I cut baltic birch. Since the laser actually burns rather than cuts, it’s no surprise that all the edges are charred. When I see fancy professionally done work, the edges are sometimes not charred. How do they / you manage that? Neither sanding nor routing seem like solutions. Is this an unsolvable problem?
You’ll find that higher power lasers are able to make the cuts at higher travel speed, which reduces or eliminates charring. When my first tube was degrading, it was taking higher power and slower speed to perform a cut and the edges were black and almost flaky charred. When I had first received the laser, this was not a problem that existed.
With the tube replaced, my speeds were back to normal and the edges were no longer charred.
60 Watt (true) tube, 3 mm birch laser-grade plywood.
I cut 3mm plywood with a 20 w. diode laser and have found that after my first attempts with charring the solution was to increase the speed by four and the number of passes by four. Now get nice clean cuts. This may help you with your problem.
It’s a bit of a shame that you do not write in your profile how many Watts you have to play with.
But as @fred_dot_u has already said, speed and power are one of the keys to clean cutting. The second key is the plywood itself. If it is exterior plywood, it is often impossible to get clean cuts. The glue and the cavities filled with waterproof glue are a bad connection for laser machining.
You can guess for yourself what is internal and external plywood that is in the picture.
And I think one can just about forget no charring on MDF. If someone has a higher power machine, say above 150W, and has cut MDF, is there charring?
I actually have no problems with charring, either on MDF or on HDF. Although the 6.2mm disc is dark there is no discoloration when I wipe them off with a cloth. However, I always have lots of evaporation which condenses on everything, that is the (only?) Disadvantage of these materials.
That’s pretty good looking results. I have a 60W machine too and now I wonder what I’m doing wrong!
Fred, in one photo are my values that I use as a starting point when I work with the different materials, are they so different from the ones you use?
I always think that MDF / HDF is great because it is so easy to work with and if laser cut, it has very stable edges. I use it for gears and similar technical items.
There’s nothing special I do to cut in these materials, normal (good) focus, air and actually reasonably fast with moderate power, it’s a bit like the settings I use when working with quality plywood.
If I can help you with anything to get you on the MDF train, please feel free to ask.
Evidently I filled that profile a long time ago. Just updated, thank you for mentioning it. 80W.
Of late I’ve been cutting 1/4" baltic birch. I was systematic at first about balancing speed, power, and passes to find the best result but evidently didn’t go far enough. High speed / multiple passes make sense but what about the power setting? just set it on 100% and go? I use an 80W laser.
… the same thing happened to me when I bought a new machine 
With 80 Watts, you should be able to cut the materials to the thickness you are referring to. Either you do not have the power you think or your setup is not optimal anyway.
I hope you find a solution.
NEVER use 100%, it will ruin your tube.
Find your max mA which corresponds to approx. 75% of the nominal power, I guess it is approx. 18-20 mA max.
Speed and power tests are the first place to start.
A wipe with Hydrogen Peroxide will remove most of the burn marks and white wash the surface.