage. I don't know if I got a bad nut, or a bad screw, or is
it's just supposed to be this way? I thought it was kind of a weird way to
build things with a screw turning a nut, because I thought that it would bind
up. But now I'm wondering if that is why it was so loose fitting (to reduce
friction)? So does it need to be that way? Or could I get a different nut? Or
is there some better way to go about fixing this issue? Or perhaps it's not
even an issue.. idk.

Solutions: Please watch the whole video to see all solutions, in order of how many people found them helpful

== This solution helped 4 people ==
It's probably intentional. Threaded rods are almost never perfectly straight.
If the nut is rigidly coupled to the carriage, then the slightest deviation in
the screw will either cause it to bind up or appear as artifacts (e.g. z-
wobble) in the print. By making the nut slightly loose, it can move around a
bit to compensate for wobble. See e.g. www.thingiverse.com/thing:20147
and this_design for how this is commonly implemented in other printers.

== This solution helped 1 person ==
I do not agree with the answer of Tom.
In a proper design, the nut is supposed NOT to be loose, especially in the Z-
direction. All options of the nut to move can cause imprecise layer heights and
Z-wobble. There is also the possibility to introduce Z-wobble by bent rods and
good contact of the nut. However, Z-wobble is not what I want to address.
Yes, to me, it seems possible that your rod or your nut (or both) are looser
than they are supposed to be. However, I don't know the exact design of your
printer. Usually there is some play along the axis, but hardly any
perpendicular to it. Typically this can introduce a en.wikipedia.org/
wiki/Hysteresis in the placement of the X-carriage. There is a nifty design
against this, which most likely should also help you to get rid of your noise:
Thingverse:_Z-axis_anti_backlash_for_Prusa_i3.
First, however, you should check the following:
 * Are both your Z-axis drives set to the same height, or is just one of
 them doing the work (which would be very rare, by the nature of the
 design)?
 * Is your nut lose in the X-carriage? While the nut should not be lose
 itself, it should be totally fixed in the X-carriage (again: typically,
 but I don't know the FolgerTech approach).
 * Try other nuts from the hardware store to be sure whether you have a
 faulty nut or not.
 * While you're there you can connect a threaded rod with nuts there to gain
 experience what the typical degree of freedom in this union is.

With thanks & praise to God, and with thanks to the many people who have made this project possible! | Content (except music & images) licensed under cc by-sa 3.0 | Music: www.bensound.com/royalty-free-music | Images: stocksnap.io/license & others | With thanks to user user273872 (askubuntu.com/users/414), user Tom van der Zanden (askubuntu.com/users/26), user kamuro (askubuntu.com/users/168), user Greenonline (askubuntu.com/users/4762), user darth pixel (askubuntu.com/users/1211), and the Stack Exchange Network (3dprinting.stackexchange.com/questions/880). Trademarks are property of their respective owners. Disclaimer: All information is provided "AS IS" without warranty of any kind. You are responsible for your own actions. Please contact me if anything is amiss at Roel D.OT VandePaar A.T gmail.com.