In the CO2 laser cutting machine, it is necessary to master and solve several key technologies for the parts with higher cutting precision or larger 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 so as to produce a narrow slit. The smaller the focal depth of the focus lens is, the smaller the focal spot diameter is. For high quality cutting, the effective focal depth is also related to the diameter of the lens and the material being cut. Therefore, the control focus is very important to the position of the surface of the cut material.
Because the laser power density has a great influence on the cutting speed, the choice of the lens' focal length is an important problem. The laser beam focus spot size and focal length is proportional to the beam through a short focal length lens focus spot size is very small, high power density, good for cutting materials; but it is a very short focal depth, small adjustment margin, generally applicable to the high-speed cutting thin type material. The long focal length lens has a wide focal depth, so long as it has enough power density, it is more suitable for cutting thick workpiece.
The relative position of the focus and the surface of the workpiece is particularly important to ensure the quality of the cutting after determining the lens with which the focus is used. Because of the highest power density at the focus, in most cases, the focus position of the cutting is just on the surface of the workpiece, or slightly below the surface. During the whole cutting process, it is important to ensure that the relative position of the focus and the workpiece is constant to obtain the stable cutting quality. Sometimes, the lens is heated because of bad cooling, which causes the change of the focal length, which requires timely adjustment of the focus position.
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with high quality laser cutting machine that can cut material like metal, jewelry, stone, wood, plastic and so on.
When the focus is in the best position, the minimum cutting, the highest efficiency, best cutting speed can obtain the best cutting results. In most applications, the focus of the beam is adjusted to just under the nozzle. The surface spacing between the nozzle and the workpiece is about 1.5mm.
In the process of laser application, focusing and other problems are often encountered. There are three simple methods to determine the location of the focus.
(1) printing method: making the cutting head moving from the upper to the bottom, printing the laser beam on the plastic plate, and the minimum point of the printing diameter as the focus.
(2) the slanting plate method: the plastic plate which is placed in an angle with the vertical axis to pull it horizontally, and to find the minimum point of the laser beam as the focus.
(3) blue spark method: remove the nozzles, blow the air, pulse laser on the stainless steel plate, make the cutting head move from top to bottom, until the blue spark is at the maximum.