How to cut high-quality products with a laser cutting machine? Focus is important!

In the CO2 laser cutting machine, several key technologies must be mastered and solved for parts with high cutting accuracy or large thickness. Focus position control technology is one of them. One of the advantages of laser cutting is that the energy density of the beam is high, so the focal spot diameter is as small as possible to produce a narrow slit. Because the smaller the focal depth of the focusing lens, the smaller the focal spot diameter. For high-quality cutting, the effective focal depth is also related to the lens diameter and the material to be cut. Therefore, it is very important to control the position of the focus relative to the surface of the material to be cut.

Since the laser power density has a great influence on the cutting speed, the choice of lens focal length is an important issue. After the laser beam is focused, the spot size is proportional to the focal length of the lens. After the beam is focused by a short focal length lens, the spot size is very small, and the power density at the focal point is very high, which is very beneficial for material cutting; but its disadvantage is that the focal depth is very short and the adjustment margin Small, generally suitable for high-speed cutting of thin materials. Since the long focal length lens has a wider focal depth, as long as it has sufficient power density, it is more suitable for cutting thick workpieces.

After determining which focal length lens to use, the relative position of the focal point and the surface of the workpiece is particularly important to ensure the cutting quality. Due to the highest power density at the focus, in most cases, the focus position is just on the surface of the workpiece during cutting, or slightly below the surface. During the entire cutting process, ensuring a constant relative position between the focus and the workpiece is an important condition for obtaining stable cutting quality. Sometimes, the lens is heated due to poor cooling during operation, which causes the focal length to change, which requires timely adjustment of the focus position.

When the focus is at the best position, the slit is the smallest, the efficiency is the highest, and the best cutting speed can obtain the best cutting results. In most applications, the beam focus is adjusted to just under the nozzle. The distance between the nozzle and the surface of the workpiece is generally about 1.5 mm.

In the process of laser application, problems such as focusing are often encountered. There are three common easy methods to determine the focus position:

(1) Printing method: The cutting head is moved from top to bottom, and the laser beam is printed on the plastic plate, and the spot with the smallest printing diameter is the focus.

(2) Inclined plate method: Use a plastic plate placed obliquely at an angle to the vertical axis to pull it horizontally to find the smallest point of the laser beam as the focus.

(3) Blue spark method: remove the nozzle, blow air, and hit the pulse laser on the stainless steel plate to make the cutting head move from top to bottom until the largest blue spark is the focus.