Introduction to Laser cutting

The various technologies for laser cutting have evolved considerably within the previous twenty years or so and now the engineer has an extremely wide choice of laser, machining principles and computerized control to precisely cut a material to an impressive level of accuracy that was not possible only a few years ago.

Common Applications for Laser Cutting

Due to the low set-up costs, rapid turnaround, low and medium volume production flexibility, laser cut parts are widely used in a number of fields and applications, including:

• Automotive parts

• Aerospace

• Recreational vehicles

• Medical

• Consumer electronics

• Furniture

Fiber lasers

With recent advances in technology and capabilities, fiber lasers are rapidly becoming the laser of choice for industrial cutting applications. A fiber laser is a type of solid-state laser where the monochromatic and pumped, intensified light is directed and wave-guided down an optical fiber towards the cutting surface and is not passed through any gas for stimulated emission (i.e. a “solid gain medium”).

Fiber laser cutter benefits include:

More rapid processing times vs CO₂

• Greater energy efficiency (2 to 3 times that of CO2)

• Greater reliability and performance; no optics alignment or adjustment

• Reduced maintenance

• The ability to process highly reflective materials such as copper and brass

• Ability to cut thinner metals (better wavelength absorption)

                                                                                                       Illustration of a fiber laser working mechanism

In the diagrammatic view below, Figure 7 shows the basic configuration of the optical circuit of a high-power fiber laser. The optical circuit consists of three major sections: Pump section, Oscillator section, and Beam delivery section. In the Pump section, laser light from pumping laser diodes (LDs) passes through optical fibers into a pump combiner. The pump combiner couples the pump light from the multiple LDs into a single-mode optical fiber.

Generally, when laser cutting metals with fiber lasers, the upper limit on thickness of the metal sheet to be cut is around 20 – 25 mm for mild steels. Above this thickness, higher power CO2 lasers are used but with specialized fiber lasers for a higher price, it is possible to cut thicker plates than this. Fiber lasers are now the tool of choice for cutting metal below 15mm thickness.

Laser Type Comparison

The choice of laser cutting technology generally comes down to material, thickness and the light reflectivity of the material being cut. Generally, fiber lasers are superior in cutting reflective material due to significantly smaller beam size, while CO₂ lasers can cut a wider range of materials. An additional complication is oxidation in the case of O₂ assisted CO₂ laser cutting. Below is a table illustrating the best laser cutting technology to use for different materials:

Advantages of laser cutting over other cutting technologies

Laser cutting offers many advantages over other cutting technologies such as mechanical die punching, saw cutting, plasma cutting and waterjet. Some of the key advantages are listed and explored below:

• Narrower kerf widths

• Less material distortion and a reduction in the heat affected zone

• Higher cutting precision

• High levels of repeatability

• Less material contamination

• Improved safety conditions for operating personnel

• Higher quality cutting edges and little secondary finishing required post-cut

• Less material wastage due to superior sheet utilization