SO3 XXL right Y-axis lub-dub

Hi all! I have completed assembly on my XXL. I have yet to fire it up. While double checking screws and movements I noticed the right Y axis seems to have a lub-dub to it, almost like a bent rim while rolling. Everything looks fine. I was thinking it may have something to do with the cable interaction but I can’t seem to find anything. Could you guys steer me in the right direction? Thank you in advance! :slight_smile:

For the cable troubleshooting see:

The other thing which comes to mind is uneven belt tension — both Y-axis belts need to be even.

Thanks Will. I’ll check the tension on the belts and the link as well.

Some thoughts based on your lub-dub description… Eccentric nuts too tight causing a flat spot in the v wheels? Or small nicks in the v wheels from the sharp ends of the y axis extrusion when you assembled the right carriage onto the right y axis extrusion? Did you loosen the eccentric nuts before assembling the y axis carriages to the y axis extrusions?

Making this noise when running it, or just when moving the carriage around by hand?

Is everything connected to the controller?

Mine does the same thing. With power off pushing the y axis it chatters, when i jog it with the CM4 app, it moves and keeps making a humming sound until i push the y jog again.

Someone please explain this?

The wheels seem fine. Just moving the carige by hand. Yep it’s all connected. I’ll have more time in a couple days to look at it more. I’ll keep you all posted. Thank you for the responses!

Can you get a video?
Hard to know for sure, but it could be the steppers enabling. When you turn a stepper motor by hand, it generates a voltage. If you move it fast enough, it will generate enough voltage to power the controller. That power will enable, and lock, the stepper. When it stops, power from your little generator is cut and it will move again.
Does the same thing happen if you move the axis very slowly?

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If you move the carriage “quickly” (for some value of quickly) there is enough back EMF to power the board, and the steppers will lock up momentarily, then the power is consumed, and they unlock again. Unplug the steppers from the board, and try again - if they move freely when NOT connected to the board, you’re good.

So basically the machine has to stutter to work? Part of the process is navigating the wasteboard area, thats a lot of stuttering.

Is that normal? Im still getting mine tuned in but daaaang i thought this would be easier that it ended up being lol

It should only stutter if it’s being pushed so hard the stepper motors act as generators and make a pulse in the stepper driver or if one is jogging in button down mode in Carbide Motion 3 — otherwise movement should be as smooth as is programmed (it is possible to program in stuttering, search for “CNC music” on Youtube).

If you get stuttering in a file or when moving a long distance under a single command, then it’s caused by something such as the Log window being open. Contact and we’ll try to help you sort it out.

After further inspection, I found a small scratch in the eccentric right Y axis wheel. (Most likely my fault during installation) Although, I homed and ran hello world with no problem. Seems to run smooth as it should when homing and jogging. :slight_smile:

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So after many tedious hours of reading and tinkering i am starting to understand this S3XXL.

I was so frustrated with it at first, that was mainly due to lack of information. My y2 motor had a wire switched so once i found out and fixed it that problem was gone. I got carbide motion installed even though the driver gave me a fail error. It works! Finally!

I would be willing to contribute to a beginner FAQ/initial troubleshooting document.

Im bummed all i have is a 1/4 straight bit until my collet adapter comes in the mail but for now i am practicing simple things on free scrap and learning to tune the drive brackets to make even surface removal.

Im glad i bought this thing but dang it was a learning curve!


I started on a bit of one here:

and did work up a function test page on the wiki: Shapeoko CNC Router, Rigid, Accurate, Reliable, and Affordable

Please feel free to comment / add to either in that thread.

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