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Fiber laser cut quality dropping over short period of time

kb0thn

Stainless
Joined
May 15, 2008
Location
Winona, MN, USA
I've got a Mazak Super Turbo X 3015 3.0 kW fiber laser. New to me, but 2018 vintage with about 600 cut hours. We got the machine online a month ago with on-site training from a Mazak Optonics application engineer. We've run about 5 or 10 sheets of material through the machine, mostly thin stuff. During the training we ran everything from 0.036 thick to 3/4" thick. Mild, stainless, aluminum, copper, and galvanized steel.

Now have a job needing 1/4" stainless. Parts take about 2 minutes to cut. They nest 5 "tall" on the 60" axis of a sheet of material. First part comes out good. And then they get progressively worse over the 9 minutes it takes to cut. First part has a small burr that can be knocked off with fingernail or quick hit of random orbit sander. Subsequent parts get bigger and bigger super hard burr that by part 5 needs an angle grinder to remove.

I tried changing the nest cutting order to see if problem was related to movement on an axis. Different orders yield the same result. Parts get progressive worse over time. Manually pausing the program for 5 minutes after each part yields 5 parts that allow look the sample 1 in the photos below. IE "fixes" the problem. Parts are good.

So issue seems to be time related. We have had some teething problems with our cryogenic nitrogen setup. Today we had the gas supplier replace the regulator in the pressure builder circuit of their tank and also the delivery regulator. So line pressure is consistent over time and within inlet specification. And the demanded and actual pressure as set and measured by the laser basically match throughout the cutting. But to further eliminate gas delivery issues, we brought in a 12-pack of nitrogen and a new high pressure first stage regulator and plumbed it directly to the machine. Same results.

Torch is freshly rebuilt with optics and seals and what not. Nozzle is new. Tape shot shows beam perfectly centered in nozzle.

Can anybody offer suggestions on what I should be investigating? I gotta figure something is getting hot (or cold) as the cut progresses. With the dwell between parts it has an opportunity to get back to the temperature it wants to be. But no alarms on the machine or anything that looks abnormal.

Thanks in advance,

-Jim
 

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I can't answer your question, but I had a pair of Mazak lasers for awhile, dealt with Mazak optonics and met several others who've had to deal with them.

My experience is they are egomaniac morons. The huge company I bought them from hated Mazak optonics too. The shop I sold them to was owned by an ex-laser tech. He had a lot of bad to say about them as well.
 
It's not just Mazak. Nobody is all that interested in customers that just buy one machine much less one machine that is used. You can ask anyone about Amada, Trumpf, Bystronic, Mitsubishi, LVD, Mazak, whomever and everyone that is spending hundreds of thousands of dollars or millions of dollars gets upset when things aren't as good as they would like.

There is quite a difference though in anybody is old CO2 lasers and anybody's fiber lasers. The fiber lasers are much simpler machines and have value. CO2 lasers these days are a dime a dozen. You can get four kilowatt CO2s for the asking with anybody's name brand you want.

Irregardless I've already spent hundreds of thousands on the machine and the building and the air compressor and the cryogenics and the crane to service it and the material racks. It is the bed I've made at this point.
 
At that time, Panasonic had an industrial laser repair division and they were great. Came recommended by many. I tried googling them and cannot find anything on Panasonic and lasers now. Maybe they just did CO2.

And yes, totally agree, CO2 is obsolete.
 
Hi kb0thn:
I may be way way off base here, but I've noticed a similar degradation of performance with my Rofin Baasel laser welder, and the problem was explained to me as a problem of the air through which the beam passes becoming roiled by the heat and causing beam coherence issues.
Waiting a few moments before recommencing welding solves the problem for me, per the recommendation of the tech I had consulted.

It intuitively makes sense to me so I accepted it as a reality I couldn't really change except by turning down my pulse frequency and jacking up the argon pressure a twitch and cleaning the parts to reduce the smoke the laser makes.

I wonder if you're seeing a similar phenomenon at work?
Of course I'm talking about a significantly different process from yours, so I may be full of it.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 
I
Hi kb0thn:
I may be way way off base here, but I've noticed a similar degradation of performance with my Rofin Baasel laser welder, and the problem was explained to me as a problem of the air through which the beam passes becoming roiled by the heat and causing beam coherence issues.
Waiting a few moments before recommencing welding solves the problem for me, per the recommendation of the tech I had consulted.

It intuitively makes sense to me so I accepted it as a reality I couldn't really change except by turning down my pulse frequency and jacking up the argon pressure a twitch and cleaning the parts to reduce the smoke the laser makes.

I wonder if you're seeing a similar phenomenon at work?
Of course I'm talking about a significantly different process from yours, so I may be full of it.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
I halved the engraving time on my small galvo by adding an air knife which clears the smoke immediately and allows the beam to hit the surface unimpeded.

Is your lens staying cool? I know on CO2 lasers the mirrors or lenses can change their focal length as they get hot. Oil on the lens is great at absorbing enough power to heat and distort it.
 
Forgive me it's been a while since I did laser troubleshooting but I'll share my thoughts.

This strikes me as a lense issue. Our lense cleaning trigger would be when parts start to look like your 2nd part. We had multiple machines fed robotically off a material tower and could go home at 10pm and come in at 5am after a few thousand parts and the parts might look like your 2nd pic. Do you have a brand new protective & focus lense to try? Usually lenses simply get gradually worse, but it's possible the lense has a deformity or debris on the surface that distorts more with heat. Your first, fresh part should not have any burning going on at the surface, it should look sanitary (no browning at the edge), unless you have a power source that's too low for that material and you're having to run really slow.

What is your nitrogen pressure coming out of the head at?

Do you have the cleaner, wipes and understanding of how to clean laser lenses?

Are you seeing this on thinner gauges of stainless?

You may also have imperfect cutting parameters exacerbating something but I couldn't quote you from memory where the focal depth, PWM, power, etc. numbers might be to compare.
 
Last edited:
I had just experienced something similar to this not long ago but so much worse.

My laser cutting machine is around 5 years old. Around 2 years ago, it started having problem cutting every material every thickness, so the cutting speed and focus height had to be constantly adjusted lower and lower. I had a service guy from the machine seller come in, and he took our laser cutting head to inspect, but he came back telling us that everything was fine and he only cleaned the protective glasses on the lenses. The problem didn't go away, but we couldn't do anything about it since the service guy said nothing was wrong.

Fast forward 2 years up until a few months ago, the problem got so much worse that it couldn't cut anything beyond a few second after it started cutting (just like your issue where the cut got worse as the time went by during cut). We replaced all the protective glasses and nozzle; it didn't work. I decided to call the sales rep that sold me the machine (she moved to another company since then), and she recommended me another service guy who was supposedly "the best". The new service guy came in; didn't even have us test run the machine, he immediately told me I needed a new laser source and a new laser head because they just got too old. So, now I had them quoted and it was like buying a whole new machine, but I really needed the machine to run the jobs, so I was about to pull the trigger to get them replaced. However, I had doubts in my mind and didn't fully believe that they suddenly just got too old, so I decided to diagnose the problems on the laser head by myself. I found something that wasn't right which was a dark spot when shining the laser pilot light on a white paper. I told the sales rep about what I found, and she immediately told me that it must be a dirty lens, and she called another service guy for me. The latest service guy came in, and found something wrong with the head: it was hot to touch after cutting abit and there was condensation on the protective glass, so he took the laser head to fully inspect. Turned out all the lenses are fine, but the chamber where the gas comes in to go into the nozzle was dirty and causing it to be "foggy", so the laser couldn't fully get through.
He cleaned it, and everything worked just like when the machine was new ! I gave him a big tip for saving me from buying a whole new machine.

Hope my anecdote help you in your case.
 
Toolmaker's experience reminds me of a very weird experience we had with a new laser we put in service. If I remember right, we would get really poor cut quality on certain sides of parts and other sides would be great. It would cause burning in consistent ways, but ways that didn't make sense per normal troubleshooting. It turned out that the fiber wire from the source to the head was bad. IPG replaced the fiber optic cable and it fixed it 100%. It was a $15,000 repair that they covered under warranty.
 








 
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