Hello! I have a Sculpfun S9 5.5W engraver. I always set the focus to 20mm, I also test the speed and power, but for some reason I don’t find the DPI setting correct. Could you help me find the ideal DPI that I could set? the very black parts are streaky and burning, and if I lower the power, the whole thing is dim.
The description says “ultra-fine 0.06mm sharp laser focus”, so start with 0.1 mm = 254 DPI.
You can run an Interval Test around that value to see how the result varies.
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Thank you 
Unless the strong vertical pattern is part of the original image, the machine seems to have a mechanical issue producing a periodic glitch as it moves along the X axis (assuming the image was produced in the same orientation).
Going through this list of mechanical checks will bring the machine closer to perfection:
But it looks a lot better than your original description! 
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Wow! Thank you!
The best way to understand interval or dpi is this video by Laser Everything. It explains how this works. Even though it’s done on a fiber, it’s easy to understand.
The procedure they use works for any laser using any material…
Good luck
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Thank you
The “real-world” standard DPI setting of the S9 laser module is 0.08mm / 318DPI. This should provide best results.
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If the squares are filled blocks, then there should not be bars or vertical lines in the output.
These are also in the image, but most visible at the top… Are these in the original?
Looks great otherwise…
Good luck
I guess that’s caused by the very poor mechanics of the S9. It’s a very outdated laser model and needs very careful setup and tuning of all mechanical parts. It uses wheels on all axis which is very hard to tune to make the laser head run in a straight line, especially on the x-axis. A linear rail upgrade will improve things, I think.
A robot with a human face tatooed on its shoulder ! Usually it’s the reverse 