Excessive Y-axis Chatter

My machine just started to chatter a great deal but only when cutting in the Y direction. The rest are fine. It is particularly bad when going toward the back of the machine and minor when moving toward the run of the machine. I have the router as far down in the clamping bracket as it can go. Not sure if this makes any difference.

I would appreciate any ideas as to what may be going on. Because of this the bottoms of my cutouts look like a lake on a windy day but only on the left and right sides of the pockets. Worse on the right side of course.

If the only recent change has been pushing the router down in its mount, I’d start there — check to make certain that it’s tight enough.

Next, check the V-wheels for the Z-axis spindle carriage plate.

Then check the belts, pulleys, pulley set screws ( http://docs.carbide3d.com/article/169-shapeoko-3-how-to-check-the-pulley-set-screws ) for the Y-axis

Check the wiring for the two Y-axis motors — since there are two, it’s possible to have a loose connection or bad stepper driver, but the machine still moves.

Lastly, if everything else checks out, release the Y-axis belts and then try to jog the machine — check that the pulleys rotate evenly and in synch.

If none of that helps, or if there’s some obvious failure in a component, contact support@carbide3d.com

Thanks Will. Nothing has changed. The router is in the same place it has been since I first started using it. I will check the thinks you suggested.

I looked the machine over and didn’t see any obviously wrong. I then tried to twist the z-axis from left to right - rigid. Back to front there is significant slop in the axis. It doesn’t seem to be in the x-rail but in the entire z-axis. Here is a video that shows it pretty well.


Anyone else experiencing this. It is definitely what is causing the chatter in that direction. You can see the top of the router move the same as it does when cutting but when cutting it is at a significantly higher frequency and amplitude.

See if you can adjust your V-wheels to remove this — if that doesn’t address it, I’d suggest removing them one at a time, disassembling them (use a bolt to pry off the bearings) and measure the precision shim and the inner race which separates the two bearings — also count the washers and verify that their placement is consistent and makes sense.

Ugh. I was hoping I wouldnt have to disassemble the machine again. Hopefully I will get some time tomorrow. If not, it will probably be next weekend. Nasty week next week.

Well I found the source of the excessive movement. It is in one of the eccentric nuts. I was hoping this would be an easy fix and all I would have to do it tighten the nut. However, when I tighten the nut to snug I lose all eccentric adjustment in the v-wheel. It will not move except in the reverse direction and then completely loosens off the bolt instead of the nut turning in adjustment.

Any ideas?

I’ve found the eccentric nuts to be difficult to manage in comparison to the original eccentric spacers (which I prefer).

When adjusting them, once they are tightened, I’ve found it best to put both a wrench on the nut, and an Allen wrench on the BHCS and then make adjustments so that the entire assembly turns in unison, and the nut stays tight (though I try to remember to hold the wrench at the end, and then try to tighten the BHCS using the Allen wrench, just to make certain it stays tight.

FWIW, we do have a note to that effect on the wiki: http://www.shapeoko.com/wiki/index.php/Makerslide#MakerSlide_Tips_and_Tricks

Would it be beneficial to Loctite the nut at almost full tightness to allow it to move both directions but still stay tight on the bolt?

I don’t think that would help — but I’m one of those people who has an aversion to the stuff (this probably comes from my childhood of having to crawl into engine bays and burning myself while holding a lighter to a bolt so as to release the Loctite).

A bolt and a nut should form an elastic tension system, which when the correct torque is applied will hold at their optimal strength.

Same experience here. I was cutting aluminum it always chatters when performing y direction cut. I have a theory tho, because the tool is off set from the gantry, any load in the y direction will not only push the bit sideways but also vertically. That drastically increase the engagement between the cutter and the stock which causes a rebound. I’ll do more investigation into it to find a sweet cutting parameters. Also I was using high helical cutter for Aluminum that might have something to do with it.

Yep, there’s a significant ‘nodding’ deflection in the machine which gives vibration and chatter in the Y Z coupled movement.

Many have found that low depth of cut but higher width of cut and feed rate works better for this class of machine.