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Remanufacturing and Advanced Machining
multi-sensor fusion technology is applied and full advantage is taken of various signal sensors. Vision sensors are at the core of this technology, so that in an established
monitoring system, an optical sensor can be combined with a vision sensor, an X-ray
system with a high-speed camera, a sound sensor assembled with a vision sensor, etc.
In order to achieve various monitoring objectives, such as parameter optimization,
feature prediction, seam tracking, defects classification, simulation validation or
adaptive control, a variety of AI techniques can be applied (Cai, 2020). Laser beam
welding is a high-quality fusion joining process that enables the welding of dissimilar components, e.g., titanium alloys with various counterparts including steel,
aluminum, magnesium, nickel, niobium, copper, etc. (Quazi et al., 2020). It has also
been reported that femtosecond laser pulses at high repetition rates can be used to
weld glasses of different combinations (Richter, 2016).
Laser marking and engraving machines experience increasing popularity across
end-user verticals due to the enhanced performance of laser markers over traditional
material marking techniques. As far as end users are concerned, they are applied primarily in machine tools sector, semiconductor and electronics, automotive, medical
and healthcare, aerospace and defense, and packaging. The machine tools vertical is
estimated to account for the largest share of the laser marking market in 2018, which
can be attributed to the ability of laser markers to provide permanent alphanumeric
details on objects in terms of product and brand names, batch numbers, manufacturer codes, 1D and 2D barcodes, logos, designs, manufacturer codes, dates of manufacturing, product-related information, and other details (Laser Marking Market,
2021). The most widely used types of lasers in this application are fiber lasers, diode
lasers, solid-state lasers, and CO 2 lasers, respectively.
Lasers also demonstrate their feasibility for micro- and nanomachining, i.e., fabrication of components or products with at least one feature size in the micrometer or
nanometer scale. Laser systems integrated into multi-axis micromachining systems
can be used for microscale drilling, cutting, milling, and surface texturing. This way,
micro-components made of different kinds of workpiece materials, such as metals,
polymers, glasses, and ceramics, may be processed. In particular, the importance
of laser micro-milling as a micromanufacturing technology is increasing in rapid
prototyping, component miniaturization, and batch fabrication methods of serial
production of micro-devices (Gao and Huang, 2017).
There are two basic approaches to laser micromachining, namely, mask projection and direct-write. Mask projection is normally performed with excimer lasers
and with a normal binary mask of 0% or 100% transmission. A material is removed
to the same depth in all exposed regions. Stepped multilevel structures can be produced using a sequence of exposures with different static masks and variable height
surfaces can be obtained by mask- or workpiece-dragging or by static projection
using a half-tone mask. For the direct-write approach, primarily solid-state lasers
are more appropriate. In this case, a focused laser spot follows a predefined tool path
on the workpiece surface, which is particularly well suited to prototyping because it
does not require a mask (Hocheng et al., 2014).
Both the approaches are also applicable to laser nanomachining. For instance,
a particle mask can be formed by depositing a monolayer of microspheres on the
Remanufacturing and Advanced Machining
multi-sensor fusion technology is applied and full advantage is taken of various signal sensors. Vision sensors are at the core of this technology, so that in an established
monitoring system, an optical sensor can be combined with a vision sensor, an X-ray
system with a high-speed camera, a sound sensor assembled with a vision sensor, etc.
In order to achieve various monitoring objectives, such as parameter optimization,
feature prediction, seam tracking, defects classification, simulation validation or
adaptive control, a variety of AI techniques can be applied (Cai, 2020). Laser beam
welding is a high-quality fusion joining process that enables the welding of dissimilar components, e.g., titanium alloys with various counterparts including steel,
aluminum, magnesium, nickel, niobium, copper, etc. (Quazi et al., 2020). It has also
been reported that femtosecond laser pulses at high repetition rates can be used to
weld glasses of different combinations (Richter, 2016).
Laser marking and engraving machines experience increasing popularity across
end-user verticals due to the enhanced performance of laser markers over traditional
material marking techniques. As far as end users are concerned, they are applied primarily in machine tools sector, semiconductor and electronics, automotive, medical
and healthcare, aerospace and defense, and packaging. The machine tools vertical is
estimated to account for the largest share of the laser marking market in 2018, which
can be attributed to the ability of laser markers to provide permanent alphanumeric
details on objects in terms of product and brand names, batch numbers, manufacturer codes, 1D and 2D barcodes, logos, designs, manufacturer codes, dates of manufacturing, product-related information, and other details (Laser Marking Market,
2021). The most widely used types of lasers in this application are fiber lasers, diode
lasers, solid-state lasers, and CO 2 lasers, respectively.
Lasers also demonstrate their feasibility for micro- and nanomachining, i.e., fabrication of components or products with at least one feature size in the micrometer or
nanometer scale. Laser systems integrated into multi-axis micromachining systems
can be used for microscale drilling, cutting, milling, and surface texturing. This way,
micro-components made of different kinds of workpiece materials, such as metals,
polymers, glasses, and ceramics, may be processed. In particular, the importance
of laser micro-milling as a micromanufacturing technology is increasing in rapid
prototyping, component miniaturization, and batch fabrication methods of serial
production of micro-devices (Gao and Huang, 2017).
There are two basic approaches to laser micromachining, namely, mask projection and direct-write. Mask projection is normally performed with excimer lasers
and with a normal binary mask of 0% or 100% transmission. A material is removed
to the same depth in all exposed regions. Stepped multilevel structures can be produced using a sequence of exposures with different static masks and variable height
surfaces can be obtained by mask- or workpiece-dragging or by static projection
using a half-tone mask. For the direct-write approach, primarily solid-state lasers
are more appropriate. In this case, a focused laser spot follows a predefined tool path
on the workpiece surface, which is particularly well suited to prototyping because it
does not require a mask (Hocheng et al., 2014).
Both the approaches are also applicable to laser nanomachining. For instance,
a particle mask can be formed by depositing a monolayer of microspheres on the