12kw/20kw/30kw fiber laser cutting machine 

12000W laser cutting machine is a very powerful cutting tool, capable of cutting through a wide range of materials, including metals, plastics, and woods. Cutting 30mm thick material with a laser requires a high-powered machine like this one, but it also depends on the type of material being cut and the specific characteristics of the laser itself.

Assuming you're cutting a metal like steel, which is a common material for laser cutting, a 12000W laser should be able to easily cut through 30mm thick sheets with high precision and accuracy. However, it's important to note that the speed and quality of the cut will also depend on the specific parameters used for the laser cutting process, such as the cutting speed, focus, and gas pressure.

If you're using a different material, or if the specific conditions of the cutting process vary, the requirements and capabilities of the laser cutting machine may also change. In any case, it's always important to consult with a professional or a representative of the laser cutting machine manufacturer to ensure that you're using the machine safely and effectively.