Text Shifting With Multiple Rotary Passes (Galvo Rotary)

I haven’t had this problem before but for some reason now with multiple passes on my rotary, the layers shift slightly (hopefully clear in the image where the letters have a slight shadow).

Using a galvo fiber laser with rotary. I have two layers, a engrave fill layer and a white clean up fill layer. For some reason it seems the engrave and white clean up layers are shifted slightly and I have no idea why.

I can’t imagine it would be slippage because its a tiny ring and its being held tightly. I also have my layers set to “fill entire shape” so it fills each letter individually but for some reason the two layers don’t seem to line up - any help would be greatly appreciated!

Can you post the lbrn2 file?

You to not yield - Ring.lbrn2 (28.9 KB)

Missed that… here’s the lbrn2 file. I tried it again but only with “not” as the text and there’s no shifting. But when I have the full sentence “You do not yield”, then the “do not” text seems to have a slight shift creating a shadow effect… What could it be?

Why do you have overscan on first layer but not second? I don’t think you need overscan on a galvo. Another thing, I always run scan angle parallel to axis (unless I have small shapes on a large circumference)
So try:
Turn off overscan.
Set scan angle to 0.
Turn off cross hatch.
What is your split size?

Firstly, I have no idea what overscan is or how to access it… I’ll test that and get back to you haha.

Regarding the scan angle, the machine came set up with it - I’ll try remove and report back.

For cross hatch and split size - because I’m using the “fill entire shape” setting, each letter is marked at a time, so to my knowledge split size doesn’t matter in this scenario because the rotary tool is only moving when it goes to the next letter, it doesn’t rotate when marking a letter. Before, I had a split size of 0.04 with a line width of 0.02 and didn’t use the setting to fill shapes individually.

I’ll try the above mentioned changes and report back.

FYI Fill entire shapes on rotary works best when the size of the object is a very small percentage of the curvature. Starts to deform pretty fast. We are hoping that we will be able to combine rotary and cylinder correction one day to do exactly what you describe. BUT, that shouldn’t affect your current problem, it would just deform your letters.
Go vote:

Okay so I think the problem must either be with my rotary machine or Lightburn (but probably my rotary). Because when I run the below settings once, it comes out fine. But if I run the whole thing and then run it a second time, there’s a slight shift… So the shift isn’t between individual layers, it’s between individuals runs.

I kept the scan angle and cross hatch and used the “Run whole shapes if possible” toggle and it seems to work find with a single run. There is no more misalignment between the text from different layers.

You do realize your settings are telling the software to run a 0.1mm wide band with 3 rotating crosshatches, then move the project 0.1mm and do it again, while the settings also telling the software to attempt up to a 10mm wide whole shape. Would you post a video of you running the project? Curious what it is actually doing.

The way I understand split size is that it is the length of laser area before the rotary tool moves the object - i.e. the increments in which the rotary moves. But this shouldn’t matter because the condition of “fill whole shapes IF POSSIBLE” overrides this because it is possible to fill whole shapes (each letter) individually, therefore the rotary moves in increments of each letter, engraving each letter individually.

Anyways, I solved the problem by choosing “run all shapes in each slice” instead of “run shapes in shape order”. This makes sure that all passes are run per shape (ie per letter) before moving, meaning that the rotary won’t come back for a second pass. This fixed the shift in-between passes, meaning that it was definitely my Rotary tool that was the problem.

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