How many types of laser cutting technology are there?

There are two types of laser cutting technology: the first is pulsed laser cutting, suitable for metallic materials, and the second is continuous laser cutting, suitable for non-metallic materials. The latter represents a significant application area for laser cutting technology.

Several key technologies in laser cutting machines involve integrated opto-mechanical-electrical systems. In laser cutting machines, the parameters of the laser beam, along with the performance and precision of the machine and CNC system, directly impact cutting efficiency and quality. Particularly for parts requiring high cutting precision or thicker materials, the following key technologies must be mastered and addressed:

Focus Position Control Technology

One advantage of laser cutting is the beam's high energy density, typically 10W/cm². Since energy density is inversely proportional to area, minimizing the focal spot diameter produces a narrower cut seam. Simultaneously, the focal spot diameter is directly proportional to the lens's depth of focus. A lens with a smaller depth of focus yields a smaller focal spot diameter. However, cutting generates spatter, and placing the lens too close to the workpiece risks damaging it. Therefore, industrial high-power CO₂ laser cutters commonly employ focal lengths of 5“ to 7.5” (127–190 mm). The actual focal spot diameter ranges between 0.1 and 0.4 mm. For high-quality cutting, the effective depth of focus also depends on the lens diameter and the material being cut. For example, when cutting carbon steel with a 5" lens, the effective depth of focus lies within ±2% of the focal length, approximately 5mm. Therefore, controlling the focal position relative to the material surface is critical. Considering factors like cut quality and speed, the general principle is: - For 6mm metal, the focus is on the surface. - For 6mm carbon steel, the focus is above the surface. - For 6mm stainless steel, the focus is below the surface. Specific dimensions should be determined experimentally.

Three simplified methods exist for determining focal position in industrial production:

(1) Printing Method: Move the cutting head downward while laser-printing on a plastic sheet. The point with the smallest printed diameter indicates the focal position.

(2) Inclined Plate Method: Tilt a plastic plate at an angle to the vertical axis and pull it horizontally. Locate the point with the smallest laser beam to determine the focal position.

(3) Blue Spark Method: Remove the nozzle, blow air, and direct the pulsed laser onto a stainless steel plate. Move the cutting head downward until the largest blue spark indicates the focal point.

For flying-optics cutting machines, due to beam divergence angle, the optical path length differs between the near and far ends of the cut, resulting in variations in beam size before focusing. A larger incident beam diameter yields a smaller focal spot diameter. To minimize variations in focal spot size caused by pre-focus beam size changes, laser cutting system manufacturers worldwide offer specialized devices for user selection:

(1) Parallel Light Tube. This common method involves adding a parallel light tube at the CO₂ laser output for beam expansion. The expanded beam increases in diameter while reducing the divergence angle, ensuring consistent pre-focus beam size across the cutting range's near and far ends.

(2) Adding an independent lower axis for a moving lens on the cutting head. This axis operates independently from the Z-axis controlling the nozzle-to-material distance (stand-off). When the machine table or optical axis moves, the beam's F-axis simultaneously shifts from near to far end. This maintains a consistent focused spot diameter across the entire processing area, as shown in Figure 2.

(3) Control the water pressure of the focusing lens (typically a metal reflective focusing system). If the pre-focus beam size decreases, causing the focal spot diameter to increase, automatically adjust the water pressure to alter the focusing curvature, thereby reducing the focal spot diameter.

(4) Incorporate compensation optical path systems in the X and Y directions on flying-optics cutting machines. Specifically, when the optical path length at the far end increases during cutting, the compensation path shortens; conversely, when the optical path length at the near end decreases, the compensation path lengthens to maintain consistent optical path length.