47
Contemporary Machining Processes
powers, and broad emission bands. With a large variety of color center types and
host lattices, the combined tuning range covers the near-infrared region from about
0.8 to 4 μm (Gellermann, 1991). Color centers exist in many types of crystalline
solids, but most promising materials, apart from alkali halides, are alkali-earth fluorides, oxides (e.g., Al 2 O 3 ), and covalent crystals, with diamond as the only available
representative. Among the alkali halides, LiF and NaF are the most outstanding
because of their low hygroscopicity, while LiF is the most durable and suitable for
high average-power laser operations at room temperature. Sapphire and diamond
feature a unique combination of thermal and mechanical properties, but they are not
as easily accessible for technology as alkali halides (Basilev et al., 2003).
Another important group of solid-state lasers, worthy of distinction as a selfstanding class, consists of high-power fiber lasers. In fiber lasers, active (laser-gain)
optical fiber is combined with one or more pump lasers, usually laser diodes. There
are various types of fiber lasers, including low-power continuous wave, low- and
high-energy pulsed, etc. Fiber lasers are relatively simple in design and easy to
maintain. Since they are pumped with laser diodes, these lasers are also rugged
and long-lived. Kilowatt-class CW fiber lasers find common application in materials
processing, such as cutting, welding, brazing, and surface treatment (Wallace, 2016).
Among benefits important for industrial purposes, the following can be listed: high
power with low beam divergence, flexible beam delivery, low maintenance costs,
high efficiency, and compact size (Quintino et al., 2007). Sadikov and Mogilevets
(2016) point out the following advantages of high-power fiber lasers used in industrial materials processing:
1. Long life of above 100,000 working hours can be further expanded at reasonable expenses, maintenance costs close to zero.
2. Very short time and low expenditure required to prepare the location and to
launch these devices.
3. Universal laser source without specific technical features, which can be
reoriented from one technological process to another.
4. It is possible to increase the power of a laser. For instance, having a 700 W
device, one can buy pumping blocks and obtain up to 2,400 W without any
additional rebuilding. These additional blocks can be installed in two or
three hours.
5. Transmission of irradiation with a 10- to 100-m long fiber simplifies the
design and composition of manufacturing and materials processing systems. Application of a wide range of industrial robots is possible.
6. Fiber lasers offer prospects of organizing multipurpose and multifunctional
technological areas to increase the productivity of the laser source.
7. In terms of staff, there is no need to employ additional specialists to maintain the laser system. An operator can be trained in a week’s time, so that
existing staff may enter a new, higher productivity level.
Another large group of lasers is based on a gaseous active medium. The working
principle of the gas lasers is very similar to that of solid lasers, but the energy of
Contemporary Machining Processes
powers, and broad emission bands. With a large variety of color center types and
host lattices, the combined tuning range covers the near-infrared region from about
0.8 to 4 μm (Gellermann, 1991). Color centers exist in many types of crystalline
solids, but most promising materials, apart from alkali halides, are alkali-earth fluorides, oxides (e.g., Al 2 O 3 ), and covalent crystals, with diamond as the only available
representative. Among the alkali halides, LiF and NaF are the most outstanding
because of their low hygroscopicity, while LiF is the most durable and suitable for
high average-power laser operations at room temperature. Sapphire and diamond
feature a unique combination of thermal and mechanical properties, but they are not
as easily accessible for technology as alkali halides (Basilev et al., 2003).
Another important group of solid-state lasers, worthy of distinction as a selfstanding class, consists of high-power fiber lasers. In fiber lasers, active (laser-gain)
optical fiber is combined with one or more pump lasers, usually laser diodes. There
are various types of fiber lasers, including low-power continuous wave, low- and
high-energy pulsed, etc. Fiber lasers are relatively simple in design and easy to
maintain. Since they are pumped with laser diodes, these lasers are also rugged
and long-lived. Kilowatt-class CW fiber lasers find common application in materials
processing, such as cutting, welding, brazing, and surface treatment (Wallace, 2016).
Among benefits important for industrial purposes, the following can be listed: high
power with low beam divergence, flexible beam delivery, low maintenance costs,
high efficiency, and compact size (Quintino et al., 2007). Sadikov and Mogilevets
(2016) point out the following advantages of high-power fiber lasers used in industrial materials processing:
1. Long life of above 100,000 working hours can be further expanded at reasonable expenses, maintenance costs close to zero.
2. Very short time and low expenditure required to prepare the location and to
launch these devices.
3. Universal laser source without specific technical features, which can be
reoriented from one technological process to another.
4. It is possible to increase the power of a laser. For instance, having a 700 W
device, one can buy pumping blocks and obtain up to 2,400 W without any
additional rebuilding. These additional blocks can be installed in two or
three hours.
5. Transmission of irradiation with a 10- to 100-m long fiber simplifies the
design and composition of manufacturing and materials processing systems. Application of a wide range of industrial robots is possible.
6. Fiber lasers offer prospects of organizing multipurpose and multifunctional
technological areas to increase the productivity of the laser source.
7. In terms of staff, there is no need to employ additional specialists to maintain the laser system. An operator can be trained in a week’s time, so that
existing staff may enter a new, higher productivity level.
Another large group of lasers is based on a gaseous active medium. The working
principle of the gas lasers is very similar to that of solid lasers, but the energy of