They are quite perfectly as I wanted but I need some advices from those who have more experience. On the back side of the cut, I have some areas with burned marks (1/8 non-proofgrade plywood with mask tape - cut 1 pass full power speed 240), not everywhere just at some points.
You have two main culprits here: flashback and corner overburn. They’re hard to avoid.
First step is to use the minimum power possible to get cuts. You’re all over that, good!
Flashback: you can reduce this by using sacrificial material underneath your plywood. Try laying heavy cardstock (or another layer of plywood, or any number of possible scrap materials) down first, then lay your plywood on top. Be sure to adjust height of focus to compensate if necessary.
There are other types of ways to shield the back— You could also use double masking on the back side. Often it comes down to what you have on hand, but try to avoid particularly flammable materials, especially layered stuff like corrugated.
Corner overburn: this is trickier to stop. There are two main strategies with different success that I know of.
One, You can avoid true corners altogether. There are four main ways to this-
engraving your lines (not practical with wood, better with paper)
extend your exterior corners past each other so instead of corners you have intersections of lines
use small radius turns instead of hard 90 degree corners
break each line segment apart and use different colors for each segment. This way you can order the cuts to ensure that no two lines that touch each other are cut one after the other.
Two, you can adjust your settings to slow the laser to minimum while reducing power accordingly. Corner overburn is caused by the slight delay of acceleration and deceleration of the laser head. Slower speeds reduce that effect.
Each of these techniques has had some measure of success that I’ve both tried and just heard about. You’ll need to see which work for you.
Further reading:
There is a possible future where laser power is adjusted while in corners to prevent this. There is no way to know if it’ll ever be implemented, but it’s discussed here:
And especially read this, it covers some of these ideas:
It would be a cool feature for Glowforge to build into their software that made the laser smart enough to know it was making a 90 degree turn and lower the power a bit on the turn.
