How to Produce High-Quality Samples with a Laser Cutting Machine
In laser cutting machines, for parts that require high cutting precision or are of significant thickness, it is essential to master and address several key technologies. One of these is the control of the focal position. One of the advantages of laser cutting is the high energy density of the laser beam. Therefore, the diameter of the focal spot should be as small as possible to produce a narrow cutting kerf. Since the smaller the focal length of the focusing lens, the smaller the diameter of the focal spot, the effective focal depth for high-quality cutting is also related to the lens diameter and the material being cut. Thus, controlling the position of the focus relative to the surface of the material being cut is crucial.
Because laser power density has a significant impact on cutting speed, the selection of the lens focal length is an important issue. The size of the focused laser spot is proportional to the lens focal length. When the laser beam is focused through a short-focal-length lens, the spot size is very small, and the power density at the focus is very high, which is advantageous for material cutting. However, its disadvantage is the short focal depth and limited adjustment range, making it generally more suitable for high-speed cutting of thin materials. On the other hand, a long-focal-length lens has a wider focal depth. As long as there is sufficient power density, it is more suitable for cutting thick workpieces.
After determining which focal length lens to use, the relative position of the focus and the workpiece surface is particularly important for ensuring cutting quality. Since the power density is high at the focus, in most cases, the focus is positioned just on the surface of the workpiece or slightly below it during cutting. Maintaining a constant relative position between the focus and the workpiece throughout the cutting process is an important condition for achieving stable cutting quality. Sometimes, due to poor cooling, the lens may heat up during operation, causing changes in the focal length, which requires timely adjustment of the focus position.
When the focus is in the correct position, the kerf is narrow, the efficiency is high, and a good cutting result can be achieved at a suitable cutting speed. In most application scenarios, the laser beam focus is adjusted to be just below the nozzle. The distance between the nozzle and the workpiece surface is generally around 1.5 mm.
During the application of lasers, focusing issues are often encountered. There are three common simple methods for determining the focal position:
Printing Method: Move the cutting head downward and print the laser beam on a plastic plate. The position with the smallest print diameter is the focus.
Inclined Plate Method: Place a plastic plate at an angle to the vertical axis and pull it horizontally to find the position with the smallest laser beam spot, which is the focus.
Blue Spark Method: Remove the nozzle, blow air, and direct a pulsed laser onto a stainless steel plate. Move the cutting head downward until the position with the largest blue spark is found, which indicates the focus.
