49
Contemporary Machining Processes
• FELs easily achieve desirable laser characteristics, such as a single transverse mode, high spatial and temporal coherence, and flexible polarization
properties.
• Broad wavelength coverage with the shortest achieved wavelength 240 nm.
However, FEL is usually large and its cost remains high, and relatively little effort
has been undertaken to produce smaller and less expensive devices. Moreover, their
utilization in scientific research and operation of the facility involve high costs of
maintenance (National Research Council, 1994).
Descriptions of other lasers and their working principles can be found in Webb
and Jones (2003).
1.10.2 laser Beam machining meThods
Laser beam machining (LBM) is recognized as suitable for the processing of difficult-to-machine materials, such as ceramics, titanium alloys, or nickel-based alloys,
because of its independence from material hardness, brittleness, and other properties. The material removal mechanism is based on an extremely high power density
of the laser beam focused on a very small area. Some of the light is reflected back, but
the remaining energy is absorbed by the material surface layer and conducted to the
lattice by means of the photoelectric effect. As a result of energy absorption, surface
atoms of the workpiece get excited, raising the temperature to material vaporization
and melting. Schematically, the mechanism of material removal can be described as
energy absorption – a rapid rise in temperature – melting and evaporation – material
removal. The latter stage may be also gas assisted (Nagimova and Perveen, 2019).
The principle of LBM is shown in Figure 1.13.
Among the several types of LBM, three variations can be classified according to
the number of dimensions:
1. 1D – drilling
2. 2D – cutting
3. 3D – milling, turning, grooving, and micromachining (Nagimova and
Perveen, 2019)
Laser drilling is a popular nonconventional microdrilling technique. Its main advantages are high processing speed, high efficiency, localized processing, high precision, cost-effectiveness, and no tool loss (Ren et al., 2021). There are four ways of
laser drilling distinguished, namely, single pulse drilling, percussion drilling, trepanning, and helical trepanning. In the single pulse drilling, a high-energy laser
pulse is used to drill either a through hole of diameter below 1 mm in a thin sheet or
a shallow blind hole in a thick plate. Percussion drilling applies a series of identical
laser pulses of short duration, directed on the same spot at a high speed. Each laser
pulse removes some amount of material down to a certain depth, obtaining a through
hole with less taper in a relatively thick plate. Laser trepanning allows for producing
large holes by drilling a series of overlapping holes around their perimeter, forming
Contemporary Machining Processes
• FELs easily achieve desirable laser characteristics, such as a single transverse mode, high spatial and temporal coherence, and flexible polarization
properties.
• Broad wavelength coverage with the shortest achieved wavelength 240 nm.
However, FEL is usually large and its cost remains high, and relatively little effort
has been undertaken to produce smaller and less expensive devices. Moreover, their
utilization in scientific research and operation of the facility involve high costs of
maintenance (National Research Council, 1994).
Descriptions of other lasers and their working principles can be found in Webb
and Jones (2003).
1.10.2 laser Beam machining meThods
Laser beam machining (LBM) is recognized as suitable for the processing of difficult-to-machine materials, such as ceramics, titanium alloys, or nickel-based alloys,
because of its independence from material hardness, brittleness, and other properties. The material removal mechanism is based on an extremely high power density
of the laser beam focused on a very small area. Some of the light is reflected back, but
the remaining energy is absorbed by the material surface layer and conducted to the
lattice by means of the photoelectric effect. As a result of energy absorption, surface
atoms of the workpiece get excited, raising the temperature to material vaporization
and melting. Schematically, the mechanism of material removal can be described as
energy absorption – a rapid rise in temperature – melting and evaporation – material
removal. The latter stage may be also gas assisted (Nagimova and Perveen, 2019).
The principle of LBM is shown in Figure 1.13.
Among the several types of LBM, three variations can be classified according to
the number of dimensions:
1. 1D – drilling
2. 2D – cutting
3. 3D – milling, turning, grooving, and micromachining (Nagimova and
Perveen, 2019)
Laser drilling is a popular nonconventional microdrilling technique. Its main advantages are high processing speed, high efficiency, localized processing, high precision, cost-effectiveness, and no tool loss (Ren et al., 2021). There are four ways of
laser drilling distinguished, namely, single pulse drilling, percussion drilling, trepanning, and helical trepanning. In the single pulse drilling, a high-energy laser
pulse is used to drill either a through hole of diameter below 1 mm in a thin sheet or
a shallow blind hole in a thick plate. Percussion drilling applies a series of identical
laser pulses of short duration, directed on the same spot at a high speed. Each laser
pulse removes some amount of material down to a certain depth, obtaining a through
hole with less taper in a relatively thick plate. Laser trepanning allows for producing
large holes by drilling a series of overlapping holes around their perimeter, forming