Re: [CAD_CAM_EDM_DRO] High pressure water jet (Lasers)

CO^2 lasers most definitly use a gas mixture if they're any good. It's
not really fair to call them CO^2 when they're not really using much of it.
Home made lasers can run off welding quality straight, better ones pure CO^2
and really good ones run on a mix, even though the mixes are not that much
more expensive. BOC actually offers a CO^2 laser mix premade. All one off
CO^2 lasers have their own ultimate mix but it's usually mostly He, some
nitrogen and a bit of CO^2. Fine tuning the gases can make for specific
characteristics you might need like a much more stable beam, but with less
overall output. Like another post says the helium is used to help dissapait
heat (As well as helping with other energy transfers) and the nitrogen helps
transfer pump energy to the CO^2. Oxygen is meant to be the killer of a CO^2
laser but infact, adding tiny amounts helps to pull the energy away from the
CO^2 quickly so's it can be pumped back again.
Argon / Kryton ion laser are some of the most picky lasers of all and
they really do need ultra pure argon. As well as fancy glass work and a
monster supply, some even run from X-Ray power supplies. They make a very
pretty teal / green / blue beam though, the best of all I reackon. Pulsed
excimer lasers using things like xeon + fluorine, or iodine and oxygen, are
incredibly tricky to keep going because the gases must be perfectly mixed
and pure to work correctly. Most of the time they need a refill after a few
weeks, even commercial tubes.
50 watts is just enough to cut metal like you said but on thicker stuff
it'll just heat the sheet up. 100 watts is sort of minimum and even then you
should really only be working stuff like steel. Copper and aluminium bounce
lots of 10.6um back so it doesn't really work for them, like trying to shine
a torch through a mirror. Oxygen is used as an assist on steel like in
oxy/fuel cutting. For metal working it might be easier to buy a CW crystal
laser, ND:YAG etc, because the 1.06um can be run down fibers to the tool tip
instead of those disgustingly expensive mirrors CO^2 armatures need.

I'm just dithering on now anyway,
John

----- Original Message -----
From: "Jon Elson" <jmelson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, March 13, 2001 6:23 AM
Subject: Re: [CAD_CAM_EDM_DRO] High pressure water jet (Lasers)


>
>
> e.heritage@... wrote:
>
> > Jon,
> >
> > I thought that as well to begin with. But in most really big
industrial
> > sized CO^2 lasers the medium is usually something like 70% He with other
> > gases for better lasing actions, N being one of them.
>
> I went out to a shop where a guy had an essentially home-made CO2
> laser cutting rig. It was only 50 W, I think, and was used for cutting
> plastics mostly. I think it could cut some metals if they were very thin.
> I'm awfully sure that the gas supply was high purity CO2, with nothing
> added.
>
> > I'm not sure but
> > doesn't He have a lower freezing point than N?
>
> Yes, around 4 K at atmospheric pressure. Nitrogen is 77 K. Oh, sorry,
> you CANNOT freeze Helium. It goes into a superfluid state around
> 1.3 K, but it will not solidify, no matter how cold you go. So, those
temps
> above are the boiling points.
>
> Jon
>
>
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