700W Fiber Laser Cold Rolled Steel Help

[Alex Smith23]

I recently took delivery of a 700W fiber laser and had decent success overall cutting stainless and cold rolled steel. I've been able to cut intricate patterns on 1.3mm stainless steel with relative ease using nitrogen. However, when I try to cut 3mm cold rolled steel with oxygen, I'm not able to replicate the same intricate cuts. It's as if the metal is heating up and vaporized when the cuts are close together trying to leave a thin strip of metal behind (I'm sure my terminology is wrong). Any thoughts or ideas? Perhaps I simply can't cut intricate stuff using thicker material?

[Kev Williams]

I don't know much about high watt machines, but I've had a bit of 'second hand' experience with the nitrogen/oxygen thing... One of my customers furnishes me with SS operator panels they cut themselves with a 2000 watt, give or take, C02 laser. When they first got the laser they was running it with nitrogen. Then a few weeks passed while tuning up the laser, and they found that all their nitrogen had vanished. So with their budget dented, they cut the next batch of stainless using oxygen. Beyond night & day difference! Whereas the nitrogen cut plates were essentially pristine, the 02 cut plates were burnt, discolored, had sharpashell little shards remaining at the start/end points where every hole was cut, severe slag edges, the edges of the cuts were washboard-y... just plain pretty nasty. And the ONLY difference was the oxygen. I think they've since gotten better at using oxygen, many different settings I'm assuming, but I can still tell the difference. Most times they use nitrogen- thankfully :)

Not sure what difference fiber v C02 will have in general-?

[John Lifer]

Not surprising at all Kev.... Nitrogen is 100% inert. Oxygen is by nature an 'oxidizer' It enhances burning. And it was the steel that was burning. Pristine cutting use Nitrogen, cheaper, nastier less reliable cutting, use oxygen.

[Trey Tull]

No experience with a 700w fiber but my 2petawatt MOPA gets real finicky when I turn the flux capacitor up past the gigawatt setting. Luckily I only have to do that when we are powering through 12" titanium. :D

[Kev Williams]

ONLY 2 petawatts? Get that from Ebay? :D

[Trey Tull]

ONLY 2 petawatts? Get that from Ebay? :D

Amazon Deal of the Day...hahahah

[Chris Thomason]

Don’t have a machine like yours, but my understanding is that the gas flow rate and nozzle size have a huge impact on cut quality. Perhaps even more than power and speed settings.

[Michael Henriksen]

That is perfectly normal when cutting mild steel with oxygen. You cannot have walls thinner than the thickness of the sheet without running the risk of burn-through. If you need the fine detail you have to switch to nitrogen. 700W should be enough to cut 3mm mild steel with nitrogen. Basically use the same settings and nozzle diameter as you would with 3mm stainless but have a play with focus if getting a lot of dross on the edges. Run the nitrogen at app. 14 bar for 3mm.

[Alex Smith23]

That is perfectly normal when cutting mild steel with oxygen. You cannot have walls thinner than the thickness of the sheet without running the risk of burn-through. If you need the fine detail you have to switch to nitrogen. 700W should be enough to cut 3mm mild steel with nitrogen. Basically use the same settings and nozzle diameter as you would with 3mm stainless but have a play with focus if getting a lot of dross on the edges. Run the nitrogen at app. 14 bar for 3mm.

I will give this a try! The walls were just about the same thickness as the sheet.

[Michael Henriksen]

If you are running Cypcut, using "cooling points" on sharp corners will help avoid burning when you cut mild steel with oxygen.