Re: [CAD_CAM_EDM_DRO] CNC Laser

The tube is filled full of a very select and pure CO2 _mixture_ it will
almost certainly not be straight CO2. Most have a number of noble gases in
them. The tube is then connected to pumps and a vacuum pulled inside it
until it gets down to a few microns. At the very least the plasma tube, the
bit in the middle where it's all at, has to be cooled down. It doesn't get
incredibly hot but the colder it is the better it works. A water jacket is
usually used, maybe yours has some sort of refrigerator. So, tube is full of
gas, vacuum pulled, the tube is 'struck' with a pulse of very high voltage
power. There is no arcing or anything like that, the discharge in the tube
glows pinky purple colour like a neon sign. After it has been struck the
voltage settles down to operating voltage and your there. One beam of white
hot (Sorry, infra red) hot energy is yours. Your tube might be a flowing gas
tube which means the vacuum pumps are on all the time and new fresh gas is
leaked through the tube.

These lasers are not very efficient. In order for the laser to work to has
to lase the gas, this only happens in a CO2 laser if it is nearly totally
optically sealed along it's discharging axis. The photons of light whiz off
the CO2 molecules and shoot down the tube, they hit a very highly reflective
mirror (Silver plated on polished silicon etc) which bounces them back down
the other way. Down the other end is another mirror (Typically Zinc
Selenide). To you this stuff looks like a smoker's yellow but to the IR it's
a mirror. Almost all of the light hits it and bounces back again, but a few
percent don't, they pass through. That's the beam you use. That's why they
laser tube is called the resonator, because it makes the photons bounce back
and forth exciting other CO2 molecules to keep it lasing and emmitting. You
will find you're putting _well_ more than ten times the energy in you're
getting out. On big constant running lasers like yours the optics may even
be water cooled by little channels dug into the material itself.

Lasers are very carefully chosen for anything industrial, there is no point
going over kill on something that might not even work. Different materials
absorb different wave lengths and energies better than others. The 3kW laser
you're running is big but I am aware of a number atleast 5 times the power
in use. The beam from CO2 lasers, 10.6um, is notoriously annoying to direct
because fibre optics won't carry it like they will the 1.06um from crystal
lasers. So every corner the beam takes must be accompanied by and expensive
and accurately aligned mirror. When it gets to the tip of the arm it is
channelled down to it's working size and shone onto the work. The beam hits
the work and is partially absorbed giving some energy to the material. Given
enough time that area will either melt or go on fire. No use to us. If
you're cutting metal you need a way to remove that molten patch, a blast of
air or oxygen helps. There you go, you now have one stream of very hot
material being blown away from the work, just like oxy / acetylene,
practically identical in mode of operation. But if you're cutting plastics
or woods blowing active gases onto them is going to set them on fire or char
them. Instead you use something like nitrogen. The gas is blown out of the
nozzle into the beam where it hits the work.

If you didn't actually build the laser yourself it's likely anything you do
to it other than feed in the gas is going to make it worthless or void it's
care package. CO2 lasers are not the worst to care for but they are very
unstable compared to something like a nitrogen laser. Amperage in CO2 lasers
is low and the voltage high. The very high voltage accelorates anything with
a charge on it, making the electrons smack into the CO2 very hard. When they
hit the CO2 they give it energy but the CO2 can't hang onto it, it wants to
get rid of it and be stable. So it does, and when it does a photon is
emmitted on the IR band frequency. Very cool stuff. Unless someone where you
work is trained specifically to do so, realigning mirrors and altering the
specified gases is a bad idea. Lasers are so popular because they use an
incredibly well confined beam of heat which means there is no need for
pre-heating, pausing or slowing down. If you don't completely understand
something I've said let me know. The competition for cutting industrially
with light is ND:YAG and it's counterparts. I like this ones more! : )
They use rare purposely grown crystals and a blinding pump light instead of
electrical terminals. The light is absorbed by the crystals and the crystal
lases emitting a beam. These are the same ones they use for cosmetics in
pulse mode. Constant mode can shatter the crystals. The ends of the crystals
are polished to a perfect finish and capped with the mirrors directly. The
first laser was infact a rod of Ruby. The crystal is very expensive, a piece
the same size as a pencil would be many hundreds of pounds. I saw one as
thick as my jumbo marker and about 20cm long being held in someones hand
because it had a tiny crack in it, making it worthless.

Regards,
John He.

> Where can I learn more about how an industrial CO2 Laser works?
> There is a 3KW cutting laser at my job and I don't like not knowing a
> thing about it.
> Need Laser 101
> Thanks
>
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