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Machining of DTC Materials (Ceramics and Composites) by Traditional and Non-Traditional Methods
Published in Helmi Youssef, Hassan El-Hofy, Non-Traditional and Advanced Machining Technologies, 2020
Nd:YAG lasers: NG:YAG lasers are solid-state lasers that use 1–2% dopants (i.e. Neodymium (Nd3+)) dispersed in a crystalline matrix (i.e. yttrium aluminum garnet (YAG) with the chemical composition Y3Al5O12) as the gain medium. Pump sources are krypton or xenon flash lamps, or recently laser diodes. The wavelength of an Nd:YAG laser is emitted at 1.06 µm in the near-infrared spectrum. The power output of CW Nd:YAG lasers are lower by some kilowatts. But the Q-switch Nd:YAG lasers can generate short pulses with peak power in megawatts, repetition rates up to 100 kHz, and pulse durations between 15–400 ns. The average output power of a pulsed Nd:YAG laser is generally lower than 1 kW. The output laser beam (at 1.06 µm wavelength) can be coupled into an optical fiber for delivery. Therefore, it is suitable to combine with robots for more flexible processing in industries. Nd:YAG lasers have been widely used for cutting, welding, cladding, and drilling of metallic or non-metallic materials. The drawback of Nd:YAG lasers is the relatively low beam quality at high output powers (M2<6), causing a large spot size, low power density, and short focal depth. Therefore, high power Nd:YAG lasers are not suitable in precision processing and thick-section machining applications. Furthermore, maintenance is also essential to Nd:YAG lasers.
Sequential Laser and Electrical Discharge Machining
Published in Basil Kuriachen, Jose Mathew, Uday Shanker Dixit, Electric Discharge Hybrid-Machining Processes, 2022
P. S. Suvin, Ranjeet Kumar Sahu
There are a variety of lasers used in machining including CO2 Laser, Nd:YAG Lasers, Diode Lasers, Excimer Lasers and Fiber Lasers. The CO2 laser is a gas laser which has a pulsed or continuous wave type mode of operation. It emits light in the infrared region. The Nd:YAG laser is short for the Neodymium ion Nd3+ doped Yttrium Aluminum Garnet laser. This laser has a pulsed or continuous wave type mode of operation and exhibits a high divergence beam quality. The pulsed mode can be accomplished by exciting either Xenon flash lamp pumped or diode pumped optical lasers. The efficiency for lamp pumped lasers is in the range 2-5% and for diode pumped lasers, 15-20%.
Sources, Detectors, and Recording Media
Published in Rajpal S. Sirohi, Introduction to OPTICAL METROLOGY, 2017
Nd:YAG laser has high gain, narrow line width, low threshold, and favorable physical properties. The spectral width of Nd:YAG laser is around 0.5 nm. The spectral width of Nd:glass laser is very large at least 30–50 times larger than that of the Nd:YAG laser and hence is used for producing mode-locked pulses.
Use of lasers in minimally invasive spine surgery
Published in Expert Review of Medical Devices, 2018
Neodymium-doped yttrium-aluminum-garnet (Nd:YAG) lasers are the most widely used laser systems in a variety of medical fields. The absorption of 1064- and 1318-nm wavelengths by biological tissue is relatively low, and thus, the scattering effect is high. The penetration depth in cartilaginous tissue reaches up to 6 mm with powers 20–40 W and pulse 0.05–0.1 s. The coagulation zone can be reduced to 0.6 mm with a contact laser probe. It has been proven to be effective for ablation and coagulation of disc tissues in both experimental and clinical studies [25,26]. Nd:YAG laser has benefits of fiber-optic delivery, applicability in dry and aqueous media, and hemostatic effect. However, it is a hot laser, which generates and transmits heat through the tissues.
Drilling of titanium alloy (Ti6Al4V) – a review
Published in Machining Science and Technology, 2021
Chua Guang Yuan, A. Pramanik, A. K. Basak, C. Prakash, S. Shankar
Aside from rotary RUD, RUAD and LFVAD, laser drilling is another type of drilling mechanism classified as non-CD method, which is capable to form high aspect ratio holes (Gautam and Pandey, 2018). Unlike CD, RAD and RUAD, laser drilling does not remove workpiece material mechanically by cutting tool. In fact, this drilling method is one of the methods, which utilizes radiation heat generated from laser beam to melt and/or vaporize workpiece material (Dhaker and Pandey, 2018, 2019b). Cutting tool and workpiece does not come in contact throughout the whole laser drilling process (Bandyopadhyay et al., 2002; Shuja and Yilbas, 2014). Due to this characteristic of laser drilling, several problems existed in tool-based drilling methods can be eliminated. Rapid tool wear in tool-based drilling is one of the reasons causing detrimental effects on burrs and surface roughness of drilled holes. Furthermore, the issue of tool bending and fracture is enhanced when extremely thin drill bits are used to perform micro-drilling (Bellows and Kohls, 1982; Chatterjee et al., 2018). Elimination of drill bits solves some limitations of CD, RUD and RUAD. These specialties of laser drilling favor the drilling process for hard-to-cut material such as titanium alloy, nickel alloy, ceramics, composites (Dhaker and Pandey, 2019a). There are several types of lasers used to perform laser drilling. Those are neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, ultraviolet yttrium aluminum garnet (UV:YAG) laser (Yung et al., 2002), ruby laser and copper vapor laser (Luft et al., 1996; Chatterjee et al., 2018). Due to exceptional beam quality along with excellent peak power, Nd:YAG laser is widely adopted for laser drilling process as compared with other lasers (Goyal and Dubey, 2016). Throughout the years, numerous researches had been done to determine parameters that are affecting quality of laser-drilled holes. Laser drilling can be classified into two categories, laser beam drilling (LBD) and laser trepan drilling (LTD). Both LBD and LTD utilize heat generated from laser beam to melt workpiece material. Due to the efficiency in terms of time and cost, LBD is widely used in laser drilling industries. The key difference between LBD and LTD is the hole forming method as illustrated in Figure 25. Despite much higher processing efficiency of LBD compared with CD, it is prone to several geometrical and metallurgical defects such as tapered holes, spatter area, heat-affected zone (HAZ) (Prithpal Singh et al., 2020). Researchers found that these defects though not eliminated can be relatively reduced when LTD is used. Some data from laser drilling of Ti6Al4V from different articles is presented in Table 3 for quick reference.