Z axis upper mounts issue  

Re: Z axis upper mounts issue

Anyone notice that the z smooth rod fits loose in the printed parts for the z upper mounts? I took mine apart and found that the diameter that the 8mm smooth rod sits in is actually 8.20mm. So in essence my z smooth rods are not fixed at the upper mount. Could this be causing my prints to have some ringing as my print speed increases?.

Yep. The MK2 is the same spec. But the ABS they used shrinks more than PETG so it fit more snugly. I was thinking of a mod for this where I fixed one side and added a set screw to the other to both fine tune the parallel and tighten up. Haven't had time yet, and I'm not sure it's a good idea.

Re: Z axis upper mounts issue

Anyone notice that the z smooth rod fits loose in the printed parts for the z upper mounts? I took mine apart and found that the diameter that the 8mm smooth rod sits in is actually 8.20mm. So in essence my z smooth rods are not fixed at the upper mount. Could this be causing my prints to have some ringing as my print speed increases?.

I doubt it. It's been discussed here at length with RHDreambox's Z axis upgrade. While the Z screw itself is floating freely, the smooth rod by it isn't. The smooth rod will ensure you keep your alignment and the slightly free floating threaded rod will be held at appropriate distance by the gantry. Removing this small amount of play could potentially introduce binding.

Re: Z axis upper mounts issue

Anyone notice that the z smooth rod fits loose in the printed parts for the z upper mounts? I took mine apart and found that the diameter that the 8mm smooth rod sits in is actually 8.20mm. So in essence my z smooth rods are not fixed at the upper mount. Could this be causing my prints to have some ringing as my print speed increases?.

I doubt it. It's been discussed here at length with RHDreambox's Z axis upgrade. While the Z screw itself is floating freely, the smooth rod by it isn't. The smooth rod will ensure you keep your alignment and the slightly free floating threaded rod will be held at appropriate distance by the gantry. Removing this small amount of play could potentially introduce binding.

He is saying the smooth guide rod is loose, and it is. Don’t know that it causes ringing which was his question, but it is loose.

Re: Z axis upper mounts issue

In MK2 they had tensions screws that took out this play but those have been removed due to confusion by users. See comments: http://manual.prusa3d.com/Guide/4.+Z-axis+assembly/296?lang=en#s5038

What I was getting at earlier was moving this screw to the z end for same purpose but could also use to fine tune parallel. Easier solution might be to tighten hole, then do same assembly trick as Y axis where you leave the mounting screws loose and move x gantry to the top and tighten.

Re: Z axis upper mounts issue

That is exactly what I'm getting at. If there is any amount of play at the top of the z axis as the speed increases in the x it will cause the entire z axis to shift small amounts and cause ringing. I may go in and modify the part and see if this fixes the problem.

Re: Z axis upper mounts issue

Anyone notice that the z smooth rod fits loose in the printed parts for the z upper mounts? I took mine apart and found that the diameter that the 8mm smooth rod sits in is actually 8.20mm. So in essence my z smooth rods are not fixed at the upper mount. Could this be causing my prints to have some ringing as my print speed increases?.

I had mine off a couple of days ago, and my z smooth rods fit quite snugly into the top mounts. This was especially clear because I had printed new mounts (from the 'fine tune your z-axis' thread) and my prints of those were not as snug. (not blaming the stl, I'm sure it was a slight variation in my slicing/printing).