The laser cutting head of a laser sheet cutting machine is a key component for beam transmission and focusing. The fiber optic interface is the starting point for the laser beam to enter the cutting head. The optical path system consists of a collimating lens and a focusing lens. The collimating lens converts the diverging beam into parallel light, and the focusing lens focuses the parallel beam onto the workpiece surface. The protective lens assembly typically includes upper, middle, and lower protective lenses, used for dust prevention, sealing, and protecting the focusing lens, as well as preventing molten slag splashing. A ceramic ring located at the bottom of the cutting head contains embedded metal wires for transmitting sensor data. The ceramic ring, made from zirconia, features high density, wear resistance, low coefficient of thermal expansion, high resistivity, and high surface finish. Sensors are mostly capacitive displacement sensors, which can automatically detect changes in workpiece surface height non-contactly, enabling dynamic height adjustment. The nozzle is the common outlet for both the laser and auxiliary gas; its geometry and size affect cutting quality and speed. As a consumable part, it is often made of copper. Other auxiliary components include LED indicators for internal status monitoring and a 19-pin high-precision connector.
Assist gas is an indispensable part of the laser cutting process. Its main functions include blowing away molten metal, cooling the kerf, protecting optical lenses, and reacting chemically with the material to improve cutting efficiency. Oxygen is mainly used for cutting carbon steel; it reacts with the high-temperature metal to release heat and improve cutting efficiency, resulting in a black or dark yellow cut. Nitrogen, as an inert gas, is used for oxidation-free cutting of materials such as stainless steel, aluminum, and aluminum alloys; no oxide film forms on the cut surface, resulting in a white cut. Air, supplied by an air compressor, is inexpensive and has similar cutting capabilities to nitrogen; however, a small amount of oxide film forms on the cut surface, resulting in a yellowish color. Argon, also an inert gas, is mainly used for cutting active metals such as titanium and titanium alloys to prevent oxidation and nitriding; the cut surface is white.