This method is also called negative focal length, because the position of the cutting point is neither on the surface nor inside of the workpiece, but is positioned above the cutting material.
Generally, when this kind of focus is used, it is because the thickness of the sheet is relatively high. If the focus is not positioned in this way, it may cause insufficient oxygen delivered by the nozzle, which will cause the cutting temperature to drop and the material cannot be cut. However, a significant disadvantage of this method is that the cutting surface is rough and not suitable for precision cutting.
This method is called positive focal length, and is generally used when cutting stainless steel or aluminum steel plate and other materials, so that the cutting focus is located inside the workpiece.
The main disadvantage of this method is that the cutting range is relatively large, and this mode often requires more powerful cutting airflow, sufficient temperature, and longer cutting and piercing time. Therefore, it is only used when cutting harder materials such as stainless steel or aluminum.
This method is the most common focus position, also known as zero focal length. It is often used to cut SPC/SPH/SS41 and other workpieces. When using it, let the focus of the laser cutting machine be close to the surface of the workpiece.
In this mode, due to the slight difference in the smoothness of the upper and lower surfaces of the workpiece, the cut surface of the side close to the focus will be smoother. Conversely, the cut surface of the side far away from the focus will be rougher. In actual use, often It will be determined according to the different process requirements of the upper and lower surfaces.
In summary, in the process of using the laser cutting machine, we choose different focus modes according to the processing needs of different workpieces, which can give full play to the performance advantages of the laser cutting machine and ensure the cutting effect.