Primer on the Three Types of Laser Cutting
Laser cutting is a process that uses a high-power laser beam to cut materials. The laser beam is directed through optics and computer numerical control (CNC) to follow a specific path. The laser beam can burn, melt, vaporize or blow away material to create a high-quality finished edge.
The laser beam is generated by stimulating lasing materials with electrical discharges or lamps. The lasing material is amplified by reflecting internally until it escapes as a stream of coherent light. This light is focused at the work area by mirrors or fiber optics.
A laser beam can be very narrow, typically less than 0.0125 inches (0.32 mm) in diameter. However, kerf widths as small as 0.004 inches (0.10mm) are possible depending on the material thickness.
If the laser cutting process needs to start somewhere other than the edge of the material, a piercing process is used. A high-power pulsed laser makes a hole in the material, taking seconds to burn through a 0.5-inch-thick (13 mm) stainless steel sheet.
There are three main types of laser cutting techniques: CO2 laser (for cutting, boring, and engraving), neodymium (Nd), and neodymium yttrium-aluminum-garnet (Nd:YAG). Nd is used for high energy, low repetition boring while Nd:YAG is used for very high-power boring and engraving. This is a rarely used laser solution but available and often found in the semiconductor industry. More specifically, Nd:YAG is used to separate microelectronic chips from silicon wafers. Fiber laser cutting which relies on solid-state technology and glass fiber technology to deliver the laser beam.
CO2 lasers pass a current through a gas mix or use radio frequency energy. The radio frequency method has external electrodes and avoids problems related to electrode erosion and plating.
The type of gas flow can affect laser performance. Common variants of CO2 laser include fast axial flow, slow axial flow, transverse flow, and slab.
Different techniques are used to cool the laser generator and external optics. Waste heat can be transferred directly to the air or a coolant can be used. Water is a common coolant.
One example of water-cooled laser processing is a laser microjet system. This system couples a pulsed laser beam with a low-pressure water jet to guide the beam like an optical fiber. The water also removes debris and cools the material.
Fiber lasers are becoming popular in the metal cutting industry. This technology uses a solid gain medium instead of liquid or gas. The laser is amplified in a glass fiber to produce a smaller spot size than CO2 techniques, making it ideal for cutting reflective metals.
Compared to a CO2 laser, fiber lasers are highly efficient and have comparatively lower operational costs. The cost per diode is dropping exponentially so Fiber Lasers are more competitive than CO2 Lasers and Fiber Laser is so cost effective it is now even competing favorably with high-definition Plasma cutting applications.
