excess heating on fiberlaser 2 kw 3

[JeanFreli]

Hi everybody,
Have an Ermaksan fiber 2 kw since december last year. Went good for a month. Since that time they came 7 times trying to fix problems. Still problem and an another guy come over again this month. Well I think I found something.
I cut almost ss all the time. Since two weeks I change the power and it work much better like that. Still have dross but at the minimum. Easier working the piece after. They told me never change the power, but the piece were awful hot. It start the first 12 inches nice and slowly the dross appears bigger and bigger. If I keep going the program I'll success to cut everything but the big dross will be there. That is if I keep the power at 2000 watt. Like I said before, now I cut everything at 1900 with minimum dross and I have to push gaz at 19 bar for almost every tickness.
I have an excess heating. The first head they changed the miror was crack. I thought it was back reflexion but now I'm wondering if it was the heat from the laser. It's like the laser send me way too much power for what it suppose.
Does somebody already had a problem like that? What can be defective before the head?

ps thanks Macgiver for the lens clue. realy appreciate.Been in holyday for 3 weeks that,s why didn't answer

 

[Foostrap]

You may have a bad lens again. This is not safe to check yourself on a fiber laser. I would recommend you get service in.
If you lower the power and it cuts better, it could indeed indicate that something is overheating; which could be caused by dust that fell on top of the lens. If that is the case, the problem will become worse over time.

 

[lasermate]

I agree with Foostrap. Get the service tech out there. You are paying for the warranty get Ermaksan to fix it before the warranty expires.

 

[JeanFreli]

Ok thanks guys,
Footstrap you were half right, one tech came and we agreed to change the focal lense. Change radically, especially on focal length. He left thinking he won the game.
Every time I was cutting something I had to readjust the parameters. Was pretty hard sometimes but anyhow I learned again. Finally the cut went perfect after I put my power at 1900 instead of 2000 (which is the maximum power of the machine).They really insist to leave it there. What happens is when I start to cut the piece it goes not too bad for about four inches after that dross appears and grows until I reach the end of the piece. If I don't stop the program all the pieces will be cut but with the same huge dross equal to the same dross of the end of the first piece. I don't know if you follow me but what I notice is the heat. The pieces are abnormally hot when I touch them. Even if I try to push more gas it stays hot and it makes and ugly side finish.
The real engineer of Ermaksan comes at the end of the month. I work seven days a week now and I love laser especially when good results appear. I would like to know a lot of technical stuff like you guys but I have to do my misery before. My strong point is finding parameters.
Thanks for your support. New idea are welcome too.

 

[RPosty]

Is the power stable at 2000 watts? Does the laser show any signs of struggle at 2000 watts like Plasma looking ratty, or tube/power supply (some lasers have tetrode tubes) current drain increasing? I am not familiar with CO2 Fiber Lasers, but if that was one of my CO2 Lasers (PRC or Fanuc Resonators), I would:

* Look at and change any external optic that looks questionable. Even a good looking optic can fool you if it is stressed.

* look at my internal optics to make sure they are clean, Check the output optic for stress with polarized filters (new 3d glasses lens work fine).

* Make sure your Internal optics are aligned properly, if not your laser will draw more current to try to keep up.

My guess is your output optic is probably stressed. I don't know how to check a fiber for stress or whatnot, My experience with Yag fibers is when they are bad, it is catastrophic. never seen one mostly work.

"I am stuck on Band-Aid brand, 'cause they are stuck on me"

 

[Foostrap]

That's the nice thing about fiber lasers, there are no external or internal optics. However you do have a collimator and cutting lens in the head. Most also have one inside the resonator to "guide" the beam into the process fiber (fiber between resonator and cutting head).

JeanFreli, how did the tech change the lens? Did he take any special precautions to make sure no dust would get on the lens or inside the head?

Did he actually replace the lens, or just the protection window?

Lenses for fiber lasers cannot cope with high gas pressure. Therefore they require a protection window (basically a clear plastic type window). Those have to be replaced once in a while.
However, the cutting lens should be completely enclosed and sealed from dust within the cutting head. Taking the head apart usually needs to be done in a clean room.

Once you get your long burr, what happens if you stop the machine, let it sit for 3 minutes, then try to cut again. Does it cut OK for 12" then get a burr?
How is the cutting head cooled on your machine? Water cooled? Air cooled? Did the tech check if water flow was sufficient going to the head?

Did he measure the power at the head?

 

[Foostrap]

And end of the month is the earliest they can send a real engineer in? If so, that's terrible service.

 

[JeanFreli]

Thanks for your help

We clean the protective lens and change the focal lenght (yes it is seal).Work not bad for a week but still had to put my power down. Anyway the guy from Ermak is coming soon.
I am interest about the 3D glass. Looking the focal lenght with that , what I'm suppose to see, dark color, spot? I'll ask the kids to borrow me there glass...I don't know who found that trick but if it really work that is cool.
Other thing. Is stressed lens the samething then burn? Can you still produce with a stressed lens. Maybe less power, slower or longer focal?

 

[RPosty]

as long as the optic is ZNSE (might work on other translucent materials, I just do not know) you can check it by:

1. Place Optic between two polarized lenses.
2. Hold up to a bright light source like Ceiling lights or even the sun outside.
3. Turn one of the polarized lenses 90 degrees.

You should see the optic (lens or output coupler etc) go from uniformly Dark to uniformly light. If stressed, you will see some kind of Cross pattern. If it has a crack starting to form, you will see a star pattern around the crack.

You will know i t when you see it.

"I am stuck on Band-Aid brand, 'cause they are stuck on me"

 

[JeanFreli]

Thanks a lot rposty. Very very interesting to know. As soon as we change the focal lens again,I'm gone use your information and check it. Not only that; it is easier to operate the machine when you understand better how it work.

 

[krugtech]

it's easier to use one ploarizer and a white LCD screen. Open notepad up on a computer so the screen is white, then hold the lens and polarizer in front of the screen. LCD screens are polarized light sources, Polarized sun glasses work too.


Chris Krug

http://krugtech.com/

Maximum Up-time, Minimum BS

 

[RPosty]

that is interesting Krug, can't wait to try that. I have some stressed optics I keep around to show people what to look for.

"I am stuck on Band-Aid brand, 'cause they are stuck on me"

 

[lasermate]

good Morning RPosty,

I would be happy to send you a polarization filter set to check for stress and coating deteriation if you don't have one. They work very well for dettecting lens quality.

 

[RPosty]

oh we have them, i was talking about trying just one against the LCD screen, that is a new thing to me.

"I am stuck on Band-Aid brand, 'cause they are stuck on me"

 

[krugtech]

RPosty, it makes it 100 times easier. LCD screen is a perfect diffuse polarized light source. I first noticed this when I got polarized sunglasses and I couldn't read the computer screen in my car unless I tilted my head like my neck was broken. Just open up something with a white screen like an empty txt document. It'll work with anything transparent I can see the stress in automotive safety glass.

Chris Krug

http://krugtech.com/

Maximum Up-time, Minimum BS