I solved my Z wobble!

If you’re having issues with Z wobble, check the nut. Mine was ridiculously loose. Here’s a video of it. Look at the left side of the video. It was hard to get a good shot. https://youtu.be/-pdvvucS3-U

And here’s a before and after photo.

Well my joy didn’t last long. Oddly enough, I’ve noticed that the wobble is much less noticeable in translucents than solids. After reprinting the R2D2, I’m getting banding. It’s not quite as bad, but it’s still terrible. I pulled the leadscrew and motor, and when the motor turns the screw wobbles like a mofo. It’s no wonder the nut worked itself loose. So I’ve ordered a new coupler that I can seat the screw further into. Right now the screw is machined down to 5mm, so the coupler I got will accommodate the full 8mm diameter. On another note, the screw in my machine is single start.

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I measured the machined end of the leadscrew, and I discovered it’s 4.72mm in diameter, not 5mm, which is why it doesn’t seat properly in the coupler.

Hi I don’t think that it s the problem
The Zim Z axis nut is really not correctly machined this makes the Z axis to wobble.
The best way to solve your issue is to buy a Nema 17 stepper with the screw directly onto the nema stepper and with a correct nut. the screw is a 2mm per turn.

@Nightmare Would all of our Zims have this issue lurking?

Did you use a single start screw or upgrade to multi start?

And the flexible 8mm couple helps a tiny amount. I’ve also printed a constraint, and when I have it in and I move the axis up and down I see less wobble. That’ll have to do until the integrated screw/motor arrives. @Nightmare is right, even with the nut tightened down, you can see lots of movement in the screw. On another note, I’ve found several stripped screws in my machine, including one of the screws that holds the nut.

Sorry to keep just throwing stuff out there, but the method for attaching the Z assembly to the body is ridiculous. Essentially two thin pieces of plastic holding it on.

This is the screw I ordered: https://www.amazon.com/gp/product/B019TRKAPO

Amazing that kind of thing is available via Amazon Prime!

@etxbkst if you could take pictures of your swap process, that will most definitely help someone in the future :slight_smile:

If you tighten the screw the stepper force and the result is worth

All the Manufactured Zims has this problem.
changng the NEMA/couple/screw with a very badly manufactured nut with a nemascrew helps to dramatically increase the print quality :wink:

If I have the time I will try to do a tutorial. It is bit complicated to do but the benefit is so great :wink:


The Motor you bought is not good. the screw is a 8mm per turn ans the ZIM uses a Screw that is 2mm per turn.
so the Screw must be TR8X2 and not 8X8

Since I’m replacing the nut as well, I decided to upgrade to a multi start screw. It’ll be as simple as updating M92 with new values.

can you clarify? Why a badly manufactored nut?

Sounds like you mean one that rubs. Delerin is popular with leadscrews nuts… I guess whats the problem wiyh the zim one a garbage nut fixes?

I finally got my solid coupler with 8mm end in, and it has solved my z-wobble pretty much completely. It makes me hesitant to pull it out now to add the motor and new screw that is supposed to arrive today.

Hi @etxbkst, what kind of solid coupler did you get? Something like this —> http://www.ebay.com/itm/2-3-4-5-6-7-8mm-Aluminum-Flexible-Shaft-Coupling-Rigid-Coupler-Motor-Connector/231744678116?_trksid=p2141725.c100338.m3726&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20150313114020%26meid%3Dff099f3005a846349684144af9c1fbe3%26pid%3D100338%26rk%3D20%26rkt%3D30%26sd%3D331200440243&var=530951264866

Also is it 5mm to 8mm? Or 8mm to 8mm?

Here’s the exact coupler I purchased: https://www.amazon.com/dp/B01M8QXY8N/

It’s a 5 to 8mm coupler. In my case the machined end of my rod wasn’t actually 5mm, it was closer to 4.8mm or so. So a pretty significant difference. That caused it to not seat properly in the stock coupler, which is made for 5mm shafts on both ends.

So how did you solve this problem? Because your prints look great now. Even without the new nemascrew motor option. Or is the 0.2 mm difference not a big deal? Also, do all the zims have this 4.8mm problem or did yours develop over time?

I ended up taking out the old motor and screw, because the problem started reappearing. What I discovered is that for some unknown and mind boggling reason the m3 holes that you’d normally use to fasten the nut were drilled out considerably. The end result is that the nut had an insane amount of play. I think with the new coupler I could have just bought a new nut. But since the screw mounted motor and nut I bought was of different specs, I had to put it in. As for whether all Zims have this issue, I haven’t the foggiest. Mine did develop over time in that the constant vibrations eventually worked the screws loose, and because the holes on the nut had been drilled out, it causes the nut to bounce around.

Replacing the nut was unnecessarily a pain because whomever built my machine saw fit to superglue the LED strips and the wires to the damned XY assembly and walls. That meant trying to detach them would strip the wires. As a result I removed and replaced the nut from the bottom with instead of sliding the Z axis out the top. Couple that with mismatching screws, stripped screws, etc, and I’m growing less and less impressed with the build quality of this thing.