While some decent lasers are out there for under $400 USD, they tend to be a little small. What if you wanted something a little nicer but didn’t want to jump to the $2,000 category? The answer for [Owen Schafer] was to build it with parts he had lying around and a few strategic purchases.
While he was initially planning on using a diode laser, doing anything more than engraving is tricky. He purchased a cheap 40 W CO2 laser tube, but it meant that he needed water cooling, mirrors, and more complex stuff that a diode doesn’t need. The frame is aluminum extrusion held together with 3D printed plates. Given there was a powerful laser bouncing around with mirrors, a plywood box formed the enclosure. Ppr Pipes Welding Machine 20-63
The stepper controller is an Arduino Mega running the Marlaser firmware, though [Owen] admits perhaps a laser cutter-specific driver board would have been better as he spent many hours trying to get the Arduino to do what he wanted. Air ventilation is a tube with a fan that vents out a nearby window. Water cooling is just a bucket of water with a pump in it. A simple nylon hose connected to a compressor with a maximum airflow valve provides an air assist while cutting. Finally, we’re happy to report that [Owen] bought safety glasses specific to his laser to protect his eyes and researched how to ground the high voltages generated.
We particularly loved seeing all of [Owen’s] test cuts. He proudly displayed his boxes, sharks, and lamp shades like anyone with their new laser cutter is wont to do. If you’re looking to upgrade your laser, there’s an add-on for detecting materials optically or a relatively cheap laser bed you can throw in your laser.
It’s work noting that your laser cutter enclosure needs to be light tight because even light leaking out the joint of two poorly joined boards is enough to damage your eyes.
Citation needed. What’s the maximum possible power density at the cornea? (hint: about the same as a 40 watt light bulb that far away) Since CO2 laser light can’t penetrate the cornea there is zero risk to the retina.
I’d prefer to assume that it is not safe until there’s a citation that it is as opposed to the inverse you suggest.
Practice based on superstition founded on ignorance is fortunately easy to fix, should you be so inclined.
Hi, military qualified Laser Safety Officer here…. The other dude it right, you are one spectral reflector away from a bad day, so um…. Close the gaps, wear the goggles, or go ahead and start accumulating damage like you are trying to fill up your punch card for a free sandwich. You only have 2eyes, so take better care of the other one.
That would be “specular reflector” Mr. military qualified Laser Safety Officer… (Here: Not military, but 40 years of work experience with lasers from 100 um to 266 nm, with industry safety training, working with argon ion, CO2, dye, DPSS, OPA, and others, up to 60 W CW and gigawatt pulsed.)
So, yes, it’s dumb idea to stare down even a CO2 laser, but think about what’s actually going on: The laser light is exiting the focusing lens in a f/8 to f/10 cone: A meter away it’s at least a 10 cm diameter spot. 40 watts of laser light on a spot that size is less than a half watt per square centimeter. If you happen to put a perfect specular reflector (aka ‘mirror’) in the beam path and arranged it to exit through a convenient hole to hit you, you’d certainly feel the warmth, but it’s not going to promptly burn you.
In particular, there is ZERO risk to the retina, because 10 micron laser light can’t even penetrate the eyeball, let alone be focused on the retina.
A much bigger danger to the eyes from using a CO2 laser is the intense *visible* light spot produced, which *can* be focused by the eyeball to produce high power densities on the retina, akin to looking at an arc welder. So don’t watch the cutting without eye protection.
Playing with (e.g.) a 5 watt 405 nm laser without protection and safeguards, however, *is* stupid, because it readily can be focused on the retina, promptly damaging it.
To add to Paul’s comment below, here’s the computation with real number. If you have truly 40W out of the laser (which I doubt, manufacturer never gives the true value since it implies a perfect coupling and many simply lie by given electrical power which is 3x to 5x higher) and the any mirror is misaligned, then you have an issue because it’s 40W on a 2mm circle area (that’s 318W/cm2).
Hopefully, you can put an metallic & matte enclosure on the mirror (you should anyway to limit dust deposition and burning them) so if it happens, the ray doesn’t hit the enclosure.
If the laser escape after the focusing lens (let’s say it’s f/10, so a 2.9° of half angle), you’ll have a spot of 100mm at 1m as Paul’s written. If all mirrors are perfect (none are) and the lens is perfect, you’ll have 40W on such spot, so 0.127W/cm2. To give an idea, the sun in the summer radiates 1200W/m2 that’s 0.120W/cm2.
So such a ray would act exactly like the sun. You can have a sunburn over a prolonged exposure, but not in a few minutes. The issue is that you don’t see the 10µm laser light but you’ll feel the heat.
In general, such system should have a light sensor that’s triggered at regular interval to ensure safety of the optical path. The safety period should be set to match the energy limit threshold of your retina/skin or enclosure before damage with a high margin.
So Paul is correct for the laser after the focusing lens, but he forgot the light path through the mirrors and the most dangerous one being the one that’s perpendicular to the enclosure’s window which must be protected by a second, internal enclosure.
> The laser light is exiting the focusing lens in
You’re assuming all of the right is exiting there. You’re so incredibly under-estimating the risk for things to go wrong: mirrors suddenly detaching and redirecting in another direction, beam hitting the side of a mirror, some other metalic/reflective surface. So much can go wrong, so much is unpredictable, especially in “DIY” systems like this.
Just be careful: it’s cheap.
You only have two eyes.
> In particular, there is ZERO risk to the retina, because 10 micron laser light can’t even penetrate the eyeball
I’m pretty sure if I stare down the end of my 40W CO2 tube, SOMETHING bad is going to happen to my eyeball, considering what happens to wood when wood does it.
So your retina is saved due to your cornea heating up and the aqueous humor behind it boiling… got it… 6 months with your eyes bandaged up, maybe some delicate reconstruction to ensure the scarring doesn’t screw up the optics and you’re as good as new.
Your derogatory/mocking replies aren’t exactly constructive or a sign of a skilled communicator. But as you say, it’s easy to fix should you be so inclined.
That’s simply incorrect. Your comparison assumes that lasers are isotropic, or approximately isotropic, radiators. They are decidedly not. That’s arguably half of what makes lasers useful. You are being a pompous jerk. Do not disseminate dangerous information and act high and mighty when you are doubted.
Yes, he’s a pompous jerk, and he does not speak for all those who have the same name.
It IS healthy to overestimate dangers you can’t see (or smell, or feel) until it is too late. It’s a survival trait.
I agree that the safety issues from the beam after the final focusing lens are pretty minimal. But the beam that travels from the laser tube to the mirrors to the moving head is much better collimated to about 2mm beamwidth. It can do serious damage even at distance.
Of course it takes particularly bad luck for a mirror to misalign so that the collimated beam escapes the box, but it is an actual concern.
“Citation Needed” /takes safety off of AR-15 “I don’t stand in front of the gun, dummy!”
Well, if there is an incident and the person is near sighted, they might get free photo refractive laser surgery. They will no longer need corrective lenses or glasses, Yay! The only side effect is the possibility of blindness. Can’t complain too much, it’s free. To settle, how’bout those who don’t think that pesky 40 watts in the eyeball is a risk try it out and get back to us with the results. Voice transcription on phones work well now-a-days. I apologise for the English still learning.
Anyone else worried about the fact that the enclosure seems flammable?
Burning wooden enclosure is mostly carbon neutral, so it depends on your insurance policy if you are ok with operating such machine.
Yes, but only because the bottom/bed is also wood. We’ve had a laser catch fire because of a lot of “junk” material below the honeycomb grid caught fire. The laser wasn’t focused there, but long enough exposure somehow did make it catch fire. Remember that auto-ignition temperature of wood is relatively low when the wood is good and dry.
If you are cutting through it might not be the laser igniting the crap directly – you are probably making some hot ember like objects that could provide the ignition source, add in some air assist with a little oil in it perhaps, could still be the laser though.
Either way I’m with Raukk an enclosure that easy for the tool to destroy seems barely better than no enclosure at all, maybe its even not better at all, as the exposed tool you can see it looks dangerous and treat it with the respect it deserves, the cover with a free bonus hole letting the laser out unexpectedly before probably burning more completely looks perfectly safe and normal for far too long after something goes wrong…
That’s actually a safety feature. If you can smell smoke you know the laser isn’t focused where it should be.
But it is being ducted out the window! B^)
I’m itching to buy an Emblaser 2. It’s pricey, and a bit limited, but it’s very safe.
What would your insurance company say in case of fire?
“Here’s the payout for your claim. And here’s your cancellation notice.”
That was one annoying video. I want to WATCH the process not READ it.
And, no matter what the math WEAR SAFETY GLASSES!!
The audio of the video would need some sound editing.. Sounds like a mosquito that goes around your head and makes this huge ass bass booms from time to time.
I am another LSO in a hospital operating room. I have seen too many “not me” injuries by ignoring basic safety. No argument replaces the fact that accidents do occur and only you can do your best to prevent or limit the damage. I know, I have heard the regrets of my patients that ignored doing something safely and now pay the price with permanent physical disabilities.
Yes, lasers are not safe to stare at. Neither is the sun or the end of a pressure washer or a shotgun..but a 40w laser needing a box for light escaping and being dangerous??? What?? That’s obsurd. The primary reason for an enclosure for a laser cnc if to be able to expell the toxic gases from plastics…40 watts doesn’t need anything like that as it can’t cut through anything robust Keep a fan blowing on it and spare your wasted efforts
My experience stems from a custom made 6’x12′ 400w gas assisted laser with a custom made magnetic “rails”. That said, fires happen, things melt, but not from poorly aligned lenses… there’s usually only one lens people.. try cleaning your nozzle and bringing your crappy laser closer to the substrate. Also, you shouldn’t be cutting reflective material with a 40w laser i.e. aluminum, brass, chrome
This is the most dangerously irresponsible comment I’ve read maybe all year.
I sold laser cutters (to fablabs, schools) for a living. Let me tell you a short story:
I once sold a laser cutter to a place. They weren’t the brightest or the more safety conscious. They were in a hurry to use the machine, so when I went away to eat, they tried to align it themselves. They started at one end of the beam, not worrying what the state of the rest of the mirrors was.
Sometime in the middle of their testing, a woman at the other end of the lab starts shouting: there’s a fire starting on a curtain right near her.
They had kept one side panel open. And one of the mirrors was in a weird position. It wasn’t all of the beam getting there, only part of it, but it was enough.
In the post-mortem for the accident, we figured out the beam went through a crowd of co-workers, passing possibly centimeters from heads.
STOP with the fucking table-top theorizing on safety!
There is a reason why the safety standards say they should be fully enclosed. And it’s not SMOKE.
If you happen to live in a place in which there are no such standards, that doesn’t mean you are magically safer, it means you live in a stupid place.
ENCLOSE your lasers. People HAVE been gravely damaged by them. This is no joke, this is no paranoia.
I’m really wondering if comments like this should maybe be reported to Hackaday for moderation…
Congratulations, Owen, on a creative solution! Lasers are interesting devices with many applications. I recommend looking at the ANSI 136.1 standard to read about some safety protocols so you can work safely around lasers.
That’s ANSI Z136 The LIA is as efficient as the ISO at keeping their documents paywalled, but useful excerpts and summaries are readily available via the usual search engines.
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