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Anet A8 single motor Z axis drive

by osadchy Nov 9, 2017
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I'm curious why an 18 tooth and 36 tooth pulleys are used and not a 16 and 32. The other pulleys on the stock A8 are 16 tooth. Does the stock firmware adjust for this?

How is this holding up after more than a year of use? is there any z-bobble coming through on prints?

Holding up great. No Z wobble, but I didn't have Z wobble to begin with. I did this to eliminate the need to re-level the gantry every time

So the question I have has to do with your rod_holder part. These as well as the upper timing pulleys have to not only hold the weight of the gantry, but they have to endure the force of that setup grinding down on the plastic. Seems to me that over time this would wear into the plastic and cause problems like putting the pulleys out of alignment. Would it not have been better to recess the flange bearings into the top and have the weight of everything on that. At least those are metal bearings that can spin and take the weight. Not to mention, doing it that way, you probably wouldn't need the rod holders at the bottom.

Something like this:

alternate bearing setting

The weight of the gantry is supported by the lead screws which are attached to the bearings which are attached to the top plates with metal screws. The rod_holder supports only the weight of the smooth rod, not the whole gantry. The gantry slides on the smooth rods without applying any up/down force on the rods.
You can recess the flange bearings into the top but remember to make the recess wider so you can adjust the bearing position so that lead screws and smooth rods are parallel.

You do need the rod holders, or they the smooth rods will fall through the hole. Before this upgrade they were resting on the Z motors

Question, when you got your flange bearings were the bearings pressed into the flange correctly for you? Mine are not and I'll have to see if I can straighten them out in my vice..

The bearings should swivel in the flange. Its a bit stiff, but when you fix the flange and put the rod through the bearing, its easy.

How snug were your lead screws inside the flange bearing? I can't seem to get mine through the hole in the bearing, and I tried both of them. I may need to ream it out with something, but i'm not sure what to use just yet. I'm thinking of using some super fine grit sandpaper around a smaller rod. Any thoughts? I just checked the pulley, and that seems to fit the lead screw perfectly.

Good to know, I was unaware of this. I'll see if I can free them up.

Yeah, I missed the fact that there are two grub screws on the flange bearings that hold the lead screw. I was thinking that the rod holders were for the bottom of the lead screws, which now I see they are not. That is good that you mention about making the bearing recess bigger to allow some adjustment. I do think though that you loose a slight bit of available printing height with them below, not that I have ever printed anything that high, but just to point that out for others that might pass by this comment.

Yes, by putting the flange bearings on top you regain the printing height that I lost by putting them below.

Hi Osadchy, Did you design and make this to free up a stepper motor socket on the orginal ANET board and is it possible to use one of the Z-axis sockets for another purpose?
I always assumed they simply ran as if connected in parallel.

I would bet that it wouldn't be hard to re-purpose that extra port to run a second extruder. You would just need to find where to make the changes in the marlin code.


I was tired of checking the level of both sides of the x gantry before each print, because when the steppers are not powered, they can slip.
Actually, It's not too much of a hassle, but I also wanted to design something :)

Free socket and free motor are just bonuses.
Haven't done anything with them yet

What's the distance between the threaded rods on an A8? I'm thinking of a similar solution for my Geeetech printer, but I think it's differently sized.
Also, do you still have the CAD files and, if so, would you be willing to share them? I wouldn't need to measure and design everything myself :)

The distance between the A8 threaded rods is 378mm.
Uploaded step files.

Hey osadchy,

thanks for your reply :) I meant the distance between the rods from left to right (in x-direction), not the length of the y-frame ;) but thanks for the step files, I can source the measurement from that :)

I desperately need this on my a6!! Is this compatible?

I'm sorry, I have no idea :(

man i wanna try this soooo bad, but do you have any issues with that timing pulley on the stepper side? It just seams the belt has minimal "bite" around the pulley.


Usually you want at least 6 teeth to engage (did some research there), so with a small pulley you need the belt to go around it. But on that 36-teeth pulley on the left I have 9 teeth engaged - so it should be good.

Never had a problem with it


I´m new to 3d Printing but im used to mecanical engeneering, there are so many problems in the original Anet A8 design,
after three weeks i sloved many of them, since i bought it i was searching for a well designed Z Axis solution with only one motor,
cause the original design uses 2 unsynchroned stepermotors (that won´t go anyway!)

I think your design is brilliant! Where did you get the different timing pulleys i cant find them anywhere!

I try it with self printet ones! Hope it works!


I got the pulleys from AliExpress. I just checked the links in the Summary, they still work.


Can you share how you did mount your bowden motor on the back ?
Perhaps you already designed something you didnt' shared ?

Thanks !


The extruder (a Titan clone) mount on the back is just a temporary thing. It is not good because I don't have access to the tension screw.
When I design a permanent mount I will share it.

Prusa Z axis, so many problems yet one simple solution !
Comments deleted.

Yes, except this one is for a different printer and is actually done well.

Same basic Prusa clone, so same mod, just more complex realization, one idler too much and a threaded rod to reinforce the crappy Anet frame. Of course no other improvement , still use the garbage LM bearings etc.... OK, better than the usual crap found here, at least the idea is OK as it is the same as mine (one single Z motor at the top, belt and pulley plus lead screws working in tension as I explained). Curious to see what you got in the making. A spool holder ? A filament guide ?