Yeah because of the higher power of the CO2 laser it’s harder to get a lighter vector engraved. Do you have the work piece at the focal point of the laser?
Diode lasers can genrally be focussed to a much smaller point than CO2 lasers. This is caused by the wavelength. Therefore you will probably not get as sharp engravings with the CO2 as you can get from the diode laser, but still pretty good.
For engraving (using an 80 W tube), I generally use speeds in the 2000-5000 mm/min range (i.e. 33-83 mms/sec). Note that a CO2 laser (especially DC-excitation types) does not perform very well at very low power levels, so you should generally go for as high speed as possible.
Excuse my ignorance, but how long of a lens is in the K40 types?
As a general rule you want the smallest dot size. I agree with most, move faster… For these to perform best all parts must work together including the dot size.
There is quite a difference going to a CO2. I suggest a few videos to assist. Check out RDWorks Learning Lab videos. I just picked one that was interesting. I have found them very informative.