Stuttering on arcs

I’m having this issue where my X-Carve stutters on arc moves. The motors have more than sufficient current, belts are tensioned nicely and wheels are good.

It does linear moves fine, but seems to struggle on arcs.

Anyone else have this issue? Any suggestions on what to do to fix this?

[Here is some a video of the behavior]

A few things to check for: First, check for any loose set screws in the pulleys. Also make sure there’s at least one set screw on the flat section of pulley shaft for each pulley. This was the problem I’ve had as well as several others. You should get some BLUE Loctite for each screw and put them into the pulleys after you have them properly aligned on the shaft. Without it, they WILL work loose again due to vibration. Blue Loctite is removable as well but keeps thread snug enough to keep them from backing out.

Second: Loose belts and loose wheels.

Third: Make sure the axis’ are square to each other.

Test it after each suggestion has been addressed and you may find that it was the first one without having to look at the other two.

You are losing steps due to hardware. The best advice I can give you is to forget this: “The motors have more than sufficient current, belts are tensioned nicely and wheels are good.”

I experienced the same thing. Run your machine and watch it closely. You’ll get it worked out.

There are sharp direction changes the moment the stuttering happens.
This seems correct to me - the direction change would be too much at this speed without decelerating first.

If you want to avoid this you can try to round the shape a bit so the directions changes are softer or decrease feedrate.

Try changing to these values in the grbl settings and see if the stuttering goes away.

$11=0.005 (junction deviation, mm)
$120=1000.000 (x accel, mm/sec^2)
$121=1000.000 (y accel, mm/sec^2)

Hey Everyone,

Thanks for the feedback, played around with the machine for several hours today and wanted to report back on my results.

At the end, I was not able to fully correct the behavior, but did want to document my learning. Firstly, adjusting the Acceleration values did result in some small improvement; however, reducing the junction deviation actually worsened the problem.

At the end, after trouble shooting for some time (belts/vwheels/ref voltage/etc), I decided to check which axis was introducing the vibration. To do this, I decided to run the same program with the X-Axis motor disconnected from the board, and then run it again with only the Y-Axes motor disconnected. Intention was to assess whether the vibration during the sharp arc was a result of one axis in particular.

Strangely, even though only one axis would be running at a time (either the X or the Y) and therefore result in what should look like linear motion (one dimension), both axis’s would still create vibration when approaching that part of the program.

This for me indicated that its probably not a me mechanical issue, but more of the speed at which I approached that particular commands. Additionally, when reducing the Feed from 150 -> 100, the issue would disappear.

At the end, i think i was just being to aggressive on the cut, furthermore, the tool pathing was sub optimal as well (thanks Easel).