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Laser Cutting Characteristics at Zero , Negative and Positive Focal Length

Aug 06, 2020

One of the advantages of laser cutting is that the energy density of the beam is high, so the focal spot diameter can be as small as possible in order to produce extremely tiny slits. The smaller the focal depth of the focusing lens, the smaller the diameter of the focal spot. The effective focal depth is also related to the lens diameter and the material to be cut. Therefore, for high-quality, high-precision cutting, it is very important to control the relative position of the focus and the surface of the material to be cut.

We analyze the following three FOCUS modes to make different choices due to different materials and requirements.

The zero focal length mode is generally used when cutting workpieces such as SPC, SPH, SS41, etc. When using, the focus of the cutting machine is located on the surface of the relatively smooth side of the workpiece. This mode should be determined according to the process requirements of the upper and lower surfaces in actual applications.

The focus of the negative focal length mode is positioned above the cut material. This method is mainly used for cutting thick materials. The main reason is that the thick plate requires a large cutting width. Positioning the focus on the cutting material can ensure that the oxygen delivered by the nozzle is in full contact with the material, and the cutting temperature will easily drop if the oxygen is insufficient. The disadvantage of this method is that the cutting surface is relatively rough and not suitable for high-precision cutting.

 The positive focus mode is positioned below the surface of the workpiece, and is often used for cutting hard materials such as stainless steel and aluminum. The disadvantage of this method is that the cutting width is larger than the zero focal length, and the cutting airflow required in this mode is larger, the temperature is sufficient, and the cutting and piercing time is longer.