Best settings to cut 6mm plywood

I’m using a SculpFun S9 to cut 6mm plywood for model ships.
I am running high power (100%) at 500mm.
Even after several runs (approx10) I am still not cutting though the wood.
I have checked and cleaned the lens, but with no success. If I run again, the laser diode does not seem to cut the wood anymore, the wood just seems to char more. If I decrease the speed really low, but then the edges of the cuts are not sharp due to charring of the wood…
Can any suggest the best settings for cutting 6mm of plywood.

Higher power is not necessarily better. Try to significantly lower your power (despite the fact that using the module constantly at 100% will decrease lifetime), the less charring will occur which will block the laser beam in the following cycle.
I’d suggest 500 or 600 mm/min as you did at 70% (or maybe 60%) and around 10-20 passes. Additionally, focus to the middle of the workpiece, e.g., 3 mm below normal focus.
Some more guidelines: Settings guide - Diode Laser Wiki

the biggest problem with cutting ‘plywood’ is that most people don’t say what kind of ‘plywood’ they talk about. in almost all hobby-laser videos and also here in the forum they always talk about ‘plywood’ and in fact it is only the light poplar-plywood. birch-plywood and especially the multi-layered aircraft-plywood is incomparably worse to cut with these small diode lasers. in addition there are also special types of plywood for laser cutting that have much easier to penetrate adhesive layers but are almost always far less stable.

here are a few values for cutting from me (sculpfun s9 with air-assist - focus middle of material):
2mm balsa: 1 x 600mm 60%
5mm balsa: 2 x 500mm 60%
12mm balsa: 7 x 800mm 80%
3mm mdf: 3 x 250mm 70%
3mm poplar-plywood: 4 x 300 30%
5mm poplar-plywood: 4 x 300 75%
2mm birch-aircraft-plywood: 4 x 250 70%

see picture - top row milled for comparison and all pieces look exactly the same from the back as they do from the front. no traces of smoke and no black crusty cutting edges just light brown: