Help with getting black streaks on wood

[bdwizard]

Hey Guys,
I've been at this laser for well over a year, and still learning. I have what to me is a weird problem. I started with Baltic Birch ply, but was soon persuaded to switch to Basswood ply. All was well for a long time.Now with bass ply, from (several sellers), with engraving as well as cutting , I am getting black (smoke I think) streaks following the grain of the surface veneer.I have tried the following...lower power faster speed with multiple passes and Higher (up to 100 %) power with slower or fewer passes. I'm STILL getting the same results! The big problem to me is that there's no way to sand it out. Am I doing something wrong, or is it just the nature of the beast? Is the best answer just to go back to the BB ply?

My setup is as follows: Sculpfun S30 Ultra, 33 watt laser.I have air assist and use it, and exhaust fan to the outdoors. Any assistance will be gratefully accepted!

Thanks!

Bruce

[LAHobbyGuy]

Got me stumped!

[tonyrogers]

not enough info to help, post pics of your setup, common question. dozens of videos out there. many factors. wood, moisture and sap content, reflection, efficiency of your air assist. more pressure is not the answer. 3 pounds of nozzle pressure that is blown THROUGH the kurf. its not about power or wattage. its about intensity and focal distance. many have invested 100 hours of videos instruction to attain a well rounded education. its all you

[bdwizard]

Just an up date on those black streaks.
After way too many hours believing that I was a maladroit, I finally figured most of the problem out.It would seem that the only time this occurs, is when I'm using Basswood plywood!!! Almost never on Birch. Then I tested end grain absorption on the end grain of the surface veneer. WOW!! The basswood was like a sponge. I guess that for the most part it is back to birch. Thanks all for the responses!

Bruce

[tonyrogers]

the purpose of air assist is to blow the sap vapors and soot -through- the kerf and keeping the junk clear of the beam for maximum efficiency. about 3 psi at the nozzle. nozzle distance from the material if critical. not all nozzles are close enough when set with the recommended optical distance. if the air assist is not around the beam it is worthless. air assist that comes in from an angle is worse / worthless. these little secrets are discussed on technical CO2 sites. most diode folks do not investigate deeper techniques / understandings.