Engraving and cutting not alligned


I’m using an Atomstack A5 laser engraver and I recently engraved a larger picture on plywood (390x300 mm). I set it so, that it would first engrave the picture, and afterwards would cut it out. The engraving took a long time, but went fine. When the machine finished the engraving it started cutting like planned, right on the edge of the engraving.
However, when it came to the bottom half of the engraving the cutting was off by a few mm to the right of the picture. I first thought the material had shifted. But when it the cutting was back to the top half, it was again right on the edge of the picture.

Does anyone have a suggestion what could cause this and how to solve this? I was thinking about checking if it square, thigthen the belts again, but find it strange that the picture has other coordinates than the cutting. So if it is the machine, the cutting and engraving should have the same deviation, right?

Are you willing and able to share the LBRN file? Some operations are more likely to cause the engraver to lose position.

If you can’t share it publicly for whatever reason, we can get it into the hands of someone who can help.

A screen-shot of the Cuts / Layers window might show how close your settings might be to the limits of the engraver.

obelix2.lbrn2 (367.3 KB)
and screenshot:

On my local engraver (when I preview) I see that the laser starts from the bottom right corner and proceeds back-and-forth line-by-line upward until the image is complete then cuts the image out by proceeding counter-clockwise from the top of the image.

The cut-out of the project shows me that the accumulated error between the cut-out and the image is smallest at the top and largest at the bottom of the image - furthest from the end of the image.

I feel that the speed or accelerations are creating a lost-motion condition and that the problem accumulates as the image is being engraved. The lost motion does not affect the cut-out because it does not scan quickly back and forth - it is not as fast - and the error can not accumulate (any more than it has) after the top of the image is engraved.

I feel that your 4000 mm/min may be a little bit fast or demanding for your engraver.

You may reduce speed and reduce power in the Image Layer to get the same image without causing a ‘Lost Motion’ problem.

You may also be successful by increasing your Overscanning to allow the engraver more room to decelerate while engraving the image.

You may also have to move all of the work, slightly to the right as the overscanning may command the engraver head to move outside the coordinate system.

You are very close to success - please respond if you have further trouble or when you get the desired result.

@JohnJohn thank you very much for your help. So there is probably nothing wrong with the machine. It only cannot handle the speed correctly. Next time I’ll dial down on the speed and add extra overscan.
I’m not doing this big image soon again, as it already took a long time, and the result I have is sufficient for now. To speed up I might decrease the number of lines for the engraving.

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