CO2 Versus Fiber: Considerations for Laser Cutting Choices

Laser cutting is a mainstay technology in industrial and metal manufacturing applications. The computerized and therefore highly accurate method works by focusing the output of the laser at the material to be cut, melting, burning, vaporizing, and blowing it away (by a jet of gas) to leave a high-quality surface finish. Industrial laser cutters are typically employed in the cutting of structural, piping, and flat-sheet materials.

Two types of lasers have found many applications in industry: fiber lasers and carbon-dioxide (CO2) lasers. A fiber laser is a solid-state laser that utilizes a monolithic design for high beam quality; it is also known as single mode beam quality. This feature permits high power density to be generated and directed to the workpiece, resulting in high processing speeds. Fiber lasers are ideal for scanner welding and in high demand for applications that require particularly narrow weld seams or cutting kerfs.

A 4 kW CO2 laser cutting machine at work. Credit: S zillayali at Wikipedia A 4 kW CO2 laser cutting machine at work. Credit: S zillayali at Wikipedia

Fiber laser light is created by banks of diodes, where the light is channeled and amplified through fiber optic cable in a similar way to that used for data transfer. The laser is guided within the fiber core, and because its interaction length is so great, it experiences a very high amplification. When the amplified light exits the fiber cable, it is straightened and then focused by a lens onto the material to be cut.

There are several advantages to using fiber lasers. There are no moving parts or mirrors in the light-generating source, unlike conventional CO2 resonator or disk lasers. This provides a distinct advantage in terms of reducing maintenance requirements and operating costs. Fiber lasers have a much higher electrical efficiency, resulting in considerably lower running costs. A 3 kW fiber laser machine uses 30 percent less power than a 4 kW CO2 laser machine with average across-the-board performance.

Fiber lasers operate at higher speeds when cutting thin material. Compared to the same 4 kW CO2 laser machine, a fiber laser is three times faster when cutting 1 mm mild, galvanized, or stainless steel and twice as fast when cutting 2 mm in a straight line. Another key feature is the ability to cut reflective materials without the worry of back reflections that can damage the machine. This allows copper, brass, and aluminum to be cut without issue. Servicing of lasers is always a consideration in adoption of the technology and machine purchasing, and fiber lasers offer 50 percent longer working intervals and 50 percent lower servicing costs.

A focused beam of even a 2 kW fiber laser will demonstrate five times greater power density at the focal point compared to a 4 kW CO2 laser. Because of their high beam quality, fiber lasers are ideally suited for high-precision applications. They are designed to produce narrow weld seams and small cutting kerfs with high quality.

When considering high power, 250 watts of average CO2 power and an impressive 700 watts of peak pulse power, CO2 lasers are the answer. The interest in carbon-dioxide lasers stems from their continuous power capability, high efficiency, and simple construction.

Compared to fiber lasers, CO2 laser differences mainly relate to the cutting speed when cutting thicker materials (above 5 mm). In this scenario, a CO2 laser machine provides faster straight-line cutting as well as faster initial piercing times. When an application calls for cutting thicker materials, a C02 laser will also leave a smoother surface finish. CO2 lasers are also the highest-power continuous wave lasers currently on the market today.

The active laser medium in a CO2 laser is a gas discharge that is air-cooled; water-cooling is used in higher-power applications. The filling gas in the discharge tube consists of approximately 10 to 20 percent carbon dioxide, 10 to 20 percent nitrogen, a few percent of hydrogen or xenon, and helium, with the specific proportions varying according to the particular laser.

As a result of their consistency, reliability, and durability as beam sources, CO2 lasers are a mainstay in the laser material processing industry, which utilizes them primarily for cutting and welding applications. The wavelength of a CO2 laser beam is 10.6 micrometers, putting it in the far-infrared spectrum.

Determining which type of laser is the best depends on your application. For cut quality, both technologies deliver high quality; in fact, the quality difference for the cutting of material up to 6 to 8 mm thickness is very close. However, for thicknesses above this range, the CO2 laser performs better.

For cutting thin-gauge stainless steel, the edge goes to the fiber laser, which is 25 to 50 percent faster, especially when cutting large shapes with simple geometries. At 4 mm thickness, the cutting speeds between the two laser types are very close. But above 8 mm, the advantage goes to the CO2 laser.

Fiber lasers have an advantage when cutting copper and aluminum alloys. CO2 lasers are better for cutting plastic and wood-based products. When comparing running costs, the fiber laser has an advantage with its lower maintenance expenses.

 

Dan Capp is vice president of sales development for Laserage Technology Corp., a precision laser contract manufacturer based in Waukegan, Ill. Laserage specializes in precision tube cutting, laser scribing, machining, drilling, welding, and other custom laser job shop services. The custom manufacturer processes metals, plastics, fused quartz, alumina, and most other materials. Laserage is registered to ISO 13485:2003 for medical device components and to ISO 9001:2008 for all other products and components. For more, visit www.laserage.com.

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