When I first built my A8 it ran smoothly and quietly. I then followed somone's suggestion and adjusted the connection of the jack screw's flex coupler to the stepper and screws so that there was several mm between the two. From that point on I had noise issues that I have been unable to solve. The gantry rises silently and smoothly, but when Z direction is towards the bed, it "gronches", is the best onomatopoeia I can give of the sound.

I know that this must have an affect on the quality of the print, simple from the vibration that it causes. What I don't know is exactly what is causing the issue.
I level the bed to my workbench and then level the gantry to the level setting on the bed. Things should be parallel all through the system this way. I use two tiny "table levels" that are X and Y axis to get the levels the same. I am willing to hear how others do this tricky equalization.

Anyway, which is grinding? The screws or the bearings? I can't tell by listening or touching the gantry slides. Any suggestions to localize the issue or solve this?

Thanks all,
DLC

You mean this [3dprint.wiki] ?

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Proud owner and maker of build from scratch FDM 3D printer [forums.reprap.org]

Of course the couplers will loose their functionality, when stepper shaft and leadscrew are in full contact. But adding a gap, allows the coupler to compress, which seems to cause the noise ( and inaccuracy )
I placed a 4.5mm steel ball between stepper shaft and leadscrew. Now the coupler can't compress, but it can flex as intended.

I am going to follow your suggestion o_lampe!
I like the fact that the coupler is able to extend, but I am not fond of the spring effect. Simple and elegant solutions are the best.

Edited 1 time(s). Last edit at 04/02/2018 05:17AM by Rossos.

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Proud owner and maker of build from scratch FDM 3D printer [forums.reprap.org]

Well, I set my A8 up as shown where the center of the coupler has nothing in it. No change, still "grinds". So, the question remains, which is the most likely candidate: the bearings or the screws? I thing that it is affecting my print quality, so there _will_ be a rebuild. I'd rather not just "shotgun", if there are any troubleshooting suggestions then I'm all ears.

So, first on my shotgun troubleshoot list is the screws. I think that I'll use my RC car bushing lube and see how that works.

I have a bunch of linear bearings, but they are all short and it looks like the bearings in the Anet A8 on the vertical shaft may be the "long" ones. If the oil doesn't work, then it will be time for bearing work.

thanks,
DLC

You mean to tell us that your Z-axis Lead Screws operate dry?

In my thingie I used Marine White Grease on the Lead Screws just after the first dry run resulted in a screech of a dying alien bug symphony.

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Proud owner and maker of build from scratch FDM 3D printer [forums.reprap.org]

Quote
Rossos
You mean to tell us that your Z-axis Lead Screws operate dry?

In my thingie I used Marine White Grease on the Lead Screws just after the first dry run resulted in a screech of a dying alien bug symphony.

That is a great description of the sound.

I "assumed" that the lead screws came properly ready to roll. Which, you know, may not be so... Gosh, it didn't say anything about that in the build instructions.

Anyway, I just gave my lead screws a couple of drops of "Matrix R392" synthetic lube and the "gronching" went away. I also gave each of the linear bearings a drop on their rods, just for good measure.
I don't know if that stuff exists anywhere anymore. I have heard that synthetic sewing machine oil, light synthetic machine oil and something called "super lube" synthetic oil are good options. The key is "synthetic", because it won't attack plastic and won't get gummy. But like all oil, it will attract dust and gunk, so obviously occasional cleaning is a must.

DLC

It's always the little things.
Happy printing!

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Proud owner and maker of build from scratch FDM 3D printer [forums.reprap.org]