In laser cutting machine, some key technologies must be mastered and solved for parts with high cutting accuracy or large thickness. Focus position control is one of them. One of the advantages of laser cutting is the high energy density of the beam, so the diameter of the focus should be as small as possible to produce narrow gaps. As the focal depth is smaller, the focal diameter is smaller. For high-quality cutting, the effective focal depth is also related to the lens diameter and cutting material. Therefore, the position of the control focus relative to the surface of the material to be cut is very important.
Because the laser power density has a great influence on the cutting speed, the selection of lens focal length is an important issue. The spot size is proportional to the focal length of the lens after the laser beam is focused. After focusing the laser beam with a short focus lens, the spot size is very small, and the power density at the focus is very high, which is very beneficial to material cutting. However, its disadvantage is that the depth of focus is very short and the adjustment margin is small. It is usually suitable for high-speed cutting of thin materials. Because the long focal length lens has a wide focal depth, it is more suitable for cutting thicker workpieces as long as it has sufficient power density.
After determining which focal length lens to use, the relative position of the focus and the workpiece surface is particularly important to ensure the cutting quality. Due to the high power density when focusing, in most cases, the focus position is only on the workpiece surface or slightly below the surface when cutting. In the whole cutting process, it is an important condition to ensure that the relative position of the focus and the workpiece is constant to obtain stable cutting quality. Sometimes, the lens is heated due to poor cooling, which causes the focus to change, so it is necessary to adjust the focus in time.
How does the laser cutting machine cut good products?
When the focus is at the correct position, the gap is small, the efficiency is high, and the cutting speed can obtain good cutting effect. In most applications, the beam focus is adjusted just below the nozzle. The distance between the nozzle and the workpiece surface is usually about 1.5mm.
In the process of laser application, we often encounter problems such as focusing. There are three simple ways to determine the focus position:
(1) Printing method: move the cutting head up and down, print with laser beam on the plastic plate, and focus on the place with smaller printing diameter.
(2) Inclined plate method: Use the plastic plate placed at a certain angle with the vertical axis to pull horizontally to find the smaller laser beam part as the focus.
(3) Blue spark method: remove the nozzle, blow air, and then hit the pulse laser on the stainless steel plate to move the cutting head from top to bottom until the large blue spark becomes the focus.
