Every fiber laser cuts with the same handful of variables. Get them right and you get a clean, square, dross-free edge at the fastest speed the material allows. Get them wrong and you’re grinding dross, re-cutting parts, or standing at the control panel guessing your way through a material you don’t run often.

Here’s what each parameter actually does, and how they play against each other.

Power and Speed Are One Decision, Not Two

Power melts the material; speed decides how long the beam dwells on any one spot. What matters is the ratio — energy delivered per inch of cut. Too much energy and the kerf widens, edges burn, and dross clings to the bottom. Too little and the cut doesn’t sever, or the machine stutters through thick plate. Thicker material generally means more power and less speed, but the relationship isn’t linear, which is why guessing from a thinner gauge’s settings so often goes wrong.

Assist Gas Decides the Edge You Get

The gas does two jobs: it blows molten material out of the kerf, and it either feeds the cut or shields it. Oxygen burns — it reacts exothermically with carbon steel, adding heat to the cut, which is why O2 handles thick mild steel at lower power. The trade-off is an oxidized edge. Nitrogen is inert — it just evacuates the melt, giving stainless and aluminum a clean, weld-ready edge, but it demands more laser power and a lot more gas pressure. Shop air sits in between and has become the budget favorite on thin material, at the cost of some edge quality on stainless.

Nozzle and Focus Are Where Good Cuts Are Lost

Nozzle diameter sets the gas flow pattern — small nozzles concentrate pressure for thin, fast nitrogen cutting; larger nozzles feed the wide kerf of thick-plate oxygen work. Focus position moves the narrowest point of the beam relative to the sheet surface: on the surface for thin material, driven down into the sheet for thick nitrogen cuts so the kerf stays open enough for the gas to clear the melt. A worn nozzle or a focus that’s drifted a millimeter will ruin a cut that every other parameter says should work.

Pierce Time Is the Hidden Cost

Before the machine cuts anything, it has to punch through — and on thick plate a pierce can take multiple seconds. A nest with 400 holes carries 400 pierces, and that time is real money that flat-rate quoting misses completely. It’s also why accurate quoting needs your machine’s actual pierce times, not a generic average.

Stop Guessing: Build a Tech Table

None of this is exotic knowledge — it’s just a lot of interacting numbers, and the shops that cut clean keep them written down per material, per thickness, per gas. That’s a tech table.

If you don’t have one, or you’re quoting a material you rarely run, our free Fiber Laser Tech Table Builder gives you recommended starting parameters — nozzle, gas, speed, focus, pierce time, and power — for stainless, aluminum, and carbon steel across 3kW to 8kW machines. Export it as a CSV, tune it against what your machine actually does, and you’ve got a real tech table. PolygonLogix imports that same CSV, which is how its quotes use your machine’s numbers instead of somebody’s averages.