CO₂ vs Fiber for Metal Cutting: What I Learned After Burning Through $4,200 in Test Runs

The Comparison You Actually Need

If you're searching for a metal cutting CNC machine or a CNC Laserschneider Metall, you've probably noticed that CO₂ lasers and fiber lasers are often pitted against each other. But the decision isn't as simple as 'fiber is better for metal.' Not by a long shot.

In 2023, I spent about $4,200 on test samples, consumables, and wasted material runs trying to answer one question: When should I use a CO₂ laser for metal, and when should I switch to fiber? This article isn't a generic comparison—it's what I found using the BOSS LS 3655 (a CO₂ workhorse) alongside a fiber laser marker, cutting and marking various metals over a period of 8 months.

Here's the short version upfront: They don't compete head-to-head as much as they complement each other. The choice depends on metal thickness, desired edge quality, and whether you're cutting or marking.

Dimension 1: Cutting Thickness & Speed

CO₂ (LS 3655): The Thick-Plate Surprise

Conventional wisdom says CO₂ lasers are bad for metal. That's outdated. With the right assist gas (oxygen or nitrogen) and a proper setup, the 150W CO₂ tube on my LS 3655 cuts up to 1.2mm mild steel cleanly. At 0.8mm, it's almost as fast as a fiber laser for thin sheet metal, about 20-30 inches per minute.

But the edge quality surprised me. A CO₂ cut on thin steel (0.5-0.8mm) often has a slightly smoother edge than a fiber cut of the same thickness, because the longer wavelength absorbs more evenly on certain alloys. The downside? Heat-affected zone (HAZ) is bigger—about 0.3mm width on 1mm steel versus 0.1mm on fiber.

Fiber Laser: The Speed King for Thin Metal

For stainless steel under 1mm and aluminum under 0.5mm, fiber is clearly faster. I tested a 30W MOPA fiber marker (not a high-power cutting fiber) and it zipped through 0.5mm steel at 40 inches per minute—nearly double the speed of the CO₂. For reflective metals like copper and brass, fiber is the only real choice without risking back-reflection damage to a CO₂ tube.

However, for anything above 1.5mm mild steel, a typical fiber marker struggles without a higher-power source (1kW+). The LS 3655, at 150W CO₂, can actually cut 2mm steel with multiple passes—something a low-power fiber can't do at all.

My conclusion: If you mainly cut thin steel (under 1mm) and need speed, get a fiber. If you cut mixed materials—wood, acrylic, leather and thin metal—the CO₂ is more versatile. For thick steel (2mm+), you need a dedicated fiber cutting machine with 1kW+, which is a different price class entirely.

Dimension 2: Marking & Engraving on Metal

CO₂ for Metal Marking: Possible but Limited

You can mark metal with a CO₂ laser, but you shouldn't expect deep engraving. I've used the LS 3655 with Cermark spray (a marking compound) to create permanent black marks on stainless steel and aluminum. The result? Durable, high-contrast marks—perfect for serial numbers and logos. But the process is slow (about 5-10 seconds per 1-inch square) and requires a consumable that costs $0.50 per application.

Without Cermark, a CO₂ laser can only anneal or discolor thin coatings (like painted aluminum). Direct marking on bare metal? Not happening with CO₂.

Fiber: The Native Metal Marker

Fiber lasers mark bare metal directly. With a MOPA fiber, you can switch between colors (black, grey, gold) on stainless steel by adjusting pulse width. I've marked 316 stainless steel tags with QR codes and text in under a second each—no compound, no post-processing.

One thing I didn't expect: Fiber can also mark some plastics and ceramics, but it's terrible on wood and acrylic (too much absorption = burning). The CO₂ handles those materials effortlessly.

My conclusion: For metal marking only, fiber wins hands-down. But if you need to mark metal occasionally alongside wood/acrylic jobs, a CO₂ with Cermark is workable—just budget for the consumable cost and slower speed.

Dimension 3: Operating Cost & Maintenance

CO₂ Laser (LS 3655): Lower Upfront, Higher Consumables

The LS 3655 (with a 150W CO₂ tube) costs roughly $6,000-8,000 as of January 2025. The CO₂ tube lasts about 2,000-3,000 hours and costs $300-500 to replace. You'll also need to change laser optics (lenses, mirrors) annually—about $100-200 per set. Assist gas (oxygen for metal cutting) costs $20-50 per cylinder, depending on your region.

But the real cost I didn't anticipate: The chiller. CO₂ lasers require active cooling. My chiller uses about 500W continuously during operation. Over a 40-hour week, that's 20 kWh just for cooling. At $0.12/kWh, that's $2.40/week or about $125/year.

Fiber Laser: Higher Upfront, Lower Running Costs

A 30W MOPA fiber marker starts around $4,000 for a basic unit, but a 1kW fiber cutting machine for thick steel costs $25,000+. The fiber source lasts 50,000-100,000 hours—essentially maintenance-free for years. No consumable optics, no chiller (air-cooled), no tube replacement.

Assist gas needs are similar, but fiber often uses nitrogen for cleaner cuts—nitrogen is cheaper than oxygen for thin metals.

My conclusion: If you're a small shop cutting 500 hours per year, the CO₂ has a lower total cost of ownership over 5 years ($10,000 vs $15,000 for a comparable fiber). But if you run 2,000+ hours/year, the fiber's maintenance-free source makes it cheaper long-term.

Dimension 4: Material Versatility

CO₂: The Generalist's Dream

With the LS 3655, I can cut wood (up to 12mm), acrylic (up to 10mm), leather, fabric, paper, cardboard, and thin metal—all with one machine. Change the lens for thick non-metals, adjust speed/power, and you're done. For a one-machine shop that handles mixed orders, this is huge.

The LS 3655's 36" x 55" bed size also means I can process large sheets of plywood or acrylic in one pass—a fiber laser of the same footprint would cost 3x more.

Fiber: The Specialist's Choice

Fiber lasers excel at metals and some engineered plastics (like ABS, polycarbonate). But put wood or acrylic in a fiber beam, and you'll get smoke, charring, and poor edges. Fiber is a metal specialist. If you only work with metals and occasionally mark plastics, it's perfect. Otherwise, it's limited.

My conclusion: If you need a do-it-all machine for prototyping, sign-making, or mixed production, CO₂ is the clear winner. If your business is 90%+ metal, fiber is the right tool.

Which One Should You Choose?

Here's my scenario-based recommendation after all that testing:

• You cut thin metal (under 1mm) 70%+ of the time, plus plastics: Get a fiber laser. Speed and efficiency on metal will pay off. Example: electronics enclosure fabrication, small part manufacturing.
• You cut wood, acrylic, leather, and occasionally thin metal: Get a CO₂ laser. The versatility of a single machine for diverse materials is worth the trade-off in metal speed. Example: sign shops, laser engraving services, small craft businesses.
• You mark metal for serial numbers, logos, or QR codes: Get a fiber laser. The speed and lack of consumables make it the clear choice for high-volume marking. Example: aerospace part marking, tool engraving.
• You cut thick metal (2mm+) regularly: Get a high-power fiber (1kW+). CO₂ can't keep up economically. Example: heavy machinery parts, structural steel fabrication.
• You're in the UK looking for the best laser engraving machine UK options for mixed materials: The BOSS LS series is a strong contender—especially the LS 3655 for large-format work. But if metal is your primary material, explore fiber options first.

In Q1 2024, I created a simple decision matrix for our workflow. If a job is 80% metal under 1mm and 20% plastic, I use fiber. If it's 50/50 metal and non-metal, I use CO₂. It took me 3 years of mistakes to arrive at that specific split. Hopefully, this article helps you get there faster.

Pricing references: Based on BOSS Laser and major manufacturer quotes, as of January 2025. Verify current pricing and specifications directly with suppliers.