What is the bright spark?

[Douglas Repetto]

Hello SC,

I've got a 60watt CO2 laser. The beam is invisible. When I'm cutting a bright white spark is usually generated. Is that just a little flame where the material is burning? From what I've read the plastic window in the case should be absorbing any stray laser light, so there's little danger of laser damage to my eyes. But I'm wondering about the bright spark...I imagine there's lots of UV energy in there, probably not the best thing to be staring at, and I'm not sure how much UV energy a simple plastic window is absorbing...

Any advice?

thanks,
douglas

[Dan Hintz]

What are you cutting? Any visible "spark" is simply the material burning away, a short-lived flame.

[Douglas Repetto]

What are you cutting? Any visible "spark" is simply the material burning away, a short-lived flame.

Cutting mostly cardboard and paper, some Thermark on aluminum. When I look at the spark through a welding mask it's still quite bright, which is what makes me think I shouldn't be looking at it...

[Dan Hintz]

When I look at the spark through a welding mask it's still quite bright, which is what makes me think I shouldn't be looking at it...
Well, I wouldn't stare at any bright light for any appreciable length of time, regardless of the wavelength... it's just not good for your retina.

[Joe Pelonio]

People watch the laser all the time, in fact I know some owners that just like to stare at it the whole time it runs. None of them have gone blind yet, as far as I know.

Welding results in UV light which is harmful to the eyes. It's my understanding that our C02 lasers do not, though I am willing to be corrected by someone more knowledgeable.

There are some other types of lasers that do produce hazardous UV light, and I heard that fiber lasers do but at low levels.

[Jerry Hay]

I admit I watch my laser all the time. It amazes me every time I do a job. I guess I am just new to the biz but it is fun. Everyone who comes into the shop has to watch when I am running a job. I was cutting music boxes last night and one of my friends stopped by, he called his girlfriend over to watch. I just laughed at him. I think I should charge admission to watch me make something. That might be a whole new revenue stream for everyone. :eek:
I am going to engrave the tickets.

By the way the nervous tick and my glowing green eyeballs are letting up.
I must be getting used to the laser.

[Bill Cunningham]

You want to see 'bright'? Run a vector bead across some ceramic tile, it's every bit as bright as a welding arc, and the trail it leaves also looks like a tiny bead of weld.. You'll be looking at floating bright spots in the air for the rest of the day..ha..

[Rob Bosworth]

I believe the bright "spark" you are seeing is called the plume. It actually is the vaporized material and effluents "burning" as it passes through the laser beam. If you run a material that emits lots of stuff, you will see the plume expand. For those who have run rubber stamp material without air assist, you have seen fairly large plumes above the material. If enough of this material is burning, it will actually absorb the energy of the laser beam. It is called thermal lensing. The effluents start to absorb the energy of the laser beam, and it actually changes the focusing characteristics of your beam. The focus raises, becomes less efficient, and the focus point raises. If you are running rubber stamp material and you see a line of material that did not engrave, that was caused by thermal lensing.

The wavelength of light emitted from a CO2 laser should be absorbed by clear plastics, like the see-through cover of your machine. The same way a pair of plastic safety glasses will protect your eyes from a reflected beam from a class IV CO2 laser system.

I have been in the CO2 laser business since 1981, and I still watch the magic of the laser beam whenever I am around it.

[Dan Hintz]

Let's try not to stare at the laser for too long, shall we? Even though the acrylic covering the gantry blocks the near-IR wavelength of the laser beam itself, you can still do considerable damage with a bright enough visible wavelength. As with the laser itself, there will be no pain (though headaches can be a common malady), but your vision will be slowly degraded over the weeks/months/years.

For example, I work with high-powered, visible-wavelength LEDs as part of my main business. There's no UV, no IR, just pure visible-wavelength light. Even so, I have to be careful I don't stare directly into the emitted beams as it can (and will) irreparably harm my retina. It's no different than looking at the sun through a window... it will block the harmful UV, but the visible light is still damaging your eyes. Something to think about...

You may not wake up one day completely blind, but you may go from 20/20 to 20/40 vision over a period of several years, and is that cost worth the fleeting joy ow staring at a laser 8 hours a day? I agree that it's fun, all I'm saying is try to limit yourself... use that will power.

Happy lasering :)

[Mark Beito]

When we engrave glass in our shop, which we are doing a lot of lately, we get a very bright white light at the point of engraving. It doesn't work to tell the operators "don't look at it." It's like they can't help themselves. I hear "sneak a peek." I hear "just want to check to see that it's working." I hear "boy, that's bright--shouldn't we have some safety glasses?"

But getting glasses to protect from the wavelength of the CO2 laser (10600 nm) doesn't seem to make sense. The laser isn't reflecting, so we don't know exactly what wavelength to be protecting from. I can buy what are labeled welder's glasses from McMaster ("protects from harmful infrared light") for under $20. But is this the right thing? These glasses are intended to protect from the light emitted from gas welding or oxygen cutting, so that may be a different wavelength, too. (BTW, these glasses would be nowhere near good enough to protect from arc welding).

[Chuck Stone]

I've been staring at my laser beam for weeks now
and it hsdb'r affwxted mr uet.

[Dan Hintz]

Pick up some static cling window tint and cut a ppiece that fits the top window. When you plan to do glass, slap it on.

[James Stokes]

I have had a laser for just about 10 years. When I got the first one my vision was 20-20. Now I can not read the numbers on my microwave. Is it the laser or just old age? I am 52

[Dan Hintz]

James,

I'd offer you a gentle warning that staring at any bright light for an extended period of time could be bad for your eyesight, but I have a feeling someone would call me an alarmist and say they've stared at bright lights for years without any ill effects.

Time to take your Centrum Silver...

[Joe Pelonio]

I have had a laser for just about 10 years. When I got the first one my vision was 20-20. Now I can not read the numbers on my microwave. Is it the laser or just old age? I am 52
That's about the age when I started wearing glasses, and didn't get the laser until I was 53!

[Bill Cunningham]

It's like when there is a eclipse of the sun, all the radio/tv stations tell folks not to stand and stare at the phenomenon:eek: When it's all over, I suppose that once again you can safely stare into the sun :D

[AL Ursich]

I got some $300.00 coated glasses for beam alignment.... You TOO can look like a Senior Citizen on the way to the Daily Specia with your left blinker on all the timel......:eek:

AL

[Rob Bosworth]

Jim, 52 is nothing. My Mom is 83 and she doesn't need glasses. She drinks right out of the bottle.:D

[Richard Rumancik]

. . .When I'm cutting a bright white spark is usually generated. Is that just a little flame where the material is burning? . . .

If I understand correctly the spark you are seeing is distinctively different from the normal "flame" you may see. A spark is of quite short duration. Flaming is ususally more consistent, although air assist and exhaust can make it vary somewhat.

The amount of flame is dependent on the material being cut and the manner in which it lasers e.g. acrylic vaporizes, so there is often little flaming; materials that "decompose" (burn) will show more flame.

A couple possibilities causing the spark - sometimes when cutting cardboard or light wood, you will generate carbon particles; these can cause sparking. This is especially evident if you have to make a second pass and are hitting the carbonized material directly.

The other possibility is that the cardstock you are cutting is made from recycled paper and has metallic particles in it. High quality paper won't have any metal so I would not expect any sparking at all. Lower grades of cardstock may have metal particles in it. Extracting all the particles during recycling can be difficult and expensive, so for some applications they may not bother trying.

Woodworkers who cut certain grades of MDF are quite aware of metal particles - in the case of MDF, the manufacturers don't try very hard to remove them. They are so large you can see them.

[Rodne Gold]

The light is plasma - superheated gasses which emit a very bright light. The laser door is probably is enough protection for UV emmisions etc of the light