Apr 21, 2020
Laser drilling is a laser processing technology through high power density, short stay (lower than laser cutting) pulse heat source. The formation of the aperture can be realized by a single pulse or multi-pulse. Compared with the traditional mechanical drilling machine, electrochemical, and EDM drilling technology, laser drilling is a more economic drilling technology when the processing depth is shallow. Although the laser heat source based on cutting design can also be used for drilling, it is more effective to use the laser heat source based on drilling design. At the same time, this high-power, repeatable pulse laser can achieve laser cutting by processing a series of closely connected holes. Generally speaking, the diameter of laser drilling is generally 0.075-1.5mm. (0.003-0.060 in.).
The keyhole prepared by laser is clean and accompanied by a small amount of recast layer, that is to say, the molten metal may adhere to the inner wall of the keyhole during the drilling process. When a large aperture is needed, the laser beam drilling technology in the cutting mode is needed to obtain the required aperture. In the process of drilling, first use the drilling mode to prepare holes of sufficient size, so that the subsequent cutting process starts from here. In the process of drilling or penetrating, a repetitive pulse laser beam with high peak power is needed, which is combined with high air pressure. After the workpiece is penetrated, the laser beam can be cut by reducing the peak power or even changing into a pulse-free mode.
The solid-state laser has a short wavelength and can achieve high-intensity pulse output, so it is more suitable for laser drilling, such as Nd: YAG laser, Nd: glass laser, and Nd: ruby laser. In engineering applications, the laser drilling of metal materials is usually realized by Nd: YAG laser. CO2 lasers are often used to open holes in nonmetallic materials, such as ceramics, composites, plastics, or rubber.
The laser drilling of metal materials needs pulse laser, and the focusing power density of the beam should be above 10 ^ 5 W / mm ^ 2 (6.5 w / in. ^ 2 × 10 ^ 7 w / in. ^ 2). In the cutting process, the focused beam hits the surface of the material, the material melts and volatilizes, and the molten and evaporated metal will be ejected, thus forming holes on the workpiece. Generally speaking, the depth of the laser hole is 6 times the hole diameter. For laser drilling of thick wall components, it may take multiple pulses to achieve complete penetration of materials. Laser drilling technology can achieve a maximum of 25 mm thick material drilling.
Focusing on the laser beam
In the laser drilling mode, it is necessary to use a short focal length lens to focus the peak power beam of the pulsed laser to a spot with a diameter of 0.6mm to achieve the power density required for drilling.
The low divergence of the laser beam can be achieved by a special laser resonator. In the process of drilling, the laser beam with low divergence changes the reflection propagation of the working beam, thus improving the quality and depth of drilling. The diameter of the beam can be controlled by changing the aperture of the focusing device. Therefore, the aperture can be used to improve the energy density and the intensity distribution of the focused beam. These principles have certain reference significance for the application of laser drilling.
Advantages of laser drilling technology
Laser drilling has most of the advantages of laser cutting. When the required hole diameter is less than 0.5mm (0.020 inch), laser drilling is particularly advantageous. In addition, when drilling in areas where conventional tools cannot enter, only a certain angle between the light beam and the material surface is needed to achieve laser beam intake drilling, effectively avoiding the occurrence of impact and fracture events caused by structural interference during machining.
Other advantages of laser drilling are as follows:
Short opening time
Strong adaptability to automation
It can be used for through processing of materials difficult to open holes
Compared with mechanical opening, there is no mechanical wear between the opening process and the workpiece