Buying a Nitrogen Generator for Laser Cutting: When Does It Make Sense?

A nitrogen generator for laser cutting lets a shop make its own assist gas from compressed air instead of buying it in packs or bulk. Once it's paid off, the gas costs little more than the power to make it, and you're no longer waiting on deliveries. But the generator is only one part of the bill, and a system sized or set up badly will leave you short of pressure halfway through a job.

This guide covers why shops use nitrogen, how on-site generation compares with delivered gas, what it really costs, and how to make sure your quotes reflect what your gas costs you.

Why nitrogen is used in laser cutting

Every laser cut uses an assist gas. It's blown through the nozzle to push molten metal out of the kerf and protect the lens, and the choice of gas shapes the finished edge.

Nitrogen is inert. It doesn't react with the metal, so the cut edge comes out bright and free of oxide. That matters most on stainless steel and aluminium, where an oxidised edge looks poor, can affect corrosion resistance, and may need cleaning before welding or powder coating. Many shops also cut thin mild steel with nitrogen for speed and a clean edge.

The trade-off is volume. Nitrogen cutting runs at high pressure and high flow, so a shop that cuts a lot of stainless or aluminium, especially in thicker material, goes through a lot of gas.

Nitrogen vs oxygen in laser cutting

Oxygen reacts with mild steel as it cuts. That reaction adds heat, which lets the laser cut thick mild steel with less power and much less gas. The edge comes out with a thin oxide layer, which is fine for most structural and general mild steel work.

Nitrogen does nothing to help the cut, so the laser does all the work and the gas pressure has to be much higher. In return you get a clean, oxide-free edge.

Because nitrogen cutting uses so much more gas, it should carry a higher rate in your quotes. More on that below.

What is a nitrogen generator?

A nitrogen generator separates nitrogen from compressed air. Air is roughly 78% nitrogen. The generator, usually a pressure swing adsorption (PSA) or membrane system, strips out the oxygen and stores the nitrogen in a receiver tank, ready for the laser.

A complete system has more parts than the generator itself:

• An air compressor big enough to feed it
• Dryers and filtration to clean the air before it reaches the generator
• A storage reservoir for the nitrogen
• Often a booster, to lift the pressure high enough for laser cutting
• Pipework from the plant to the machine

Systems vary by purity, flow rate, pressure, storage capacity and energy use. Those numbers decide whether the generator can keep up with your cutting.

Why shops consider nitrogen generation

Lower cost per cubic metre

Delivered nitrogen carries the supplier's production cost, delivery, cylinder or tank rental and margin. Generated nitrogen, once the equipment is paid for, mostly costs the electricity to run the compressor. Per cubic metre, that's usually far cheaper than packs or bulk.

More price certainty

You swap one exposure for another. With a generator you're exposed to electricity prices instead of gas contracts, but you know what the gas is costing you. Supply contracts tend to creep. Fuel service levies get added to delivery charges, the price per cubic metre rises "because energy costs have gone up", and rental terms escalate.

No waiting on deliveries

A generator removes the supply chain. As long as it's maintained, the gas is there when you need it. For regional shops this can be the deciding factor. One Tempus Tools customer, who runs a small single-laser shop in a regional town, bought a generator because they could never get enough packs, there was no room for a bulk installation, and a big job could stall while they waited for the next truck.

Safer handling

Without packs, you're not moving high-pressure cylinders around on a forklift. A cylinder that's knocked over and has its valve snapped off can take off like a missile.

The real cost of a nitrogen generator

The price quoted at a trade show is usually just the generator. A $100,000 sticker price can be well short of the real project cost, which often includes:

• A bigger compressor, because the existing one can't feed the generator as well as the rest of the shop
• A new location for the compressor and generator, usually outside or in a separate room because of the noise
• New air and gas lines to the generator and on to the laser
• Dryers, filtration and drainage
• Installation and commissioning
• Floor space, which you're paying rent on

Then there are running costs:

• Electricity. This is the main ongoing cost. The figure to ask suppliers for is the specific power: the kilowatt-hours needed to produce each cubic metre of nitrogen at the purity and pressure you need. Some shops offset it with solar on the factory roof.
• Servicing. Expect a service roughly every six months for the generator, plus the compressor's own servicing.
• Filters and consumables.
• Depreciation on the generator and the compressor.
• A backup supply (see below).

What determines whether a generator will work for you

Purity

There's a big difference between 95% nitrogen and 99.99% or 99.999%. Higher purity gives a cleaner cut, but takes more energy to produce. Find out what purity the system will actually deliver from day one, not just what it can reach. The regional shop above struggled to get past 96% at first and only reached 99.99% after work on the system.

Purity also depends on the air going in. If the compressed air isn't clean and dry, the nitrogen won't be pure either. Filtration before the generator matters as much as the generator itself.

Pressure and flow at the machine

What matters is the pressure and flow at the cutting head, not at the generator. Packs usually sit right beside the laser. A generator usually sits outside near the compressor, so the gas has further to travel and loses pressure in the lines on the way. A generator that can't deliver enough pressure at the point of use is no good.

Capacity for your thickest work

Thick stainless uses gas fast. The regional shop's generator can't sustain long runs of 16 mm or 20 mm stainless. The reservoir loses its head pressure after a few hours, so they cut thick stainless for a set time, then switch to oxygen work or thinner stainless while the pressure builds back up. For big thick-stainless jobs, they bring in three to five packs to get the job done.

Your plans for the next five to ten years

A generator is a large capital investment, so it needs enough capacity for where the business is heading, not just where it is now. Size it for the cutting volume you expect, not today's.

Your premises

Generators, compressors and their pipework are effectively part of the building. As a rule of thumb, plan to pay the system off over about ten years, or two cycles of a typical five-year property lease. If you might move premises before then, the numbers get much harder to justify.

When a nitrogen generator makes sense

A generator is more likely to pay off when:

• You cut a lot of stainless and aluminium, or thin mild steel on nitrogen
• Your cutting volume is steady and growing
• Delivered gas is expensive, unreliable or hard to get where you are
• You have space, power and compressor capacity, or can add them
• You'll stay in the premises long enough to recover the infrastructure cost
• You can keep up the daily maintenance

Higher volume makes the case stronger. The regional shop runs its laser at about 50% beam-on time, around 22 hours a week, and still found it worthwhile because of supply problems. A shop in a city without those supply problems would want more cutting hours on nitrogen to justify it, but higher volumes are also more likely there.

When a nitrogen generator may not make sense

• You mostly cut mild steel on oxygen and use little nitrogen
• Your volume is low or unpredictable
• You don't have the space, power or compressor capacity, and the upgrade costs blow out the payback
• You may move premises within a few years
• Nobody will own the daily draining and filter checks

Even then, review your gas contracts. Many shops are paying more than they need to for delivered gas.

Keep a backup supply

A generator is a single point of failure. If it stops, the laser stops cutting anything that needs nitrogen. Keep at least one pack on site as a backup, and have a supply arrangement for extra packs when a large job will outrun the generator.

In practice, most shops with a generator end up running a hybrid: generated nitrogen for day-to-day cutting, with packs for backup and peak demand. As one shop owner told us: "The hybrid option is really the best option. You must keep some packs ready."

Maintenance and quality assurance

Generators aren't fussy machines. They run much like a compressor and need far less attention than a laser. The weak point is the air supply between the compressor and the cutting head.

That makes daily discipline important:

• Drain the compressor every night
• Drain the filters every night
• Keep filters and dryers serviced on schedule

If moisture or oil gets into the lines, impurities reach the gas and the cut quality drops. A bad cut usually shows quickly, but not always before you've cut a sheet of expensive stainless. Check the first parts of each run, especially after any maintenance.

Nitrogen safety

Nitrogen is odourless and displaces oxygen. A leak in an enclosed space can drop oxygen to dangerous levels with no warning, and people have died this way. The risk exists with packs, bulk tanks and generators alike, and bulk tanks hold the most gas. A bulk vessel can hold 2,000 cubic metres or more.

Simple rules reduce the risk:

• Turn the nitrogen supply off at the end of every day
• Check lines and fittings for leaks
• Keep the cutting area well ventilated, especially in well-sealed buildings
• Consider an oxygen monitor where gas is stored or used indoors

Delivered nitrogen: watch the contract

If you're staying on packs or bulk, the contract terms matter as much as the gas price.

• Pack rental. Some suppliers charge rental by the day. Negotiate a fixed number of packs on a monthly rental cycle instead.
• Price creep. Watch for fuel service levies on delivery charges and per-cubic-metre increases between contract reviews.
• Bulk venting. Liquid bulk tanks boil off gas over time and may need to vent before a refill, so you pay for gas you never use.

Our earlier article on how much nitrogen is costing your job shop covers the delivered-gas side in more detail.

How nitrogen costs affect laser cutting quotes

Assist gas is part of what it costs to cut, and on thick stainless it's a big part. Yet in our experience, many small shops don't think about gas enough.

The risk is pricing nitrogen cutting as if it were oxygen cutting. Charging $600 an hour for oxygen cutting and only $650 an hour for nitrogen on thick material can wipe out the margin. You'll still turn over money, but you won't pay off the laser. As a rough benchmark, gas should sit somewhere around 5 to 6% of revenue across all your processing. If it's well above that, check your rates.

A generator changes your cost base, and it can change where you compete. Market prices still set what you can charge. But lower gas costs let you price stainless and aluminium more competitively than shops paying for packs, especially on thicker material. The regional shop priced nitrogen cutting at around 20 to 30% above its oxygen mild steel rate. Competitors on packs were charging much more for thick stainless, so the shop built a reputation for stainless and aluminium work. Whether you pass savings on or keep them as margin, it should be a deliberate decision, not an accident of an out-of-date rate.

How to build gas costs into your quoting

• Work out your real gas cost per cutting hour for each gas. For delivered gas, include rental, delivery and levies, not just the gas. For a generator, include depreciation, power, servicing and backup packs. Our gas cost calculator gives you a cost per cut from your gas price, flow rate and cutting time.
• Feed it into your machine rate. The laser cutting hourly rate calculator shows how gas sits alongside machine, labour and overhead costs. Our guide to what goes into a laser cutting hourly rate explains the rest.
• Use separate rates for oxygen, nitrogen and air cutting, not one rate for everything, reflected in the hourly rate multiples applied to different materials and thicknesses.
• Review the rates whenever your gas setup or contract changes.

In Tempus Tools, cutting rates are set up per machine and material, so nitrogen work on stainless can carry a different rate from oxygen work on mild steel, and every quote picks up the right one automatically. See laser cutting quoting software for how pricing rules work, or our free guide on how to set laser cutting prices.

Questions to ask before buying a nitrogen generator

1. How much nitrogen do we use per month, and on which materials and thicknesses?
2. What purity and pressure do we need at the cutting head?
3. What is our real delivered gas cost per cubic metre, including rental, delivery and levies?
4. What will the full project cost, including compressor, pipework, filtration, installation and floor space?
5. What is the specific power (kWh per cubic metre) at our required purity?
6. Can it sustain our thickest stainless jobs, or will we need packs for those?
7. What backup supply will we keep?
8. Who will drain the compressor and filters every night?
9. Will we be in these premises for the next ten years?
10. How will this change our cutting rates and quoting assumptions?

Get the gas cost right either way

A nitrogen generator can be a strong investment for a shop that cuts plenty of stainless and aluminium, has the space and power for it, and plans to stay put. It can also be an expensive way to save on gas the shop barely uses. Get the full project cost, check purity and pressure at the machine, and keep packs on hand as backup.

Whether you buy nitrogen or make it, it's a real cost of cutting. Put an accurate number on it and make sure your quotes carry it.

Frequently asked questions

What does nitrogen do in laser cutting?

Nitrogen is an assist gas. It blows molten metal out of the cut and shields the edge from oxygen, so the cut comes out clean and oxide-free. It's used mostly for stainless steel, aluminium and thin mild steel.

Is nitrogen better than oxygen for laser cutting?

It depends on the job. Nitrogen gives a bright, oxide-free edge and suits stainless and aluminium. Oxygen reacts with mild steel to help the cut, using far less gas, and is usually the better choice for thicker mild steel where an oxide edge is acceptable.

What is a nitrogen generator for laser cutting?

A system that produces nitrogen on site from compressed air, usually with PSA or membrane technology. It includes a compressor, air treatment, the generator, storage and often a booster to reach cutting pressure.

Is a nitrogen generator worth it for laser cutting?

It can be, for shops with high and steady nitrogen use, the space and power to run it, and plans to stay in their premises for around ten years. Shops that mostly cut mild steel on oxygen, or use little nitrogen, may be better off negotiating a better gas contract.

How do nitrogen costs affect laser cutting prices?

Nitrogen cutting uses far more gas than oxygen cutting, especially on thick material. If quotes use a single rate for both, nitrogen jobs can lose money. Shops should calculate a gas cost per cutting hour and use separate rates for nitrogen and oxygen work.

What should shops calculate before buying a nitrogen generator?

Monthly nitrogen use, current delivered cost per cubic metre including rental and levies, the full project cost including compressor and pipework, power use per cubic metre, servicing, backup supply and the payback period over the time they expect to stay in their premises.

Use accurate gas and machine costs when setting your laser cutting rates. Try the gas cost calculator, or see how Tempus Tools keeps them consistent across every quote.