Lightburn 0.9.09 engraved image shifts when printed

I’m running a K40 CO2 laser with a C3D Mini board and authoring the design with Lightburn 0.9.09. My son wanted a Lightburn file printed, which contained vectors generated using the trace feature. The preview window image looked OK, but when the project was printed, the bike wheel was distorted and the d p_xmas.lbrn (929.0 KB) rectangle and mountain image was shifted. I’m attaching the project file and a picture of what the print looked like. I tried this twice, and got similar results. Any insight on what is going on would greatly be appreciated.

d p_xmas.lbrn (929.0 KB)

I’m running the latest Smoothieware release from C3D. It is quite possible that there is a bug there, just not sure. Not sure if I’m overrunning a GCode buffer, should be running GRBL firmware or what. I reviewed the C3D v2.3 Smoothie FW notes again and found that I had not enabled “Smoothie Clustering” on Lightburn. This helped but the contents in the center rectangle are still slightly shifted down. I’m leaning toward a config issue with my C3D board at this point.

You likely have the acceleration or speed set a little too aggressively. You haven’t mentioned the speed used for the job, but the file has a lot of small cuts that are going to bounce the machine around a lot, so you might need to lower the acceleration setting in the config to keep the motors from missing steps. I had to drop mine a bit from the default.

I had the speed set to 100mm/s. I will try playing with acceleration setting to see if that helps.

@LightBurn Do you have any hints on your acceleration reduction?
I’m using the default: 2000mm/s for ‘acceleration’ on a C3D.
The default for the rotary was 500mm/s, which is much lower.

I think I dropped mine down to 1200 to 1400 and found I got much better results that way. GRBL unfortunately doesn’t have different settings for rastering and normal cutting. When the machine is just going back & forth in a straight line you can get away with being more aggressive.

Thank you! Actually, I’m using Smoothieware on the C3D mini and the config file will have to be updated. At least with GRBL, I could just send a new $ command to change it before raster cuts. This is a reason to consider GRBL that I have not considered before. All my other CNC devices are using GRBL or similar, where you can change settings through the console.

Editing the config file isn’t hard, but yes, it’s more convenient being able to do it from a single interface and without having to reset the controller and fuss with the SD card.

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