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Newbie Querry regarding Nd YAG

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Feb 3, 2011
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Hi,

I am a newbie to the laser field and yet I am interested in building a laser welding machine for myself to tinker around with metal. My interest was really triggered from watching this video a couple of days ago :drool:
Laser Welding Steel Sheets - YouTube

I am impressed with what lasers can do and I cant stop thinking about building one. The only hindrance is my knowledge about them since I am a Mechanical Eng. I have been searching the net on how to put together an Nd YAG laser, but have been unsuccessful to find the right kind of source to explain it accurately.

Please someone tell me the concept of the Nd YAG laser? What are the major components of this laser system ?

Thanks and can`t wait to see a reply:D
 





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Feb 3, 2011
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ok guys I got good links to Laser Basics and Laser Bible from -- Tech Junkie --and I am reading it and looks like it will explain a lot about lasers.
 
Joined
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To put it simply a water cooled rod of Nd:YAG glass is placed in a reflective cavity with powerful flashlamps that emit light at the spectral point of absorbance of Nd:Yag. The flashlamps are flashed which excites the Yag which then causes it to emit light at 1064nm. Mirrors, or coatings at the edges of the rod allow the light to amplify, and you have a laser.

For metal fabrication laser powers often exceed the kW level and such units are often out of the range of hobbyist and DIY approaches. If you want to fiddle with metalwork I suggest looking in to a CO2 laser system, they can be built from scratch by DIYers or assembled from readily available parts by the hobbyist and are often under $1000. Power levels are in the tens of watts which is enough to cut/melt most very thin materials. CO2 lasers are also much safer and easier to shield against.
 
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To put it simply a water cooled rod of Nd:YAG glass is placed in a reflective cavity with powerful flashlamps that emit light at the spectral point of absorbance of Nd:Yag. The flashlamps are flashed which excites the Yag which then causes it to emit light at 1064nm. Mirrors, or coatings at the edges of the rod allow the light to amplify, and you have a laser.

For metal fabrication laser powers often exceed the kW level and such units are often out of the range of hobbyist and DIY approaches. If you want to fiddle with metalwork I suggest looking in to a CO2 laser system, they can be built from scratch by DIYers or assembled from readily available parts by the hobbyist and are often under $1000. Power levels are in the tens of watts which is enough to cut/melt most very thin materials. CO2 lasers are also much safer and easier to shield against.

First of all Thanks Sigurthr for directing me in the right direction.

I got some more of queries (sorry, could not stop myself from asking)

As you said that there are reflective mirrors at the edges of the Nd YAG rod so then, will the Flash lamp be placed perpendicular to the length of the Nd YAG rod? I am thinking, If some how the flash lamp be placed between one of the edge mirror and YAG rod(flash lamp light traveling parallel to axis of YAG rod), then the flash lamp itself will cause hindrance in the light being reflected between the mirrors.

The second point that YAG based lasers are out of the DIY approaches broke my Heart. I am not at a knowledgeable stage to challenge or comment on using Co2 lasers against YAg. I have seen all the good stuff being done by Nd YAD type lasers in the welding field. I do not know, but if I want to weld Stainless Steel sheet(melting temp = 1510 deg Celsius) or Aluminum sheet (melting temp = 660 deg Celsius)not more than 1mm thick (0.03936 inch) then would the requirement for YAG lasers go in the kW range?
 
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The one you posted a video of was a multi killowatt range laser. YAG lasers are pulsed and with pulsing you can get a very high power because the pulse length is so short.

As per the flashlamp question just do some online research of "ruby laser" and you'll find all the answers. A Ruby laser is a YAG with a different rod and different end mirror/coatings. Pictures work better than me trying to explain in words.

Btw, I'm a TIG welder, so I know a bit about this. CO2 tubes under $1000 can easily cut 1/8" steel, most of the cutting action is due to an oxygen jet directed at the heated metal. With welding metals it's a requirement that you provide shielding gas (argon) because oxidation prevents the weldpool from forming.
 
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Here's a simplified view of a laser Nd:YAG to see in a simple way how it works.


Image437.jpg



To add some information to what Sigurthr said, this type of laser also can be pumped with laser diodes,
in this case the efficiency is higher than pumped with lamps, but is more complex to perform.

For welding applications with difficult access, Nd:YAG lasers are better than the CO2 lasers due to the
system flexibility offered by an optical-fiber delivery for the laser beam, if required.

Also the Nd:YAG wavelength is absorbed more readily by most metals than CO2 laser wavelength,
further improving process efficiency with less power, especially for welding processes.

As Sigurthr said, develop an Nd:YAG laser of high power, is something beyond our reach.

But anyway I leave these links to give you an idea of ​​welding calculations, and also an idea how to make one.


The Professor's Homebuilt Lasers Site - YAG Lasers

http://etd.lib.metu.edu.tr/upload/12605521/index.pdf

http://lasers.org.ru/forum/attachments/q-switched-ndyag-laser-system-pdf.11336/

Laser Welding Article By Carl Miller

Enjoy :beer:
 
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As per the flashlamp question just do some online research of "ruby laser" and you'll find all the answers. A Ruby laser is a YAG with a different rod and different end mirror/coatings. Pictures work better than me trying to explain in words.
Yes I did online research for ruby laser and it cleared all my doubts about flash lamp in a sec. Pictures work better:)
Thanks for all the help Sigurthr

For welding applications with difficult access, Nd:YAG lasers are better than the CO2 lasers due to the
system flexibility offered by an optical-fiber delivery for the laser beam, if required.

As Sigurthr said, develop an Nd:YAG laser of high power, is something beyond our reach.

Enjoy :beer:

Thanks piferal for the image and links:) Those are gonna help me a lot.

I will do some research on the optical fiber as there must be several parameters set for use with YAG lasers.

Since developing Nd YAG lasers of high power is beyond our reach even though if I wanted to pursue it, What kind of specialized engineer would be able to do the job? I am personally good at CAD/CAM and machining and can design the Nd YAG casing, arm etc, but Power electronics I have to be dependent anyway.

:beer: :)
 
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It depends on how high power you want, and it you want it CW or pulsed. Via Sam's laserfaq you can find various projects done by hobbyists, some have quite big lasers running.

It's a rather big step to start with such big laser as first DIY project, maybe a smaller solid state laser from parts would be an idea to get a feeling. A lot of laser specific things are important and bigger lasers are usually more difficult to do right.
 
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Use an arc lamp and an active q-switch. Then you can run it CW or Q-switched. Metal welding will require a huge power system and cooling system. Most multi-kW YAG systems run on commercial 480VAC 3-phase.
 




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