Dots at the start of a line at high speeds when doing scanning offset adjustment

[ednisley]

@NellCo

<9kmm/m it’s almost as if overscan isn’t working on the controller

For my 60 W laser, the offset correction became significant over 100 mm/s, so it’s not surprising (to me, anyhow) that you don’t need it below 150 mm/s.

The offset timing depends on the HV power supply timing, so it will be different with the 90 W supply. Measure and correct as needed!

@NellCo

a dot or two at the start of the line

That looks like a rather orderly version of the random dots I explored:

Where Those Random Dots in Engravings Come From

It seems everybody engraving acrylic with a CO₂ laser has seen random speckles appearing in places where the design shows a blank. Regardless of the suggested remedy in the many threads on this topic, nothing stops the dots. It turns out the problem lies inside the high-voltage laser power supply, which occasionally fires the tube at random, even though the controller has disabled the supply’s output. Although I’ve measured only two power supplies, other folks report random dots regardless of t…

They’re probably on the tail end of the engraved line, where the tube has been lasing and the HV power supply can’t tamp down the tube’s conduction. You may get fewer dots when you run at higher speeds with higher powers.

If they happen with regularity on every engraved line, no matter what power you use, a warranty replacement seems appropriate. Definitely let us know how that works out!