Z-Axis Wobble - this seems like too much?

Hello! I’m still calibrating my X-Carve 1K a little bit at a time as I delve into various tests and projects. I still need to set the pots for my NEMA 23 motors, but since the test carves seems reasonably accurate, I hadn’t bothered yet. I’m hoping to do that tomorrow and see if it affects my current project.

The current thing that is repeatedly catching my eye is the amount of seeming wobble in my z-axis. Nothing is loose, but either the Delrin nut is funky or the ACME rod is not straight (unless I’m overlooking another possible cause). I’ve noticed that when I have 1mm deep passes and Fusion 360 uses a pronounced plunge between layers, I’m seeing a little notch in the cut that. This, I suspect, is the cutting manifestation of what is otherwise just a visible shimmy in the Dewalt as it rides up and down.

It turns out it’s incredibly hard to get a decent video where the wobble is as obvious as it is to your naked eye. Ultimately, I decided to shoot it looking straight up from the work surface. Despite the bluriness from being too close, you should be able to make out the wobble pretty clearly.

YouTube video of Z-azis wobble

Thoughts on how best to proceed?

  • Aaron
1 Like

It is the threaded rod. Test it against a flat surface, it is probably slighty bent. You can try to unbend it (I tried with my prusa rods: https://www.youtube.com/watch?v=dy64oB7fG-k) but it is very hard to get it perfected.

I’ll second the bent rod. My washer was bent when I got it but was easy to flatten out. I had an issue where I didn’t have the nut tight enough and the acme rod had about 1/8" of vertical movement. Easy fix.

Pull the rod out and roll it on a flat surface.

Thanks to you both for confirming the rod. It was my gut feeling, but thought I’d ask before hassling with the process of removing it. I know the nut on top is crazy tight and took some real work to originally get seated (and, no, it’s not cross threaded or anything), so I need to figure out how best to remove it without causing damage to anything. Thoughts there before I tackle it tonight?


I used some pliers on the “gear wheel” (sorry brain not working) to hold it.

Very ingenious method there. Is that M8, though? I’m not sure I have anything similar on hand nut-wise that would thread properly on my Acme screw.

Wondering if this might be more of a replacement request from Inventables unless there are other reliable techniques?


  • Aaron

At first I didn’t see much issue when rolling it on a flat surface. I decided to put it in my drill and check. Unless the chuck of the drill is a big factor, yeah, it’s got about the same wobble I see when the spindle is riding up and down.
Here’s a video:

So, I either figure a way to straighten it or hope Inventables can send me a better one…

  • Aaron

These ‘ACME’ threaded screws are very hard to bend, are you sure that’s not a threaded rod? Can you unbend it with your hand?

My method for straightening was intended for threaded rods, that was an M8, 2mm per turn rod.

I had the same issue with my Acme rod and a stripped out delrin block. I called customer service and explained what happened and I had a replacement Acme rod kit the very next day.Thanks Sam!

Over the weekend I had a failure where by the xcarve decided to try to drill straight down and through the wasteboard. Once I got everything back to normal, I noticed I had some wobble in the z-axis. I thought it had somehow bent the rod (ACME rod) when it tried to go through the wasteboard.

I checked to see if all of the nuts and bolt were tightened and noticed that one of the lower v-wheels, with the eccentric nut, was loose. So the wheel wasn’t in contact with the slide. I tightened that up and now I don’t notice any wobble.

I’ll have to do some test cuts to see if everything is working well. Also, I didn’t remove the rod to see if it was straight.