Four Essential Elements of Laser Cutting Quality

In laser cutting, the laser beam and assist gas are two sides of the same coin. Andujo states that problems often lie in the flow rate of the assist gas. If the machine requires a certain PSI pressure, the gas source needs to be 100 PSI higher to compensate for pressure losses. A 350 PSI gas source cannot generate 350 PSI pressure at the cutting head. Therefore, it is helpful to first consider the required pressure and flow rate at the nozzle tip, and then work backwards through the entire system to compensate for and correct for unavoidable pressure losses.

2. Inspect Optics, Ceramic Components, and Nozzles

Dirty lens hoods and/or focusing lenses can affect the laser beam and the entire processing, including its stability. The beam changes as it passes through dirt and dust on the optics, leading to unpredictable and often poor cut quality. Optics also generate heat as they absorb and scatter the laser beam. In some cases, this can even scorch the optics and create holes approximately 3/8 inch (9.5 mm) in diameter in the lens hood.

3. Center the Beam
“Centering is crucial,” Andújo says. “To ensure the airflow can cut in any direction at any time, the nozzle must be absolutely centered to maintain coaxial airflow around the laser beam. The smaller the nozzle, the more critical centering becomes. Sometimes, it can even determine the success or failure of a cut.”

Operators need to inspect the nozzle orifice to ensure it is perfectly circular, free of dents, spatter, or other defects that could alter the orifice shape. Dents in the nozzle itself may affect the capacitive sensors used to maintain the nozzle gap during cutting, but not the beam itself. However, scratches or buildup on the orifice circumference can cause damage. “The gas stops flowing and starts trembling, which affects the cutting results,” Andújo says.

While some machines now have automatic beam centering, many do not—even so, understanding the basic principles of beam centering is still helpful. This involves the operator pressing tape onto the cutting nozzle orifice and then applying the tape.

4. Don’t Forget the Basics
To illustrate the basic focusing steps, Andújo uses a caliper analogy. Just like using calipers, before use, you need to open the calipers, clean the jaws, zero them, and then open them three times. If the reading is the same each time, you can start using it. "Laser cutting has the same requirements. You need to find the thinnest kerf. This thinnest kerf should correspond to an accuracy of zero focal length ±0.5 mm."

The basic focal point sets the zero point of the cutting head gears, which drive the optical elements to move, thus achieving the focal position required for the operation. If the laser's zero point deviates, all other focal positions will also deviate.

All these factors constitute what Andujo calls "the first stage, the foundation of laser cutting," laying a solid foundation for process optimization. He uses a car analogy, comparing people learning to drive manual and automatic cars. A person driving a manual car knows very well which gear is most suitable for various driving conditions. Over time, shifting gears becomes natural. A person driving an automatic car, however, needs to understand the gearbox and know how to maximize every acceleration. Although the process is automated, they still understand how the gearbox works internally.

The basic principle of laser cutting is similar. Operators who understand the key elements of high-quality cutting can lay a solid foundation, thereby maximizing the value of laser cutting equipment (the largest capital investment in a processing workshop).