The Original Prusa i3 MK3 is the successor of the award-winning Original Prusa i3 MK2 3D printer.

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Z-Axis screws are not perfectly vertical and cause rattle/ vibrations

The printer prints just fine and I am very very impressed with the quality it delivers!

Anyhow, I am having these very annoying vibratory sounds that happen at the top orange holders ("Z-axis top parts") of the smooth rod/ Z-axis screws (left and right). It happens each time the X-Axis changes directions quickly, letting the Z Axis wobble a tiny tiny bit. The Z-axis screws then touch the holders and makes a contact sound. During infill of a layer (with lots of X-Axis movement) the sound is very annoying!

I measured the distance of the smooth rod and the srew:

  • at the motor level (bottom) it is 2.53 mm
  • directy above the x-axis is is 2.54 mm
  • at the z-axis top parts it is 2.61 mm

I tried to get the z-axis screws perfectly vertical by:

  • turning the bottom z-axis motor holders as much as possible. There is not much play here
  • turning the z-axis top parts as much as possible. There is not much play here either.

A quick and dirty fix is to use zip-ties to gently bring the smooth rod and the z-screw a bit together. But I would rather not use them and fix the root of the problem. What else could I do? Any help much appreciated! Thx!

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Chosen Solution

Have you tried loosening the bolts on the black leadscrew nuts and trying to centre the leadscrew a bit more? This seemed to work for me.

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Courtesy of https://www.facebook.com/groups/Prusai3u... (an excellent group to join by the way for helpful information on the MK2/3)

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Thanks for your remark! You are right, I could fix the misalignment by rotating the black parts are tiny bit. The lead screw now has the same distance from the smooth rod, no matter at which spot I measure. Thanks!

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Most Helpful Answer

I had a similar issue when I disassembled and reassembled my x-axis. The problem was that my x-axis smooth rods were not pushed fully into their holes and that caused the z-axis leadscrews to get missaligned. Check that the smooth rods of the x-axis are fully inserted into their positions.

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Hi Guntor,

I'm sorry for the delay. Printed parts for MK3 are redesigned and the issue from GitHub was fixed.

Are all four screws tightened equally between the motor and holder? This can also introduce slight tilt.

Also, check the X-axis is assembled properly, there are control holes for the smooth rods: https://d17kynu4zpq5hy.cloudfront.net/ig...

Wider X-axis can cause tilting of the Z-axis leadscrews.

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Thanks for your replies! I checked several times if the screws are equally tightened and I even tried to tighten them differently to improve the misalignment of the rods. That had no success.

I will check iloosion's remark about the x-axis smooth rods beeing not pushed in all the way. That didn't come to my mind yet and makes perfect sense. Thanks for the hint! I will report back as soon as I could check..

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Yes, it might be the X-axis being too wide, see the link in my previous post to check this.

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I checked the seating of the smooth rods on the x-axis, there were ok, they are all the way in.

But I think I found the reason for the rattling sound of the z-axis lead rods at the top holders: the distances of both (z-axis) lead screw/ smooth rods is not constant. If i measure at the bottom, right next to the stepper motors, the distance is 2.52cm (B in the pic below). But the distance just above the x-axis holder is almost 1mm wider (A in the pic below). When the x-axis is all the way at the bottom, both lead screws are therefor pushed to the center. With heavy x-axis movement, the z-axis lead screws then touch the inner perimeter of the top holders and create the rattling.

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Am I the only one where the distance between the z-axis lead screw and the smooth rod is not all the same when measured above the x-axis and above the z-axis motor?

Printing the z-axis top holders with wider inner diameters (of the lead screw cavity) may solve the annoying rattling/ vibrations but why is the z-axis smooth rod and the lead screw not parallel? The distance is only defined by the printed parts and cannot be influenced much..

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I measured the A vs B distance on several MK3 and it is almost the same. Anyway, I will do further tests. Thanks for the observation and try to release the trapezoidal nuts and retighten.

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Is the other side off but opposite?

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Both sides were leaning inwards. So yes, the other side was off, too but in the opposite direction then the other side.

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Guntor H will be eternally grateful.
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