How many kilowatts does your fiber laser need?

Laser power is the first number on every fiber laser quote, and the easiest one to overspend on. A 12 kW machine will cut anything a 6 kW machine cuts, and faster. The real questions are whether your parts need that, and whether the rest of your shop can keep up with it.

Maximum thickness is not production thickness

Manufacturers publish a maximum thickness for each power level and material. Treat that figure as the upper limit the machine can cut with a good setup, good material and patience, not as the thickness you want to run all day. Near the maximum, cutting speed drops, piercing takes longer, edges get rougher and small setting changes matter more. Most shops plan everyday work comfortably below the headline figure. How far below depends on the part and on the edge quality your customers accept.

Published figures also vary between manufacturers for the same power class, which is why the table below gives ranges rather than single numbers.

Typical maximum thickness by power class

These are typical maximum thickness ranges taken from published manufacturer cutting charts and datasheets. They are a starting point for a conversation, not a guarantee for any specific machine. Always ask for the cutting chart of the exact model and laser source you are quoted.

Laser power	Mild steel	Stainless steel (nitrogen)	Aluminium (nitrogen)
3 kW	16 to 20 mm	8 to 12 mm	6 to 10 mm
4 to 6 kW	20 to 25 mm	12 to 25 mm	12 to 25 mm
9 to 12 kW	25 to 35 mm	20 to 40 mm	20 to 30 mm
20 to 24 kW	30 to 50 mm	30 to 50 mm	30 to 40 mm

Typical manufacturer ranges, not guaranteed values. Thick mild steel is normally cut with oxygen; on higher-power machines, thinner mild steel is often cut with nitrogen or clean dry air. Some manufacturers sell thick-plate packages or special processes that push the maximum above these figures.

Speed: where extra power actually goes

On thin sheet, more power mostly means more speed. Published charts put 1 mm stainless with nitrogen at roughly 15 to 25 m/min on a 3 kW source, 30 to 45 m/min at 6 kW and 50 to 70 m/min at 12 kW. On 3 mm mild steel the pattern is similar: a few metres per minute at 3 kW, around 8 to 12 m/min at 6 kW and 15 to 20 m/min at 12 kW.

Those are straight-line speeds. Corners, small holes and pierces slow the machine no matter how much power it has, so on a nest of small, detailed parts doubling the power gains less than the chart suggests. The benefit also flattens as power climbs: going from 3 to 6 kW is usually a bigger jump in daily output than going from 12 to 20 kW on the same work.

Assist gas changes cost and edge quality

• Oxygen is the traditional gas for mild steel. It runs at low pressure, typically well under 2 bar, and uses little gas, because the burning reaction adds heat to the cut. The edge comes out with an oxide layer, which may need removing before painting or welding. It remains the usual choice for thick mild steel.
• Nitrogen gives a clean, bright, oxide-free edge on stainless, aluminium and mild steel. It needs high pressure, often in the region of 10 to 20 bar depending on thickness and nozzle, and far more flow, so it is the most expensive gas to run. Supply options are cylinders, liquid nitrogen in dewars or a bulk tank, or an on-site nitrogen generator, which only pays off with steady, high consumption.
• Compressed air can cut thin and mid-range mild steel, stainless and aluminium at a fraction of the gas cost. It needs a dedicated high-pressure compressor with drying and filtration; ordinary shop air can damage the cutting head. Edges come out darker than with nitrogen, which can matter for visible or powder-coated parts.

Ask every seller for gas pressure and consumption at your typical thicknesses. Two machines of equal power can have very different running costs depending on how you plan to cut.

Bed size

Match the bed to the sheets you buy and the longest part you cut. A 3000 x 1500 mm bed, often called a 3015, takes a 5 x 10 ft sheet and is the common starting point. Larger formats such as 4000 x 2000 mm and 6000 x 2500 mm suit shops that buy bigger sheets or cut long parts. A bigger bed costs more, takes more floor space and needs more extraction, so buy it for real parts, not for flexibility you may never use. Most production lasers have an exchange table so one sheet loads while the other cuts; plan floor space for it and for any loading automation.

When more power pays off

• You regularly cut stainless or aluminium above roughly 10 to 12 mm and want nitrogen-quality edges.
• The laser is your bottleneck and most jobs are long cuts in mid-thickness plate.
• You run two shifts with loading automation, so faster cutting is not wasted waiting for an operator.
• You want to cut mild steel with air or nitrogen at thicknesses where a smaller source would force you onto oxygen.

More power is harder to justify when most of your work is thin sheet with detailed parts, when bending or welding downstream is the real bottleneck, or when your electrical service would need an expensive upgrade. Higher-power sources also draw more electricity, need bigger chillers and cost more to repair.

Look beyond the source

Compare the cutting head and whether it has automatic focus, the nesting software and its licence terms, the chiller, and the extraction and filter unit. Also ask whether another process fits part of your work better: a tube laser for tube and profile, or a plasma table for thick mild steel where tolerances are looser and cost per metre matters more than edge finish.

Checklist

• List your top 20 parts by volume with material and thickness.
• Mark the thickest material you cut every week, not once a year.
• Decide which edges must be oxide-free.
• Note your sheet sizes, your longest part and the floor space, including the exchange table.
• Check your electrical service and where a compressor or gas supply would go.
• Ask for the cutting chart, gas consumption and included options for every machine quoted.

Compare models in the fiber laser section of our catalog and request a quote with your parts list; we will quote the machine together with freight, installation and operator training.