Fiber Laser Cutting Machine Materials: What Goes on the Bed

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  Key takeaways
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  Why wavelength decides which fiber laser cutting machine materials work
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  Carbon steel and stainless steel
• 4
  Aluminum, brass, copper, and titanium
• 5
  Plastics, composites, and ceramics
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  When laser cutting is the wrong process
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  Material vs. maximum cut thickness

A fiber laser runs at about 1,070 nm, in the near-infrared. Metals absorb that wavelength well once they are molten, which is why the beam couples into steel and aluminum so efficiently. Clear plastics and glass transmit or scatter most of that light instead of absorbing it at the surface. The beam passes through, and you get a weak mark rather than a cut.

The second factor is thermal conductivity. Mild steel conducts heat slowly, so the melt pool stays tight and the kerf stays narrow. Copper and aluminum pull heat away quickly, so the cut edge needs more power and a faster gas flow to stay clean. This is why 1 mm copper behaves like 3 mm steel on the same machine.

The third factor is how the material breaks down under heat. Some plastics vaporize cleanly. Others decompose into hydrochloric acid or cyanide-bearing fumes that attack the lens and the extraction filters. That is a chemistry problem, not a power problem, and no parameter change fixes it.

Carbon steel is the workhorse. A 6 kW source cuts 20 mm plate with oxygen assist, and 1 kW handles 6 mm comfortably. Below 3 mm, use nitrogen for a clean edge that needs no post-processing. Above 6 mm, oxygen gives a faster cut but leaves an oxide layer you will need to grind or machine off.

Stainless steel behaves differently because it does not burn. It melts, so you cut with high-pressure nitrogen, typically 12 to 18 bar, to blow the melt out before it re-solidifies on the edge. A 6 kW source reaches about 12 mm on 304. Thicker than that, dross builds on the underside and the cut slows sharply.

Both families are common in our own shop. GreatLight runs 127 high-precision CNC machines in Dongguan and Singapore, and laser-cut blanks usually move straight to a 5-axis mill for the finished geometry.

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  Mild steel 1–3 mmNitrogen assist, sharp edge, no oxide.
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  Mild steel 6–20 mmOxygen assist, faster, oxide on the edge.
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  Stainless 304 / 316LHigh-pressure nitrogen, 12–18 bar.
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  17-4PHCuts like 304 but harder on the nozzle; inspect more often.

Aluminum reflects the beam when cold but absorbs it once molten. The trick is a pierce that punches through the reflective window fast. Once the kerf is open, a 6 kW source cuts 12 mm 6061 cleanly. Alloys with high magnesium content, like 5052 and 5083, cut slightly slower because they form a tenacious oxide skin.

Brass and copper need more power for the same thickness. A 3 kW source cuts 3 mm brass and about 2 mm copper. Below that, the beam tends to reflect back into the delivery fiber, so back-reflection protection is not optional. We check the protective window every shift on copper work.

Titanium cuts well but reacts with oxygen at temperature. Use argon or nitrogen, never oxygen, or the edge will embrittle and turn white. Grade 5 (Ti-6Al-4V) cuts to about 6 mm on a 4 kW source; thicker sections usually go to the mill instead.

Some non-metals do cut. PMMA, POM, PA, and PEEK absorb near-infrared light well enough for a clean edge, but only with the right assist gas. Acrylic cut with air turns brown and re-deposits on the surface. Cut with nitrogen, it stays clear. PEEK needs higher power and a slower feed because it chars before it melts.

Carbon fiber is a mixed case. The resin vaporizes and the fibers need a second pass. Edge quality is rough, and the dust is conductive, so extraction is critical. For structural parts we usually mill carbon fiber on a CNC rather than cut it on the laser.

Ceramics, glass, and silicon do not cut on a standard fiber laser. They are transparent or brittle at this wavelength. A CO2 laser at 10,600 nm handles glass and ceramics; that is a different machine with a different beam delivery.

Thick sections are the first limit. Above 20 mm on steel, the kerf tapers and the cut slows to the point where a waterjet or a milling operation is faster and cheaper. The taper is geometry, not a tuning issue, and no parameter set removes it.

Reflective and highly conductive metals are the second limit. Copper above 4 mm and pure silver reflect too much energy back into the optics. If the part is a heat sink or a busbar, we usually mill it from plate instead.

The third limit is the material itself. PVC, polyurethane, and any plastic containing halogens release hydrogen chloride when cut. That corrodes the lens, the nozzle, and the extraction duct. We will not run those on our lasers, and no reputable shop should.

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  Above 20 mm steelWaterjet or milling wins on both cost and edge.
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  Copper above 4 mmBack-reflection risk; mill from plate.
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  Halogenated plasticsCorrosive fumes; never on a fiber laser.
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  Tight 3D geometryLaser cuts flat stock; 5-axis milling handles contour.