Rotary Question, Why does it turn at start

Testing some settings on my chuck rotary since a local jeweler has asked me to engrave some rings for them. With the rotary homed, and my artwork where I need it, the rotary spins a little on start up. I was testing a straight line, so my thought the rotary would spin at all when I click start, but it does. Is there a setting that controls this, or is it standard behavior, or am I doing something wrong?

video here →

Looks like it’s working to me…

The rotary is on the X axes… when you draw a line that goes along the X axes and it’s centered on the machine, it doesn’t need to rotate to engrave the line…

Make sense?

Rotate the line 90 deg to vertical, then the rotary should move. You will see how it frames differently.

Of course, it’s too long for the circumference of the screw driver shaft.

Your rotary is setup for a 10mm diameter, that screwdriver is not 10mm in diameter at it’s shaft, is it?

Good luck


I know the diameter is incorrect… What I am asking is why does the rotary make the small rotation before engraving the the small rotation back after engraving when the line is straight.

It’s centered on the work area, as far as I can tell. Mine is always centered and moves back to the graphics origin.

Can’t say I’ve ever tried to run a horizontal line on the rotary, so I’m not sure what it might do…

Mine, is centered where ever it is. I have mine set to return to start or something, so it goes back to where it was before the engraving.

I ran the line on my machine with the rotary enabled, same operation…

Have a video, but it’s the same as yours.


not centered but set the output center in the rotary settings. Ive been meaning to adjust the head so it is centered with the rotary but just havent done that yet. I havent used the rotary at all but will need it for the rings.

Mine is centered and it steps before engraving just like yours.

Maybe @JohnJohn knows if this is an issue…

What version are you running?

Mine is

Program Build
LightBurn 1.4.00 Sat 2023-03-18 @ 12:55

Mine is the beta…


so if I need to line up ring to engrave in specific location, how am I suppose to do that when there rotary turns a bit first?

I guess if the offset is consistent you could allow for it by loading the ring slightly off centre. Sounds risky though.

Another option might be to see if earlier versions of LB have the same behaviour.

Also, since I don’t have experience with your particular device, are there any separate origin settings in your controller?

You got me, I’m hoping John will chime in about the operation.

Hope it’s a round ring with nothing to decern which side is which :rofl:


Even though it probably would not be put on a rotary… I’d be kind of unhappy if someone was off that much doing the artwork on my pistols slide…

There must be some reasoning behind it’s operation.


I’m on version 1.3.01

I have both installed, but I doubt there will be much point of checking that version, seems you confirmed it’s operation already.

Let’s hang on until Lightburn people can get back to us…

I’d sit on the ring until I got some kind of clarification…

How much it changes is relative to the diameter…


Let me take this one to the developers.
I’m not currently testing a Galvo Rotary.

Are you engraving the outside of the ring?

I can post a video of mine doing it if you need it, but it looks just like his…

I know I gave it a diameter of 0.1mm and it really spun the rotary around… It was unexpected for a diameter change…



It will be both, outside and inside. They gave me a handful of rings that were to be melted down to test with so they can get an idea of our capabilities.

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Okay, so if a small circumference gives a large initial rotation, what happens if you specify a huge circumference? Does the initial rotation go away, or almost so?

It moves less… However it must be some kind of bug for it to move at all…

If you can’t set the proper diameter, that’s an issue.


Very true. I was more interested in behaviour. So if it’s linear to diameter it’s more likely trying to move a fixed distance.

A workaround might be to offset the image in the rotary axis (y in this case, as I understand) so the rotary doesn’t have to move for the head to be at the job origin. It might be worth trying, it might not. It’s certainly not a permanent solution, but it really depends on how much pressure Dan is under as to whether it’s worth trying or not.

The rotary moves a bit at the start to reach the center of the first split - in your case the split size is 1 mm and you have a line positioned right along the center point/origin in LightBurn, so it needs to move your object’s surface .5 mm to reach the center of the split. For an object with a very small diameter relative to the chuck’s, the chuck’s movement will be fairly pronounced, but the movement of the object’s surface (ie movement along its circumference) will not be. Reducing the split size will make this movement less pronounced, or even imperceptible. Try a split size of .1 or under.

Tyler, that makes sense… Thank you… I wont have a chance to try it until tomorrow but makes sense.