Re: High press. or Laser

Most of the small CO^2 lasers used for marking and cutting are RF-
excited allowing the laser output to be easily modulated and are
sealed to eliminate the need for flowing gases (and replacing gas
bottles). The construction, and more importantly, cleaning process
of this type is well beyond the hobby skill level.

Also keep in mind that raw output power is not as important as
irradiance, the output power/area of the focussed beam. So while you
could build a 100W laser, it may have less useful power than a 25W
laser. As an analogy, think of burning something with a magnifying
glass on a sunny day.

The output beam quality is important in that only power that can be
focussed into a small spot is useful for doing the work of cutting or
marking. So those plans to cool a diode laser to increase power
output are missing a fundamental limitation with laser diodes--the
output beams are eliptical with an extreme variation in divergence in
each axis making it nearly impossible to achieve a small focussed
spot without disgarding much of the power.

Also as someone has already pointed out, the beam delivery system is
as important as the laser. The real advantage of using a laser
instead of a mechanical cutting head is that the laser and workpiece
can be stationary while the beam is deflected to the spot to be cut
or marked allowing for very rapid movement IF enough laser power is
available. This is fundamentally different than the approach
required for the CNC systems usually discussed in this group.

While you can build your own circa 1970-style laser as John has
suggested, if you're serious about a CO^2 laser, keep your eyes open
for a used Synrad 10 or 20 watt RF-excited, sealed laser. They're
compact, have a built-in 110 VAC switching supply for the RF laser
supply, and a TTL input for modulation.

I've spent the last 15 years designing CO^2 lasers medical and
military applications and have worked with some of the leading
experts in this field. While rolling your own laser may be a useful
learning excercise, I'd hate to see anyone too excited about
building one only to find out they could do little useful work with
it.

Steve Wojcik
Seattle, WA

--- In CAD_CAM_EDM_DRO@y..., <e.heritage@b...> wrote:
> Hi Tom,
>
> There are far too many Jo(h)n's on here, we must just be
naturally
> talented I guess. : )
> I'm John, and started this post. In answer to your question yes a
laser can
> be built at home, or more likely in the shop. It's a VERY realistic
goal to
> set out to build one. People seem to assume that if you mention the
word
> Laser it's instantly something space-aged that only guys in white
jackets
> can even begin to dream about. There are MANY home built CO^2
lasers, in
> particular they follow the plans set out first in Sci.-America.
This was a
> design for a 30watt laser and I'd say have a read of the article
(If you
> could find it) but it's been improved so much since then it's almost
> unrecognisable now. I was on a list for a while and one of the
posters was a
> 17 year old lad who'd built his own, it even looked a lot better
than some
> I've seeen made by 'professional hoobiests'. Most of them are
30watt tubes
> but there a few 100watt ones made as well. There's nothing
complicated at
> adding 70watts more it's just most people don't need it for burning
bits of
> paper and things at science fairs. The power requirements for CO^2
lasers
> are anything but complicated. I'd trust my little brother, maybe,
to do it
> from a sheet of instructions. All they need basically is a neon sign
> transformer. 30 watt tubes are typically run off 15kv transformers
at 120ma
> or so. A Variac transformer (Variable) can control the actual
output. IR
> crystal lasers are used in industry because they're easy to guide
and have
> emense pulse power, single shot mode, but the crystals bring all
sorts of
> problems with them. They're quite expensive (ND:YAG is usually a
few hundred
> for a stuby 3cm long pencil sized rod), break relatively easily and
home
> made lasers using them will only really operate in single shot (One
every
> few minutes, continuous operation takes expensive bits). If you
wanted to
> make one you'd be looking at something like the below (30 watts): -
>
> Optics:
> Zinc selenide, transmitting mirror:
> £30 - 60
> Copper / Aluminium mirror for
back: £30 -
> 50
> or, silver / gold mirror on silicon:
> £40 - 100
> Glass for tube and water jacket:
> £20 - 40
>
> Power:
> Neon sign tranformer:
> £20 - 100
> Might even be free, neon sign shops give away ones
sometimes
> that they have spare.
> Variac:
> £30 - 60
>
> Vacuum:
>
> 20 micron vacuum pump:
> £125 - 180
> Digital vacuum guage:
> £25 - 50
> Greases, seals etc:
> £20
>
> Gas:
>
> Laser mix CO^2:
> £70 - 100
> Regulator:
> £30 - 70
>
> Extras:
>
> Hosing, metal base, supports etc:
> £20 - 40
> If you're a machinist you'll most likely already
have all
> this, plus you could mill some
> VERY fancy mirror mounts.
>
> If anything I've over estimated those prices by quite a bit. Most
of the
> stuff you can pick up second hand or even free, except the optics.
You'll
> need a ZnSe lens to focus the beam but it's not too bad. Guiding
the beam to
> cut is really going to rack the cost up. The cheapest way would be
to just
> mount the tube facing into a moving bed, or to have a single
45degree mirror
> over the bed and the laser off to the side. The only other bits
you'd need
> would be maybe a fan to keep the smoke off your expensive optics.
You could
> build one for much less then I've said above it just depends how
good you
> are at finding the bits for free. They're typically 10 - 15%
efficient, so
> to make you're laser 100watts you'd just need to make the power
supply a bit
> bigger. Anything too big and you're into water cooled optics and
all the
> rest. You can add special line filters and bits to it to make
it 'special'
> but they're not essential. I read running them on DC can achive a
much
> better efficiency. You can pump them with a tesla coil ro even a
really big
> microwave tube. I'd suggest normal AC first though. The big
capacitors you
> mentioned are associated with things like copper halide (Emerald
green ,
> golden yellow) lasers and also crystal lasers, which use VERY
powerful
> flashlamps for a pump. The caps. in crystals lasers are typically
many times
> that in a heart jump set (I can't spell the word). In terms of wat
a 100watt
> tube will do you need to think about what you're cutting. It's all
dependant
> on how much of the light at 10.6um IR will be absorbed. Cystal
lasers,
> ND:YAG (Neodymium: Yttrium Aluminium Garnet) emit 1.06um which you
can steer
> with fibers. Have a look at
> http://www.pemed.com/surgery/lasers/ndyaglsr/ndyag.htm to see one.
Alone
> CO^2 will weld metal and engrave stone / mineral rocks. To cut you
need a
> gas to assist it, oxygen for steel and an inert gas like nitrogen
for non
> ferrous and wood. It's the same as when you use a cutting torch,
it's not
> the neutral flames that cut but the stream of oxygen pushing the
material
> away.
> I would VERY strongle suggest you have a look at Sams laser site.
It's here
> at http://www.misty.com/people/don/laserfaq.htm don't be fooled
by it's
> simple layout. The bits you want to read are the CO^2 laser
sections in Part
> 3 and 4. They are PACKED with info now and loads of pictures, just
about
> everything you'd need an answer for. You might want to look at the
other
> lasers as well on that intro page. The nitrogen laser is incredibly
simple
> and can even pump a dye laser for loads of different colours, no
burning
> though. : )
>
> Best wishes,
> John (Mail me off list if you want, info.host@b...)
>
>
> ----- Original Message -----
> From: "Tom Eldredge" <harmonyt@r...>
> To: <CAD_CAM_EDM_DRO@y...>
> Sent: Wednesday, March 14, 2001 2:22 PM
> Subject: Re: [CAD_CAM_EDM_DRO] High press. or Laser
>
>
> > Jon, and the other laser experts:
> >
> > I hope I am not amiss in shortening the thread title, but it
really seems
> > like you all are now talking about lasers, not high pressure
water jet
> > cutting anymore.
> >
> > I have stayed out of this thread because I know nothing about
lasers,
> except
> > some very basic theory.
> >
> > Can people really put together laser systems in their home shops?
> >
> > I have heard that the power supply needs are really challenging.
Large
> > capacitors etc. Can big capacitors be homemade if the physical
size of
> the
> > system is not an important factor?
> >
> > How much do you think would it cost to be able to do engraving
in wood,
> or
> > build a 50 or 100 watt system like the one you saw, Jon?
> >
> > Although I love creative machinery, I am not sure I could market
the
> things
> > it could do anyway, but I thought I would ask the above questions
anyway.
> >
> > Tom Eldredge
> > ----- Original Message -----
> > From: <MIADSGNS@a...>
> > To: <CAD_CAM_EDM_DRO@y...>
> > Sent: Wednesday, March 14, 2001 3:10 AM
> > Subject: Re: [CAD_CAM_EDM_DRO] High pressure water jet (Lasers)
> >
> >
> > > I have been part of this CAD CAM group but have missed some of
this
> > thread.
> > > Can someone share an Email of this guy that has been
experimenting with
> > > lasers?
> > >
> > > Thanks.
> > > Mario