Using various gases for cutting

[Scott Shepherd]

On our laser, it has the hookup for "Gas In" next to the "Air In". In the driver, you have a choice of Air or Gas, along with flow rates. I've seen Rodne mention it before. In the manual it doesn't really mention what gases you would/could use, and what their use would be.

I don't plan on using it any time soon, but I am a bit curious at to what gases you would use and what material that would be used on, along with the benefit of why you would use that combination.

Maybe some of those who have been around the block a time or two could educate us on this subject? (Please :) )

[Mike Null]

There is some reference to that on the Synrad site. I've found their tech support to be helpful in the event you don't find what you need on the site.

[Brian Robison]

I'm guessing a nitrogen or argon. Inert gas so that you get no contaminants from compressed air?

[Mike Mackenzie]

Nitrogen gas is used to prevent any and all burn this is the most common gas used with the systems.

Oxygen can be used as well however I do not recommend it Most of the large lasers use this when cutting metal in fact Kern uses this with there metal cutting option.

Using this gas can be volatile and not my recommendation with any of these Laser systems.

Argon can be used as well in working with metal but it is not as good as oxygen.

These are the most common gasses that are used with Laser cutters. If you choose to use any gasses you must be careful and be sure you know what you are doing and how it is being done.

A mixture of Oxygen, C02, and flame inside a closed container can be a bad mixture.

[Scott Shepherd]

Thanks Mike! When you mention that nitrogen is used to prevent any and all burn, can you explain what you mean by "prevents burn"?

I recall from my apprenticeship days in welding classes how deadly oxygen can be. If I recall correctly, I think he's the one who taught me how to cut through a 2" x 4" with nothing but pure oxygen. All you need it a little bitty amount of source, like a small flame, and introduce oxygen to it and it would cut and cut and cut, all right through a 2x4 with no gas but oxygen.

[Dana Florian]

You would not use gas because you get contaminants in your compressed air supply. If that is the case, buy a new compressor or filter it better. Using a gas instead of "air assist" or in place of air assist can benefit you greatly if what you are cutting is catching on fire. I dont believe you can light a match in an inert atmosphere. Picture a column of flowing inert gas around the laser beam. If your cutting something volitile it wont ignite. Therefore, Yes we can cut that for you! $$$ Hope it helps! Dana

[Scott Shepherd]

Dana, can you give some examples? I don't plan on using any gases, I'm just curious and would like to know what types of things you would use them for.

[Rodne Gold]

I use Nitrogen at about 20 psi for cutting multiple paper layers , some fabrics , thicker board etc, it minimizes edge charring.
O2 is generally used with lasers of 200+ w to cut stainless , it promotes a thermal reaction.

[Mark Winlund]

I have tried both nitrogen and argon, and could not detect any difference in charring when engraving wood. It might prevent a fire, though. I've never had a fire, so I don't know!

Mark

[Mike Hood]

I've used both Argon, Argon CO2 80/20, and Nitrogen. They're all about the same when it comes to inerting. I keep the Argon piped in through a MAC valve so I can switch over by simply flipping the switch.

I've done so right in the middle of cuts, and frankly the difference is so slight, it's hardly worth the effort... (and I get my gases free) :)

Just use compressor air (IMO)

[Richard Rumancik]

When I bought my laser several years ago, I thought that I would try nitrogen assist gas. I bought a valve, investigated gas prices etc, but never have had enough reason to actually try it. On the Synrad site they do show various "case studies" where nitrogen is used, (that is probably what originally influenced me) but I found the following note in the Synrad "Materials Processing Technology" manual:

"When cutting non-metals, nitrogen or air are usually interchangeable therefore the selection can be based upon local availability".

So if you happen to have lots of bottled nitrogen sitting around, and are short of compressed air . . .

The tanks usually have to be rented even if you don't use the gas regularly. You will need a valve for the tank and a way to transport the tanks safely. If you have automatic control of the gas by the laser system that would be good; otherwise you could end up wasting a lot of gas.

I also looked in a table in the LIA Handbook of Laser Materials Processing and there are few non-metals where they show something other than air. eg. for plywood, they show argon as an option to air; thin paper - oxygen; leather - argon; glass cloth- argon; ceramic - nitrogen or argon; polyethylene - nitrogen; quartz - oxygen; etc.

In most cases they show air as an option to the specialized gas. The point is that alternate gases may be useful for very specialized applications where you need a very specific effect or cut quality. But in reading about it, there seems to be a lot of trial and error involved.

In the meantime I will continue to use a mixture of 78% nitrogen and 21% oxygen (I can get that for free too!)

[Mike Hood]

I live next door to a regional manager for a gas distribution company here. He provides any gases I want. They're all free. All I have to do is drop the empty into the back of his truck on my way to work in the morning... and a new one shows up on the way home. :)

I've rigged my laser with two MAC valves that will switch on either air or whatever gas is hooked inline. I use the switched compressor outlet on the laser to control the switches, so it's as easy as checking the air block in the driver. It does seem to make some difference, but really nothing I'd waste much time with. Cutting paper seemed the most advantageous.

[Bill Cunningham]

I use Nitrogen at about 20 psi for cutting multiple paper layers , some fabrics , thicker board etc, it minimizes edge charring.
O2 is generally used with lasers of 200+ w to cut stainless , it promotes a thermal reaction.

O2 will not produce a thermal reaction with stainless, or anything that does not contain a significant amount of iron.. The O2 does not blow the metal out, but rather rapidly oxidizes it, turning it to slag. It has no effect on non ferrous metals.. However, in ferrous metals, once the kindling temp. is reached, and you hit the O2 the oxidized metal slag is ejected from the kerf in the same manner a OxyAcet or Mapp gas torch cuts.. If the O2 is forced through a ferrous metal lance, the lance becomes part of the exothermic reaction and produces an enormous amount of heat. I have used 10 foot thermic lances fed with pure O2 to cut through concrete and rebar, and smaller hollow exothermic rods (actually just insulated thick wall hydraulic tubing), are regularly used with a Broko or Arcair torch to cut steel underwater..
Some of the exo rods (with additional ferrous content) can be started with a 12V battery, and then keep burning(even underwater) on pure O2 even after the power is cut.As long as the O2 is flowing, the rod keeps burning.. Amazing stuff, and darn fun to use too...

Below is a ten foot lance burning a I beam in 2 feet of water.. Great visibility eh!!

[Mike Hood]

I've played with exothermic torches in damage control schools in the Navy. VERY cool toys. We lit them with steel wool and a lantern battery... then stand back :)

It'll cut through most anything... Not something I'd wanna see anywhere near my laser though :)

[Rodne Gold]

Sorry Bill , what exactly is the composition of Stainless steel ? AFAIAK its mostly iron? It's a ferrous material.

Pure N stops charring or minimises it , it will not stop stuff like wood charring as the char is mostly due to resins or glues etc , not "oxidation"

We deal with a laser cutting co with 500w machines and the only way they can cut Stainless 2mm thick at reasonable speed is to use Oxygen assist. Go figure - if apparently none of these strategies work in theory , I wonder why Air Liquide has developed specialised O2 and N gasses for laser cutting called Lasal.
http://publication.airliquide.com/business/industry/welding/laser_cutting.pdf

[Bill Cunningham]

Cutting with Oxygen relies on the rapid oxidization that occurs when pure O2 comes in contact with metals containing mostly iron at their kindling temperature. If your using O2 with Stainless your just wasting your money.. Stainless does not have enough iron to oxidize, and 'burn' thats why you can't cut it with a oxy or mapp gas torch. Thats the same reason you can't cut 'any' non ferrous metal with a oxy or mapp gas torch, and the same would hold true trying to cut with 'any' heat source, laser or otherwise.. The best that you can hope for is to either vapourize the metal, or vapourize and 'blow' it out of the way. Argon, nitrogen, C02 or even Helium is a far better choice on any non ferrous than Oxygen.. Not saying that Oxygen would not 'blow' stainless out of the way when trying to cut it, just that it would be a tremendous waste of money and offer no benefit to the cut. Even 'air' will work better than O2 for any non ferrous.. And stainless although it does contain a small amount of iron (not even enough to make it magnetic) , IS classified as a non-ferrous metal in the welding industry, and anyone in the industry will probably not waste their time trying to cut it with oxygen.. Lasal was developed primarily for cutting high carbon alloys by exothermic reaction with the iron content.. However, it 'will' blow out the molten stainless, but does not 'cut' it in the true sense of the term..

[Mike Hood]

the same would hold true trying to cut with 'any' heat source, laser or otherwise.. The best that you can hope for is to either vapourize the metal, or vapourize and 'blow' it out of the way. Argon, nitrogen, C02 or even Helium is a far better choice on any non ferrous than Oxygen..

I have a plasma torch here that does just that.

I wish someone could miniaturize a CNC plasma into the small cabinet footprint of a laser... now THAT would be a toy worth owning (err... I mean tool) :)

I think there's a Torchmate or ShopBot in my future just for that reason. :)

[Bill Cunningham]

I remember way back in the 80's when the plasma torch first came out in an affordable state.. Made the job of cutting non ferrous as simple as using the old standby OxyAcet. was for steel.. I brought one into the college for a student demo, and put the sawsall away forever..ha.. Virtually all of our cutting gear was for underwater use, but the plasma torch had not been certified for underwater safety at that time.. It's now used underwater all over the world with a Plasma mixture of argon, hydrogen and nitrogen. Wish I had one now at times Mike... It sure makes life a lot easier for some projects..

[Mike Hood]

Yeah... you can get some pretty nice ones for $1500-$2000. It's like the hack saw of the 21st century. :)