I have been using a 5W diode for the last couple of years, and just upgraded to an Omtech Polar 350 (a 50W CO2 machine). While I mostly use my laser for layered artwork, I had also just started getting into photo engraving with the diode before the upgrade.
I am having a very hard time getting good results with the CO2 machine. I have attached a test grid indicating speeds from 100 mm/s to 500 mm/s and power from 20% to 40%. On the diode laser, I was able to get nice dark burns without engraving very deeply into the wood (baltic birch 3mm plywood). With the CO2 machine, any setting I have used that creates dark engravings also cuts through a portion of the wood, and what remains is flakey and falls apart when touched, which is just not really acceptable for the products I am trying to make. Photo engravings end up with some actual depth to them and honestly it gives them a sort of creepy 3D effect that is not pleasing.
Is this normal for CO2 lasers, or is there a setting or consideration I’m missing? I have tested variations in power, speed, lines per inch, and wood grain orientation and haven’t found a satisfying result. I haven’t been able to find any discussion on this topic, which leads me to believe that either this is abnormal for a laser, or it is such common knowledge that no one feels the need to comment on it.
I assume it has to do with the spot size of a diode laser.
I defocus quite a bit, with success (to get a darker result), when I engrave with my CO2 laser.
It is also important to find the appropriate line spacing to prevent over-burning of the same spot.
It has been my experience that my C02 laser does not get the dark burns like my Diode laser does. It produces more of a light brown color unless I really overburn, like you’re experiencing. If I need a dark engraving I still turn to my Diode machine.
Despite increasing power by about 8 times, what kind of interval are you using? Most co2 have a dot size of about 0.20mm, so base your interval relative to dot size.
500mm/s is way too fast if you want to control the co2 lps. If you’re just doing fills for material tests, you can probably get away with a small interval. Although mine will run 1650mm/s, it’s purely academic as it will easily outrun the lps.
I run most of my stuff around 200mm/s, depending on the job.
Thank you, this is helpful! I got a similar response in another forum I posted to. I’ll try defocusing a bit and see if that yields better results, and play around with the line spacing a bit more. Thank you!
Ya, I’m wondering if I should keep my Diode around specifically just for this purpose. It’s just hard to want to do larger engravings at 23 mm/s, but I guess that is the price we pay for good results
I’ve tried intervals from .06 to .12, but I felt like I could see some line separation at the higher interval. Other posters have suggested defocusing a bit to get a better burn, so I am going to give that a try and increase my interval a bit to see if that can yield better results. Thank you for your reply!
The theory is one thing, practical attempts often something else entirely. Therefore, I like to try out the topics we talk about here in the forum, it gives (me) often a more nuanced picture.
Jack, will you give a qualifying bid for what line spacing this little test is made with?, And how much overlapping/space there is between the lines?
Unless you physically measure yours on the same material, then, yes, it’s theoretical, but still useful. Many of these are shipped with different length lenses, which have different sized spot.
All I’m saying is generally most of these appear to be ~0.20mm. Gives you some idea of what kind of interval you may want.
I think using the interval properly, helps significantly.
Definitely!
In my image, line spacing is 0.1mm and deffinitive not enough to fill an area perfect. The lens is my standard 2 "and I used 300mm/s and 10.1% power (on mirror). It also fits nicely with my kerfsettings which I use for tight connections, they are 0.075mm.
