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What am i doing wrong? line engraving not connecting on corners

So i have a Heart shape (Just and example i had to test with but also effects other shapes) and when i engrave it doesnt connect on the corners, I assume this is due to the reducing power when it hits a corner, how do i prevent this?  running it at constant power mode just causes it to burn all the way thru at the corners.

thoughts and suggestions welcome, have had to go back to the M2 board just to get stuff working to finish orders.

Uploaded files:
  • IMG_2047.JPG
  • IMG_2048.JPG

@paul and @dancolwp1974


anything i can try?  im feeling like this wasnt the board I should have gone with at this point but would love to get it working and prove myself wrong.

Hi Mark,

Sorry for the delay in responding.

Yes, you’re right - the GRBL firmware which MiniGerbil (and other products) use automatically scales down laser power when the gantry changes direction sharply. This is done because the lasering effect on material is a product of both laser power and the time duration of the burning. Because a sharp change in direction involves slowing down before moving in another direction, the duration has to be longer, so GRBL scales back the laser power so you don’t end up with burnt corners.

So what is happening in your photo is that the scaling back of the laser during the sharp changes of direction seems to be taking the laser underneath it’s minimum threshold. On my K40, the minimum laser level is about 9% - nothing visible happens below that level. So if, for example, you were burning at 10% and the scaling back of the laser was 2%, then the corners would blank out.

All of this is a result of movement in a vector engraving context - raster engraving doesn’t suffer from this, as the user can allow additional margin on the side of the image for the gantry to slow down and turn around.

How to solve it? Here are my suggestions, easiest first

  1. Experiment with different speeds and laser strengths. My first guess would be stronger laser, moving a bit faster. It seems in your top image there are a number of different hearts burnt with different intensities – the bottom heart in that top image looks the best, so use that as a good starting point. If you advise what speed and power you’re running at, we can try it ourselves and see if our results differ
  2. Different acceleration settings can help, see https://forum.lightburnsoftware.com/t/laser-not-cutting-in-the-corners/27418/2 You can change acceleration settings via the Lightburn interface or via https://awesome.tech/what-are-settings/
  3. Take advantage of symmetry - you could try dividing your heart image down the centre (vertically). Cut one half (eg. The Left Hand Side) and then cut the other half (Right Hand side). The different dynamics of the laser starting the cut (as opposed to flowing through the cut) would probably solve the problem. This solution only applies readily to some geometries.

The results you’re seeing are the worst I’ve seen of this kind. Just check that everything else is ok, for example:

  • have you changed your acceleration settings from standard? If so, this may be the problem
  • check the thermal aspects of your laser are ok - it should be at a consistent operating temperature with cooling system working well.
  • keep in mind that as your laser tube ages your threshold level can change.

Let me know how you go.




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