Questions about CNC engraving (power, wavelength), and safety

Hello everybody, :yh:
I’m currently in study phase for building a laser module for engraving and cutting on a CNC machine, and I have some questions about it.

First of all, I would like to say that I am a newbie in lasers (ignorant but not stupid ), but I read quite a lot about it in the last weeks, and I also made a few searches over here before posting. I assume what I’m asking is not extraordinary at all, but I’d like to be advised by experts specifically for my needs, to get the most accurate answer to my issues.

First thing is the power and the wavelength. I was first opting for a 2W 445nm module. But then I found this comparison. I did some search, and it seems clear that 405nm is better for engraving or cutting that 445nm (at same power). But since our dear provider DTR sells only 900mW 405nm modules, the question is: what’s the best, 900mW 405nm or 2W 445nm ? I guess that is a great difference on power. And also the fact that 405nm can be focused to a smaller dot (better engraved image’s definition), do you have an opinion on that?

Second thought was about the choice of the lens, but with these comparisons (1 and 2), if I can choose one wavelength, I may be able to choose a lens.

Third was the driver, but that’s not really an issue, I guess. I saw the Flexmod P3, that seems to fit perfectly for my use, and read reviews telling it’s a great driver. So unless you have something to contradict, I will go for it.

And last, the safety. I have read much about it, especially on this forum, so I can tell I am pretty aware of the risks of the laser and I absolutely do not want to mess with it. Still, I haven’t chosen yet what glasses I should buy. I read about, and understand what OD is. But I’m also wondering, if the OD is too high, does the laser spot become invisible? Wouldn’t it be safer then to have a lower OD, that allows to see the dot a bit, making it easier to avoid a shot, knowing where the laser points to? Then again, I will not use the laser as a pointer but on a mount pointing down to the engraving target, so I would like to see the dot, but be protected from reflection. What OD do you suggest?
I saw the Eagle Pair (the true ones, not the fake) and read that they are great, but they protect from a lot of wavelengths I will not use, so maybe there are cheaper and more specific glasses that will be just fine for my use? Also I’d like them to be CE certified (European norm), since I’m living in France.

Sorry for being long, but I’m asking myself a lot of question I couldn’t answer with searches.
I hope I will get good advice for my issues, so if you can help me for one step or another, thank you very much. :yh:
I will soon post in the welcome section to introduce myself and present my project, in case people are interested in it. :yh:

Hi BaifSigurdson, welcome to the forum. A 2 watt or less laser is is okay for etching materials such as wood, leather, paper, cloth, plastic or cardboard. You state cutting also. What thickness, material and color are you planning on cutting?
The safety goggles should be at a minimum around 3+ OD You are correct that if the OD is real high it might make the dot not visible. It will not be detrimental to have the goggles protect your eyes from a wide spectrum of wave lengths.

Hi Laser Chick, thank you very much for your answer !
For the cutting, I'm don't really know, I just feel like it would be good to have the ability to cut, then if I need to later, I can. If I can cut thin plastic, cardboard or plywood, it can be cool. But since the laser will be mounted on an existing CNC milling machine, I can already cut a lot of stuff. So the laser is more for engraving, but laser cutting might be a good extra if needed.

Okay, so maybe I can go instead for this pair or this one (better the first thanks to its frame?), with OD 4 instead of 5, more visible light transmission, and a few dollars cheaper?

Either pair will do for a 2 watt laser or less as long as the wave length of the laser you get stays in the parameters of the laser goggles protection. The first pair does have a note of only 2.5+ OD for the wave length in the red range of 635nm.
Please remember that laser goggles are not 100% protection for a sustained direct or reflected shot to your eyes as stated on those links you included.
About cutting, it requires a lot more power than etching and I mean a lot. If you are cutting black colored items such as open cell foam then 2 watts will do it if the beam is nice and tight creating higher beam density/energy at a specific point. If you want a decent rate of travel you probably will not want anything under 20 watts and that will require external cooling, venting to get rid of smoke or fumes, very serious eye protect and so forth.
So you will have to ponder if you really want to cut or not. You can always add it later on if you want to. Good Luck!!

Thank you again for your answer.
For me it's fine because I'm not going to use 635nm red laser on this application.
When I talked about reflection, I meant the dot of the laser, impact point of the beam, reflecting on any surface (not mirror) like the wood I'm engraving for example. For this, it's okay, right? But I must be careful with reflects, when engraving metal for example (I read that you have to apply a black surface on it like black tape, to absorb to beam power and avoid reflection).
Allright, that's okay if I cannot cut with this as I said. Maybe another time, to build a more powerful installation as you say.

And about the choice of laser, what do you think? Would you use 2W 445nm or 0.9W 405nm laser?

BaifSigurdson said:

Thank you again for your answer.
For me it's fine because I'm not going to use 635nm red laser on this application.
Allright, that's okay if I cannot cut with this as I said. Maybe another time, to build a more powerful installation as you say.

And about the choice of laser, what do you think? Would you use 2W 445nm or 0.9W 405nm laser?

Click to expand...

Personally, I would go for the cheaper diode as both burn equally well

Hi marcuspeh, thank you too.
That was a bit the point of the question. How can you tell they will burn equally well ? Does the benefits of the shorter wavelength overcompensate superior mean power (factor 2 here) ?

Hi BaifSigurdso,

i have read a lot about CNC engraving with laser. Very often they use CO²-Laser with more than 20W ..... like Laser Chick tell`s you. Even infrared lasers are often used with 3-5W and 909nm or higher.....but they are dangerous because the Laserbeam is invisible and goes deep into the skin......you need good protection. For engraving in Wood you can start with 300mW 405nm Blue Ray.....but it is very slowly. With 2W 450nm is it a little bit faster, but for cutting it is too less Power....only for thin material like foamed material.
Maybe with 5-7W Blue 445/450nm you can work fast enough and with Analog Driver you can control the output performance for different material.


Raveman

The easiest to protect your eyes against is a co2 laser @ 10600nm , 50p clear plastic goggles would work perfectly well and the absorption on organic materials is very high but as mentioned the need a HV supply and water cooling ( PC radiator would be fine )


I did use a 4W 808nm diode to do engraving , setup was rushed but it worked .

https://www.youtube.com/watch?v=wGKeiGgDI0s

for the sake of power/cost I would use a 445nm diode , googles are easy to get and its able to engrave wood/card ect well .

I'll maybe do a larger setup with CO2 or anything on another project later on, for this on, I'll stay with 2W max. I saw people doing amazing engraving stuff with 200mW diodes, I just expect to be faster.
Still in search of opinions to choose between 2W 445nm and 900mW 405nm.
Thanks anyway for you answer.

This thread also has a lot of great info on engraving with the 445nm diodes.
CNC Laser Engraving 8bit Shades of Grey 445nm

CO2 will be more powerful but more expensive. As for cutting Jtech has some pictures of different materials and thickness you can cut with a 2W 445 at the bottom of this page. The thicker the material the slower the cut.
https://sites.google.com/site/dtrlpf/home/laser-cnc-engraving

BaifSigurdson said:

Hi marcuspeh, thank you too.
That was a bit the point of the question. How can you tell they will burn equally well ? Does the benefits of the shorter wavelength overcompensate superior mean power (factor 2 here) ?

Click to expand...

Lower wavelength will definitely burn better. Maybe I shouldn't have said they burn equally well but both are equally good for a cnc engraving. So, personally I will go for the 2w 445nm.