G.WEIKE Metal and non-metal CO2 laser

[Mike Lysov]

As I said, Nitrogen is used as a shield gas, but the lasers they are using are measure in kiloWatts... in those cases, the laser itself is doing the cutting. In the prior scenario, the low-power laser (150W) is just heating the metal and the high-pressure oxygen is doing the actual cutting. Different machines, different processes, and you can't mix half of one process with half of another machine.

Ok I see what you mean. Can you explain the fact that Firestar says on their website that you can cut metals with nitrogen and at least 200W tube? I have seen nitrogen as a solution to cut metals in some researches found on the Internet. Almost all of them mentioned a few kilowatt lasers but then I have seen that calculator on the Firestar(http://www.synrad.com/Applications/c...or/launch.html) website and it has an option to cut 0.1" steel at 3ipm and nitrogen as a gas.

I do not think it's mistake in the calculator because they have some tough logic built into it. If you try to get the result with less than 200W tube it will tell you that you need to choose at least 200W to cut steel.

[Matt Turner (physics)]

FWIW, Kern also says that they can cut metal with just nitrogen assist. (They do use Synrad lasers for some of their machines.) A key point may be that these are RF lasers, not glass tube. From what I understand, the RF lasers can get higher peak powers than glass tubes of the same nominal power, because they pulse the output instead of just staying on.

[Dave Spitzer]

Anyone interested in cutting metals with a Co2 lasermay want to do more research; this link may help answer many questions: https://www.mitsubishi-world.com/ind...50&Itemid=1842

Because of cost it may not be feasible for most.

Also zoning regulations in some areas may prohibit the use and storage of high pressure gas bottles.

Dave

[Dan Hintz]

That's a decent high-level article, David. Here's an appropriate quote from the middle section:

There are benefits and drawbacks to using oxygen instead of nitrogen and air. First, oxygen requires a much lower flow and pressure than nitrogen, meaning the consumption—and ultimately the costs—are lower. Also, at thicknesses of more than .08 inches, oxygen cuts faster.

Using oxygen as an assist gas also has its downsides—namely oxidation. The reaction from oxygen assist gas causes oxidation that can negatively affect surface quality, remove surface coatings and prevent the ability to paint finished workpieces. Oxide that is not cleaned off will chip away and cause surface corrosion. In general, the overall edge quality of workpieces cut with oxygen is inferior to that of workpieces cut with nitrogen.

Nitrogen provides a clean, precise cut without oxidation, since it doesn’t cause a reaction to increase heat and aid cutting, but rather serves only to remove the molten metal. Nitrogen is ideal for stainless steel and aluminum, and can cut mild steel much faster than oxygen when metal thicknesses are less than .08 inches (see figure 1). While nitrogen requires higher pressure and flow than oxygen when cutting thick metals, the amount of nitrogen required (and the pressure and flow) drops as metal thickness decreases.
In most situations, using nitrogen instead of oxygen comes with a much higher price tag. Also, except with very thin metals, nitrogen is the slowest assist gas. For this reason, it is typically only used for mild-steel cutting applications in which surface quality is extremely important.

Shop air can be a viable alternative in some applications, with the obvious bonus being that there are no direct consumption costs. The reaction air cutting causes creates plasma, an extremely effective heat conduit that allows the fastest speeds in mild-steel and aluminum laser cutting. While compressed air does leave behind oxide, it is less than straight oxygen; also, the edge quality of the resulting workpiece is not as high as with nitrogen.

While shop air can be cheap and effective for thinner metals (it works best with mild and stainless steel less than .06 inches thick and aluminum less than .08 inches thick) establishing a system that maintains proper air pressure and air filtration can be an obstacle for many manufacturers.

Of course, the article makes no mention of the power levels being used. I would imagine 200W of power would be the minimum starting point of cutting thicker metals (I can cut thick aluminum foil with my 60W if I pre-treat it), as the calculator shows, but notice the speed... 3ips isn't exactly a race to the finish, and that calculator also makes no note as to the finish quality.

[Dave Spitzer]

Dan,

I agree, I feel the bottom line (and I believe you mentioned earlier) is a person wanting to cut metals need's to do some research.

[Martin Boekers]

I guess depending upon the quality some are looking at, they may want to consider a plasma CNC

[Bert Kemp]

Sorry, Mike, I got your post confused with Daniel's request to purchase a new laser. In his case, purchasing a machine to cut metal would be a waste of money... in your case, you already have the machine, but it would be a waste of your time to try to cut metal using nitrogen.

As I said, Nitrogen is used as a shield gas, but the lasers they are using are measure in kiloWatts... in those cases, the laser itself is doing the cutting. In the prior scenario, the low-power laser (150W) is just heating the metal and the high-pressure oxygen is doing the actual cutting. Different machines, different processes, and you can't mix half of one process with half of another machine.

I'm sorry I didn't read all the post on this but if cutting metal is your primary concern I think a CNC plasma cutter is the way to go .

[John Minton]

Check very carefully !!! cutting metal with anything less than 500W is going to be a tough. I have a 1500W which I something run at 500 for thin metal With O2 or Nit but not much below.