Anyone have info about using compressed air with fiber laser cutter?
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  1. #1
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    Default Anyone have info about using compressed air with fiber laser cutter?

    I was nice and included the Metric values for those poor souls still using that archaic system


    I am in the process of upgrading my shop air, and I wanted to see if maybe I can justify going to a larger compressor and better filter and dryer to also reduce my need for gas tanks.

    Does anyone know that the air purity requirements are?
    On thin metal like say 22ga (.7 mm) what am I going to see for performance drop vs oxygen on a small 500 watt machine, currently I'm running something like 11 meters a minute on 22ga (.7mm)

    My understanding is that compressed air will basically behave like Nitrogen so the nozzle sizing would be adjusted to nitrogen levels. About 3/4 of my cutting is 22ga (.7mm) carbon steel, I do a little 18ga (1.2mm) and 16ga (1.5mm) and once in a great while I'll do a sheet of 14ga (2mm) but that is a once a year thing.. I'd be fine keeping a couple oxygen tanks for thick stuff.

    My Nitrogen chart says I need around 90-100psi (6.2-6.9 bar) and about 280-320 scf/H (8-9 CM/H) for 18ga, I'd imagine 22ga (.7mm) would be slightly less.. Compressor I am looking at can do 140-175psi (9.6-12 bar) and 15 cfm (.42 CM/M) at max pressure.. So it looks possible with fairly off the shelf stuff unless I'm missing something.

    Now I'm sure I'll need one of those refrigerating dryers since I'm in Florida and my average temperature and humidity is about 95F and 90% (35C)

    Link to compressor
    https://www.northerntool.com/shop/to...0475_200350475

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    Quote Originally Posted by csspecs View Post
    I was nice and included the Metric values for those poor souls still using that archaic system

    Whatever, I see the derating by using compressed air.

    Why not "roll you own":
    AirSep Markets Served | Chart Industries

    So instead of dryers, get this air separator made for laser work.

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    So your using 6 cfm roughly which sounds about right - a little low, a good honest real world 3Hp compressor will have no issue keeping up with that. but just google up nozzzel sizes for your given pressure to get flow rates. Dry is a must, refrigerant dryer minimum but you say carbon steels? As in higher carbon than mild steel sheet?? if so hydrogen embritlment may be a serious issue for you, post bending parts cut on air are more likely to crack from the cut edges. hence you might be better with oxygen, a couple of bottles are cheap and you would get a fair cutting time out of a bottle, especially if you use the smallest nozzle you can + the least pressure, oxygen normally cuts with a lot less pressure than nitrogen.

    biggest issue cutting on air is edge quality. You will have more adhered slag and nitrogen settings really are not right, your going to have to experiment, because with just the 20% oxygen in air your going to lose sharp corners and have some burning, expect more fine smoke too to extract. Rough guess the settings your after will be between nitrogen and oxygen.

    As to real cutting speed, yeah you may programme 11 meters a minute, but over what distance does your gantry move to hit that? How many long straight cuts etc, Depending on your parts you may find a 20% loss of speed has nothing like a 20% increase in cut time. Way to many people fail to consider that aspect of machine motion, more acceleration can often be far more valuable than outright speed when it comes to cnc cutting systems.

    Size driers for compressor output, go compressor, dryer, storage, if you put dryer after storage you then have to size dryer for peak demand which is high, unlike compressor output. Not much point going to 175, 150 ish in the tanks plenty enough and more is just costing you in electric.

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    Go careful with the oxygen - nitrogen generator’s, for some tasks there gas outputs plenty pure enough, for others its a noticeable disappointment, the oxygen generators + nitrogen ones (same machine, same beds, just depends on which product you capture as you swing the pressure on the beds, you either capture what passes through till it eceeds purity levels and then vent - drop the pressure and free the absorbed gasses and collect thoes (yeah that also involves re-compressing them)) don't hit really high purity levels with out a lot of wastage, to cut with a gas torch even 1-2% impurities has a noticeable and large loss in cutting speed, not a issue for medical oxygen use, but a major problem for a lot of industiral gas stream uses. would expect the same on a laser, same goes for using the nitrogen from the same setup, theres still some impurities and your cut edge won't come out as clean but still be far far better than cutting on air!

    Pressure swing absorption works well for the right things don't get me wrong, but its far from perfect and if your running from "shop air" you have some very stringent quality stds to meet to not stuff up the beds, think very low dew point as in regenerative dryer low and and very high level oil filtration.

    Theres costs also and every were i have been thats looked at it decided against, you can buy a hell of a lot of years supply of gas before you break even, even in a 24 hour around the clock laser cutters. The power to compress the air to feed the system aint free either.

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    You say reduced edge quality using air on carbon steel. What about on stainless in thin sheet metal like 24-18 ga? I would assume it would still be better than plasma cut with air? I'm cutting on my plasma now, and keep dreaming about a laser, but wondering if the nitrogen is really needed or not. I can see on thicker stuff it would help edge quality a bunch but just wondering if on thin stuff if a guy can get by decent without to help keep costs down on parts that are currently plasma cut so if the quality was somewhere in between plasma on air and laser with nitrogen I think it would be a win.

    Just stuff floating through my head while watching the plasma at 200 ipm and dreaming of how fast a laser could do it....

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    Quote Originally Posted by digger doug View Post
    Whatever, I see the derating by using compressed air.

    Why not "roll you own":
    AirSep Markets Served | Chart Industries

    So instead of dryers, get this air separator made for laser work.
    My comment about metric was in jest.. Honestly I can and do work in either, but I figured since I'm asking an odd question I better cast a wide net and excluding almost the entire world is not a great idea.

    If a nitrogen generator is the only way then I'll be sticking with bottles.. I can justify filters but at a certain point the complexity crosses over the possibility of paying back. On an heavy week of production I go through two bottles of Oxygen, because the laser is a very small part of the job. I just want to know what happens if you feed clean dry shop air into a laser assist line rather than oxygen or Nitrogen.

    Adama have you used clean shop air with a laser? Your saying that the edge quality will go down fairly substantially, is that something you have seen? I tumble a fair amount of parts so I could probably tumble some parts but switching to shop air for a few parts would not be a worth the time.. I would like to get some info about the edge quality with air just to know if buying the filters is worth the money or not. I may see about getting some bottled air to try the idea before wasting to much time on it.


    This is a video I saw that got me thinking about it, this is a Bordor 1KW laser cutting some 2mm stainless with filtered shop air.
    F153 Fiber laser cutting machine cut 2mm steel by air - YouTube

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    ^ yes, but im talking a 4Kw amada sub 10 years old and impeccably maintained, edge quality is less, fine details get affected. Cut speed goes down. We ended up switching to cut all materials under about 3mm with nitrogen, cuts better, parts are cleaner and cut speeds only a little less than O2. Edge is totaly clean and that made tigging up the little shit we were frequently cutting way easier and faster, with a nitrogen cut edge, the tig puddle just for want of a better word wets to it better.

    Air we had screw compressor, refrigerant dryer, storage, oil removal filtration, desiccant dryer with twin chambers - self regen and then a final sub micron particulate filter bank, air was above breathing stds - border line semi conductor manufacturing grades, dew point under -60 Celsius. That was all left over from a previous laser that had a air purged beam path, the beam path on the laser we had when i was there was running a nitrogen beam path purge, but then we had large onsite nitrogen storage, then ran cylinder pallets of 12 bottles for 02.

    Jp 200 IPM seams slow, my little plasma is rated at 300 IPM in stainless 18g at 30 amps, going that slow your going to get more melt than cut, speed matters with thermal cutting because its all about haveing as big a thermal gradient bettwen the bit your removeing in the cut and the uncut edge. Go slow the heat conducts and edge quality worsens, more speed and only what the jet is in contact with gets removed and edge quality goes way up. What plasma is it your using? I rate hypertherm heavily, there cut and consumable life just far out paces the competition in my experience. That said air plasma on stainless is not the best, try nitrogen, just get a bottle and try it if you have a regulator, think you will be impressed!

    Dryness really affects edge quality with plasma, you don't need high filtration, you just need nice dry air and lots of it. that means refrigerant or desicant dryer ideally!

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    I have to stiffen up my Z axis to get rid of some torch wiggle at higher speeds. Though with fine cut nozzles I'm already getting a dross free cut at 200ipm in 20 ga. I can go faster but then I get wiggles on corners.

    This is a job that will hopefully get to be pretty large, so I'm also just always trying to learn and research about what I could do if it gets bigger and I'd like to think that means fiber laser, but that also means a new larger shop as well, so a ways off.

    Anyway back to fiber lasers on clean dry shop air

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    I have a 2KW IPG Bodor laser that we use everyday. Before Christmas we switched to high pressure shop air. To use shop air you use High Pressure Nitrogen settings in the 280 to 300 psi range. You can go as low as 250. Our is ran by custom made pressure booster on a 10 gal high pressure vessel. You will need around 8 to 10 cfm at the laser. You will need a compressor of at least 30 CFM at 60psi to run it. I have a 30HP screw on a 280 gal tank. It is so much cheaper to run air. We were using a 240 liter Nitrogen dewer every 2 days and $200ea. The booster costs around 8k.

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    We did about 8.5 million pounds of material annually through our 2 lasers. Lowest power was 3KW so it's in a different realm but the same ideas apply. Principles below:

    - We used Air on any carbon steel 12ga or under
    - We used Oxygen on any carbon steel 10ga or thicker
    - We used Nitrogen on all Stainless
    - Oxygen lets you cut steels at thicknesses that are pretty wild for the power of your laser, but the quality, speed and draft are still directly related to your lasers power

    Nitrogen was trucked in 3 times a week.
    Shop air came from a screw compressor outside, that went through a second-stage Kaeser piston compressor inside, then through a high filtration unit. You MUST have CLEAN, DRY AIR for laser use or you will trash your lenses and ruin your cuts and be throwing big money away. I mean CLEAN and DRY. Our air was 280psi to the machines. The settings are definitely different than Nitrogen settings, your laser manufacturer should be able to provide you with baseline settings to start with.

    Air is very cost effective when you can use it. It can be used for stainless but you get a rougher and uglier edge than with Nitrogen. Thinner the material the better the cut. I highly recommend setting up for air (I hope that recommendation holds, I've never used a laser with that low power). You definitely want a compressor designed to run constantly. Either a Kaeser screw compressor, or if you need to keep it more budget, check out the piston compressors from Polar Air (Eaton), they have nice features and a constant-run setting designed for all day use.

    You are not ready to look for Nitrogen/Oxygen generators with that level of laser. Even we found that they were not cost effective, and we were a 24/7 robotic-load/unload operation making our own parts.

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    Funny, nearly a year later and I'm finally getting the bottle of air sometime next week to try this... I'll try to remember to post the results.

    I figure a couple bottles will let me see if it is possible on the small machine. The little 500 watt is still cranking out piles of parts. It would be nice not to move bottles around.

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    So finally got all the parts in to do the testing. On the little 500 watt fiber laser.
    Air was bottled breathing air not from a compressor.. Pressure that worked for 22ga and 16ga was 150 PSI and the nozzle used was the single type 2.0mm We had been getting close with a 1.5mm nozzle

    Overall cutting was slightly more difficult to get dialed in, but eventually we found the ratios that worked.. 22ga actually cuts faster on air than on oxygen at roughly 12 meters per minute instead of about 8, and 16ga was slightly slower on air vs oxygen at 3.5 meters per minute instead of 4.5.. Cut quality was equal or improved on the 22ga and roughly equal to O2 on the 16ga.

    So basically on the small machine it is possible to use air for cutting and actually come out ahead.. The investment for the compressor multi stage chiller dryers and filtration, will be fairly steep and take several years to pay off as the laser is used intermittently, maybe five full days a month. Currently the O2 bottles are annoying but I'll probably stick with them until near the end of the year.

    Break even point for us is about 100+ bottles of O2.. A slightly larger machine such as a 750 watt or 1000 watt could see a more significant improvement, but may also require more air pressure and volume to make it work.

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    Those findings are similar to what we found on the bigger lasers. Have you considered buying compressed air like buying O2? Being able to do it yourself is nice but when your cost equation is really close then any time a part in the system breaks or you have to pay to maintain it or for a service call, a wrench gets thrown into the calculation.

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    Bottles of compressed air are roughly the same cost as O2, since most of the cost of O2 tanks is the handling of the tanks. Only problem with air is that you are using about 4-5 times more, with a compressor it is vastly cheaper since there is no transport or handling.. Roughly $3-5 per O2 tank worth of asist gas.

    At present I'll likely be sticking to O2 until I can justify the larger compressor. My current compressor is obsolete so if anything breaks on it and I can't easily make the part, then I'll need a new compressor and I'll spend the extra $500-1500 to get one that will also run the laser.. Then I'll just need to pick up the dryers and filtration when I want to switch to air.

    I'd love to buy every new cool toy I see for the shop. But I need to pace my shop upgrades.

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    Quote Originally Posted by csspecs View Post
    Bottles of compressed air are roughly the same cost as O2, since most of the cost of O2 tanks is the handling of the tanks. Only problem with air is that you are using about 4-5 times more, with a compressor it is vastly cheaper since there is no transport or handling.. Roughly $3-5 per O2 tank worth of asist gas.

    At present I'll likely be sticking to O2 until I can justify the larger compressor. My current compressor is obsolete so if anything breaks on it and I can't easily make the part, then I'll need a new compressor and I'll spend the extra $500-1500 to get one that will also run the laser.. Then I'll just need to pick up the dryers and filtration when I want to switch to air.

    I'd love to buy every new cool toy I see for the shop. But I need to pace my shop upgrades.
    Hay you have proven the idea works, so you now know the extra for the compressor makes sense, just realize the driers and filtration will be more than the numbers you quote there. Not having to mess with tanks cost aside is a real time saver though!

    Only thing i would advise is start looking for a deal on the compressor front and get it preemptively by a bit if you can, having a little life left in the old one as a back up is always a useful option long term. Being with out compressed air gets costly fast if you have much in the way of staff or overheads. Equally you can't always find the bargains when you need them!

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    Dear,

    Willing to start using 1kw fiber laser,i have atlas copco gn7 can provide 11 cfm 10bar dryed nitrogen 97% purety.

    Is that going to be enouth for cuting 3mm stainless steel?

    Thanks

    Sent from my CLT-L29 using Tapatalk

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    If thats 3% oxygen, you may still get some discoloration, but it would be a lot lot better than air. With most pressure swing absorption nitrogen generators though, there pretty dang good at stripping the oxygen off, hence a lot of the impurities in the nitrogen stream are largely the other inert gases, hence this is a bit hard to advise on accurately, other than to say it will be lots better than air only cutting.

    Volume wise that's probably about enough to cut 3mm at lower settings, might well be enough with only a 1Kw fibre source, all the lasers i have been around were more like circa 14-17 bar and about 4x that flow rate with a circa 3mm nozzle. You need to speak to the laser OEM.

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    I thought I would share some cutting samples for various materials and purity of nitrogen. Note the discoloration difference based on purity. Unfortunately I do not have a sample for air only. All of these cuts were done using a nitrogen generator feeding a Trumpf laser. I hope they help. If you have any specific questions regarding nitrogen generation and laser applications please let me know.
    I can also email this file to you that shows the full high resolution images if you like.
    Cheers.
    nitrogen-generator-laser-cutting-sample-stainless-steel-0.25-inch.jpg
    nitrogen-generator-laser-cutting-sample-aluminum-0.18-inch.jpg
    nitrogen-generator-laser-cutting-sample-steel-0.12-inch.jpg
    nitrogen-generator-laser-cutting-sample-steel-0.04-inch.jpg
    nitrogen-generator-laser-cutting-sample-stainless-steel-0.04-inch.jpg

    You can view sample systems by clicking here.
    Nitrogen Generators for Laser Cutting

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    I'm bumping my thread back up because we actually switched to compressed air about three months ago and it has been working just fine.
    We cut a small amount of 14 gauge but pretty much everything is 16 gauge or thinner, mostly small stuff.

    We are a small shop with just a handful of workers making a handful of products, our one 500 watt laser has been working great for us. I know big shops have huge machines and much more demanding requirements. But for all the small shops I think most of us can get by with a compressor setup instead of O2 for sheet metal. Now I do have an O2 bottle still for doing thicker stuff from time to time, but I ended the lease on the other 6 bottles I had for the last two years.

    video comparing some sample parts.


    Showing the compressor assembly.

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    That was interesting how the thin sections were destroyed by O2 but not air.
    How was the backside dross (burr) between the two?
    I'm going to try that on my 6k fiber laser. I normally cut steel 1/8"-1/4" thick using nitrogen to avoid welding/painting/flaking issues with O2. Thick steel like 1/2"gets tricky with N2, I'll try air and see what happens. One advantage of N2 is the pressure available, I use 16-24 bar N2 which is about twice my available compressed air.


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