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Inventor needs laser cutting questions answered, distance thru fiber

Darp (Industrial) (OP)
24 Feb 12 21:08
Hi,  Just signed up.

Have a use for a cutting laser of about 2KW size.  Am a newbie to cutting lasers but have been a newbie in several discplines and done OK.   Two major question,

1. Can a beam strong enough to cut 1/16" steel be transporated long distances through fiber?  Like 1,000 feet or 4,000 feet?  What is a rough ballpark loss of power per 1,000 feet?  Been looking for this info and can not find it so far, guess no one is trying to transport cutting power very far.

2. On CO2 machine understand that it would likely not work if you turned it upside down, but what about thse new fiber/solid state machines.  Are there 2KW sized machines that could be rotated while working upside down?   

Some additional things wondering about:

3. Also if you do say do a 2" radius bend on a fiber would there be much cutting power loss?

4. Am thinking about muliplexing one beam to 50 different fibers so the pulses would be spaced out longer but all 50 would be cutting, although at slower rate.  Does such an ability to muliplex one beam to many fibers exist?

Thank you greatly in advance.

Also if any of you are in the Reno NV area we are looking for an laser cutting expert on a project.

-Darp
MacGyverS2000 (Electrical)
25 Feb 12 9:25
Darp,

You're not real clear on your requirements, and it appears you may be mixing medias, too.  CO2 laser wavelengths can not be transported through fiber.  For true fiber lasers, the fiber itself is the pumping medium... more length = more power, up to the point where fiber losses cancel out power gains.  You'll have to do some calculations on that yourself, but I have no doubt you'll find problems long before you get anywhere near 1 mile of fiber.

I'm not sure why you'd want to turn a laser machine upside down, but there's nothing stopping the beam from being sent through the bottom of a substrate other than dross cleanup... it simply makes sense to do it from the top and let gravity/air pressure clean out the cutline.

Loss due to small fiber diameters, again, will depend upon the fiber... 2" is pretty small.  Is there a reason you need such a sharp bend?

Multiplexing between fibers is certainly possible, but again, why?

Dan - Owner
http://www.Hi-TecDesigns.com

Darp (Industrial) (OP)
25 Feb 12 13:38
MacGyver,

Thank you very much for your answer!  It has helped me already.  Did not know CO2 could not be put into a fiber.  And thought that fiber lasers were separate from the the transporting fiber.   So have found out am a bit more ignorant than thought.  Do understand the pumping aspect.

"I'm not sure why you'd want to turn a laser machine upside down"
        
   Cause likely need to as part of rotating apparatus,  the cutting would normally be downward, but not always.  So this is a case of rotating the machine 180 while fibers are cutting downward at a considerable distance.  I have to be somewhat cryptic am in process of filing a patent.  Do not want to turn upside down, during operation, have to.  Thought CO2 with gases consumables etc. might not take to being upside down and knew maybe no one has ever needed to turn laser machine upside down.

WIKI:http://en.wikipedia.org/wiki/Fiber_laser    "A fiber laser or fibre laser is a laser in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, and thulium. They are related to doped fiber amplifiers, which provide light amplification without lasing."

McG: "For true fiber lasers, the fiber itself is the pumping medium... more length = more power, up to the point where fiber losses cancel out power gains.  You'll have to do some calculations on that yourself, but I have no doubt you'll find problems long before you get anywhere near 1 mile of fiber."

    This is very encouraging for me, that Wiki article says longer is better and it can be coiled, thus better news than expected. smile

QUESTION:  Doping is mentioned,  if I have 50 fibers going 4,000'(and it could be over 15,000 feet in future) is this doping expensive?  I was thinking a fiber laser coupled to normal fiber to transmit the cutting power.  And am just guessing that normal fiber is much less expensive than the doped fiber for pumping.  And guessing the doping is done by manufacturer not user on site, so you have to buy.  If am wrong please let me know.


McG:  "Loss due to small fiber diameters, again, will depend upon the fiber... 2" is pretty small.  Is there a reason you need such a sharp bend?"

    Yes would like to do it in .5" radius, figured that 2" would be more likely to work.  It is simply necessary to do a 90 deg bend in fairly short distance.    BTW from your  info and Wiki info instead of losing power with distance, sounds like will gain power, most encouraging.  


McG: Multiplexing between fibers is certainly possible, but again, why?

   My use needs laser cutting applied over a multiple places but not continuously   Away to look at is that a part needs to be inserted into place get a quick pulse to cut through then removed and a new one put in place. The time to move the part may be 100 times longer than the time to bore through it.   So it would be a waste of power to leave the machine off 99% of the time, and 50 times more productive to multiplex one beam over 50 fibers.

   That would if there was one source of the beam.  Maybe with fiber lasers it would be possible to multiplex applying the power to 50 different fibers that go all the way to the cutting location.  On Multiplexing I see it mainly referred to for a skin laser and for communications, have not been able to find much of anything on multiplexing laser cutting beams.   Can you point me to an info source on how lasers are multiplexed?  I might be using the wrong word with multiplexing, the need to switch the power between multiple fibers from one power source, not sending different frequencies down same fiber.

Thank you again, greatly appreciated!

 
MacGyverS2000 (Electrical)
25 Feb 12 17:23
I don't think you understand as much as you think you do, and any patent put together under false information will be worth less than the paper it is printed on.

I won't cover all of your points because you're just so far off on many points, but here are a few:
1) Longer fiber does not necessarily = more power... read what I wrote again.  Coiling is usually done on a 12" scale, not 2"... bending with 0.5" radius is going to be a major power loser.
2) 2kW is a massive amount of power for fiber... very few systems are capable of that compared to 2kW CO2 systems.  Multiplexing over multiple fibers will be tricky... multiplexing over 50 will be a royal PITA, and doing so with 2kW is highly unlikely for anything but the most customized of systems (no COTS systems here).
3) Aiming the fiber is always preferable to moving an entire system... and I don't think you comprehend the size of such a system in the first place.
4) You don't mix standard fiber and doped fiber, so 15,000' of transport is, well, ludicrous.

If your patent depends upon even 10% of your listed wants, I'd give up on it right now as you'll just waste time/money.

Dan - Owner
http://www.Hi-TecDesigns.com

Darp (Industrial) (OP)
25 Feb 12 20:12
Hi McGyver,

What I am doing requires a laser, it is a meams to an end.

"1) Longer fiber does not necessarily = more power... read what I wrote again.  Coiling is usually done on a 12" scale, not 2"... bending with 0.5" radius is going to be a major power loser."

Am not coiling it for gain,  although that may be standard way it is done.  The radius is to follow a bend for cutting, nothing to do with trying to get gain.

It terms of my ignorance indeed it may be extremely high. On patents I have succesful ones that became products that sold over a million units,  in an area had zero knowledge before creating the invention (Optical Character Recognition).  Necessity is the mother of inventions.  I am not inventing laser technology, using it to an end.

"2) 2kW is a massive amount of power for fiber... very few systems are capable of that compared to 2kW CO2 systems.  Multiplexing over multiple fibers will be tricky... multiplexing over 50 will be a royal PITA, and doing so with 2kW is highly unlikely for anything but the most customized of systems (no COTS systems here)."

1KW may be enough, but I see IPG ones that big and bigger.  Multiplexing is big concern area, it can greatly reduce the laser power required, but not sure if the technology exists to do it.

"3) Aiming the fiber is always preferable to moving an entire system... and I don't think you comprehend the size of such a system in the first place.  "

Yes. The reason why to rotate it complicated and if I can figure out how not too, will do so.  The IPG one looks like it weighs under a ton so that is not a problem size wize.


"4) You don't mix standard fiber and doped fiber, so 15,000' of transport is, well, ludicrous."

The prototype will be about 20' but there is potential to go much further.  The concept of using the entire transport fiber as the laser beam generator had not occured to me,  but the cost may be very high for the doped fiber.

Thanks for your onfo on this,  what I am using it for is a new use for lasers.


 

 
MacGyverS2000 (Electrical)
27 Feb 12 6:40
Looping does not cause gain... you're reading too much into what I wrote.

The rest there's no point in me responding to as it's app specific...

Dan - Owner
http://www.Hi-TecDesigns.com

MacGyverS2000 (Electrical)
27 Feb 12 6:41
Looping does not cause gain... you're reading too much into what I wrote.

The rest there's no point in me responding to as it's app specific...

Dan - Owner
http://www.Hi-TecDesigns.com

MacGyverS2000 (Electrical)
27 Feb 12 6:41
Looping does not cause gain... you're reading too much into what I wrote.

The rest there's no point in me responding to as it's app specif

Dan - Owner
http://www.Hi-TecDesigns.com

MacGyverS2000 (Electrical)
27 Feb 12 11:17
IR,

I have to question the validity of that... it's the only company claiming to have a CO2-through-fiber, and it's a medical device manufacturer, not an end component manufacturer (not even the laser manufacturers claim that).  Glass/plastic fiber is pretty darn opaque to CO2 wavelengths, so if their claims are true, they have a huge moneymaker on their hands (and as I said, I have serious doubts).

Dan - Owner
http://www.Hi-TecDesigns.com

MacGyverS2000 (Electrical)
27 Feb 12 11:33
Did a little research on that company.  Their literature says that machine uses their slimline one-use fibers... and other literature by them says those fibers are good for Holmium and Nd:YAG lasers.  Those are perfectly acceptable wavelengths (2.1um and 1um, respectively), but I see no mention of their use with CO2 wavelengths.  My guess is it's all creative marketing...

Dan - Owner
http://www.Hi-TecDesigns.com

Darp (Industrial) (OP)
27 Feb 12 12:52
McGv,

I was aware that your looping comment was for increasing length in a small area, and in fact looping (bending) would likely cause some loss of power.  My radius issue is strictkly to get cutting beam into a tight location.

Have done some research on IPG site and found that several of my desires are addressed and can be done by their machines/design.  For multiple reasons for my app now know that fiber laser is the way to go, am going to call IPG to see if they can meet all the needs or if will have to find more solutions to issues.
analogkid2digitalman (Electrical)
27 Feb 12 14:31
Dan:

I know that what that 'fiber' for the Lumenis Laser is. Let's just say it is manufactured and tested within 10m of my desk. It is actually a hollow waveguide. We guide CO2 10.6um through it all the time for testing. It can only be fabricated in length's of 10's of meters, nowhere near long enough for the OP's application. See:

http://www.polymicro.com/products/opticalfibers/products_opticalfibers_hw.htm

-AK2DM

 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"It's the questions that drive us"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

Darp (Industrial) (OP)
27 Feb 12 20:01
Talk with IPG went well, the base price on 2kw fiber laser is only $110,000, less than I expected.  

That unit can be turned upside down.

Length does not seem to be an issue, they have already tested their unit at 1 KM distance over fiber and said it had more than enough power at that distance for 1/16" steel, and had maybe 15% loss, most encouraging.  Said they knew on no reason it would not work at 2 or 3 KM, although to best of their knowledge, no one has ever tried that.

Multiplexing.  They have off the shelf multiplexer they sell that do 1 to 6, that work roughly as had expected.

2" 90 deg radius would work, but would cause power lost, he suggested several solutions to that.

So far cladding seems to be an issue.  The fiber they did at 1 KM was 1/2" thick.  Almost all of it being cladding/protection.   So will have to look into that issue more.  They suggested I would have to do custom cladding.

Being asked the questions, wanted to share what found out.


 
MacGyverS2000 (Electrical)
28 Feb 12 8:22
I would have expected more than 15%/km loss (25-30%), but if they say it has been done... I'd be curious to see the power loss figure on that 2" bend (may take you to that 30% loss figure).  Of course, 4km+ is pretty much right out of the picture, even at those low loss figures.



analog... I was starting to pick up on the hollow waveguide idea for that fiber after doing some more digging.  It seemed the only logical conclusion, but without confirmation it was only a guess on my part.  I may have to ping you offline for more info... durability, flexure, efficiency, cost, etc.

Dan - Owner
http://www.Hi-TecDesigns.com

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