PWM frequency, power levels and 2.5D wood engravings

[aaataamKl]

Ok, bit of complicated one to explain but give me a chance:

I did some test with 2.5D engravings on wood, just for the fun of it with no intention to create anything of use.
The base for all this is a chinese K40 clone running on Marlin.
During my tests I noticed that at certain power levels the wood tends to vaporise rather than to burn and turn black.
Of course this all depends on the wood, grain and how much sap/resin you encounter on the way.
But it got me thinking...
So I started to find some power level that worked good for evaporating my cheap 3mm plywood.
Once I ran out I cut a bit of a new sheet and of course all the values I found before did not work out the same on the new piece LOL
Anyway, I now also started to play with the PWM frequency and here I noticed that lower values in the region of 6-15kHz result in mainly charring of the wood with no real evaporation at any power level.
In the region between 20 and 30kHz this a totally different story as here we can find quite a few power levels that make the wood disappear.

Has anyone experimented in this field?
Are there any references for energy levels and PWM frequency is this regard?
Or is anyone interested in doing some tests to confirm or rip my findings apart? (Then at least I can put it off based on cheap chinese hardware LOL)

[Howaredug]

Played around a bit more and there is a relation betwen PWM frequency and wether wood is burnt or vaporised.
So for 2.5D engravings it pays off to create a mask just for the all-black areas and to vaporise them first with one or more passes.
After that the maskis reversed and the other shades are done.
Running low on both time and proper wood but hopefully will have some time next month for more tests and to upload some pics and vide

[kagtinyzs]

Hi, right now, in my machine (golden laser), the propietary software dont let me change frecuency
I am waiting a new control that i bought in china (ruida rdsc6442s) that allow me to change a lot more.
You are not talking about pwm to control power supply, you are talking about flecuency of pulsed laser I think.
But, a lot of chinese vendors recommend not change the frecuency, and set to 20 khz. they tell that this changes of pwm affect the life of tube.
Apparently supposed to leave it at 20khz and not change it for glass tubes, different story for RF tubes
I admit that I think in the cost of tube and in a first moment I accept the chinese vendor speech
Martín.-

[Michealpync]

The frequency provided by the original controller is actually 23.5kHz.
But the machines are shipped with three different types of controllers, one analog, two digital versions.
All share the same power supply and tube.
Difference is provided PWM signal, mine was 23.5kHz, the analog ones often sit at 18kHz and the other digital one on 25kHz.
So there is already quite some variation in the PWM frequncy for the same hardware running.

Due to the nature of the beast and the involved variables it is very hard to find a common ground to get a baseline established.
Guess for the time being I will simply do some tests first to find a good power level for evaporating and just leave the frequency alone.
Was just thinking how great it would be to have a baseline and be able to adjust the parameters on the fly so 2.5D engravings can be done without too much charring.