Laser drilling is a laser processing technology that USES a pulse heat source with high power density and short stay (lower than laser cutting) to drill holes.Aperture formation can be achieved by single pulse or multiple pulses.Compared with traditional drilling techniques such as mechanical drilling machine, electrochemical and electric spark discharge, laser drilling is more economical for shallow hole positions.Although the laser heat source based on the cutting design can also be used for drilling, it is more efficient to work with the laser heat source based on the drilling design.At the same time, the high-powered, repeatable pulsed laser can cut through a series of closely connected holes.Generally speaking, the diameter of laser drilling is generally between 0.075 ~ 1.5mm.(0.003 ~ 0.060 inches).
The laser-made holes are clean and have a small amount of recast, meaning that molten metal may stick to the inside of the holes during the drilling process.When large aperture is needed, laser beam drilling technology in cutting mode is needed to obtain the required aperture.In the drilling process, the perforating mode is first used to prepare holes of sufficient size so that the subsequent cutting process starts from this point.The drilling or penetrating process requires a repeatable pulse laser beam with peak power and high air pressure. After the workpiece penetrates, the laser beam can be cut by reducing the peak power or even changing to a pulseless mode.
Solid-state lasers have a shorter wavelength and can achieve high intensity pulse output, so they are more suitable for laser drilling, such as Nd:YAG laser, Nd: Glass laser and Nd: Ruby laser.In engineering applications, the Nd:YAG laser is often used for laser drilling of metal materials (as shown in Figure 1).CO2 lasers are commonly used to open holes in nonmetallic materials such as ceramics, composites, plastics or rubber.
Metal laser drilling requires a pulsed laser beam focusing power density of 10^5 W/mm^2 (6.5 W/in.^2 × 10^7 W/in.^2) or more.When the focused beam hits the surface of the material during cutting, the material melts and volatilizes, and the molten and evaporated metal is ejected, forming holes in the workpiece.Generally speaking, the depth of the laser opening is 6 times of the aperture.Multiple pulses may be required to achieve complete material penetration for laser openings in thick-walled parts.Laser perforation technology can be up to 25mm thick material drilling.
Focus of the laser beam
In laser drilling mode, a short focal length lens is used to focus the peak power beam of the pulsed laser onto a spot with a diameter of 0.6mm to achieve the level of power density required for drilling.
The low divergence of laser beam can be achieved by a specific laser resonator.In the process of drilling, the low divergence laser beam changes the reflection propagation of the working beam, thus improving the quality and depth of the hole.The beam diameter can be controlled by changing the aperture of the focusing device.Therefore, the aperture can be used to improve the energy density of the focused beam and the intensity distribution of the beam. All 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 you need the hole diameter less than 0.5 mm (0.020 inch), laser drilling particularly beneficial, and in conventional tools can't enter the area during the opening, only need to make the beam and the material surface to form a certain Angle of laser beam can achieve intake holes, effectively avoid the interference with mechanical processing with the structure of the impact crushing events occur.
1 Other advantages of laser drilling are as follows:
2 Short opening time
3 Strong adaptability to automation
4 It can be used for penetrating machining of refractory materials
5 In contrast to mechanical opening, there is no mechanical wear between the workpiece and the opening