During laser cutting, its energy density is very high, usually around 10W/cm2. The energy density of this density is proportional to 4/π d2, so the diameter of the focal spot can be minimized as much as possible to facilitate cutting narrow cuts.
The diameter of the focal spot can also be directly proportional to the depth of focus of the lens. The smaller the depth of focus, the smaller the focal spot. However, there may be splashing during cutting, and if the lens is too close to the workpiece, it can easily cause damage to the lens. Generally, high-power laser equipment is applied with a focal length of 5 "~7.5" (127~190mm) during operation, and the standard diameter is between 0.1~0.4mm.
High quality laser cutting is closely related to the effective depth of focus, lens diameter, and the material being cut. For example, for a 5 "lens cut from carbon steel, the depth of focus is within+2% of the focal length, which is basically around 5mm. So the control of the focus has a great impact on the cutting quality, and the cutting quality and speed are closely related. Generally speaking, 6mm is a boundary, and 6mm of metal material focuses on the surface; 6mm carbon steel, with the focus on the surface; 6mm stainless steel, with the focus below the surface, this is only theoretical and can only be determined through experimentation.
High power laser equipment has a direct impact on cutting quality in terms of laser beam parameters, machine and CNC system performance and accuracy, mainly manifested in the processing of some larger parts. Now it is necessary to master and solve the following key technologies, which are focal point position control technology.